13/06/2009 by David Slade.

The current thinking is that smart homes will incorporate smart electricity meters by the supply authority (and metering operators). This will have the ability to monitor and administrate the export of electricity to the grid from homes generating their own energy on site. This will be of increasing value as microgeneration becomes more widespread.

Progress so far
The government aims to see smart electricity meters in all homes within the next ten years (i.e. by 2017). This ambition was set out in the 2007 energy white paper and was followed by a UK government consultation on metering and billing.

The main driver is the reduction in domestic carbon dioxide emissions that smart electricity meters are expected to provide.

In addition, the UK has to comply with the EU Energy End Use Efficiency and Energy Services Directive by May 2008 and it is widely seen as a key opportunity to promote smart meters. As long as it is financially reasonable, the directive requires:

• meters that accurately reflect energy consumption and provide information on time of use

• billing based on actual consumption that is presented simply and frequently enough for customers to regulate energy consumption

Smart electricity meters are the obvious way to comply with these requirements. When paired with a display unit they will fulfil the first requirement and they will allow suppliers to meet the second, as consistently accurate and informative bills will only be possible once suppliers can remotely obtain meter readings through smart electricity meters.

Smart electricity meters are also key to the government’s vision of a shift in the energy industry to a business model where it becomes profitable for companies to work with their customers to lower energy use. Suppliers will need the information that smart electricity meters provide on how their customers are using energy if they are to work with them to reduce their use.

For these reasons we would like to see the government provide a mandate for a smart electricity meter roll out in the near future that requires smart electricity meters in all homes within 10 years. The roll out will not happen immediately, but setting a requirement will be an important first step that will enable energy companies to start making real progress. In the context of smart homes, smart electricity meters are a critical first step in enabling the spread of other smart features.

Posted in microgeneration, smart meters, Smart homes, Renewable power | No Comments »

13/06/2009 by David Slade.

Building owners and facility managers have long awaited the means to break the proprietary lock of the building control manufacturers. BACnet and LonWorks are two protocols that are competing to be the key that unlocks the lock.

Not everyone is enthusiastic about LonWorks and BACnet. There are some who want one to win at the expense of the other, and there are a few who are still hoping against hope that both will somehow disappear. So, amidst the hype and the claims there is also accusation and confusion.

 “First they ignore you, then they ridicule you, then they fight you, then you win.”

  —  Mahatma Gandh

This article represents a view of what is real and what is not.

Myth #1: It’s a duel to the death - only one will be left standing.

Not so. This myth often cites as supporting evidence the Betamax vs VHS knockout that occurred. But the comparison is flawed because Betamax and VHS were mutually exclusive products, whereas BACnet and LonWorks products can interoperate in the same system.

LonWorks and BACnet are competitors, yes; but they both have a place in the industry, and they both have a critical mass of customers.

There are even some building control manufacturers who are purposefully designing their product lines with a hybrid of BACnet and LonWorks as their standard offering.

Consider the four configurations below.

A. The legacy proprietary system
This is a design from yesterday with an attempt to adapt to the industry standard, but not adopt it.
This system is still proprietary, and over time will fade from the scene, or will be relegated to speciality niche market applications where interoperability is not an issue.

B. Lonworks system with gateway to LAN networks to PC workstation to the BACNet link

Configuration B is maybe better, maybe worse. It seems to have been dreamed up by a marketing department.

It allows the marketeers to claim “we have adopted LonWorks to allow you, the customer, to mix and match different manufacturer’s components.”

Sounds good, but what is left unsaid is that the customer is still not free to mix and match different manufacturer’s systems. In other words, if the customer wants to contract for an addition to an existing system, he can only entertain a bid from a competitor if he agrees to use the original supplier’s proprietary workstation, and agrees to pay the original supplier’s price to reconfigure it for the new addition.

Lets consider this arrangement, with the original supplier’s proprietary grip still in place …thanks a lot!

C. Lonworks network, LON conponents controlled via  LON controllers, talking through a gateway direct to a BACNets network and components.

Configuration C begins to address the needs of the customer. The customer can now interoperate different manufacturer’s systems without being locked into a particular supplier, and can mix and match different supplier’s components (although at the component level, it may not be as cost effective as it sounds).

D. Lonworks network, LON conponents controlled via  LON controllers, talking through a gateway direct to a BACNets network and controllers and components.

Configuration D also addresses the needs of the customer. The customer can interoperate different systems, and can mix and match components (again, it may not be cost effective at the component level).

Why would some manufacturers choose configuration C, while others choose D?
There are as many reasons as there are engineers designing them, but from the customer’s point of view, it probably matters little.

So, LonWorks is not going away because some manufacturers are designing LonWorks components into their product line, and it is very costly to change later on. BACnet is not going away because it is the protocol of choice at the system level - A number of top building control manufacturers have chosen LonWorks for this purpose, but they don’t want to you to know that its based on Lonwork system. If they are embracing interoperability, as in configurations C or D, they are choosing BACnet to do it.

Myth #2: It’s a lovefest - they are working together in perfect harmony.
No, it is not a lovefest - they are competitors, remember? Yes, they are both chasing the same goal, interoperability.
But within each group there are a few who still believe in Myth #1, and want their side to win. Pointed jabs in the ads and hype are not uncommon.

