HVAC RTU shut downs

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Smart $

Smart $

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stevenbouf said:
... Another problem I have is hvac RTU shut downs. The system is non addressible and the fire panel is hundreds of feet away through other units. I have a zone to use already how can I shut down these. I was thinking useing a relay on the horn circuit but when the alarm is turn off by the fire dept the relay would allow the rtu to start and they may still be operating. Know what I mean
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Smart $ said:
Let me re-word the question:

How do or can you shut down an AHU with the FAS?
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BUMP (30 views and no replies at this point)

I suggested in the other thread that the RTU would be interlinked with a duct smoke detector and the FACP. In my experience, the shutdown contacts are in the duct smoke detector. Any alternatives?
 
Smart $ said:
BUMP (30 views and no replies at this point)

I suggested in the other thread that the RTU would be interlinked with a duct smoke detector and the FACP. In my experience, the shutdown contacts are in the duct smoke detector. Any alternatives?
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Can you get a latching relay with a manual reset? You could piggy back it on a Siemens RPR-1 reversing polarity relay which could be parked on a nearby NAC loop. The RPR would reset when the system is reset, but the latching relay would need to also be reset to enable the HVAC.
 
gadfly56 said:
Can you get a latching relay with a manual reset? You could piggy back it on a Siemens RPR-1 reversing polarity relay which could be parked on a nearby NAC loop. The RPR would reset when the system is reset, but the latching relay would need to also be reset to enable the HVAC.
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It's not my situation, so I can't say. I started this thread on behalf of stevenbouf, as his other thread was about bathroom exhaust fan on paralleled occupancy sensors.

His reply to my duct smoke detector (DSD) suggestion in the other thread was...

stevenbouf said:
I have never seen an rtu shut down with a duct smoke maybe if the system was addressible there was a relay in the rtu seeing the duct smoke would require a slc loop. This set up is not addressible and the fire panel is hundreds of feet away. Just looking for an altenative than running back too it.
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I was of the impression many RTU's have FA shutdown terminals, which are jumpered if not connected into the FAS. When wired into the duct detector, the jumper is removed and wired to a set of normal-operation closed contacts of the DSD that open on alarm, effecting a shutdown of the RTU. Rest of the DSD, and effectively the RTU, can be effected several ways, including through the FAS... possibly?
 
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Smart, there are many ways.

Some RTUs have shutdown terminals, some of them are make to shutdown, some are break to shut down.

If there are no factory terminals for it we break the control circuit at the transformer of the RTUS so it is an instant off.

It can be done with the contacts in a duct smoke but much more often specified to be with a relay module. By doing it with a module it gives you more control. Such as the ability to shutdown all the RTUs on any alarm condition, not just the RTU that is in the smoke.

It can go further if the FD wants it by giving manual shutdown controls at the fire panel for the FD to use.

Most of our systems are addressable, if not you may have to run extra conductors to each RTU.

I have never shutdown RTUs using the signal circuit, I have shutdown PA and music systems via a relay driven by the signal circuit.
 
masterinbama said:
You should have some dry contacts in your FACP, you need to use those. They will not change status when the alarm is silenced, only when the alarm condition is cleared.
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That works for one RTU if you are not already using the panels alarm contacts to drive something else. Otherwise you will still have to set up a bunch of fire alarm listed relays to break the multiple control circuits from different RTUs. I am often involved with buildings that have 2 to 25 RTUs to shutdown.


We also need to keep in mind Smart is not doing a FA job, just asking questions. :)
 
This is the kind of question I would put to the FA contractor. Better to let them design something. Even if they screw it up (40% of the time) it gives us a general idea of what to shoot for.
 
Granted I am going by what our local fire marshal wants. If you have more than 2 units in a building with a FACP they must be controlled by the panel and not stand alone duct detectors.
 
masterinbama said:
You should have some dry contacts in your FACP, you need to use those. They will not change status when the alarm is silenced, only when the alarm condition is cleared.
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You said it right. " they will not change status when the alarm is silenced." As i said in the other thread the panel is hundreds of feet away through multiple units I have no other reason to run anything to the panel. If i could find a way to make it work it would save tons of time and money. But has to be to code or just right. The fire dept is the ones the recommended useing the nac circuit.
 
Another thing I didnt mention where going to be adding a nac booster of some kind because where adding to much load to the nac circuit. I have never seen a non addressable nac panel. But would they have contacts in them. I would still see the same problem through. I might have to go back to the panel. Any other options thank you all.
 
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