# Adding a common wire for new thermostats



## aNYCdb (May 18, 2017)

Continuing work on the cabin. I picked up a couple wifi thermostats to replace the old mercury switch models so that I can monitor/control things when I'm not there. First issue was the existing wire was only two stranded so I pulled new wires. Now my issue seems to be connecting it to the Relay (which at this point I'm starting to think may not be possible).

Current setup is an oil fired burner feeding a two zone hot water system, with a relay or what I'm calling a relay (see pictures) for each zone. One relay is a Honeywell RA89A, which doesn't have any place to connect a common wire. The other is a Honeywell Triple Aquastat (L8124A), which I can't seem to find much in the way of documentation on.

So here's my question, what's the easiest way to get a 24v common that I can feed to the thermostats? Can I somehow connect to the "Triple Aquastat"? Should I add another transformer? Replace the Relays?


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## nealtw (May 18, 2017)

This should help. 
https://diy.stackexchange.com/questions/10482/how-can-i-add-a-c-wire-to-my-thermostat


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## aNYCdb (May 19, 2017)

nealtw said:


> This should help.
> https://diy.stackexchange.com/questions/10482/how-can-i-add-a-c-wire-to-my-thermostat



Somehow this was able to simultaneously make me feel like it was providing no new information, and make me question everything I thought I know. 

That said I guess its helping me narrow down my question which becomes does the Honeywell Triple Aquastat (L8124A) have a location for a common wire connection? If so where is it? If so can I also use the same connection for the second zone relay?


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## nealtw (May 19, 2017)

aNYCdb said:


> Somehow this was able to simultaneously make me feel like it was providing no new information, and make me question everything I thought I know.
> 
> That said I guess its helping me narrow down my question which becomes does the Honeywell Triple Aquastat (L8124A) have a location for a common wire connection? If so where is it? If so can I also use the same connection for the second zone relay?



Now you are above my pay grade.

Others that know this stuff should be along.


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## nealtw (May 20, 2017)

aNYCdb said:


> Somehow this was able to simultaneously make me feel like it was providing no new information, and make me question everything I thought I know.
> 
> That said I guess its helping me narrow down my question which becomes does the Honeywell Triple Aquastat (L8124A) have a location for a common wire connection? If so where is it? If so can I also use the same connection for the second zone relay?



Try this on for size  

http://www.dslreports.com/forum/r29...ng-from-Boiler-Panel-for-Honeywell-Wifi-Smart


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## Chris (May 21, 2017)

I've done the swap my fan wore for C wire but I think you have plenty of wires just nowhere to connect it? Correct? I am thinking you need to bust out a volt meter and see what you have from each spot. If you are lucky one will work if not I think they make resistors to race the 120 down to 24v.


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## Chris (May 21, 2017)

Here is what this guy did.

http://tdmblr.tumblr.com/post/68459847609/nest-thermostat-and-honeywell-l8148a-aquastat


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## Chris (May 21, 2017)

Also I see that the E model of your aquastat is a 24 volt model, not sure how much work it is to swap it out.


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## Chris (May 21, 2017)

Just talked to my neighbor who is and electrician, says you can ad a transformer, he can tell you which one if you know if you need AC or DC


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## aNYCdb (May 22, 2017)

Thanks, I'm going to take a closer look at the circuit board to see if soldering on feed would work.


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