The vast majority of the members of the LonMark and BACnet groups, however, see the fallacy of Myth #1, and understand the need for both groups to work together. A working relationship exists today between the two groups, and it is getting better as the reality sets in.

Myth #3: One is expensive, the other is affordable.
Claims for cost effectiveness abound, but the bottom line is there is no significant difference in the cost of manufacturing controls based on a proprietary protocol, the LonWorks protocol, or the BACnet protocol. If
there is a difference, it will be lost as a rounding error on bid day.

If cost is the primary criterion, compare the life cycle cost of configurations C and D versus configurations A and B. That’s where the big bucks are.

Myth #4: One is complicated, the other is simple.
Here we go again. Some folks spend their time on this type of argument because they still believe in Myth #1.
LonWorks and BACnet are both like an Internet browser - they are complicated if you want to know how they work; they are simple if you want to know how to use them.

Myth #5: Specifying either one is a nightmare.
Sure, if you are trying to force a controls manufacturer to interoperate with a competitor through the specification process, when the manufacturer is not committed (or when they are covertly opposed to it), then it is indeed very, very difficult and will likely result in a nightmare. On the other hand, if a controls manufacturer is committed to interoperability, and some are, then the specification process is simpler than it has ever been.

If you want interoperability, first spend your time determining which controls manufacturers are committed and which ones are not. Then, use the specification process to spell out your performance and functional requirements.

It works.

Posted in BACnet, Lonworks | 5 Comments »

13/06/2009 by David Slade.

 An introduction to Lonworks

Lonworks networks really describe a complete solution to the problem of control systems. Like the computer industry, the control industry was, and in many cases is, creating centralized control solutions based on point-to-point wiring and hierarchical logic systems. This meant that you had a “master” controller, like a computer or programmable logic controller, physically wired to individual control, monitoring and sensing points, or “slaves.” The net result worked, but was expensive and difficult to maintain, expand, and service. It was also very expensive to install.

Lonworks networks started out with some very simple notions - control systems are fundamentally the same regardless of application; a networked control system is significantly more powerful, flexible, and scaleable than a non-networked control system; and businesses can save and make more money building control networks over the long term than they can with non-networked control systems.

Where and how is Lonworks used?
Lonworks networks can be found in all key building automation sub-systems including heating, ventilating, and air conditioning, lighting, boilers, air handlers, security, elevators, fire detection, access control, energy monitoring, irrigation control, and window blinds. In factories, Lonworks technology can be found performing a multitude of industrial tasks — from running wastewater treatment plants to checking paint colors to monitoring the arrival of parts at assembly stations. Lonworks is supported by Echelon.

Background

LonMark is a proprietary protocol developed by the Echelon Corporation in conjunction with Motorola in the early 1990s. The LonMark standard is based on the proprietary communications protocol called LonTalk. The LonTalk protocol establishes a set of rules to manage communications within a network of cooperating devices. To simplify implementation of the protocol, Echelon chose to work with Motorola to develop a specialized communications microprocessor called the Neuron. Through the use of this chip and its supporting software, the protocol establishes how information is exchanged between devices. Because much of the communications protocol is contained on the chip, system designers and installers can focus on other aspects of the system.

While LonTalk addresses the issue of how devices communicate, it does not consider the content of the communication. A second protocol, known as LonWorks, defines the content and structure of the information that is exchanged. LonWorks is a distributed control system that operates on a peer-to-peer basis, meaning any device can communicate with any other device on the network or use a master-slave configuration to communicate between intelligent devices. The LonWorks platform supports a wide range of communications media.

LonWorks-compatible devices communicate with each other through what is known as a Standard Network Variable Type or SNVT. While a SNVT defines a device just as an object does for BACnet, its approach is somewhat different. For a SNVT to function, both the sending and the receiving devices must have detailed knowledge of what the SNVT structure is. Therefore each SNVT is identified by a code number that allows the receiving device to properly interpret the transmitting data.

Initially, LonWorks did not define what a particular SNVT code meant. This resulted in confusion between vendors who used the same code to mean different things. To eliminate the confusion and to standardize SNVT codes, the LonMark Interoperability Association was formed in 1994. Made up of hundreds of manufacturers and integrators, one of its primary goals was to lay out standard methods for implementing the LonWorks technology.

To ensure that any device installed in a LonMark system will work properly with other devices, LonMark requires that in order to carry the LonMark logo, products must have been verified to conform to the LonMark protocol. LonMark uses a Web-based tool to reduce the time and cost for certifying devices.

One of the more recent innovations made by LonMark is the network profile. The idea behind the network profile is that no matter who makes a particular device used in a building system, such as a variable speed drive, all like devices will perform a similar function. To ease and speed system installation, LonMark then defines how a particular device should function on the network, from the points included to how they are named. This predefined network profile is the minimum profile for any connected devices. Manufacturers can add additional items to the predefined profile based on their particular product, giving them flexibility while maintaining simplicity and interoperability.

LonWorks has been accepted and adopted by the international standards organizations (ANSI/CEA 709.1 and IEEE 1473-L).

