Upgrading my Thermostat to wifi without C wire / Using switch relay with internal transformer
Hello!
I moved into a house with steam radiators run off an oil burner. I'd love to upgrade to a wifi thermostat that would require a C wire for power. I bought this universal relay with internal trasnformer to help resolve the issue of not having a C wire availability to connect to my Ecobee thermostat.
https://www.supplyhouse.com/Resideo-R8845U1003-Universal-Switching-Relay-w-Internal-Transformer
Does this wiring look correct?
This is to the universal switching relay with internal transformer
This is the wiring to the Ecobee thermostat:
Tied the two R/W wires to the Carlin TT slots. Power is coming from the L1/L2 lines, but no power coming to the thermostat.
Any considerations are welcomed! TY in advance
Comments
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How's that 1 amp fuse looking?
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wiring looks correct,
did you check that fuse?
known to beat dead horses0 -
thanks for the suggestions… just checked it and the fuse is working…
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Jump R to W in the Honeywell. If the relay clicks, check your wiring & Nest (we just condemned a Nest with a defective subbase in a different thread). If it doesn't, you don't really have power to the Honeywell or it's defective.
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I appreciate you helping me out! I will try…
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it clicked so the Honeywell is working… I will recheck wiring… but so far no luck
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clicking doesn’t mean the contacts opened / closed.
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It looks right. The red and white from X1 & X2 on the relay go to the burner T & T correct??
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Does the Green 'Call for Heat' LED ever light up ?
What happens when you push the square Red 'Test' button ?
Cables mixed up ?
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Try using terminals A & B. They switch at the same time as X1 & X2.
You can check X1 & X2 by removing the wires & checking for continuity/resistance. Should be continuity/low resistance (≈<1Ω) with a heat call and no continuity/open circuit (OL etc.) with no heat call.
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Yes, they do.
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I know the Ecobee thermostat works because I tested it on my AC unit that already had a built in C wire… May end up running it from there and connecting AC/heat units from that?
It is bothering me why I cannot get this relay to work though…
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Not on it's own, but when I press the red test button it blinks green.
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Yes
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Well when the Red test button is pressed it mimics a contact closure between the R(T) & W(T) (a thermostat call for heat). When you press the Red button and hold it briefly the Green 'Call for Heat' LED should light up and you should hear the relay(s) click and the boiler should start.
If you jumper R(T) & W(T) the Green 'Call for Heat' LED should light up you should here the relay(s) click and the boiler should start. If not try just jumpering the wires connected to X1 & X2, the boiler should start.
Even if the boiler was disconnected a call from the thermostat should activate the Green 'Call for Heat' LED and energize the relays.
Again, I suspect the multi wire cables are reversed. Or something was damaged in the transition.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
Thank you for taking the time for a thoughtful response. I will recheck this tomorrow! I appreciate you.
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Also.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Not the relay I would have selected for this job. But since you already own it this is how to connect the wires.
Tied the two R/W wires to the Carlin TT slots. Power is coming from the L1/L2 lines, but no power coming to the thermostat.This statement sounds like this.
I know that this will not work
I believe you have it wired this way by the looks of the wires in your photo.
I know the Ecobee thermostat works because I tested it on my AC unit that already had a built in C wire… May end up running it from there and connecting AC/heat units from that?It is bothering me why I cannot get this relay to work though…
Does the same thermostat operate the air conditioner and the heat? In the thermostat subbase photo, it appears that you have heat only wires
Areyou sure that you have the proper common wire connected?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Sorry, I did not explain myself well… I have it wired like your second photo. Also the bottom arrow in your photo is the blue wire (C wire) is the one connected to the thermostat. When I run the test button, the heat to call button lights up. Also, when I jump it/test it, it turns on Carlin. However, no power runs to the thermostat to turn it on. (I have checked the thermostat and it works because I tested it out on my central air unit… which is separate from what I am trying to do here).
Out of curiosity, what relay would you have used? I was initially debating on what to buy… I would be open to buying something else.
Ed, Thanks so much for taking the time you already did on this…0 -
If the test button works, turning on the Carlin. Jumping the R(T) to W(T) should also too.
