Need help with 4-wire smoke wiring

[john999]

I am working on fixing a 4-wire smoke system that a previously installer screwed up when he installed a new panel at my parent's home. I have a Vista 20P panel, 449CST smokes and a 405-03 reversing relay (the last smoke also has an EOLR built in). The previous installer did not hook up the reversing relay or attach the smokes to a switched power source.
 
I am trying to figure out how to wire up all of these devices properly.
 
I originally, purchased a separate power source to power the smoke detectors because the combination of the smoke loop with the other devices will exceed the panel's aux power circuit when in alarm. After looking at the schematic for the reversing relay, however, on alarm the reversing relay switches the power source to pull power from the bell output which is more than enough to power the siren and the smoke detectors. So I assume I no longer need the supplemental power source.
 
Now my question is 1) will the use of the reversing relay work to disconnect power to the smoke detectors and reset them once the alarm is silenced and the relay switches back to its normal configuration? 2) is there something in this reversing relay that is able to only activate the other smokes when one is in alarm or will all of the smoke activate every time there is an alarm event regardless of whether it is fire or burglary? I thought I read somewhere that this was the case, but cannot find anything in the literature.
 
Thanks in advance for the help.

 

[RAL]

1) No, the reversing relay won't work to reset the smoke detectors.  The 20P doesn't momentarily switch off the power for the smoke detectors to reset them.  So use trigger output 17 from the 20P to control a relay that interrupts power to the switched smoke power inputs of the 405-03. Configure Trigger Output 17 for "Fire Zone Reset."  There is a more detailed explanation and a diagram in the 15P/20P Installation Manual.
 
2) If you are using the bell output to activate the reversing relay, then I think you are going to activate the internal smoke detector sounders even when it is a burglar alarm.  The reversing relay doesn't know the difference between the alarm conditions.
 
You can use Trigger Output 18 to activate a relay that in turn applies power to the 405-03 coil/reverse power inputs. Configure the Trigger to activate when the fire alarm zone input is triggered.
 
Is there anything else connected to the Bell Output? If you are also driving a siren or bell, you need to be careful about how much current the combined load of the smokes in alarm mode plus the siren will draw.

 

[Del91574]

First, replace the smokes. 449CST's haven't been available for years, which mean they're past their 10 year service life.
 
Second, you didn't provide the details of how many smokes are on the system.....that's going to be part of the equation for whether or not T17 can sink the current or not (or if you need an aux relay-TTL or low current).
 
You're actually going to need a second relay and additional programming to connect the smokes to the bell output on fire alarm, so that means T18, otherwise you're looking at a 4204 or a 4229.
 
For total power draw, you'll need to look at the system as a whole, then decide what to load shed to the supply. Even if you're close, it might not be a bad idea to go that route.
 
The detector reversed power is not drawn off the bell output, it's drawn off the NAC terminals on the reversing relay (whatever those are connected to)

 

[RAL]

The detector reversed power is not drawn off the bell output, it's drawn off the NAC terminals on the reversing relay (whatever those are connected to)

 
 
I think the OP is saying that he would connect the NAC terminals on the reversing relay to the bell output on the 20P.

 

[john999]

Appreciate the responses. I thought these detectors might have a 10 year shelf life but didn't see anything in the materials indicating the need to replace. I will do that.

I've got 9, so yes, it's too much for T17, so I believe I will need to use a relay in front of the reversing relay. I was hoping that the reversing relay switching back from reversed to regular might be able to cut the power long enough to perform this function but I guess not.

And yes, RAL is correct, I would use the bell output to the NAC terminals. 2A there would be plenty.

All of this said, if I need to replace them, it might just be easier to change to 2-wires with a cosmod2w.

 

[pete_c]

it might just be easier to change to 2-wires.
 
yes
 
Did the 4-wire smokes with one OmniPro 2 panel putting them adjacent to GC connected smokes and skipped the alarm panel smokes for another OmniPro 2 panel (which had GC smokes in every room).
 
DIY'd wiring my 4-wire smokes.  I enjoyed wiring them up so much that I will probably never do it again.

 

[Del91574]

I think the OP is saying that he would connect the NAC terminals on the reversing relay to the bell output on the 20P.

He'll need a secondary relay to be wired NO and triggered by the system on fire alarm, otherwise any alarm will cause the smokes to sound, and subsequently, the zone will report as trouble. Remember, the 20P's bell output is not always going to be coded, nor is it a NAC.
 
I wouldn't grab the power off the bell terminal. 360 mA in alarm, on top of whatever siren(s) or driver....easy to run out of voltage and draw the surplus off the battery, which means more calcs and most likely, oversizing the battery. Better to grab it off a separate supply and use an aux relay connected to the bell output to get the temp 3 coding/pulse from the panel, but I'd look at a TTL relay driven off T18, programmed to only connect on fire alarm. Use T17 with a secondary relay for reset.

 

[john999]

Thanks all. Any reason why I can't use a standard 12v relay rather than spend $80 on a 4204?

 

[RAL]

Thanks all. Any reason why I can't use a standard 12v relay rather than spend $80 on a 4204?

 
You need 2 relays to do what DEL described.  The 20P has two outputs, T17 and T18, that can be used to control relays.  If they aren't already being used for other purposes, then you can use them to control a 12V relay.  But if they aren't available, then you'll need to expand the 20P's output capability with a 4204, which provides built-in relays.
 
When choosing a 12V relay to use with T17 and T18, make sure it is one that has coil current specs that are lower than the limits of what the 20P can deliver (100 mA for T17 and just 20 mA for T18).   A good choice for these would be the Elk 924 or Altronix RBSNTTL.

 

[john999]

Ok. Based on the age (and DEL's recommendation) I am just going to replace them all with 2WTA-B's. With an auxiliary power source and the RRS-MOD, it looks like I can avoid the relay mess and significantly reduce the complexity of the wiring.