Posted in Standard Network Variable Type - SNVT, IEEE 1473-L, ANSI/CEA 709.1, LonTalk, Echelon, Intelligent building, Lonworks, Introduction | No Comments »

13/06/2009 by David Slade.

Overview

Section 20 of the London Buildings Acts (and subsequent amendments) is concerned with the danger arising from fire within certain classes of building which by reason of height, cubic extent and/or use necessitate special consideration. The principles incorporated the provision of fire-fighting facilities that would enable the fire brigade to tackle the fire with utmost speed, but also provide warning of fire, contain an outbreak of fire and to prevent its spread.

This is quick guide to section 20 building requirements. But remember, always seek professional guidance.

Especially in relation to escape routes, building services, sprinkler or other automatic fire extinguishing,  or suppressant system, including hose reels; smoke extraction / venting system,  and vertical transport (including fireman’s lifts).

The London Building Act (Amendment) Act: 1939 Section 20
(Buildings of excess height and / or additional cubic extent)
(As amended 1985 & 2005)

Do the proposed works attract an application under this Legislation?

NEW BUILDINGS:
Application will be required if the building is:

• More than 30 metres in height;
• More than 25 metres in height with an area of any floor more than 930m 2.
• A building of the warehouse class, or is a building or part of a building used for the purpose of trade or manufacture exceeding 7100m3 (250,000ft3) in cubical extent  unless it is divided  by division walls (with 4hr FR) such that no part of the building exceeds 7100m3 (see note 1).

EXISTING BUILDINGS (NON-SECTION 20):

If the proposed works bring the building into one or more of the above listed categories the building will then become subject to the above legislation requiring an application.

EXISTING SECTION 20 BUILDINGS:
An Application is necessary if the works affect any of the following:

• Sprinkler or other automatic fire extinguishing or suppressant system, including hose reels;
• Smoke extraction / venting system;
• A change to the access to the site for the Fire & Rescue Service;
• Work that affects or impacts on any special fire risk areas (see Note: 2).

INITIAL NOTICES:
Where Approved Inspectors propose works within a building subject to LBA Section 20 it is mandatory that this local Legislation is recognised in the Initial Notice; failure to do so will result in rejection of the Initial Notice. Please note that this is irrespective of whether the proposed works impact on the criteria listed above or not. If the Council decides that a Section 20 Application is necessary then the Council will ask for this but will not delay validating the Initial Notice, providing that this local Legislation is expressly referred to in the Initial Notice, and confirmation is given that if necessary an application will be submitted in due course.

NOTES:
1)A building of the warehouse class means a warehouse, manufacturing, brewery, distillery with a cubic extent exceeding 4,247m3 (150,000ft 3) which is neither a public nor a domestic building. Please note for the purposes of this legislation the definition of a domestic building includes office use.
Height is taken from street level at the centre of the face of the building to the ceiling level of the top storey. Where more than half the roof is covered by a plant room such room becomes the top storey.

Cubic extent in relation to the measurement of a building means the space contained within the external surfaces and roof and the upper surface of the floor of its lowest storey but including any space within any enclosure on the roof of the building used exclusively for accommodating a water tank of lift gear or any like apparatus.

2.  Special Fire risk Areas:

• Heat producing appliance above 220 kilowatts (heat);
• Internal combustion engine producing above 44 kilowatts (power);
• Oil-filled transformer or switchgear over 250 litres of oil and voltage above 1000 volts;

Flammable or combustible solids, liquids or gas manufactured, treated, handled or stored in quantities likely to constitute a fire hazard including any of the following:
i.    Fuel oil, diesel or petroleum;
ii.    Nitrate film or celluloid;
iii.   Cellulose or flammable liquid spraying

Posted in smoke extraction, venting system, fireman's lift, sprinkler, switchgear, diesel or petroleum, Generator, Transformers - Liquid filled, section 20 building, Fuel oil, Buildings | No Comments »

13/06/2009 by David Slade.

Introduction
Earthing of installations and equipment is an issue that crosses the boundaries of the various disciplines involved in the construction and equipping of a modern commercial or industrial building. Construction engineers need to talk with instrumentation engineers and IT professionals need to discuss matters with electrical engineers and so on. Sometimes, however, these individual engineers do not speak the same technical language or are not even aware of the needs of each other’s installations. In this document an overall earthing approach is presented to serve as a basic guideline for earthing and interference suppression that can be used by multi-disciplinary teams.

In general any earthing system needs to satisfy three demands:

1. Lightning and short circuit: the earthing system must protect the occupants, prevent direct damage such as fire, flashover or explosions due to a direct lightning strike and overheating due to a short-circuit current.
2. Safety: the earthing system must conduct lightning and short-circuit currents without introducing intolerable step-voltage and touch-voltages.
3. Equipment protection and functionality: the earthing system must protect electronics by providing a low impedance path to interconnect equipment. Proper cable routing, zoning and shielding are important aspects and serve the purpose of preventing sources of disturbance from interfering with the operation of electrical equipment.

Although requirements for these three aspects are often specified separately, the implementation of them requires an integrated systems approach.