If the thermostat is also good, the only thing left is the wiring (and any unmentioned equipment) between the thermostat and the R(T) and W(T) terminals.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
" I know the Ecobee thermostat works because I tested it on my AC unit that already had a built in C wire… "
Did you test the W1 functionality ?
What happens when you touch the Red wire to the White wire at the thermostat base ?
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
When I touch the Red wire to the white wire it turns on the boiler…
how would I test the W1 functionality?0 -
If the AC unit thermostat is a different thermostat and does not use the W1 (Heat) function testing it on that base does not prove much, other than it powers up.
" Red wire to the white wire it turns on the boiler "
So that proves those two wires are good.
So what is the present problem ? Does the thermostat not power up ? Or just no heat ?
The relay box seems to work fine.
Do you have a multimeter ?
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
The present problem is there is no power going to the thermostat via the c wire. Thermostat won’t power on. I bought that relay pictured above to get a c wire to run power to my new WiFi thermostat. (I had no c wire and previous thermostat was an old battery powered unit).
For the AC - I was testing to see if my new WiFi ecobee thermostat was even working (maybe thinking the new thermostat defective, but it’s not). I wanted to see if the c wire would power it up, which it did. I was not testing the W1 (heat) with the AC unit.
Yes, I have a voltimeter. How can I test the W1 for the heating? What should I do?
Thanks for your response. Sorry if I’m not being clear throughout my messages..0 -
Is there 24 VAC between the Blue wire and Red wire at the thermostat base ? Is the Blue wire seated correctly in the base connector ?
Some thermostats need a jumper between Rc and Rh, some have a switch, not sure about the Ecobee thermostat.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
The figure on the right side is basically what you have now (yours is just all in one box with extra relays), try the Red wire connected to Rc as shown.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Did you try to put the Red wire from the R on the R8845U1003 and connect it to the Rc on the thermostat?
You only need to separate the Rc and the Rh when the same thermostat is connected to two different systems, a separate heater and a separate air conditioner. Your heating system is only one system and the Rc to C is how the thermostat gets power.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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@ggsoap822 said: "Out of curiosity, what relay would you have used? I was initially debating on what to buy… I would be open to buying something else."
I personally like the RIB U1C and a separate 24 VAC 40 VA transformer since you have an oil burner control that does not have a R and C that you can connect to on the primary control. The 24 AC transformer can be an inexpensive one with 20 VA power rating or less. The thermostat will not need more than that. Those two parts would be on my service truck stock and I would not need to drive to the supply house to get what I would use If I knew what I wanted ahead of time.
Another part I like to carry on my truck is this Mars Fan Center relay. Many boilers use this control as the burner and circulator relay, It is also good for old school fan relay for add on air conditioners, before all the newer furnace models come equipped with Air Conditioning fan timers as standard equipment.
It has a 40 VA transformer that can be powered by 208/240/115 VAC and there are 2 sets of contacts available for more than just isolation relay uses. It is inexpensive and does the same job as those you can purchase from the original equipment manufacturer's for over $80.00. See how much Rheem and Weil McLain mark this stuff up. If folks that repair heaters only knew that it is the same part in a different box.
The R8845U you purchased is more expensive and does more than you need it to do. The on board transformer has only a 12 VA rating, much less power than the other options I provided above only. You are not operating the system circulator pump, a boiler pump, or any additional devices that require all those relay contacts in there.
I hope that you only need to swap the Rh wire in the thermostat to the Rc terminal to get your system up and running.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Thanks for all of that!! Putting the wire into the Rc worked!! Everything worked beautifully and the boiler turned on, ecobee is powered up!!
One more question to pick your brains, if I wanted to connect my central air system to the same ecobee thermostat, now that the Rc is occupied by the heat wire, where would I plug in the AC wire (now that the Rc is taken up by the heat)?
PS. I owe you both some coffees!0 -
You have a separate AC system with its own air handler, with an internal transformer? If yes, then you'll need to remove the common that you just added, move the R from the external transformer back to the Rh terminal, and then power the stat from the air handler, Rc & C, and connect G (fan) & Y (cooling) from the air handler to the stat. If you want to keep the existing power wires, you'll need to add two relays (G & Y), if the AC does not have its own transformer then you'll need to take the common from the stat to the air handler & condenser.
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