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Designing drains for stormsDecember 2007

BSRIA's Librarian Stephen Loyd shares the answers to the more frequent technical enquiries from BSRIA Members.

Does magnetising a fuel line have an effect on combustion efficiency?

The assertion of installing a magnet on an incoming oil or gas fuel line is to align the ions in the mixture, so that when entering the combustion chamber of the boiler it combusts more efficiently. This leads to a hotter flame temperature or reduced fuel use at the same heat output.

Some years ago BSRIA tested a variety of these devices from various manufacturers on both gas and heating oil for central boilers up to 200 kW. None of the magnet devices had any effect on energy efficiency or emissions when tested under controlled laboratory conditions in a boiler test laboratory.

This experience does not mean that magnets can't have an effect on the oil or the combustion process.

Heavy fuel oil contains material with paramagnetic and diamagnetic properties that may be influenced by strong magnetic fields and these characteristics are used in filtration technologies. However, you cannot get more energy out of the fuel than the fuel contained in the first place.

If the magnet improves boiler efficiency then it can only be by a small amount, equivalent to the unburned fraction of the fuel such as CO and soot, and a possible influence on heat transfer efficiency in the combustion chamber such as a change in flame profile or temperature. The latter effect, if it enhanced efficiency, would result in a decrease in measured flue gas temperature, not the increase that some magnet proponents claim as evidence of effect.

There are many variables that influence fuel consumption on site, so it is practically impossible to reliably quantify a real magnetic effect from site data.

Some operators claim they are benefiting from the devices, but BSRIA's experience, at least for gas and light heating oils, is that claimed savings evaporate when the magnets are brought into the controlled environment of a boiler test laboratory.

What are the space requirements for access for servicing switchgear?

There are potentially two answers to this. The Wiring Regulations BS 7671 clause 131-12-01 simply calls for "sufficient space" without specifying distance and leaves this open to interpretation. However, there is a more specific answer provided by the HSE in its publication HSR25 Memorandum of guidance on the Electricity at Work Regulations 1989.

This publication confirms the validity of dimensions given in the 1908 Electricity (Factories Act) Special Regulations, whereby all working area access for switchboards shall have a clear height of not less than seven feet and a clear width measured from bare conductor of not less than three feet. A rare case of old design data surviving 100 years.

There is also BS 6423:1983 Code of practice for maintenance of electrical switchgear and control-gear for voltages up to and including 650 V.

I am designing roof drainage and need to know details of likely storm events

This past summer has highlighted the need for this information. Drainage design needs to achieve a balance between the cost of the roof drainage system and the frequency and consequences of flooding.

The capacity of systems should be adequate to dispose of intense rainfall that usually occurs in summer thunderstorms. The frequency and severity of the intense short duration rain-storms varies throughout the country, but are more frequent in lowland areas.

Statistical meteorological data for the UK is given in the National Annex in BS EN 12056-3:2000 Gravity drainage systems inside buildings â€" Roof drainage, layout calculation.

Maps show rainfall intensity for a two-minute duration with return periods of one, five, 50 and 500 years in litres per second per metre squared. Given the UK's flooding problems in 2007, this criteria may soon need updating.

What are the environmental conditions for an IT facility?

The environmental conditions for IT equipment play a key role in ensuring the equipment is dependable. If conditions are not controlled within certain parameters, processor temperatures will fluctuate and ultimately the equipment could fail.

The table provides simplistic environmental conditions for IT equipment and the room environment.

Do you know the origin of the term Muzak, that describes piped music?

Muzak is a trade name for the Muzak Corporation, who began supplying its patented system of background music for workplaces in the 1920s. Soon after the first elevators were introduced, building owners found that many people became nervous, so soothing music was played in the elevators to ease passengers' fears.

In multi-occupancy buildings, who should conduct the fire risk assessment?

Any premises with five or more employees must conduct and record a fire risk assessment. The landlord-owner/managing agent of multi-occupancy buildings is responsible for the areas which affect the life-safety and property-protection systems. These include the fire alarms; detection systems; emergency lighting; fire extinguishers; sprinklers; risers; fire dampers; staircase pressurisation; signage; means of escape; and maintaining service records.

The occupier of any leased space in a multi-occupancy property who employs more than five people will be responsible for carrying out a fire risk assessment. This will include hazards/mitigation in the space, portable fire equipment, training, maintaining any special fire safety systems, means of escape, and development of emergency procedures.

The BSRIA library holds copies of government guidance on fire risk assessments for different types of buildings.

The member enquiry service is one of the many benefits to being a BSRIA Member. For more information about these benefits and how to become a BSRIA Member contact:

Tel: +44 (0) 1344 465600
or email Membership



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