Hello. I currently have a Honeywell standard display T-stat. It has only 2 wires connected to the R & W terminals to control my Weil-Mclain steam boiler. The T-stat is battery operated.

I have spare wires in my current T-Stat wiring which I would like to utilize to hook up a Wi-Fi T-stat. The Honeywell rep I spoke to in tech support said to put the 2 existing wires to the R & W terminals, and to connect a separate 24VAC Power source ( which I have in my basement) to the C & RH terminals, with all jumpers removed.

Just wondering does this sound correct?

Mikepier wrote:
Hello. I currently have a Honeywell standard display T-stat. It has only 2 wires connected to the R & W terminals to control my Weil-Mclain steam boiler. The T-stat is battery operated.

I have spare wires in my current T-Stat wiring which I would like to utilize to hook up a Wi-Fi T-stat. The Honeywell rep I spoke to in tech support said to put the 2 existing wires to the R & W terminals, and to connect a separate 24VAC Power source ( which I have in my basement) to the C & RH terminals, with all jumpers removed.

Just wondering does this sound correct?

Hi,
When you get the new 'stat, the installation manual will clearly show
how to hook up that wire. It'll have diagram. I did same with Eco Bee
'stat for my daughter's cabin in the mountain. You don't believe
Honeywell tech support guys?, LOL! I retired from that company after
~40 years. If you ask same question with email they may attach diagram
in reply. Or you can download manual in advance to double check it.

On Monday, October 20, 2014 11:03:16 PM UTC-4, wrote:
On Mon, 20 Oct 2014 18:32:01 -0700 (PDT), Mikepier

wrote:



Hello. I currently have a Honeywell standard display T-stat. It has only 2 wires connected to the R & W terminals to control my Weil-Mclain steam boiler. The T-stat is battery operated.



I have spare wires in my current T-Stat wiring which I would like to utilize to hook up a Wi-Fi T-stat. The Honeywell rep I spoke to in tech support said to put the 2 existing wires to the R & W terminals, and to connect a separate 24VAC Power source ( which I have in my basement) to the C & RH terminals, with all jumpers removed.



Just wondering does this sound correct?



Your stat is operating as a simple 2 pole switch. The Red is 24v in

and the white is "heat call" out. The common is in the boiler.



You could use an unused wire to bring the common to the WiFi

thermostat from the transformer, hook it to C and you are done.


+1

As you say, the only thing it needs to power a smart thermostat is
one additional wire to the common. And as Tony said, the instructions,
which should be available online should confirm that.

On Monday, October 20, 2014 11:03:16 PM UTC-4, wrote:
On Mon, 20 Oct 2014 18:32:01 -0700 (PDT), Mikepier
wrote:

Hello. I currently have a Honeywell standard display T-stat. It has only 2 wires connected to the R & W terminals to control my Weil-Mclain steam boiler. The T-stat is battery operated.

I have spare wires in my current T-Stat wiring which I would like to utilize to hook up a Wi-Fi T-stat. The Honeywell rep I spoke to in tech support said to put the 2 existing wires to the R & W terminals, and to connect a separate 24VAC Power source ( which I have in my basement) to the C & RH terminals, with all jumpers removed.

Just wondering does this sound correct?

Your stat is operating as a simple 2 pole switch. The Red is 24v in
and the white is "heat call" out. The common is in the boiler.

You could use an unused wire to bring the common to the WiFi
thermostat from the transformer, hook it to C and you are done.

What he said.

http://www.behvac.com/troubleshooter41.htm

Use a black wire if you have it for the common.

nate

OK, I got it hooked up ,and its working great. But I have a question concerning the wiring from my steam boiler. Attached is the wiring diagram. My boiler is on page 8.
http://www.weil-mclain.com/en/assets...0-031_1112.pdf

As you can see on the ladder diagram, The T-stat R wire ( which in this case is terminal G on boiler terminal block) is going through the low water cut-off feed.

So this means that everytime the LWCO calls for water, which is not often, the power to the t-stat gets killed because the relay opens up, which I understand this is the way its suppose to work for safety. I confirmed this by testing yesterday, I drained boiler until light on LWCO kicked on.
Is there any way around this? Not a big deal, but just curious.

On Sunday, November 2, 2014 8:04:44 AM UTC-5, Mikepier wrote:
OK, I got it hooked up ,and its working great. But I have a question concerning the wiring from my steam boiler. Attached is the wiring diagram. My boiler is on page 8.
http://www.weil-mclain.com/en/assets...0-031_1112.pdf

As you can see on the ladder diagram, The T-stat R wire ( which in this case is terminal G on boiler terminal block) is going through the low water cut-off feed.

So this means that everytime the LWCO calls for water, which is not often, the power to the t-stat gets killed because the relay opens up, which I understand this is the way its suppose to work for safety. I confirmed this by testing yesterday, I drained boiler until light on LWCO kicked on.
Is there any way around this? Not a big deal, but just curious.


The obvious way around it would seem to be to not wire it in series with the
low water cut-off switch. But I don't understand what the issue is. If the
boiler is working properly, the boiler should maintain the proper water
level. If it's not, then you want the boiler shut off because it's a
hazard, which is what the install intruction wiring would seem to be doing..

Well, a steam boiler will always lose some water normally, so it's always going to need to be refilled. Not often, but it is normal.

On Sunday, November 2, 2014 1:57:41 PM UTC-5, Mikepier wrote:
Well, a steam boiler will always lose some water normally, so it's always going to need to be refilled. Not often, but it is normal.

Doesn't it have an automatic fill? And regardless, if the water gets so
low that it triggers the low water cut-off, why would you have an issue
with the thermostat being wired in series with it? It sounds like they
open the thermostat circuit to keep the boiler from firing when the water
is too low.