Trying to figure out wiring for my thermostat

rahm0277

I'm trying to figure out the wiring in my thermostat, to be able to replace it with a newer one, but what I have doesn't seem to coincide with anything I've come across online. I don't have a c-wire, neither a g-wire it seems. I have heating only (no cooling). Can anybody tell me if this is wired incorrectly, or this is some different setup? If I want to get a new thermostat, how should it be hooked up? (see URL for the picture below)

https://ibb.co/KhmLtzx

STEVEusaPA

What kind of thermostat are you trying to install? Make/model #?
Most likely you may need to run new wires, or use an add-a-wire kit, or maybe an additional transformer.

Alan (California Radiant) Forbes

If you have heating only, all you need is a Rh and W wire to be able to turn on your heating system with a regular thermostat that has a battery. If you want a fancy, hipster Nest, Ecobee or other kind that of stat that can be accessed with an app, you will need a C wire to power the thermostat.
A “G” wire is used for forced air heating systems to allow you to control the fan independently of the heating system, like on a hot day when you just want to circulate air. 

EdTheHeaterMan

Your thermostat IS wired correctly.
A "heating only" thermostat requires only 2 wires. When there is a call for heat by the thermostat. the R and the W terminal are connected to each other completing the electric circuit much like a light switch completes the electric circuit to a light bulb.

Your thermostat has more capabilities than you need. On your thermostat, Rh is the R terminal needed to turn on the heating system when the temperature drops. The Jumper between Rc and Rh makes both R terminals active and may be necessary for the thermostat's internal battery to use the heater's control power to charge the battery. Rc is for cooling (that you don't have) but may need to be connected for proper operation of the thermostat over the life of the thermostat.

What new thermostat are you interested in installing? Nest on many systems do not need to have a C wire. If you have selected a thermostat that needs the C terminal connected, you will need to see if there is an extra unused wire behind the thermostat. If the wire from the heater to the thermostat has only 2 conductors, you will need to run a new wire with at least 3 conductors (But I would use a 5 or more conductor for future use).

This is because the new thermostat is more than just a switch. it is also a Load. A load is a device that uses the electricity. The thermostat's onboard computer is using power to do all the smart functions. R is the source of the power, C is the return path back to the power source that is always available for the computer to function.

The W is the switch that turns on the heater. This switch in the thermostat allows the power from the source to continue to the heater to operate the burners and the other motors that circulate the heat in the home.

Now that you are totally confused with this post. have you already selected your thermostat? let us know which one.

rahm0277

Hi All, this is all very helpful. Most of the wiring I've seen didn't have two wires going to one connection (in this case, the Rh). No other wires exist. Out house is old (1901), and so is the heating system, so fully expected.

I'm only looking because the buttons on this one is kind of busted. I now have a rite-temp 8022c. I'm looking to get something with wifi. I looked for a bunch that doesn't need c-wire, but the ones that came up are misleading. I saw this Emerson Sensei (https://www.amazon.com/Emerson-Thermostat-Version-Energy-Certified/dp/B01NB1OB0I?ref_=fsclp_pl_dp_1&tag=androidcentralb-20&ascsubtag=UUacUdUnU71492YYwYg) but it says it needs c-wire for heat only systems (I guess thats what I have), so that rules it out. I also read that ecobee can work without the c-wire (not sure). If nest can work, I can get that, too - but I'm not sure if nest will work. It would be a little costly to get a c-wire run (1901 house is all plaster I also read somewhere that the lux geo wifi thermostat would work because it can be powered by batteries.

My main thing was wifi, so if you all know any wifi thermostats that can work without the c-wire, please let me know

ratio

The Honeywell 9000 & 8000 series work with a wireless EIM that can power the stat via the two existing wires, so no batteries; & a RedLINK (Honeywell's flavor of wireless) gateway will get it on the Internets. The Honeywell app has a demo account you can test drive even.

rahm0277

@ratio what is EIM? Also, most of the 8000 and 9000 models say "requires pro" - am I able to do this myself?

rahm0277

Also, if I DO find a thermostat that will work with 2 wires, do I still need to jump the Rc and Rh (like in my photo)? Or does it depend on the thermostat?

Alan (California Radiant) Forbes

EIM = Electronic Interface Module

If you have heating only, you do NOT need the jumper. The jumper is there to power the cooling circuit.

Some more information:

https://www.thermostatistics.com/what-is-a-c-wire-and-why-do-you-need-one/

How to use a 1K resistor when you only have 2 wires:
http://www.taco-hvac.com/uploads/FileLibrary/102-397.pdf

https://forum.heatinghelp.com/discussion/180066/taco-sr502-zone-controller-with-nest-stat