A systems approach
The original purpose of the protective earth was to ensure the safety of people and property within the zone served by the earthing system. This requires a high current capacity path with relatively low impedance at the fundamental frequency so that voltages developed under high fault current conditions are not hazardous.

It is very easy to make a good low impedance connection to ground. All that is needed is a high conductivity, corrosion resistant conductor (copper is a good choice) buried in the earth at such a depth that it will neither freeze nor dry out, large enough to contact a suitably large volume of earth, covering a sufficiently large area and in such a position that it is not influenced by other earthing systems. A large volume of earth reduces the current density in the soil and therefore the resistance to earth. A large area connection allows shaping of the electric field to be accomplished, reducing touch and step voltages. This is a clean earth – at least, as clean as it gets.

Problems arise as soon as equipment is connected to it. In practice, the cleanliness of the earth is affected by other, nearby, earthing systems and, usually more seriously, by the equipment of the installation itself.

The use of a combined protective earth and neutral (PEN) conductor, as used in a TN-C system, cannot be reconciled with the principles of good design outlined in this application note. In a TN-C system neutral currents - including third harmonics - and earth currents mix in neutral conductors, protective conductors and connected metalwork.

Installations should always be TN-S, even if they are derived from TN-C systems on the supply side of the point of common coupling (PCC). The presence of a single earth-neutral bond is very important.

Traditional installation practice focuses, correctly, on safety. Originally, it was thought sufficient to simply provide a low impedance path to earth. Modern practice requires ‘shaping’ of the field in the ground to control the voltage gradients around the earth electrode.

The ‘protective conductor’ must also provide a functional earth to the equipment operating on the system - that is, it has to provide a path for the leakage currents (at the fundamental frequency) and the high frequency noise currents arising from, for example, switched mode power supplies via radio frequency interference (RFI) filters as well as being a voltage reference for signal interfaces.

The magnitude of leakage currents varies around the installation. Since the earth leakage current originates mainly from single-phase equipment on each of the three phases, balanced components of the fundamental from each phase will tend to cancel, so that the current in the protective conductor may increase or decrease as circuits are combined along a distribution system. Often, it is worst at a (single phase) final circuit supplying IT equipment. Leakage currents are harmless while flowing to earth, but can easily reach lethal levels if the connection fails and therefore a high-integrity design is required. In essence this requires duplicate paths (each capable of carrying the full fault current) and robust and reliable connections – for example, long-life, corrosion-resistant, copper conductors installed by electricians rather than steel cable trays installed by building workers. Where the armour of cables is used as one of the routes, special attention is required to ensure that reliable connections are achieved and maintained at glands.

High integrity design principles must extend throughout the system, including right up to the desktop, by fitting sufficient socket outlets for example, so that extension blocks, with their single, low integrity, protective conductor, are not required.
High frequency currents can be a bigger problem as far as functionality is concerned. Much of the equipment that produces noise on the earth is also sensitive to it – but there is a difference; the equipment produces noise currents and it is sensitive to noise voltages. If the noise currents can be transported to earth without producing noise voltage drop, all will be well. This requires a connection to earth that has low impedance at all frequencies. To decrease radiated noise, the earth path for the noise current should run close to the supply conductors. It should be noted that in this context we are more concerned about the impedance of the connection to the earthing system, which represents the equipotential surface we colloquially call ‘earth’, rather than to the physical earth itself. This is different from the contexts of safety and lightning protection where the impedance to the earth itself is of critical importance.

When the amount of equipment installed was small it was common to run a separate large size earth lead straight back to the main earth terminal, or even to a separate earth rod (also bonded to the main earth terminal to comply with local regulations). This was usually satisfactory, partly because these systems and their peripherals were co-located in a geographically small area and so could be maintained at an equipotential (if there is such a thing), rather than at zero potential. The noise return path was also close to the supply conductors, reducing radiated noise. However, the long radial earth connections exhibit quarter-wave resonance1 effects that increase impedance at some frequencies, making this an unsuitable technique for modern widely distributed installations. Modern computer systems usually extend throughout several floors of a building. Maintaining an ‘equipotential’ (at high frequency) between these scattered devices requires a better solution.

It is a fact that most distributed computer systems work. As microelectronic devices have developed and operating voltages have reduced, the energy required to switch logic states and the immunity to voltage noise have generally decreased making them more sensitive to noise. The effect of this trend has been offset by improvements in system design to improve noise immunity. These measures include the use of differential interfaces and better software design, such as the use of error detecting and correcting protocols on networks. These techniques are very effective, but reduce network throughput by sending redundant (error control) data and requiring re-transmission of failed data packets. As the electrical noise increases, the error rate increases, and throughput decreases until useful communication ceases completely. To the user it appears as if the system has suddenly failed, whereas in fact it has merely degraded so far that the recovery mechanisms provided can no longer cope. If the electrical noise can be reduced to a low enough level, the error rate will reduce also and data transmission will again be possible. High noise levels reduce throughput by requiring repeat transmission and reduce efficiency. Clearly, network efficiency is related to data processing efficiency, which is related to business efficiency. As with many things, efficiency is worst when the need is greatest – when the network is busy. Reducing the level of electrical noise in the data processing environment is crucial to increasing efficiency. It is unfortunate that, in speculative developments, the most popular data cable for networks is unshielded twisted pair. For IT-intensive buildings and for 100 Mb/s data rates, the use of shielded twisted pair cable (STP) should be preferred.

