Need help in wiring Nest E w/o C wire
kyrral
| Posted in Energy, Heating & Insulation on
I am trying to wire a Nest into a gas heater. I have a 24amp transformer with two wires that plugs into a wall outlet. I assume one wire plugs into the C slot. What about the other?
Then what wires do I run from the Nest to the heater. I assume I use the middle and right screws. The middle screw has a wire that connects with a wire from the left screw that connect with a thermocouple.
I called Nest and was on hold a long time with two operators. They told me they didn’t know how to wire this and suggested I call in a technician!!! I’m up in the mountains and techs are expensive and scare. This is terrible tech help.
My goal in using Nest is to turn on heater before I get to cabin.
Replies
How did the heater work before you purchased the nest? did the heater come with a plug-in transformer? Is there an on/off switch? Where does the thermocouple come into the connection? is it really a thermal on/off switch, and does it turn the valve turn on or turn off? Does this heater just have the gas burner, or does it also have a fan to distribute the heat?
I am going to guess you have a 24 volt transformer. (not 24 amps) it will have a volt-amp rating.
You may have never seen the tech-school parsing of "assume" which when viewed as "as /U/ ME" indicates the potential to make an A** out of both of us.
the gas valve has two relevant connections, TH and TR. the TR is a return, the TH will operate the valve when voltage is applied (relative to the return) the value of the voltage applied needs to match the design of the gas valve. If you do not see the valve labeled with 24 volts, You should stop. probably need to look up a part number of the gas valve to verify. verifying the control voltage is the first step.
the transformer will have two outlet screws, one for common, aka return, aka 0 volts.
the other screw will provide the hot side of the output, or 24 volts referenced to the return screw.
the nest thermostat needs to see the common, and also the 24 volts.
the C terminal is for common. It will need to connect to the transformer common terminal.
The transformer 24 volt terminal needs to connect to the nest R screw. This provides power to run the thermostat, and to send on to the gas valve.
the W terminal of the thermostat is set to provide voltage when the thermostat calls for heat. You would want to connect it to the TH terminal of the gas valve, while the TR terminal of the gas valve needs to be wired to the common terminal of the transformer. (which also remains connected to the thermostat R terminal(screw).
Before hooking this all up, need to understand the ratings of all the components to be sure they are matched (or the part that needs to have greater ratings does so) this includes the wires.
Also need to understand the thermocouple, and if it is set to turn the gas on, or if it is a limit switch set to a higher temperature and meant to turn the gas off in case of an overheat.
you don't want the internet enabled nest to be a cabin burning device, so it pays to be careful.
The heater was used. No idea if it works properly. The thermocouple immediately disintegrated. I beleive its only function is to light the pilot light (if fact its probably not called a thermocouple. Maybe an ignighter. I leave the pilot light lit all the time becasue its extremely difficult to keep lit (drafts from outside I beleive).
There isn't an on/off switch. There isn't a temperature dial either (which I just discovered), so it has to run off a thermostat to raise the heat,
This is a fairly new cabin that runs off electrical heat, but not very well, hence the gas addition.
No transformer came with the unit. I researched thermostats and 24 amp power was mentioned a lot.
Is this a wall heater, that you vent exhaust to the outside?
It is important to find out if it is working properly, and to have a good CO detector if/when you use this.
electricity includes volts and amps, but they are quite different. the details do matter. Also, keep in mind that just because some info comes up in a search, it does not mean that the author actually knows what they are writing about.
do you have a model number and make for the heater? you might be able to find installation instructions online.
It is also possible that the thermocouple is like this item:
https://www.grainger.com/product/WHITE-RODGERS-Thermocouple-2E337?opr=OAPD&analytics=relItems_4E125
it's function is to turn off the pilot light gas supply if it does not remain lit. (which is why you need to hold the pilot control valve in until the thermocouple heats up and keeps the pilot light gas supply running when the valve control is released.)
this is important to avoid the pilot setting from venting unburnt gas into your space, where it could build up and fuel an explosion.
If your thermocouple is not intact, you will want to get it replaced with a functioning unit.
A rechargeable lithium ion battery powers the Nest thermostat. In a system with a C-wire, the Nest charges itself using the current from the C-wire, and everything works perfectly. Nest, on the other hand, recharges its battery when the heating or cooling is turned on in a system without a C-wire https://asianfriendly.com/blog/,
For use in a cabin, which might go for weeks without turning on the gas heater (months in the summer) , it would be better to run a common wire to the thermostat.
just my 2 cents, have a working carbon monoxide installed before firing up the gas heater.
A place heated with electric heaters wouldn't be required to have a CO detector since there's no source of combustion, a smoke detector only would have been installed.
Some place in my past, I heard about a plumber who worked on a heating system, and thinking the property would be vacant, left the stack disconnected. Owners decided to take a unexpected trip to the property and used the wifi thermostat to turn up the heat. CO levels went thru the roof, owners showed up, entered the cabin, passed out from the excessive CO levels, and died.
little off topic, but something to consider
good luck
reading the post again, if the pilot is difficult to light due to drafts, as Uncle Mike 42 pointed out, if it goes out and gas continues to flow, at some point you'll be in the explosive range and if there's any electrical spark, like from a light switch, then the cabin goes BOOM, and yes, it is that simple for a house to blow up.
OK, I'm warned. Bought a CO2 detector. I already have one but suppose its defective?
Until I get the Nest going (connect C and R to 24 amp power. Run W wire to thermostat) can you show me how to hook up this Honeywell? I want to use it to see if the heater really works as I've never turned it on.
You mean run wire from the thermostat W to the burner control TH
And the transformer provides 24 volts. Not 24 amps.
If you want to see if the heater works, wire it right up to the transformer, and plug it into the wall (If you have a switched outlet, or a plug strip like for your computer equipment, you can plug the transformer into the switched outlet and use the switch to turn the burner off and on.
Needless to say, unplug everything before you leave the area.
You said the thermocouple fell apart. have you replaced it, and put the hot end where the pilot light keeps it hot? Does the pilot stay lit?
If you can post the honeywell thermostat part number, it would help.
Honeywell Model is RTH 2410 B
https://digitalassets.resideo.com/damroot/Original/10011/33-00110EF.pdf?_ga=2.177261925.1349998205.1634846382-982155552.1632908327
That honeywell operates only from the AAA alkaline batteries you have to install. it does not use the common wire, but will connect the R wire to the W wire when you set it to a higher temp than the room.
you would want to run the common wire from the transformer only to the heater TR screw.
Wire the hot (24 vAC) transformer terminal to the honeywell R screw.
wire the honeywell W screw to the heater TH screw.
Thanks. That's coherent. Tpp bad honeywell techs couldn't tell me. I think their data base is on one 3 x 5 index card.
Please update us on how this is going.
Did the heater fire right up?
Does the pilot stay lit and reliably turn off the gas if you blow out the pilot?