perky

Thanks Harry

Thanks Tom. Yes, Dorgard type fire door retainers. I was wondering whether the rubber ferrules need any special fire retarding properties in their own right.

Hi All, What is the rule for using rubber ferrules on the plunger type door retainers? Do they have to be fire retardent, or can they be normal rubber? As far as I can see I think the answer is they don't need to be fire retardent as long as the door retainer does not compromise the integrity of the fire door itself, is this correct? Thanks Mark.

Sorry, I didn't see your reply until now! Thank you, I'll ask there.

Thank you, I'll ask there.

Hi, I'm hoping someone can help me deciding the best way to interface a device to a fire alarm for Critical Category BS7273-4 compliance. I'm trying to decide which is the most common interface type that is generally available on fire alarm panels without having to use volt-free relays or anything that might 'steal' valuable resources from the fire alarm panel for a dedicated interface. According to BS7273-4 diagram C1.b, I'd need an output from the alarm that is passes in series through a normally closed fire relay and normally closed fault relay (at least one being normally energised) and a power supply in series with this too. I assume the AUX 24V supply could be used for this supply which I also assume is short circuit protected (?). That would normally provide a 24V signal that is removed on either a fire or fault condition, and would provide fail-safe short and open circuit protection on the two wire interface to my device. 1) Are my assumptions above correct? 2) If so, do fire alarm panels provide these as single outputs that effectively do the above? Are they called auxilliary outputs? 3) Can such a output be used to trigger multiple devices? The BS7273-4 spec does show a single 'auxilliary output' (figure C4) triggering a radio TX device, I assume the ground return isn't shown but to make this Category A compliant it would I think need to use the same methodology as above, namely fail-safe and triggering by fault or fire. Thanks, Mark.

OK, thanks. BTW it is impossible to release the doors 'immediately' if the fire alarm operates assuming no fault conditions, so my question is how long does the spec allow (since it can't be zero)? Is operation under normal conditions (i.e. no fault) actually covered in the BS7273-4 spec, or is that just all about failing safe? My local library doesn't have BS specs so I'd like to know it has the information I need before purchasing one. Thanks, Mark.

Hi All, As far as I can gather BS7273-4 stipulates certain maximum times for failing safe with door closers which are different for Category A, B or C. Can someone with access to the spec please tell me if there is an maximum activation time from normal fire alarm specified? The maximum time to activation for faults such as short or open circuits is 2 minutes and 6 minutes for loss in radio comms for Cat A and 120 minutes for Cats B & C. There are other documents I've seen that state that the system should behave in fault conditions exactly as it would in fire alarm conditions, so does that imply a maximum of 2 minutes from fire alarm activation? Also if BS7273-4 are guidlines, and a piece of equipment fails certain time criteria (but otherwise still fails safe in conformance), can that equipment be given a Category A certification if those conditions are noted on the conformance certificate? Thanks for your help! Mark.