Which thermostat

crhyner

Hi,

I have an oil fired furnace that we only use once in a while - when going away on vacation in the winter, for example. My home is heated with a wood stove and the furnace stays off almost all of the time.

The current thermostat only uses an R and W wire - it's heat only. I was hoping to find a smart thermostat that would let us monitor the furnace and temp when we're out of town once a winter. However, even if there was a C wire, it wouldn't be supplying power to the thermostat because the furnace is shut off - correct? So is there a solution to this? Or is a smart thermostat out of the question because we're barely running the furnace at all?

thank you,

Charlie

Jamie Hall

You don't have to power the thermostat from the furnace. You can power it from an independent 24 VAC transformer or one of the "wall wart" adapters. The furnace would still use R and W, and the independent power would be on R and C. It might be better to use a relay with the coil powered by R and W and the dry contacts connected to the furnace.

HomerJSmith

You will need a router and an internet connection, too.

EdTheHeaterMan

What Jamie said ...Or, You could leave the power to the furnace ON and set the thermostat to OFF. Then if you are away from home and you decide that the furnace needs to operate, You can turn the thermostat to HEAT and set the temperature low, so the pipes don't freeze.

But you will still need a router and an internet connection, too. Dah!

crhyner

OK, noted, thank you.

If I leave the power to the furnace on, with a C wire to provide power to the thermostat, and the thermostat set to OFF, just confirming that the furnace won’t burn any oil?  It won’t burn oil to maintain its temperature at all?  Goal is no oil consumption, but power being sent to smart thermostat.

Thanks.

EdTheHeaterMan

crhyner said:

OK, noted, thank you.

If I leave the power to the furnace on, with a C wire to provide power to the thermostat, and the thermostat set to OFF, just confirming that the furnace won’t burn any oil?  It won’t burn oil to maintain its temperature at all?  Goal is no oil consumption, but power being sent to smart thermostat.

Thanks.

That is correct. If the thermostat is set to OFF there will be no oil burning. To burn oil there must be a call for heat from the thermostat. To have a call for heat from the thermostat, the thermostat must be set to HEAT and the desired temperature must be set above the room temperature. That means that if you are not home and someone that is home, goes to the thermostat and changes the setting from OFF to HEAT and then sets the desired temperature to 85° that the oil burner will operate. Nothing will prevent the burner from operating in that scenario outside of turning the electricity to the oil burner OFF.

If however no one is going to be that bold as to adjust the thermostat when you are not home, then my advise is to leave the oil burner electricity ON and the thermostat set to OFF

Edit: If you are referring to a Boiler that heats water or makes steam, as a "furnace", then there may be a case where leaving the switch ON will burn oil. If your Boiler made Domestic Hot Water (DHW) in the distant past, AND the plumber who installed the first stand alone water heater, never told the oil burner control to stop making hot water, (that would make the boiler a cold start boiler), then you could burn oil if you left the switch ON. Can you take a picture of your OIL BURNER "FURNACE" and post it here. From far enough back to see from floor to ceiling. That way we can see if it has ductwork or pipes.

If you have the Boiler that maintains water temperature for DHW, even if the DHW pipes are not connected to it, then we can offer you a way to solve that, in order to make your oil burner only operate when there is a call for heat from the thermostat.

But if you have a "furnace" (ductwork) then I stand by my original statement.

Mr. ED

HVACNUT

Unless of course it's not a furnace but a boiler, and there's a B, dual, or triple aquastat that maintains a minimum boiler temperature. 
If that's the case, then oil will still be consumed even if the thermostat is off.
Can you provide info on the heating system and controls? Maybe some pics?

pecmsg

crhyner said:

OK, noted, thank you.

If I leave the power to the furnace on, with a C wire to provide power to the thermostat, and the thermostat set to OFF, just confirming that the furnace won’t burn any oil?  It won’t burn oil to maintain its temperature at all?  Goal is no oil consumption, but power being sent to smart thermostat.

Thanks.

How much oil does it burn maintaining the boiler temperature? 1 gal a day maybe.

crhyner

Thanks, here's the setup. Yes, that is an indirect water heater. I just purchased a heat pump water heater and will be putting that in soon.

HVACNUT

Can you get the model of the aquastat? The grey rectangular box. 
Loosen the 1/4 hex screw on the bottom and the cover will pull off.
The boiler is a WGO, not a WTGO, so it's probably an L8148A, and thats good for you... if it's wired correctly. If it is wired correctly, you could either just turn down the temperature all the way on the water heater (recommended), or remove one wire from the water heater aquastat or relay.
Keep in mind when a system goes cold for an extended period of time, sometimes gaskets and seals will shrink and it might develop some water leaks. Circulator gaskets, relief valve seat, etc.

And the most important part is, you'll need a separate transformer and isolation relay as recommended above because there's no component on your system that offers a Common for the thermostat. 

crhyner

Thank you, here's some more pics. I see a hookup for a C wire on here, no?

HVACNUT

No hookup for a C anywhere. The switching relay that offers the C is 1: controlling the water heater, and 2: it's only rated for 1 amp and will likely not handle the load of the thermostat. 

And for some reason, the aquastat is an L8124 triple. Even if you turn the low all the way down, it'll still cycle periodically. 

What climate are you in that you feel confident shutting off the whole system?

EdTheHeaterMan

This is the wrong control for what you want to do. BUT...NO FEAR by removing one wire you can make that control work the way you want it to. Remove the Blue Wire from the LO side of the WHITE aquastat block to make this control a cold start boiler.

SEE illustration


Since you have the newer control, the blue wire has an insulated cover on it. All you need to do is remove it and let it hang freely inside the control box.

EdTheHeaterMan

Now that we can make your oil heater a cold start boiler, you need to select the WiFi thermostat that will work for you. Unfortunately the oil burner control that runs the thermostat has no access to a C wire, you need to get a thermostat and the auxiliary transformer kit for whatever thermostat you select.

https://www.amazon.com/Amazon-Smart-Thermostat/dp/B08J4C8871/ref=sr_1_4?crid=15Q080H7P1E6I&keywords=smart+thermostat&qid=1672711741&sprefix=smart+thermostat,aps,142&sr=8-4&ufe=app_do:amzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc. Get the $79.99 version without the C wire adaptor. That adaptor will not work with the oil burner control.
Or you could get the Nest or ecobee. The choice is yours

You will need this kit to connect the thermostat to a separate transformer
https://www.amazon.com/Adapter-Transformer，C-Wire-Thermostat，Compatible-Honeywell-Thermostat/dp/B07L4DN5R2

HVACNUT

@crhyner and @EdTheHeaterMan, that's all well and good, but since the boiler will no longer maintain temperature, the relay for the water heater needs to get wired to ZR, ZC on the triple so the boiler knows when there's a demand for domestic hot water. 

EdTheHeaterMan

HVACNUT said:

@crhyner and @EdTheHeaterMan, that's all well and good, but since the boiler will no longer maintain temperature, the relay for the water heater needs to get wired to ZR, ZC on the triple so the boiler knows when there's a demand for domestic hot water. 

Did you see this about that?

crhyner said:

Thanks, here's the setup. Yes, that is an indirect water heater. I just purchased a heat pump water heater and will be putting that in soon.

No need to use ZC/ZR if the indirect is no longer in use.