topic Re: Google nest hookup for a millivolt gas heater in Nest Thermostats

Google nest hookup for a millivolt gas heater

Novice — Wed, 05 Jan 2022 17:03:19 GMT

I have a 2-wire millivolt gas heater. It seems I need to connect the two wires from the gas valve to W1 and RH and then use a 24V transformer and connect them to C and RC on the more expensive google nest. The basic google nest has G, R and OB on the right side and Y, C and W on the other side. How do I translate W1, RH, C, RC to the basic google nest terminal labels?

Re: Google nest hookup for a millivolt gas heater

dhx227 — Thu, 06 Jan 2022 02:33:34 GMT

I'm pretty sure the Nest will not work with a millivolt system without the use of an external 24VAC-based relay. The Nest is not like a thermostat that typically uses internal relays to switch on/off the call for heat/cooling and thus don't really care what the voltage being switched is. The Nest is all solid state, so likely will not work to switch a millivolt relay. What you could do is use something like a RIB U1C (https://www.amazon.com/Functional-Devices-RIB-U1C-Relay-Box/dp/B006YVL93Q/) to switch the millivolt side, then you supply the Nest with 24VAC and wire the RIB U1C as if it were the furnace.

This would be your wiring guide:

24VAC transformer wire 1 - to (C)ommon on Nest and WHT/YEL on RIB-1UC.
24VAC transformer wire 2 - to Rh on Nest (Rc is for power to cooling circuit switch)
Nest W1 to WHT/BLU on RIB-U1C
Boiler wire 1 to YEL on RIB-U1C
Boiler wire 2 to ORG on RIB-U1C

Re: Google nest hookup for a millivolt gas heater

Novice — Thu, 06 Jan 2022 03:46:22 GMT

@Novice wrote:
I have a 2-wire millivolt gas heater. It seems I need to connect the two wires from the gas valve to W1 and RH and then use a 24V transformer and connect them to C and RC on the more expensive google nest. The basic google nest has G, R and OB on the right side and Y, C and W on the other side. How do I translate W1, RH, C, RC to the basic google nest terminal labels?

Thank you! The only issue is that basic google nest has terminals G,R, OB, Y, C and W as in the photo I attached. What would be the proper wiring for basic google nest?

Re: Google nest hookup for a millivolt gas heater

Novice — Thu, 06 Jan 2022 03:48:16 GMT

Thank you! The only issue is that basic google nest has terminals G,R, OB, Y, C and W as in the photo I attached. What would be the proper wiring for basic google nest?

Re: Google nest hookup for a millivolt gas heater

dhx227 — Thu, 06 Jan 2022 04:11:20 GMT

Per the wiring above, just use the R instead of Rh, and W instead of W1.

Only FYI, this is the meaning of each of those wires:

C - common
R - power source to use when calling for heat/cooling or switching heat pump operation
W - call for heat
Y - call for cooling
G - independently controls the fan only
O/B - typically used to control the direction of a heat pump (heating or cooling mode)

Note: the thermostat will effectively connect R to any particular wire of the last four to enable that function. Classic thermostats would do this through the use of internal relays.

I'll also add that the reason the other Nest has the more complicated wiring is because when you have independent heating and cooling units, they often each have their own transformer. You can't intermix the power from one transformer to another (it simply doesn't work). So, in those cases, you need a separate Rc (for the transformer used in the cooling system) versus an Rh (for the transformer used in the heating system). The thermostat then needs to appropriately switch Rc with Y1 (and optionally the second stage Y2), and Rh with W1 (and optionally second stage W2).

Re: Google nest hookup for a millivolt gas heater

Novice — Thu, 06 Jan 2022 04:25:44 GMT

Thank you so much! Please bear with me: Does this mean that I need 3 components:

nest thermostat
a 24V transformer
RIB-1UC

Or does RIB-1UC also provide the 24V power that nest needs?

Re: Google nest hookup for a millivolt gas heater

dhx227 — Thu, 06 Jan 2022 05:52:18 GMT

Yes, you will minimally need those three components. And no, the RIB-U1C is just a relay.

As for the transformer, I would recommend you get a UL-listed Class 2 or 3 transformer. It doesn't need to be very strong transformer. Transformer's are rated in VA and for this job you really only need one that is minimally rated 10VA. But the smallest 24VAC transformers tend to be either 20VA or more commonly 40VA - that is fine, it's just way more than what you actually need to drive power for the Nest and operate the RIB relay.

