Reddit reviews Aube RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer

You're looking for a relay. I used a few of these when I renovated my basement:
https://www.amazon.com/dp/B0037MXM1C/

It replaces the built-in rheostat on the baseboard heat, and you then use low-voltage wiring to connect it to a "regular" 24v thermostat.

OK. Here is what you are dealing with:

1.(L) black. Line voltage load. Either 110v or 220v. Need to verify with a voltmeter.

2.(W/Y) orange. W=heating and Y=cooling. Used for a two pipe hydronic heating/cooling system. That means water.

3.(Y/A) yellow. Y = cooling. A = electrical heater output. Heat and cool active to any relay.

4.(G1) red. Low speed fan. Through a relay.

5.(GM) blue. Medium speed fan. Through a relay.

6.(GH) brown. High speed fan. Through a relay.

7.(N) white. Line voltage neutral. Either 110v or 220v. Need to verify with a voltmeter.

What is missing is the "C" and "R" wires. Nowhere is there a low voltage 24v load and common wire. Your current thermostat does not use it.

You have two options that I know of. Purchase a transformer to supply the 24v to your new thermostat. Or return the Honeywell and purchase a wifi enabled line voltage T-stat.

Transformers. Here are two that may work:

http://www.amazon.com/gp/product/B0037MXM1C/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A26RBB5XP2LWJC
For 240 volts

http://www.amazon.com/Honeywell-RC840T-120-Electromechanical-Relay-Built/dp/B00D5YLY2G/ref=sr_1_1?ie=UTF8&qid=1464560168&sr=8-1&keywords=Aube+RC840T-120
For 120 volts

Line voltage T-stat:
https://casaconnect.com/en/shop/smart-thermostat-caleo/

Note: Since you have hydronic heating and cooling, in addition to HVAC, either choice for the thermostat will likely mean that you will loose that option. I have not evaluated the new Honeywell or Casa to see if they support hybrid systems.

The American nest needs 24vac. If you only need to control central heating (on and off only) you can hook the Nest up using a transformer/relay combo. Something like Aube RC840T-240

Something like this should work. SHOULD. I don't know the exact specifics of your setup, but it looks like 240V line-voltage baseboard heating based on your existing thermostat.

If you get this thing, connect all 3 wires to the Nest. It just saves headaches to have a C wire.

You’re looking for something like this. It is essentially a 240V relay with a 24V control circuit, which allows you to switch a line-volt heater using a low-voltage thermostat. Then you can choose any thermostat you like.

Aube RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer https://www.amazon.com/dp/B0037MXM1C/

I don’t have any direct experience with it unfortunately, but maybe this will at least give you a place to start.

You want a thermostat switching relay like this one

Then use any smart thermostat you want.

Step 1. If it is the cheapie electric baseboard heat, you most likely have a 120v or 240v thermostat. Find out which.

Step 2. You'll need this for 240 (or if you can find one to mount in a switch box, that would be better): http://www.amazon.com/Aube-RC840T-240-Switching-Electric-Transformer/dp/B0037MXM1C/ref=pd_sim_60_1?ie=UTF8&dpID=31RasVuVDpL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=1K9Z0QT4F1AHDX7W166G

Or this for 120v: http://www.amazon.com/Honeywell-RC840T-120-Electromechanical-Relay-Built/dp/B00D5YLY2G/ref=pd_sim_60_4?ie=UTF8&dpID=41c-k5UMUgL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=1K9Z0QT4F1AHDX7W166G

Step 3. Use the above relay to hook up an Insteon Thermostat.

Don't worry about the overall shape of the system. All that matters is what the wires behind the thermostats are and do.

Ecobees don't run on mains voltage; in typical US thermostat wiring, there's a 24V (AC) potential between the "C" and "R" wires on the thermostat harness designated specifically for thermostats that need external power, and this is what Nest, Ecobee, et al run on in the US. In fact, thermostats that go anywhere near mains voltage are very rare in the US. Your diagram implies that these are, in fact, mains voltage thermostats... fun.

Looks like Nest has a "Heat Link" appliance specifically for this scenario. If you like Nest, well, there you go.

More generally, this is an adapter that converts 208-240V "mains relay" thermostat wiring to a US-style 3-wire interface. This could be used with basically any standard US thermostat. It looks like European thermostats differ quite a bit, but it's likely there's similar units out there.

Install the following, then you can choose the smart thermostat of choice:

Aube RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer https://www.amazon.com/dp/B0037MXM1C/ref=cm_sw_r_cp_api_uITLBbZFN4PYX

Not officially supported, but you can use Nest and Ecobee with a transformer and relay, like this: https://www.amazon.com/Aube-RC840T-240-Switching-Electric-Transformer/dp/B0037MXM1C

Check this out - looks to be a workable solution:

https://www.quora.com/Is-there-a-work-around-for-the-Nest-Thermostat-to-control-line-voltage-electric-baseboard-heaters

http://www.amazon.com/gp/product/B0037MXM1C/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A26RBB5XP2LWJC

Good luck!

Never used this but could bridge your line voltage heaters to a low voltage thermostat.

https://www.amazon.com/gp/aw/d/B0037MXM1C

Use a relay + Nest, Ecobee, etc. Common for controlling line voltage baseboard heaters.

https://www.amazon.com/gp/product/B0037MXM1C/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

> Absolutely no way to use Nest/Ecobee/other similar products.

Wrong. You can absolutely use a low voltage (24VAC) thermostat (Nest/ecobee etc) to control line voltage (120VAC/240VAC) equipment. This requires something like an Aube Relay with a built-in 24V transformer.

There are plenty of examples of folks connecting Nest thermostats to line-voltage heating equipment. Here is one. Here's another.
Here's a third. And for good measure, here's a fourth.

Yes.......BUT


Where in the world are you located?

What type of system?


Here is a 240v to 24v transformer & relay that lets you control 240v systems from a 24v thermostat(nest)

Aube RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer https://www.amazon.com/dp/B0037MXM1C/ref=cm_sw_r_cp_apa_i_eSa4DbEXQ2SG7

I assume that means I need one of these? Will that work for the double pole wires I have currently? It looks like that uses 3 wires, I have 4, 2 reds and 2 blacks. Is there a different transformer with relay I should use?

This can be used to hook up baseboard to a thermostat.

http://www.amazon.com/Aube-RC840T-240-Switching-Electric-Transformer/dp/B0037MXM1C

with how many you are wanting to hook up, i honestly couldn't offer any advise there. I know the nests are designed so they can network together and work in sync to keep all the rooms on the same temps, but that would be a very pricey undertaking with around 8 different units, as well as 2 AC units.

you could with something like this aube relay. That gives the necessary 24v transformer to be able to use a normal hvac thermostat like the nest. But unless you wire multiple relays together, and lose you zones, you would need nests for each zone which is big $$$.

Here is an example of a combination relay & transformer that would work:

Aube RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer https://www.amazon.com/dp/B0037MXM1C/ref=cm_sw_r_cp_api_qSldAb96GGBRE

Get a baseboard heater transformer/relay such as an Aube RC840T-240.

If you can get an IOT device to provide a basic dry relay closure (Insteon 2450 looks good), and can wire the relay transformer into your appliance or its receptacle, it should work.

It looks like the Insteon 2477SA1 might be able to control your 240V load, but still needs wired in.