The best way to reduce noise to a minimum is to use a copper grid ground plane. This technique was often used for ‘computer rooms’ when data processing was centralised and is still frequently the only viable solution. It works because there is an infinite number of paths through the grid with different apparent electrical lengths – while some of these paths may be multiples of a quarter wavelength, there will undoubtedly be many other parallel paths which are not. The result is a low impedance connection over a wide frequency range. Such a grid should cover the whole of the area of the installed equipment – these days usually the whole building – and it should not be forgotten that this applies to the vertical direction as well as the horizontal. There is little point in having horizontal meshes on every floor connected to a single vertical downlead. Grids are normally constructed using flat strip to keep skin effect to a minimum. Where structural elements are used as a grid, such as the supports for a raised floor that have been selected for their mechanical rather than electrical properties, it is important to ensure that the elements are electrically bonded together – using short copper braids – at each intersection.

It may be thought that a complete copper grid installation is rather expensive for ordinary commercial buildings – particularly in the case of speculative buildings. However, the cost is not great and it is obvious that the lowest overall cost is achieved by incorporating grids at the design stage, and that the most expensive route is to retrofit grids after occupation. An effective earthing system ensures that the building is suitable for a wider range of uses and is thus more marketable. The building can attract a higher rent, justified by the reduction in the frequency (and cost) of problems to tenants and the consequent operating costs.

Electromagnetic compatibility
Every piece of electrical and electronic equipment produces some electromagnetic radiation. Similarly, every piece of equipment is also sensitive, to a greater or lesser extent, to electromagnetic radiation. If everything is going to work, the cumulative level of radiation in an environment must be rather less than the level that will disrupt the operation of the equipment working in that environment. To achieve this goal, equipment is designed, built and tested to standards to reduce the amount of radiation that is emitted and increase the amount that can be tolerated.

EMC is defined in the IEC 61000 series as:

‘The ability of an equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment.’

Maintaining this compatibility in practice requires great care in the design and implementation of the installation and the earthing system. Only a general overview only is presented in this document.

In traditional electrical engineering separate earthing systems were used, for example, signal earth, computer earth, power earth, lightning earth etc. In today’s electrical engineering new insights have been gained on the aspect of earthing and grounding and its relation to instrument protection. The concept of separate earthing systems has been abandoned and the international standards now prescribe one overall earthing system.

There is no such thing as ‘clean’ and ‘dirty’ earth.

This single earthing concept means in practice that protective earth (PE) conductors, parallel earthing conductors, cabinets and the shields and screens of data or power cables are all interconnected. Also steel construction parts and water and gas pipes are part of this system. Ideally all cables entering a zone must enter at one point at which all screens and other earth conductors are connected.

To reduce interference on equipment the earthing loops between cable-screens and other earthing structures must be kept small. Bonding cables against metal structures makes these structures act as parallel earthing conductors (PEC). Parallel earthing structures are used both for data and power cables.

Examples are, in ascending order of effectiveness: earthing wires, cable ladders, flat metal surfaces, cable trays or ultimately metal pipes. The PEC reduces the impedance of the loop formed by the cable and the earthing network. The earthing resistance to mother earth is mostly not important for the protection of equipment. A very effective form of a PEC is a densely woven or completely closed cable screen with a large metal cross-section, connected all around at both ends of the cable.
To keep the impedance of bonding connections in the earthing network small for high frequencies, litz wire (stranded, individually insulated) or metal strips with a length to width ratio smaller than 5 must be used.

For frequencies higher than 10 MHz round wires should not be used.

A raised floor can serve as a good equipotential plane. The copper grid underneath it must have a maximum spacing of 1.2 metres and be connected to the common bonding network via many equipotential bonding conductors. The grid should be connected to a 50 mm sq copper ring placed around the raised floor area, within the boundaries of the floor, at 6 metre intervals. Power and signal cables should be at least 2oomm apart and where they cross, they should do so at right angles.

Conclusion
The earthing system of a building or site is a critical part of the electrical infrastructure and can determine the future viability of businesses operating in it. It is required to deal with short duration fault currents of several hundred Amperes, standing currents of a few Amperes and high frequency noise currents returning them to source or ground with close to zero voltage drop for noise currents and with no risk of damage for fault currents. At the same time, it must protect the equipment and personnel housed in the building during lightning strikes (fast transients in the kiloampere region) in the interconnected earthing system.

The design of the earthing system of a building, including the lightning protection system, requires great care if all the objectives are to be met. It is, as usual, best and cheapest if it is designed correctly from the start, considering the lifetime of the building and, as far as possible, the potential usage during that lifetime.

Re-engineering after the building has been occupied is always an expensive exercise.

Posted in shielded twisted pair cable (STP), Electromagnetic compatibility, protective earth (PE), radio frequency interference (RFI), equipotential earth, point of common coupling (PCC), clean earth, protective earth and neutral (PEN), TN-C, third harmonics, Earthing | No Comments »

13/06/2009 by David Slade.