Re: Google nest hookup for a millivolt gas heater

Novice — Thu, 06 Jan 2022 12:41:35 GMT

Thanks a lot for edcating me!

Re: Google nest hookup for a millivolt gas heater

tgadgets — Thu, 03 Feb 2022 02:48:08 GMT

This worked perfectly. Thank you.

Re: Google nest hookup for a millivolt gas heater

tgadgets — Thu, 03 Feb 2022 02:50:40 GMT

I had the basic Nest and I used terminals R, W and C.

Re: Google nest hookup for a millivolt gas heater

tgadgets — Thu, 03 Feb 2022 02:57:12 GMT

I have what you have and I used R, W and C but in the drawing above they do not have the relay in there like

dhx227 told you that you needed. I used another drawing to help me with what dhx227 was saying...

Re: Google nest hookup for a millivolt gas heater

dhx227 — Thu, 03 Feb 2022 17:13:49 GMT

Nice! And thanks for finding the perfect picture to complement my instructions!

Re: Google nest hookup for a millivolt gas heater

tgadgets — Thu, 03 Feb 2022 18:55:47 GMT

dhx227 really thank you for the instructions. I have wanted to put my gas stove on a Nest for quite a while and Nest just kept telling me it was not possible. I bought the relay that you had a link to above and a 120v to 24VAC tranformer. I had a light switch in the wall below my thermosat so I pulled out the box and put in a three gang two of which were for switches... the third I filled with transformer, wiring and screwed the relay on the outside of the box (but in the wall) with wires coming into the box from rear. I put a blank in the third opening for a switch for the cover and everything turned out beautifully. Thermostat works like a charm and I can control it like my house thermostat with Google Home. Very happy with this setup. Thanks again for taking the time to type up the answer above.

Re: Google nest hookup for a millivolt gas heater

Novice — Fri, 04 Feb 2022 14:46:46 GMT

I thank both of you (dhx227 and tgadgets)! I have not yet bought the components needed for this solution. tgadgets: Since you have already implemented the solution, will you please share with me the exact model of the nest, relay and transformer that you bought? As my name shows, I have to make sure that I don't make any mistakes along the way to this solution. Thank you all again!

Re: Google nest hookup for a millivolt gas heater

goalie6966 — Mon, 11 Jul 2022 14:08:07 GMT

I only have the red and white wire from the boiler and the 2 wires from the 24v transformer, how does that get wired to the Google nest smart thermostat, do I add a wire from the relay???

Re: Google nest hookup for a millivolt gas heater

AVHVAC — Thu, 01 Dec 2022 00:49:16 GMT

@tgadgetsI am also interested could you please share?!

thank you all for paving the way

Re: Google nest hookup for a millivolt gas heater

AVHVAC — Thu, 01 Dec 2022 00:52:02 GMT

That or @Novice did you end up purchasing anything?

Re: Google nest hookup for a millivolt gas heater

Novice — Thu, 01 Dec 2022 01:16:55 GMT

After getting all the details, my new dilemma is this: With the current milivolt thermostat, my gas heater will work even if there's a (long) power failure. With the modified nest thermostat, Gas heater will not kick in if my cabin loses power. Since I also lose water when there's a power failure, I have focused on getting a proper size UPS before I switch to Nest.

Re: Google nest hookup for a millivolt gas heater

AVHVAC — Thu, 01 Dec 2022 02:07:33 GMT

Got it. After more research I might just get a programmable thermostat and wait till my next place before I get a switch

Re: Google nest hookup for a millivolt gas heater

tgadgets — Thu, 01 Dec 2022 04:59:01 GMT

Transformer: https://www.amazon.com/gp/product/B086S79N1C/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Relay: https://www.amazon.com/Functional-Devices-RIB-U1C-Relay-Box/dp/B006YVL93Q/

Nest Termostat: https://store.google.com/us/config/nest_thermostat?sku=prd_7577_5352&utm_source=sem_pla&utm_medium=dr&utm_campaign=GS107233&utm_term=dtb&utm_content=ds_prospect_platform&gclid=Cj0KCQiAm5ycBhCXARIsAPldzoXH0nhatcMTRUsIdD-bA43DDF_wTW1Sa_f_kEMZHSY2_fSA-PXoIyoaAq6TEALw_wcB&gclsrc=aw.ds&pli=1&hl=en-US