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Hello everyone, asking a little help on my Weil-McLain boiler and Honeywell aqua


Lunacy7916's Avatar
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01-12-18, 08:33 AM   #1  
Hello everyone, asking a little help on my Weil-McLain boiler and Honeywell aqua

hello I’m installing a Honeywell WiFi thermostat. I needed to run new cable, which I did (18/5) for both of my zones. That was the easy part lol. Now I’m at a loss on how to bring the 24v to the t-stat.
Here’s the specs - Weil-Mclain boiler Cp# 739769 with a Honeywell Aquastat L8148G 10551 and a Honeywell R832a for the 2 zones control. I’ve attached all the pics, please tell me the proper way to wire this for both zones with the required 24v common. Thank you! If you need further pics or they are of not good enough quality please let me know, I will rectify it!

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Last edited by PJmax; 01-12-18 at 09:21 AM. Reason: reoriented/resized pictures
 
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PJmax's Avatar
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01-12-18, 09:35 AM   #2  
Welcome to the forums.

I have good news and bad news.
The good news is you'll need the extra conductors you've run.
The bad news is you can't get a C connection from those older aquastats.

You can add a 24vac transformer near the boiler for running both the stats. You can use a plug in wall wart or a transformer on a plate or mounted to an electrical box. These are just a few choices. Also available at home improvement stores.

Transformer-Honeywell-Thermostat-Fyve-Global
Honeywell-AT140A1000-40Va-120V-Transformer
Emerson-S84A-410-Class-2-Transformer


~ Pete ~

 
Lunacy7916's Avatar
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01-12-18, 11:07 AM   #3  
PJmax, would I need 2 24v transformers for both zones t-stats?

 
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01-13-18, 05:47 AM   #4  
Lunacy7916 does not need a transformer. In the pictures both the aquastat and circulator units have 24 VAC xformers.

The aquastat has three screw terminals at top left TV T and Z. The Z is C

Pjmax original post read
The bad news is you can't get a C connection from those older thermostats.
Now it reads "older aquastats". Either way it is wrong.

C does not originate in thermostats. It is one side of the 24 VAC transformer some place in system. Old 2 wire thermostats only connected to the other side of that transformer.

Thermostats that use a C connection consume very little power. Any 24 VAC xformer already in system can provide it.


Last edited by doughess; 01-13-18 at 08:19 AM.
 
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01-13-18, 11:31 AM   #5  
To the OP: A single transformer can run both thermostats.

The bad news is you can't get a C connection from those older aquastats.
That is precisely what I posted last night. Even I cannot make a change after 15 minutes without it showing "edited by".

Yes Doug both units have a 24vac transformer in them. Please describe in detail how to connect C to theses two units.

Please show me a C connection on this relay
. There is a set of TT contacts for the thermostat and a set of TT contacts for the output relay.

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This aquastat is a variation of the old L8148. Some of them could possibly offer a C connection but many of them with the three thermostat terminals only offered a line back to the anticipator.

How would you connect for C to this one ?

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Last edited by PJmax; 01-13-18 at 11:49 AM.
 
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01-14-18, 10:39 AM   #6  
Low voltage 24 VAC controls to activate a 120 VAC unit are very basic. Have a transformer for 24 VAC, a temperature activated switch/thermostat and a relay to connect 120 VAC to heating unit. R terminals are connected one side of 24 VAC xformer. The C terminal/wire is connected to the other side of 24VAC xformer.

Virtually all 24 VAC controls systems have transformer. It is just a matter of finding it and which side to use for C.

Lunacy7916 did not provide control model number. For reference here is a typical Honeywell control circuit diagram. One picture in post seems to match diagram on Page 3 Figure 4.

https://s3.amazonaws.com/s3.supplyho..._PROD_FILE.pdf

Specifics to find a C connection point start with locating the xformer 24 VAC wire that goes to one of the control T terminals. The other xformer 24 VAC wire that connects to one side of relay coil is C. Other side of relay coil goes to second T. When thermostat calls for heat it connects TT's starting something.

Pjmax How would you connect for C to this one ?
Answer: Use Z terminal for C.

Pjmax Please show me a C connection on this relay. There is a set of TT contacts for the thermostat and a set of TT contacts for the output relay.
Answer: see paragraph above for finding a source to use for C. Some TT contacts go to R and W on thermostats. Not all have C.


Last edited by doughess; 01-14-18 at 11:01 AM.
 
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01-14-18, 10:57 AM   #7  
I thought that was a T. Yes...you can use the Z on the aquastat for a C connection. So that aquastat can run a wifi stat but a transformer would still be needed for the other control.

Yes.... you can always find a C connection but that requires taking controllers apart which is not something I advocate.


~ Pete ~

 
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01-15-18, 08:16 PM   #8  
Thermostats with electronics circuits that need 24 VAC power use the C wire to get it. That power is for the logic, clock and control functions. If they also have circuits to communicate with outside world, those circuits will also use 24 VAC but that is secondary to primary need.

On many controllers the transformer 24 VAC wires are exposed and it is just a matter of making electrical connection.

Each DIYer makes his own decision.

 
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