Please help!! Installing Digital Thermostat


  #1  
Old 01-26-05, 05:38 PM
balladish
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Please help!! Installing Digital Thermostat

I just bought a Honeywell Digital Thermostat, model # T8601. I'm trying to replace an old dial-style 'Robert Shaw' thermostat. There are three wires coming out of the wall: red, white, and black. I successfully got the new thermostat to be powered by the AC power by connecting red to R and black to C (connecting it to B would not yield power). I then connected the white one to W, hooked the system up, and made the thermostat click on for heat. My boiler did not go on. I checked the rear of the device, where there is a screw that needs to be turned out one full turn for Gas water heat, which is what we have. I did that, and hooked it back up. Boiler still did not go on.

Can anyone help me? I need to get this heat on or we'll sleep cold tonight.

Thanks!
 
  #2  
Old 01-26-05, 06:45 PM
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redwire to R (hot)
white wire to W (heat relay)
black wire to B (heat damper)

connecting to RC won't work if it is not bridged to R
Also ensure that the unit is seated properly in the base and that you have not bent any of the pins.

Try and post back
 
  #3  
Old 01-26-05, 06:51 PM
balladish
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I tried that, and I got a "-AC" message on my device, which means no AC power. I used a Voltmeter to measure voltage, and got no reading. If I connect the black wire to "C", however, I get a steady 24 volts, and the unit works, but the boiler won't turn on.

(Could it be that "C" stands for 'Common Wire'?)

I'm back to square one, it seems.

Any advice? Thanks a ton.
 
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Old 01-26-05, 06:54 PM
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which colour wires give you 24 volts AC

Ok I assume you mean white and black give you 24V AC
 
  #5  
Old 01-26-05, 07:00 PM
balladish
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No - Red and Black give me 24V, red being the live (hot) one.
 
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Old 01-26-05, 07:03 PM
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ok connect red to R
black to W

? how were the wires connected to your old thermostat; which lugs?
 

Last edited by Exile; 01-26-05 at 07:16 PM.
  #7  
Old 01-26-05, 07:19 PM
balladish
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Done.

I get no power to the device. "-AC" message is on.

How about if I connect red to R and black to C?

On the old thermostat, red was to R, white to W and black to B.
 
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Old 01-26-05, 07:47 PM
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yes red to R and black to C

now all you need is the zone valve relay connection
 
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Old 01-26-05, 07:52 PM
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You should put back the old thermaostat and call honeywell for help in the morning. Your install guide should have an 800 number for tech support.

I wish I could help you more, but think that you need someone with some more experience.
 
  #10  
Old 01-26-05, 07:53 PM
balladish
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I did that, and the heat fired right up.

Yep - I'ma call Honeywell in the morning.

Thanks for your help!
 
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Old 01-26-05, 07:57 PM
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Yes but I am assumi ng that that last wire is for a zone valve and part of your house will be very cold if it does not open. (the zone that you are working on....)
I think that you should replace with the old one to keep any pipes from possible freezing....just my thoughts...better safe then sorry
 
  #12  
Old 01-26-05, 08:01 PM
balladish
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I know - that's why I've reinstalled all old thermostats, and turned them to hear the valve click, and my boiler fired right up. So we'll be warm tonight.

Thanks again.
 
  #13  
Old 01-27-05, 03:28 PM
balladish
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OK - I hope someone still reads this thread. I'm completely lost.

I spent a big chunk of today speaking to people from Honeywell (new thermostat), Robertshaw (old thermostat), and the guy who sold me the thermostat, who happens to have been the greatest help of all. Here's what I KNOW:

My old thermostat, even though there were three wires hooked up to it, only used two: red and white. The black wire gets screwed in but goes nowhere. So whenever the thermostat wanted heat, it connected red to white, and voila, connection.

The problem is that my new thermostat requires a common wire to operate. If I only hook up red to R and white to W, I get no power to my thermostat - it runs off the batteries included, but won't switch on heat - all I get is an '-AC' notice. So - how do I get a common wire in there? Do I need to run a new wire from the boiler room into all three zones? That would be BAD news. Is there a way to hook up the existing three wires so that I can supply the thermostat power AND hook up red to R, white to W, and black to B (as the seller said is the proper way to hook this up)?

Please, I'm lost - any help is appreciated. Thanks in advance.
 
  #14  
Old 01-28-05, 08:18 PM
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Balladish

Does the black wire go back to or near the boiler? If it does, connect it to the common side of the transformer & "C" on the stat. You should be in business. If you are going to have to fish wires, I suggest you get a different stat. One which does not require a common.
 
 

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