The location of a site sub-station needs to be carefully considered, the key factors being:

Proximity to the heaviest loads
Equipment with heavy loads is generally grouped together into what is termed a load centre, and ideally the sub-station should be located as close as possible to the load centre. This avoids the need for lengthy runs of low voltage cable which is relatively expensive and can cause a degree of power loss under heavy loads. Large installations may have several load centres located at different points around the building and may consequently require multiple sub-stations.

Supplier access:
The supplier must have easy access to their high voltage switchgear. This can either be located in the same area as consumer’s switchgear or alternatively in a separate switch room.

Transformer type:
There are a variety of different types of transformers that can be used, all of which fall into two basic categories: liquid-filled and dry type.

Liquid filled transformers:

Key points:

• Mineral oil transformers are relatively cheap but present a slight fire risk
• Liquid-filled transformers are generally more energy efficient than dry transformers

Limitations:

• Mineral oil transformers generally need to be located outside due to the fire risk
• Internally located mineral oil transformers may require automatic fire extinguishers and a purpose built soak-away to deal with any oil spillages
• Synthetic ester filled transformers provide a non-flammable alternative but cost approximately 30% more than the mineral oil option

Dry transformers:

Key points:

Limitations:

• More expensive than oil-filled transformers, especially the cast resin type
• Dry transformers tend to be significantly heavier and larger than oil-filled transformers, which can be a problem where space is restricted
• At low to medium loads, dry type transformers tend to be less efficient, which results in more electrical energy being converted to heat and lost to the atmosphere. This wasted energy must be paid for by the consumer and represents a significant operating cost

High voltage distribution:
In many buildings such as offices, a single sub-station is often all that is required to supply the low voltage distribution system. In such cases, the incoming high voltage supply and substation can be located in a single area and that will be the extent of the high voltage system.

Larger commercial buildings and industrial applications may have several load centres and will require a high voltage distribution system to serve multiple sub-stations. There are two systems which can be used, each of which has advantages and disadvantages. These systems are:

• Ring main

The high voltage distribution circuit is arranged in the form of a ring which starts and finishes at the high voltage intake. The load centres are connected at convenient points around the ring main. The benefit of this system is that each load centre effectively has a high voltage supply from either side of the ring main, so if a fault occurs with one of the supplies, the load centre can still operate.

• Radial feeder

In a radial feeder system each load centre is fed separately from the consumer’s main high voltage switchboard. The main benefit of this system is that a fault in the supply to one of the load centres should not affect the others.

Posted in Transformers - Dry, High voltage distribution, Substations, Transformers - Liquid filled | No Comments »

13/06/2009 by David Slade.

Introduction

In order to design a suitable Data Centre for an organisation it is vital to consider a multitude of interconnected factors. In the fast moving world of IT, where the physical sizes of types of technology assets can change regularly, it is a challenging task to design a Data Centre that will cater for the needs of an organisation for the next ten years or more. This document will discuss some of the factors to be considered when developing the design of a Data Centre, and will provide advice on how to maximise the opportunities for future proofing the facility.

Location
Historically, most companies have based their Data Centre facilities within the same buildings as their staff. If this is the proposed strategy for your new facility, then you need to consider whether the Data Centre should be located on a basement floor or on an office floor. Typically, basement rents are approximately one quarter of office floor rents, and your stakeholders will probably prefer that you do not take up valuable office floor space with technology equipment that does not necessarily justify a prime location on the floor. Another factor to consider is support. If your
support staff require access to the facility on a regular basis then you need to determine whether it is acceptable for them to be continually going from the office floor to the basement.

Size
This is probably the most challenging factor of Data Centre design. In addition to rental costs, it is expensive to provide power and cooling facilities to large areas so you will be under pressure to make sure that the Data Centre is not excessively large for the requirements of the organisation. However, it can be equally expensive and time-consuming to extend a Data Centre that is initially designed too small. A reasonable method for calculating the size of the room is to plan for day one and then to add an additional 30% space for expansion. You also need to factor in whether mechanical and electrical plant will be located within the Data Centre and if so, to ensure that these devices are coordinated with the overall design of the room

Power
The design of the power solution will depend on the business need for the Data Centre to ‘stay up’. Where the failure of a Data Centre has direct financial implications for a company, then a business case needs to be established to understand the costs of a failure versus the expense of installing a highly resilient power solution. Similarly, if a temporary Data Centre failure does not directly affect the revenue generation of the organisation, then it could be seen as a waste of money to specify a highly resilient solution.
There are a number of resiliency factors to consider:

• Cabinet Power. Ideally, power strips within a cabinet should be fed from two separate Power Distribution Units (PDUs). This is relatively easy to implement at design stage but can be expensive to change later. Breaker sizes also need to be considered carefully, and will be defined by the equipment that you are planning to install on day one as well as the likely requirements for ‘future’ equipment.

• An Uninterrupted Power Supply (UPS) will allow devices to stay up while mains power is restored, or at least will allow equipment to be shut down safely. You might specify a central UPS that supports all Data Centre active equipment, or alternatively you might install separate UPS devices for each individual system. The important factor to consider is how long the IT team needs to safely power down systems in the instance of a mains power failure. The UPS design will be based on this important time period.

