Converting line voltage to low voltage


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Old 01-14-23, 08:05 AM
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Converting line voltage to low voltage

I am trying to convert my current line voltage tstat(LuxELV4) that has 2 line voltage wires 1 black and 1 white coming out of the j box to low voltage smart tstat. I have the burnham hydronic boiler series 2 that is heating my house with baseboards in each room of the house. What is the easiest method for me to accomplish this? I have looked at Aube relays but I am unsure which one I need. My setup is really weird as the boiler is from 2008 and is running off of line voltage and not low voltage which is very weird to me
 
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Old 01-14-23, 09:15 AM
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It is normal for the boiler to run off line voltage but the thermostat would be normally low voltage 24 volts. Being your boiler is from 2008 I would suspect this would be the case. Being that your stat only has two wires you may not have the required wires to run a smart thermostat.

Please post the model number of your boiler and any wiring diagrams you may have.
 
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Old 01-14-23, 11:29 AM
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Welcome to the forums.

Lazy installer.

Easier to wire your new boiler as line voltage instead of rewiring for 24v.
As mentioned... post some pictures.....How to insert pictures.
Pictures of the aquastat/control box are needed.
 
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Old 01-14-23, 01:05 PM
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Last edited by PJmax; 01-14-23 at 07:47 PM. Reason: resized pic
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Old 01-14-23, 01:06 PM
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Yea I’m trying to do it the lazy way or I will just leave it how it is if I can’t. I am not trying to run new wires from the boiler all the way to the second floor of the house. I do not see an aqua stat anywhere on this boiler. I will try to upload pictures model number is 205ncl-tei2 burnham hydronics low pressure boiler series 2. 2 wires in the thermostat only line voltage wires black and a white wire
 
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Old 01-14-23, 01:14 PM
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There is a field control box attached behind the vent that I can’t get a good picture because of tight space
 
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Old 01-14-23, 01:18 PM
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Old 01-14-23, 01:21 PM
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That is a transformer 24v that is mounted on the ceiling right above the boiler. I assume those are the line voltage wires connected leading up to the tstat
 
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Old 01-14-23, 02:15 PM
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Those are the pictures sorry for the overload, if you guys need more just let me know
 
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Old 01-14-23, 07:52 PM
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I resized one of your pics and removed a few duplicates.
You can lift the boiler cover up by the two round holes. The bottom comes out and then the top.
The aquastat is behind that panel.

However... that probably won't be necessary. You have a 24v transformer because you have two zone valves. That means you have two low voltage thermostats. Not sure why there is a line voltage thermostat.

Do you have more than two zones of heat ?
Do you still have knob and tube wiring there ?
 
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Old 01-14-23, 08:13 PM
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I have a t stat downstairs and a t stat upstairs, they both run on line voltage 2 thick wires black and white. The transformer that’s on the ceiling says primary 120v and secondary 24vac.
 
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Old 01-14-23, 08:14 PM
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Old 01-14-23, 08:15 PM
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Old 01-14-23, 08:29 PM
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I should have checked earlier. The Lux ELV-4 is a high voltage switching battery operated thermostat. It will switch any load from 24v up to line voltage. More than likely your wiring has already been converted to low voltage.

Do you have a meter..... make sure stat is in off position.
Measure across the wiring. You should see 24vac.

FYI.... inside your boiler I see a white three wire cable with the green unused.
It connects the fan center to the zone valves. That is a 24v connection.
 
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Old 01-14-23, 08:45 PM
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I don’t have a meter to measure, what would you recommend to get my setup up and running, would I only need to buy the Aube rc840 relay and some low voltage wire
 
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Old 01-14-23, 08:59 PM
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I'm fairly certain that you don't have 120v at those thermostats.
Without checking them with a meter I don't recommend doing anything.
Pick up an inexpensive analog meter from depot or lowes. They run about $15-20.
 
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Old 01-14-23, 09:06 PM
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Ok gotcha will do, thanks for the feedback, if it turns out the multimeter is showing I have 24v then all I would need to do I buy low voltage smart t stat?
 
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Old 01-15-23, 07:51 AM
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I am getting a 52 reading
 
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Old 01-15-23, 08:02 AM
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I measured the black and white wires coming out of my tstat with the black and red terminals of the multimeter just to give more clarification as to why I did that. I couldn’t find a ground terminal to measure
 
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Old 01-15-23, 08:16 AM
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Last edited by PJmax; 01-15-23 at 09:24 AM.
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Old 01-15-23, 09:28 AM
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That is correct. There may be a ground as it looks like a metal clad cable.
You are ok. You have low voltage and can use a 24v thermostat.
The 52v is coming from two transformers out of phase.

I believe the two line voltage thermostat cables are in that junction box. They connect to that white cable going to the zone valves and the transformer. I'm guessing that white cable coming down from the ceiling is using three wires.
 
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Old 01-15-23, 09:54 AM
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So I can just buy a nest smart thermostat and connect the 2 wires I have currently in the t stat and I should be good to go?
 
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Old 01-15-23, 10:06 AM
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IIRC smart thermostats often require a common (C) wire which would require a total of three wires to the stat.
 
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Old 01-15-23, 10:08 AM
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You could try it however the newer nest thermostats don't always operate properly without a C connection.
They make a power adapter to allow the thermostat to run better on two wires.
Your wiring is not currently set up to easily install the power adapter.
 
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Old 01-15-23, 10:09 AM
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Right. But from my understanding though the nest doesn’t require a c wire? That is correct?
 
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Old 01-15-23, 10:10 AM
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Before I bought the lux elv4 thermostat, I bought the nest and tried that with the same setup I currently have but didn’t work.
 
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Old 01-15-23, 10:11 AM
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That’s when I figured the wires to the t stat were line voltage so I bought a luxelv4 and that worked with my heating system
 
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Old 01-15-23, 10:14 AM
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They claim it doesn't need a C wire but the latest (newer) models.... that is no longer true.
Most people using them have not had great results on two wires.
 
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Old 01-15-23, 10:14 AM
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All of the Nest thermostats I have installed required a C wire. However, it has been a couple of years so things may have changed. Please check the requirements of the stat you are looking to buy before making the purchase.
 
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Old 01-15-23, 10:24 AM
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Which smart tstat would you guys recommend me getting with my setup with no c wire?
 
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Old 01-15-23, 01:12 PM
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Smart or wifi ?
I always install the needed wiring. I believe the Sensei can run with no C.
Emerson Sensei
 
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Old 01-15-23, 01:25 PM
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Wifi
 
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Old 01-15-23, 09:16 PM
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I have ordered the Emerson Sensi st55 thermostat and will receive it tomorrow. Can you tell me how I should wire it? I have a black wire and a white wire see above pictures. Using it for heating only, so I assume the black wire would go to rh terminal of the Sensi and the white wire would connect to the w terminal of the Sensi?
 
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Old 01-16-23, 09:32 AM
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Update: I have gotten the Sensi thermostat to work using only the 2 wires I have! Thank you all for your help!
 
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Old 01-16-23, 09:42 AM
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Great job. Thanks for letting us know how it worked.
 
 

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