Thermostat Wiring

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Old 10-27-20, 01:53 PM
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Thermostat Wiring

Good afternoon, based on the installation manual and my systems current set up, can you tell me if my system is missing a jumper from W2 to W1/E? The manual makes it seem like there should be a jumper, but maybe there is a reason there isnít? Here are the pictures. I only ask because I may upgrade to a new thermostat and want to make sure I wire it correctly. Thanks in advance







 

Last edited by PJmax; 10-27-20 at 03:05 PM. Reason: resized pics
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Old 10-27-20, 02:35 PM
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Hi, is the system working as expected now? If so I would install the new one the same way .
Geo🇺🇸
 
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Old 10-27-20, 02:55 PM
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Yes.... install that jumper to activate emergency heat.
 
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Old 10-27-20, 03:22 PM
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Thanks for the info.....but it looks like I got 2 conflicting answers. Yes, the system is currently working, but I have not had the need for emergency heat so I wouldn't know if that aspect is working properly. I guess my question is, when wiring the new system, should I wire it as though the jumper is there on the current system?

If I were to put on the "emergency heat" on my current system the way it is currently wired, would it do anything?

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Last edited by sguarrera; 10-27-20 at 04:18 PM.
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Old 10-27-20, 04:17 PM
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You can verify emergency heat. Set the stat to em heat. The outside compressor should not be running. Just the electric reheats will be active so you should feel mildly warm air.
 
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Old 10-27-20, 08:02 PM
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Thanks PJ. How would you recommend wiring a new thermostat? Add the jumper that looks like it is supposed to be there from W2 to W1/E?

 
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Old 10-27-20, 10:33 PM
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I thought that was your new thermostat.
If not.... what will you be installing ?
 
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Old 10-28-20, 09:29 AM
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Sorry, I should have been more clear. That is my current thermostat and I was perplexed by the lack of jumper from W2 to W1/E and wondering if it is missing that jumper. I am thinking about installing the Emerson Sensi Wi Fi Smart Thermostat (ST55) and am wondering if I should wire that one as if the jumper is present on the current set up.

Thanks

 
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Old 10-28-20, 10:46 AM
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Every stat is different. 99% do not require any jumpers between terminals.
In fact ..... most thermostats now have terminals that will only allow one wire per terminal.

That jumper on your current stat is supposed to allow the electric heat only to run in emergency mode. Did you check your system like I previously mentioned in post 5 ?
If you have no need for e heat..... don't bother with the jumper.
 
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Old 10-29-20, 07:37 AM
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A jumper at Rc/Rh is normal; most systems use the same power feed for heating and cooling mode. As for W1/W2, if I were to guess based on your current wiring, I would say you are in a mild climate where you do not have any primary heating; just the electric as back up? If that is the case, it makes sense to only have a wire at W2, especially for a simple stat.

Is the manual you showed pictures of for your current thermostat or the new one? It does mention with a heat pump that you MAY need to have the jumper installed. It goes on to qualify that that statement is dependent on if a separate relay is installed to activate the emergency heat. My guess is, because (1) you don't have primary heat, (2) there was no jumper originally, and (3) your e-heat has been working with the current set up, that a jumper isn't necessary; the the e-heat has a separate relay cause its likely the only heating relay.

Ultimately, whether the heat wire goes into W1/E or W2 will depend on the thermostat you are using. Some smart thermostats will allow you to set the emergency heat as just that, regardless of the terminal, while others will designate the heat mode based on the terminal the wire connects to. Furthermore, different thermostats will give you different levels of control as to when e-heat can engage.

I would check out the smart stats and pick one based on suitable features (I like ecobees but haven't used them with aux/e-heat so I can't comment to those features). Once you know that, the respective stat's manual will likely tell you to just connect the e-heat line to W2.

In the end, its practically impossible you will break anything if you choose W1 vs W2 wrong, it just most likely wont engage the e-heat at all or engage it as you want. in that case, just swap it back. With any HVAC wiring, always take detail pictures and notes of the current set up, especially if that current set up works as you intend.

In sum, I would review manual of the stat I want to install for how it recommends connecting e-heat. My gut says wiring it up just how it was originally will work just fine for you. Stats are just dumb switches that close and open circuits to send on/off signals to various equipment. Smart stats still do just that, with a bit more tech and advanced features inside them. Smart or dumb, low voltage stats all the same take a 24V signal in, and then upon call for heat, send that signal to your heating unit (or AC on call for cool or a blow fan on call for fan mode). That is slightly over simplified but not by much.


I should add; most thermostats do not want you to jumper Rc/Rh. They typically will detect just one how source and make the hypothetical "jump" internally to allow power for both heat and cool modes.
 
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Old 10-29-20, 09:34 AM
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Thank you all for the replies, I appreciate it. And yes, you are correct, I live in a mild climate. I will wire the new one, just like the current one is wired.
 
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Old 10-29-20, 09:53 AM
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I would say you are in a mild climate where you do not have any primary heating; just the electric as back up?
The heat pump is the primary heat and the electric is aux.
 
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Old 10-29-20, 12:13 PM
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The heat pump is the primary heat and the electric is aux.
Ah that would make sense. I am not familiar with heat pumps and how they are normally wired but I guess its controlled via Y (same as cooling) since its the same unit and w1 isnt used in the pictures above? Someone more versed may be better suited to answer your question but I will still give my 2 cents (just take it with a grain of salt). I took a quick look a the ecobee 3 wiring diagram. It has you connect e/aux heat into the W1 terminal (and use W2 if there is a 2nd stage in your e/aux heat). The thermostat is then programed to know that is your e/aux heat, which I bet is the case for most smart thermostats.



I noticed you mentioned the ST55. Check out the last diagram on pg 12 (https://sensi.emerson.com/documents/...en-4849238.pdf)

That wiring diagram should work for you (just ignore 2nd stage cooling (Y2) and heating (W2), since based on old stat photo, you dont have two stage heat or cool).
 
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Old 10-29-20, 02:02 PM
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Thank you. pbct, on that diagram, what would "L" be? Also, I would put the wire that is in W2 in my current system, in the W/E terminal? or would that go in the W2/* terminal on the sensi unit?
 
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Old 10-29-20, 02:35 PM
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L = light for trouble. Not used - cap off.
The white goes to W/E.
 
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Old 10-29-20, 02:49 PM
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The L terminal is usual for a diagnostic or status light from the heat pump. Sometimes it is used to indicate a fault or possibly that Aux/E heat is on. Since you don't have that wire currently attached, I wouldn't worry about it. If you have an extra wire and your heat pump has an "L" terminal, feel free to hook it up.

Your current "W2" wire will go to "W/E" on the ST55. Also, if you see a jumper at RcRH on the ST55, leave it intact.

 
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Old 10-29-20, 03:51 PM
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Thanks guys. Appreciate it
 
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