• A Generator can keep equipment running in the case of an extended failure of mains power. Generators can take up a significant amount of space as there is a requirement for the storage of fuel to run the generator. However, they are vital to organisations who cannot afford a power outage to affect their IT  operation.

Air Conditioning
As with power, the required level of resiliency will be determined by the costs to the business of Data Centre failure. An important consideration is that air conditioning units require chilled water to cool the environment, and where possible you want to ensure that water does not get inside your Data Centre. Consultants are now recommending the construction of a service corridor outside the Data Centre. This corridor contains the air conditioning units, which can blow cold air in to the room, but can also be serviced outside the room. The wall between the service corridor and the Data Centre is water sealed; therefore if an air conditioning unit should fail the water will not be able to penetrate the Data Centre.

Where it is necessary to install air conditioning units within the Data Centre, thought should be given to leak detection and also to the ongoing servicing of the units. Thought also needs to be given to UPS support for the air conditioning equipment: there is little value in IT equipment remaining up and running if it will overheat and fail due to a lack of available cooling.

Raised Floor
The height of the raised floor will be determined by a number of factors:

• Distance between the slab and the soffit. This distance might limit the amount of available space for the raised floor void.

• Height of the raised floor across the rest of the office space. Normally, the office floor will have a raised height of 200mm whereas the Data Centre raised floor height will be anywhere from 300mm to 750mm. In order the bridge the gap between these heights, steps and\or a ramp will need to be installed and space restrictions within the room might prove prohibitive.

• Depth of structured cabling. The air conditioning units generally tend to push cold air in to the floor void. For this system to work effectively there needs to be sufficient space for the air to circulate. Therefore, a large volume of structured cabling will require a higher raised floor to allow the cold air to circulate above it.

When installing a raised floor, thought also needs to be given to the size of floor tile that is specified. The majority of floor tiles are 600mm square, whereas the cabinets are 800mm square. When designing the cabinet layout, care should be taken to ensure that no tiles are ‘trapped’ and that the tile cut-outs are in sensible positions.

Suspended Ceiling
Consultants are now recommending that suspended ceilings are not installed in Data Centres. The recommended solution is for suspended light fittings to be hung from the soffit, and also for power to be presented at high level within containment also hung from the soffit. There are a number of advantages to this solution:

• Cost savings are achieved by removing the suspended ceiling from the construction budget.

• There is a greater fire risk when power and data cabling are located in close proximity. By locating data cabling in the floor void and power at high level, the risk of fire is significantly reduced.

• It is easier to control maintenance works within the Data Centre. The electricians will not need to get in to floor void, and the data cabling engineers will not be working anywhere near power.

• It is easy to ensure that cabinets are fed by power from two separate PDUs.

When power is installed within the floor void, power strips are often cabled to the same PDU and this is not known until failure occurs. When power is visible at high level, it is easy to identify poorly configured cabinets.

Whilst power at high level is an ideal solution, thought needs to be given to the configuration of cabinets. Only recently manufactured cabinets will have holes in the top for power cables to pass through, therefore older cabinets might need to be modified if no holes exist.

Fire Suppression

Most office floors are protected from fire by sprinkler systems (this is a requirement of ‘Section 20’ buildings). Data Centres also require protection, and this will normally take the form of a ‘pre-action’ sprinkler system or a gas based fire suppression system.

The following items are worth considering in your design:

• If power is presented at high level, there is a minimal risk of fire within a Data Centre. In this case, a sprinkler system might be the most cost effective system as it is highly unlikely to be ever be set off.

• Most gas based fire suppression systems work on the principle of reducing the percentage of oxygen within an enclosed space in order to extinguish a fire. These solutions require that the room is fully sealed to ensure that the gas does not seep out of the room when it is released. When carrying out new installations which require running cables in to the room, engineers need to ensure that the room is sealed after any work. If this does not happen then the gas might fail to extinguish the fire.

• The gas required to protect the space needs to ideally be stored relatively close to the Data Centre. Where you are protecting a large area, the gas bottles can take up a large amount of space within your building.

• The main positive of the gas based system is that if one piece of equipment catches fire, then the fire will be extinguished with hopefully no damage being done to your other equipment. Sprinkler systems can not necessarily claim this advantage.

• Fire protection can also be enhanced by the installation of a fire detection ‘sniffer’ aspirating system (VESDA) which samples the air and gives early warning of any hot spots within the room.
• Alternatively there are also water misting systems and N2 Oxy reduction systems, that have sometimes been installed.

Security
The criticality of most Data Centre facilities means that security is a vital element of the design process.

Items that need to be considered include:

• Is it acceptable for the Data Centre to be visible from outside the building? If no, then windows might need to be blacked out or an interior wall built between the glass façade of the building and the Data Centre.

• How many doors does a person need to get through before they can get access to the Data Centre? There is a balance to be found between locating a facility near to a goods lift to facilitate easy delivery of new hardware, and exposing the facility to risk of intrusion from external parties.

