I am trying to add an external thermostat to my garage heater: https://www.ghpgroupinc.com/product-...EG5000DGP.html
This unit has a switch to bypass the built in thermostat and control with a wall thermostat. I purchased the matching 240v double pole line thermostat but the wiring diagram is confusing me. The unit works great using the built in thermostat but it is 10' high and I can't reach it to adjust. I would like to understand how to wire the heater to the thermostat. If someone can explain this to me, I would be very grateful. -Terry

 

I would take the power feed to the thermostat and connect the line side. Then take the load side to the heater. Turn the stat on the heater all the way up.

 

Thanks. That makes logical sense. I may just do it that way. I really am curious though how they intend it to be wired on this diagram. To me it makes no sense and I have this need to figure things out. I had an electrician acquaintance look at it and he was also confused.

 

The internal thermostat only switches L1. With the external thermostat L1 is redirected out to the external stat for switching.

With the switch on external L1(RED) stops at selector switch after the internal stat. L1 goes out to the external stat and comes back through the switch to the heaters (red) and the selectable wattage heaters (blue) and returns to L2 purple.

external stat
With the switch on internal L1(RED) goes through selector switch after the internal stat to the heaters (red) and the selectable wattage heaters (blue) and returns to L2 purple.


internal stat

Hope that makes sense.

 

It does. A lot! Thanks you.

 

If only 1 leg runs through the thermostat, what about the other 2 wires on it?

 

Spares. You don't use them. It is made to switch both wires but you don't need to switch both to turn the heat on and off.

 

Awesome. Thank you so much.

 

Some electric thermostats will switch one set of contacts when the stat is turned on and the other set cycles based on set point. Make sure your heater cycles on a call for heat.

 

The manufacturer says that it must be a double pole line thermostat. Wouldn't this setup use a single pole since only one leg is going through the stat?

 

What manufacturer? The wiring diagram for the heater only show single pole wiring available for an external stat.

 

https://www.menards.com/main/heating...9111520397.htm

 

As per my previous explanation..... the run both sets of thermostat contacts in series for positive shutoff.
Wire it as shown in the thermostat box on the wiring diagram.

 

Got it. Thank you for the explanation. So line wire connects to the one labeled "Line Red" , "Black Load" wired to "3" , then "4" going back to terminal 2 on the heater?

 

Since this is a 5,000W heater make sure you use an appropriately rated thermostat most "normal" ones are only rated at 22A or 5,280 @ 240VAC not much room for margin and those cheaper thermostats are known to have the "cycling" contact weld closed as what happened to a CT410B that was contolling a 2,00W baseboard heater.

 

Here's another option that is a little more expensive but allows you to use any 24V thermostat. I've used it with baseboard heaters. It gives you more options and better control.
You use a 24V transformer, a relay, and a 24V thermostat.
https://www.functionaldevices.com/pr...ails/RIB24P30/
https://www.functionaldevices.com/pr...ils/TR50VA015/
You can mount all of the 240V wiring up by the heater and just run a low voltage wire down to the thermostat.
That's a 20A relay in the picture. The link is for a 30A which is what you want.

 

Oh that is neat I was going to ask if that was possible because the cheap POS Honeywell CT410B that maintenance installs in the place I live keep welding the temperature cycling contact closed (heat is always on no matter the room temperature). You can then use any "normal" HVAC 24VAC thermostat? how does that work as most have cool - off - heat settings and Fan Auto - On settings how would that work with a 240VAC baseboard heater which has no fan?

 

"how does that work as most have cool - off - heat settings and Fan Auto - On settings how would that work with a 240VAC baseboard heater which has no fan?"

The 24V common from the transformer is connected to the thermostat (C) and one side of the relay coil.
The 24V hot from the transformer is connected to the thermostat (R).
The heat (W) on the thermostat is connected to the other side of the relay coil.
The thermostat is used in heat mode only. The fan mode does not function.
When the thermostat calls for heat the coil is energized and 240V is sent to the heater.
There are different relays and transformers to choose from.
https://www.functionaldevices.com/pr.../relays/#power
https://www.functionaldevices.com/pr.../transformers/

 

What one is good for a 2 pole 20A (240VAC) breaker?
The bedroom and bathroom heaters are on the same 20A breaker but they both have independent thermostats.

The 12/2 goes to the box where the bedroom thermostat is with 3 cables in that box (one from the panel - one to the bedroom heater - one to the bathroom thermostat - the other cable in box 2 (bathroom) goes to the heater in the bathroom the circuit ends there.

The living room heaters 5'/60" and one 6'/72" heater are on one 20A 2 pole (240VAC) with one thermostat.

 

Any of the 20 or 30 Amp relays with a 24 Vac/dc coil will work.
Look at what you can get online.

If you only need to break one of the 240V wires look at a SPDT like:
https://www.amazon.com/Functional-De.../dp/B000LEUJU6

I just saw this from a different post. 22A, SPST for heater, built in 24V transformer:
https://www.amazon.com/gp/product/B0...k_ql_qh_dp_hza

The DPDT will break one or both of the 240V wires. Here is a 20A and a 30A.
RIB24P
RIB24P30