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BS7273-4 compliant interface to fire alarm panel
#31
(11-01-2018, 03:19 PM)CaptainSlog Wrote:
(11-01-2018, 09:55 AM)Gaaaazzzzaaaa Wrote: I know absolutely nothing about BS7273 but it seems that CaptainSlog is talking about Control Panel Relays and that Monkeh is talking about Loop driven relays. If the relay was loop driven then I assume it would have to be a BS7273 approved output to monitor the protocol. If the relays were panel driven then it would not need to monitor the protocol as it is not connected to either the loop protocol or the communications protocol. 

This is only my assumption. 

To answer the question about a dedicated panel output for combining fault and fire, usually, the answer is NO. Most panels should have a Fault output relay which is usually 'Energised'. Some panels have a dedicated fire output which is usually 'Non-Energised'. Again, a lot of panels have programmable outputs that can be programmed for either Fire or Fault or Both if required. I don't think you will find a common scenario for all panels that provide a 'standard' means of connection. It will be panel dependent and may require the use of 2 separate panel relays on most occasions.

Thanks, control panel relays is exactly what I was talking about.

From what you've said it would seem to me the most flexible way would be to assume the panel could be wired so that the 24V aux supply passes through a normally closed (and normally energized) fault relay, then through a normally closed fire relay to form the output. That output could be used to trigger multiple devices while still being fail safe, and may well have already been configured that way for something else in the system so additional relays wouldn't necessarily be needed.

Mark.
I personally cannot see anything wrong with doing it this way. Again I don't know about the BS but the Aux 24v is provided to supply power to critical signalling equipment (amongst other uses) and the fire & fault relays wired as said would provide a fail-safe operation. 

The only consideration to your comment about not requiring additional relays would be that it is never a good idea to switch different types of output equipment through the same relays as they could impact each other. IE the fault relay may well be connected to a BMS system for signalling common fault as a volt free contact. Adding power to it to power a door release signal would affect the volt free BMS signal. You would also have to ensure that the Aux 24 is not overloaded and that any earth monitoring/issues on your equipment do not affect the earth monitoring on the control panel as your 0v rails will potentially be common.

As an aside from the BS, you may also want to check into CE approval as I believe (though am not certain) that any equipment connected or designed for use on fire alarm equipment has to go through additional tests for EMC to achieve CE approval.
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#32
(12-01-2018, 09:43 AM)Gaaaazzzzaaaa Wrote: I personally cannot see anything wrong with doing it this way. Again I don't know about the BS but the Aux 24v is provided to supply power to critical signalling equipment (amongst other uses) and the fire & fault relays wired as said would provide a fail-safe operation. 

The only consideration to your comment about not requiring additional relays would be that it is never a good idea to switch different types of output equipment through the same relays as they could impact each other. IE the fault relay may well be connected to a BMS system for signalling common fault as a volt free contact. Adding power to it to power a door release signal would affect the volt free BMS signal. You would also have to ensure that the Aux 24 is not overloaded and that any earth monitoring/issues on your equipment do not affect the earth monitoring on the control panel as your 0v rails will potentially be common.

As an aside from the BS, you may also want to check into CE approval as I believe (though am not certain) that any equipment connected or designed for use on fire alarm equipment has to go through additional tests for EMC to achieve CE approval.

Thanks. I'm not sure if I fully agree with the statement that it's 'never' a good idea to switch different types of output equipment with the same relays, as long as the engineer is fully aware of the compatibility and requirements of all the interfaces he/she is wiring up including existing ones, which should be the case anyway in order to certify compliance, I can't see a problem in doing that. But I take the point that it may be more prudent to use separate relays.

I wonder whether you could shed some light on this little anomoly I found though. Take a look at the Radio Activated Systems wiring diagram in this Geofire help guide. It seems to use a different wiring technique for radio activated door holders rather than the conventional technique, but I'm unsure why. I don't know whether this requirement is specific to the Salamander radio interface, I can't see anywhere in the BS7273-4 spec that would mandate such an interface, in fact that interface as shown doesn't seem to be fail safe as it doesn't cover the case of the fire and fault lines being shorted in the cable:

https://www.fireproductsdirect.ie/wp-con...-Doors.pdf

Mark.
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#33
(12-01-2018, 04:52 PM)CaptainSlog Wrote:
(12-01-2018, 09:43 AM)Gaaaazzzzaaaa Wrote: I personally cannot see anything wrong with doing it this way. Again I don't know about the BS but the Aux 24v is provided to supply power to critical signalling equipment (amongst other uses) and the fire & fault relays wired as said would provide a fail-safe operation. 

