Confused on furnace wiring.

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Old 12-23-18, 10:33 AM
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Confused on furnace wiring.


This is for forced hot water cast iron radiators.


I have Honeywell 6500 WiFi thermostat which replaced a mercury dial thermostat. There was only two wires connected to it which was black and white. I was able to find a third wire which was red that was hooked up to nothing. I looked at furnace also and the red wire was hooked up to nothing there also. I made an extension at furnace since red wire there was short and connected to the C terminal. I noticed the R terminal had the black wire upstairs and at furnace. So I hooked that up to R on thermostat. (Black on R). I also hooked up the red wire which is hooked up to the C terminal on furnace to the C terminal on thermostat. (Red on C). The white wire I’m confused on because it is attached to the G terminal on furnace but it appears I don’t have a fan and there is a blue wire that goes to G terminal to C terminal on furnace. I ended hooking up white wire to W on the thermostat and everything works. I guess I’m confused because of the way it’s hooked on furnace. I just want to make sure everything is fine. The G wire has another black wire that goes to the manual and auto device at top left.
 

Last edited by PJmax; 12-23-18 at 04:04 PM. Reason: removed non working links
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Old 12-23-18, 10:56 AM
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Welcome to the forums.

Please follow this for picture posting..... How-to-insert-pictures

Your boiler is using a fan center as it's control. When doing that..... the G terminal is the call for heat as that terminal activates the relay.

You should unify your wiring for the future.
At the stat.... red to R..... white to W...... black to C.
At the boiler.... red to R..... white to G..... black to C.
 
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Old 12-23-18, 03:02 PM
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Files are to large it says when I try uploading. I tried making them smaller but still saying large. Here is a link to see pictures. https://providence.craigslist.org/wa...779262512.html
 
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Old 12-23-18, 03:30 PM
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It’s also a boiler not a furnace. So I shouldn’t have a fan. Overall please let me know when you have a chance on the wiring setup
 
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Old 12-23-18, 04:03 PM
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We have/had a system in place so that a new member needed to make xx posts before he could post pictures. I'm guessing that's what the issue is as I went over your pictures and put them into my system. I cannot put them in your post yet but I will.

Ok..... so I've seen the pictures..... what's your question ?
 
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Old 12-23-18, 07:19 PM
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My question is if It’s hooked up right based on pictures. Thermostat it’s hooked up to w,r and c. I was able to verify the R and C are hooked up right. I’m not sure if the W is hooked up right because on furnace it connects to the G. It appears there is nothing hooked up to G and is hooked up to the C. Overall is it hooked up right based off pictures? I also went under system type and changed it to option 2 which is heat only with no fan and no central air. I don’t believe a boiler would have a fan? Heating cycle I put to option 3 which is hot water or high Efficeiney furnace. Thanks for the quick follow up and helping with pictures.
 
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Old 12-23-18, 08:21 PM
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It turns out there is a global problem with picture posting on the board right now.
This would be easier to explain with a picture.

If you look your third picture...... look at the back of the terminal board. You'll notice there is nothing on the Y or the W connection. They are just splice points. You'll see two blue wires coming from the back. Those are from the control relay. You'll see one connects to the C terminal and the other connects to the G terminal. That means 24vAC on the G terminal will activate the relay. In a furnace..... that relay controls the fan. In a boiler that relay controls the burner.

That part is called a fan center. It was designed to be used in a furnace but it works well to switch 120v to the burner. They all have those blue wires soldered to the C and G terminals.
Fan center
 
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