Weil Mclain he-3 common wire location

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  #1  
Old 12-14-19, 10:41 AM
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Weil Mclain he-3 common wire location

Hi,

I just pulled new tstat wire (5 strand) through for my boiler that is about 30 years old. Previously there was just the red and white wire, we want to use our wifi thermostat so we needed an extra wire.

When I disconnected it the red wire from the tstat came to the G and the white wire went to the Y. Looking at the wiring diagram it seemed like the C is where I should hook up the new blue wire and I put the other two back where they were.

There are 3 zones but again everything remained the same except for the wire getting changed out and the blue being used as the common. The two unchanged zones seem to be working normally but the WiFi thermostat wonít turn on. Iím wondering if my connection to the common is wrong at the boiler. I tried searching for this issue and it seems like in different models (he2) the wiring is different.

Trying to get some pictures added but I might need my computer for that.

Thanks,
Adam
 
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Old 12-14-19, 10:47 AM
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G and Y are not correct terminals to use. A thermostat should be using an R and W.

You left a boiler model number but that has nothing to do with it.
How are the three zones controlled..... three thermostats to three zone valves ?
Probably going to need pictures..... how-to-insert-pictures.
 
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Old 12-14-19, 12:51 PM
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These may help.

Each zone now has it's own electronic thermostat (2 are basic with aaa batteries) I just swapped out the first floor mercury dial one for the wifi one. All the thermostat wires go into a box which has wires to the 3 zone pump switches and 1 wire going to the boiler.


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Old 12-14-19, 01:37 PM
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That's a fan center used for boiler control. That is the control point where all three zones report to.
I need to see where the actual thermostat wiring is. You have three thermostats. That means three cables to some type of pump control or relays.

Your pictures could be larger too.
 
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Old 12-14-19, 02:44 PM
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The 3 thermostat wires come into a junction box with an additional wire going to the boiler and a 5th wire going to the shut off fuse. There are 2 red and 2 yellow wires going to each of the 3 ciculator pumps.

Sorry for the picture size, I think they are automatically getting resized when I upload them. I've tried uploading smaller and larger sizes and they all seem to end up tiny.

I appreciate the help!

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Last edited by PJmax; 12-14-19 at 03:54 PM. Reason: removed one pic/enlarged other
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Old 12-14-19, 03:52 PM
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You look to have one pump and three zone valves ??? That's what I asked earlier.

The red wires on the zone valve operate the boiler and circulator. Ignore those.
The yellow wires are the valve motor.

Since you have three zone valves...... there should be another transformer. Based on that wiring.... it would be doubtful it was done correctly so they may have used the fan center transformer to run the the zone valves.

You need to locate the valve and the thermostat cable that is associated with the thermostat you want to replace. The circuit is very simple but you need to know the wiring connections.
 
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Old 12-15-19, 08:19 AM
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PJ,
The attached picture has the 1st floor valve in it and the two yellow wires coming from it are hooked into the white and black wire nuts visible near the center of the picture. The black nut has the white wire coming from the first floor tstat.

The white cap has a wire previously labeled to power/relay.

Edit: I think I figured it out.... I disconnected the extra wire to /from the boiler and connected the common wire to the white wire nut with the yellow valve switch and the white power/relay wire. It all seems to be working now


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Last edited by Adam L; 12-15-19 at 09:52 AM.
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