2 wire smoke/heat detector and 4 wire smoke/heat detector

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Old 04-05-18, 06:59 AM
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2 wire smoke/heat detector and 4 wire smoke/heat detector

I have 2 smoke detectors currently connected to my system, one is wireless and one is a 4 wire connected to PGM2 and Zone1.
Now I bought a 2 wire smoke/heat (FSA-2104AST) detector and can't figure out how to install it. It has 2 + and 1 - connections.

It says to wire it to the PGM2 but if its a heat detector not to wire it to PGM2. Also my board has PGM3 and PGM4 available not sure if these can even be used.

This is from DSC pdf instructions:

Technical Tips:
1. Do not connect heat detectors to PGM2. They must be connected to a zone input.


Can this 2 wire be connected to a zone? From my understanding it can't.
 
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Old 04-05-18, 04:57 PM
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What you have is a 2 wire smoke that also has a thermal sensor. It would normally be hooked up as a 2 wire smoke, which you cannot do, because your system is configured for 4 wire devices (2 wire smokes on DSC panels normally connect to PGM2, but you have it configured for resettable smoke power). Regular heat detectors are strictly contact closure devices, which can't mix with 2 wire smokes (on your system), but _can_ be mixed into a 4 wire loop.

Your best bet is the get the 4 wire version of the same device, and extend your existing 4 wire loop. Alternately, you can get a 2 wire smoke and convert the loop to a 2 wire version. All of this presumes that you have installer programming access.
 
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Old 04-05-18, 06:57 PM
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So I can't connect the two wire smoke detector into the four wire one in series? They are both DSC brand (4 wire is a FSA-410B).
 
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Old 04-06-18, 03:31 AM
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No. 4-wire smokes are a contact closure device (essentially a fancy relay). 2 wire smokes work by changing their internal resistance. They cannot be comingled.
 
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Old 04-06-18, 06:29 AM
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That sucks...guess I'll have to sell it and get a 4 wire. Thanks for your input!
 
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Old 04-06-18, 07:06 AM
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OK just read that my 4 wire can be hooked to any other PGM pins while the 2 wire can only be hooked to the PGM2. All I need to do is wire the 4 wire smoke detector to any other PGM and then connect the 2 wire to PGM2.
 
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Old 04-06-18, 04:53 PM
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Yes, if you aren't using PGM1 and have programming access, then swapping the reset to PGM1 is an option.
 
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