Honeywell CT8775A 24vac help?


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Old 06-25-13, 07:18 PM
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Honeywell CT8775A 24vac help?

I have this t-stat and wondering how the wiring goes from the transformer to power on the t-stat since it doesnt have a battery. thanks
 
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Old 06-25-13, 07:55 PM
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Old 06-25-13, 07:57 PM
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Are you installing a new thermostat or do you have it already installed and just want to know how it works ?

If you are going to install one be sure to turn the a/c power off to the air handler/furnace.
When you remove the thermostat you must identify what color wire is on what terminal before disconnecting them. A picture is ok too.

That's a cool little thermostat. Pretty easy to program.

When the thermostat calls for heat it creates a short on the two heating wires and you get heat. When the thermostat is satisfied the contacts open and the thermostat is in series with the load and steals a little bit of power to keep the unit active.
 
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Old 06-26-13, 07:09 AM
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This is a new t-stat i'm using on a hot water loop in my basement. when i touch the ends directly to transformer it illuminates. some reason maybe not hooked up right between the boiler and transformer.?

The thermostat is just a basic 2 wire digital round non-programmable.
 
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Old 06-26-13, 07:39 AM
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Yeah....and I posted easy to program I meant pretty easy to install.

What happens when you short the two wires out at the thermostat location ?
Does it activate anything or zone valve ?
 
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Old 06-26-13, 07:47 AM
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Exactly what is your question. You should not plug the stat directly to the transformer.
 
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Old 06-26-13, 09:34 AM
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LOL. I wasnt sure if you meant same t-stat. well i have it hooked up into a Taco SR503. I want it to run zone 2. theres a 24vac transformer built in that and trying to get power from there for the t-stat.
 
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Old 06-26-13, 09:38 AM
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My ? is how come its not lit up when mounted on the wall.? got 2 t-stat wires going to relay/switch. well it works when plugged directly to transformer. i wanted to see since it was used and wasnt getting nothing on it there other way..
 
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Old 06-26-13, 09:43 AM
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It wont work with your taco switching relay.
 
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Old 06-26-13, 10:15 AM
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It wont??? WHY? Has the 24vac transformer built in it. i'm guessing thats for hooking up this type of t-stat..
 
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Old 06-26-13, 11:15 AM
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No. There is a different type of voltage on those 2 wires at your thermostat location that go to the 503. The transformer is for something else. I can't remember. You can get it to work by installing a relay though.
 
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Old 06-26-13, 06:23 PM
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Oh cool. what kind of relay do i need? Part # if you have it. Also i'm hoping to hook up at HW L6006A to the 503 for my hot water loop. would that get hooked into that 503 box to? thanks
 
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Old 06-26-13, 06:27 PM
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You need to ask that question over in the boiler forum.
 
 

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