• It is good practice to ensure that security cameras monitor all entrances to the Data Centre.

• A permit to work system should be established for all Data Centres. Access to maintenance staff should only be allowed when the proper supervision is in place.

Operating Model
When designing the Data Centre, it is important to think through the operating model of the facility. If cabinets or servers need to be brought in to the Data Centre on a regular basis, you need to ensure that the facility is easily accessible from the goods lift, and also that the Data Centre doors are sufficiently high and wide to allow
cabinets to be taken in and out.

Mechanical consultants are also now recommending a hot aisle\cold aisle principle for cooling Data Centres. This requires that rows of cabinets face each other. This design will work effectively in a ‘lights out’ Data Centre but if you run a facility where cabinets are constantly being worked on, then it would be difficult for support staff to work on two cabinets that face each other. Therefore, the mechanical and electrical services designs need to reflect the operating model of the facility.

Off-Site Hosting Facilities
Companies are now able to benefit from remote Data Centre hosting facilities offered by third party vendors. These sites are designed to be highly resilient and to cater specifically for only the IT requirements of an organisation. One major advantage is that the IT strategy of an organisation can become relatively independent of the Facilities strategy.

For example if an organisation decided to relocate to a new HQ building, the majority of equipment can remain in the remote Data Centre, thus significantly reducing the cost and risk of the project.

The majority of remote Data Centres are also able to offer scaleable facilities. For example, on day one you might rent 12 data cabinets, with the option of increasing this whenever you need extra space. You can also build in to the contract an option to reduce space should the equipment you install become smaller in the future.
Again, this can significantly reduce financial risk for the IT Director.

Whilst these off-site facilities might initially seem expensive, when compared with the true cost of building and managing your own Data Centre, they can seem competitive.

The main negative of a remote Data Centre is that control is ceded to the third party that runs the facility. Whilst the majority of providers run highly professional facilities, they are unlikely to understand the urgency of fault diagnosis and resolution that your own internal staff would take for granted.

Summary
The sections above highlight a number of key areas that need to be considered when designing a Data Centre. As a facility of this kind is normally designed for a minimum ten-year period, it is unlikely that you can design the perfect environment. The best you can hope to do is to consider all of the design parameters outlined above and fit them to the technology requirements of your organisation.

Posted in Air Conditioning, Raised Floors, leak detection, Oxy reduction system, section 20 building, Facilities strategy, Suspended Ceilings, Fire Suppression, Uninterrupted Power Supply (UPS), Power Distribution Units (PDUs), Generator, resiliency, Section 20 buildings, Data Centre Design | 1 Comment »

13/06/2009 by David Slade.

Hotel solutions come in all levels of systems and user complexities.

For a quick overview of a traditional typical basic hotel system, here is a quick description of the typical systems:

First system included to increasing the overall energy efficiency of a hotel complex, a Building Management System (BMS) shall be installed to provides a central point of control for  the heating, security, booking, and financials, dramatically, reducing the operating costs and simplifying the management of a hotel system(s). This can be dramatically improved by combining these systems into an integrated system.

Central control made easy
For heating and ventilation control, a good system systems will use zone controllers as opposed to room thermostats, which are a far more economical solution to temperature control, leaving your guests warm and cosy with consistent temperatures around the whole building. Because reception areas, restaurants, conference rooms, offices, pools, spas and fitness centres all have different climate and security needs, a BMS solution is a simple way to control all these areas centrally.

Behind all of this, sits a comprehensive range of advanced electrical distribution equipment.

Resulting in a ….

Reliable, maintenance free and efficient energy management system.

This overview is deliberately simple to convey how a hotel complex can be made into an efficient business machine that delights its guests. The offer includes everything from single products to scalable integrated solutions.

 Gym/Pool

• Building Management Systems
• Lighting Control
• Temperature Control
• Closed Circuit Television
• Electrical Distribution

 Reception/Communal Areas

• Building Management Systems
• Closed Circuit Television
• Lighting Control
• Audio Supply
• Wiring Accessories
• Cable Containment Systems

Car park

• Closed Circuit Television
• Electrical Distribution
• Energy reduction in lighting

 Guest rooms

• Wiring Accessories
• Lighting Control
• Integrated Installation Systems
• Audio/Visual Connectivity
• HVAC
• Key / card / biometric Switches
• Electrical Distribution
• Cable Containment Systems
• Wi-Fi
• TV
• DAB’s
• Intergrated Broadband connection

 Hallways / Corridors

• Electrical Distribution
• Integrated Installation Systems
• Lighting Control
• PIR (Movement sensing)
• Cable Containment Systems
• CCVT
• Wi-Fi

 Services

• Electrical Distribution & Control
• Variable Speed Drives
• Energy Management Systems
• Metering & Monitoring
• Maintenance Contracts
• Uninterruptable Power Supply
• HVAC

From the plant room to the penthouse . . .total electrical and IT control

With individually tailored solutions and specialist product knowledge. This article was intended to described as basic hotel system, a lot more sophisticated systems can be adopted. Which I may describe if  future articles.

Posted in zone controllers, heating and ventilation control, Building Management System (BMS), Hotel Solutions, Integration | No Comments »