The only consideration to your comment about not requiring additional relays would be that it is never a good idea to switch different types of output equipment through the same relays as they could impact each other. IE the fault relay may well be connected to a BMS system for signalling common fault as a volt free contact. Adding power to it to power a door release signal would affect the volt free BMS signal. You would also have to ensure that the Aux 24 is not overloaded and that any earth monitoring/issues on your equipment do not affect the earth monitoring on the control panel as your 0v rails will potentially be common.

As an aside from the BS, you may also want to check into CE approval as I believe (though am not certain) that any equipment connected or designed for use on fire alarm equipment has to go through additional tests for EMC to achieve CE approval.

Thanks. I'm not sure if I fully agree with the statement that it's 'never' a good idea to switch different types of output equipment with the same relays, as long as the engineer is fully aware of the compatibility and requirements of all the interfaces he/she is wiring up including existing ones, which should be the case anyway in order to certify compliance, I can't see a problem in doing that. But I take the point that it may be more prudent to use separate relays.

I wonder whether you could shed some light on this little anomoly I found though. Take a look at the Radio Activated Systems wiring diagram in this Geofire help guide. It seems to use a different wiring technique for radio activated door holders rather than the conventional technique, but I'm unsure why. I don't know whether this requirement is specific to the Salamander radio interface, I can't see anywhere in the BS7273-4 spec that would mandate such an interface, in fact that interface as shown doesn't seem to be fail safe as it doesn't cover the case of the fire and fault lines being shorted in the cable:

https://www.fireproductsdirect.ie/wp-con...-Doors.pdf

Mark.
The schematics in the guide appear to be very similar. The only difference seems to be that the wireless system has separate inputs for fire and fault and instead of the power being 'commoned' at the control panel, two separate wires are used. 

I'm not sure if I can see any benefit in doing it this way personally. The doors will release on either a fault on the 'Fire' wiring or a fault on the 'Fault' wiring which is what is required. If there was a requirement for the 'Fire' signal to operate regardless of whether a fault is present or not then this configuration would have an advantage, however, since the doors have released anyway it doesn't make a difference. 

If the positive feed to the 'Fire' and 'Fault' signal were wired in a single 2 core cable, a short on the cable could prevent one of the outputs from operating correctly. IE a short on the cores would provide 24v onto the fire input from the fault output even if the fire output had operated. I would assume that this kind of arrangement would have to be wired in two physically separate cables. Doing this would ensure the integrity of the 'Fire' signal regardless of what happens to the 'Fault' cable but as I mentioned above, the doors should already be released if there is a fault on the 'Fault' wiring.
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#34
(15-01-2018, 09:48 AM)Gaaaazzzzaaaa Wrote: If the positive feed to the 'Fire' and 'Fault' signal were wired in a single 2 core cable, a short on the cable could prevent one of the outputs from operating correctly. IE a short on the cores would provide 24v onto the fire input from the fault output even if the fire output had operated. I would assume that this kind of arrangement would have to be wired in two physically separate cables. Doing this would ensure the integrity of the 'Fire' signal regardless of what happens to the 'Fault' cable but as I mentioned above, the doors should already be released if there is a fault on the 'Fault' wiring.

Thanks. This all comes down to how the BS7273-4 standard is written I think. There's a definition of a 'circuit' being 'assembly of components supplied from a single source and protected against overcurrent by the same protective device(s) or current limitation arrangements'. A rather stange definition. It mentions open and short circuits on 'any' circuit being considered a fault, so what does that mean? Individual cores in a cable? Any combination? It's woolly wording has led to the interpretation that all cores in a cable must either short together, or all cores go open circuit for there to be a fault. Given that a partially damaged cable could have exposed some conductors potentially shorting them and completely severing others in the same cable, and that this is significantly more likely than all cores shorting, it would appear this can lead to unsafe systems if that assumption is made.

If you take the above loose interpretation of faults then all cores in the cable shorting would short the fire, fault and GND signals together and a single cable would suffice, but I think your gut response, just like mine, was not to assume that happens as it goes entirely against the fail safe goals of the standard. The standard even relies on the 'inherent fail safe nature' of these interfaces! This standard needs a re-write IMO.

Mark.
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