Frequently Asked Questions

This page provides a list of recent frequently asked technical questions and suggested responses or sources of answers:

Where can I get information about compliance with the F Gas Regulations?

The UK Government Department responsible for the F Gas Regulations (DEFRA) have set up a helpline which can answer specific questions and provide a range of guidance notes. Contact details:

• www.defra.gov.uk/fgas
• F-Gas Support Helpline 0161 874 3663 0161 874 3663 (9-5 Mon-Fri)
• email - fgas-support@enviros.com

What are the considerations regarding the venting of Pressure Relief Valves to atmosphere? (June 2010)

It depends on the quantity of refrigerant in the system and the size of the room into which the refrigerant would vent.  If the total
refrigerant charge could exceed the practical limit for the room -defined as the refrigerant concentration limit for the refrigerant -
then there would need to be gas alarms and remedial action - in this case that would mean emergency ventilation.  This requirement is common to EN378, ASHRAE 15 and ISO5149 (although phrased differently).

A further consideration is that the most likely cause of a relief valve lifting is in the event of a fire in the vicinity of the vessel.  As the products of combustion of HFC refrigerants are highly toxic (much more so than ammonia) the concept of a relief valve lifting while someone is trying to fight the fire is a significant concern.  If the design of the machinery room ensured that this was not possible then that would be OK.  However the easiest way to achieve this requirement is to pipe the valves to atmosphere, or at least into an extract ventilation duct.  This point is not covered by EN378, but would be taken into consideration by HSE in the event of an accident investigation.  Since the size of the relief valve is calculated on the basis of the heat from a fire around the pressure vessel it is not a valid defence to say that fire was not foreseeable.

If the system is sufficiently small, and the room is sufficiently large and the vent from the relief valve would not pose any
danger to personnel then it may well be acceptable to vent within the machine room.

NB: Outlet piping should not be added to CO2 relief valves because there is a danger of dry ice formation which could plug the pipe and prevent safe release of the system pressure