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Technical questions - small power, sprinkler systems and O&M manualsMarch 2009

BSRIA shares the answers to the more frequent technical enquiries from BSRIA's consulting and contracting membership. This month's problems aired and solved include small power loads in laboratories, testing of sprinkler systems and standards for O&M manuals .

Small power loads in laboratories

What are small power loads for laboratories?

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Laboratories tend to have unique loads and operational characteristics. Equipment load data for Laboratories can be hard to find, so designers tend to estimate equipment loads based on nameplate data or experience from past projects. This can lead to overestimating peak equipment loads and oversized HVAC systems.

However, a recent US study does provide a rule of thumb from actual measurements. This found a wide range of data for biology laboratories of between 1 W/ft2 to 10 W/ft2.

For chemistry laboratories, loads were less than 4 W/ft2. In equipment rooms, loads exceeded 15 W/ft2. (Source: HPAC Engineering, December 2007, 27-30.)

The testing of sprinkler systems

How frequently should sprinkler systems be tested?

This depends on whether the system is for life safety or property protection. If for life safety, then under the Fire Safety Order it is deemed to be a 'relevant system' and therefore must be maintained, usually to the relevant British Standard. If the system is for property protection it is not a 'relevant system'. As such, there is no requirement under the Order to test the system.

However, the insurer of the building would require the sprinkler system to be tested and maintained as part of the terms of the insurance, and to be tested and maintained in accordance with the relevant standards, such as LPC Rules for Automatic Sprinkler Installations incorporating BS EN 12845: Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance, or BS 5306-2: Fire extinguishing installations and equipment on premises.  Specification for sprinkler systems.

Venting for refrigerant leaks

How much ventilation is required for a plant room refrigerant leak?

In the event of a refrigerant leak, plant rooms should be vented to outdoors using mechanical ventilation. This system should be independent of any other ventilation system on the site and activated by a detector(s).

Two independent emergency controls should be provided, one outside the plant room and the other inside. The emergency ventilation system should be capable of 15 air changes per hour (BS EN 378-3:2008).

The right length of a deadleg

What is the permissible length of a deadleg in hot water services?

There is no specific requirement other than the somewhat generous rule in HSE AcoP L8 on Legionnaires' disease that pipe branches to the individual hot taps should be of sufficient size to enable the water in each hot tap to reach 50°C within one minute of a tap being turning on.

Standards for O&M manuals

I have to produce an O&M manual to BSRIA Class D. What is this?

System-based manuals should outline the operation of each building services system installed, together with manufacturers' data and commissioning information. They are usually delivered as part of project handover documentation.

Since 1984, BSRIA has specified four classes of manuals:

  • Class A: basic record drawings and manufacturers literature or manuals
  • Class B: record drawings, manufacturers' operating instructions and manuals, test certificates and parts lists
  • Class C: purpose and planning information, technical documentation (including record drawings), full operating instructions for each system, detailed maintenance instructions and schedules, parts lists, modification instructions, and disposal instructions
  • Class D: as Class C, with procedures and results of all tests undertaken during the commissioning process and plant and system warranties.

For further information see BSRIA Guide 1/2007 Handover, O&M Manuals, and Project Feedback.



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