No power at thermostat

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  #1  
Old 01-11-17, 08:41 PM
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No power at thermostat

So I wanted to switch out a HoneyWell T8001C with a NEST (1stGEN). They said it would be easy .

So I verified the wire settings with Nest and then connected it, no power at the NEST, I thought maybe that the NEST was bad, so I replaced it back with the original Honeywell, now I have no power at the unit.

I used a multimeter to test the wires and do not show anything from any of the wires.
First one should be the before, and the second one is after reverting back.

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Last edited by PJmax; 01-12-17 at 09:34 AM. Reason: enhanced pictures
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  #2  
Old 01-11-17, 09:05 PM
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Did you shut power down to the air handler before changing the thermostat?
Looks like you have a heat pump from the wiring. That is a wire on the B terminal, right?
 
  #3  
Old 01-11-17, 09:27 PM
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I switched off the A/C at the circuit breaker, there was nothing listed on circuit breaker for a heat pump. Have central air with an A/C unit outside.

And yes that is a brown wire @ B
 
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Old 01-11-17, 09:53 PM
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Are you sure you switched off the right unit? The indoor unit has the transformer. And its where you'll need to start with troubleshooting
 
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Old 01-12-17, 09:22 AM
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Dont recall anything internal except for the circuit breaker. I was reading somewhere else that it could be the transformer? Would that be in the A/C / Heater (think mine is dual) Its a Carrier (cant remember exact model. Not at home currently.

As its outside and raining have not had a chance to look over the A/C unit, also read that there should be a fuse (is that also in side the the A/C unit?

Think Im way over my head for what should have been a simple thermostat replacement.
 
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Old 01-12-17, 09:40 AM
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You must have a Ruud or Rheem unit outside to be using B on the stat.

Since you have a W connection it means there is electric heat inside the air handler inside.
That would mean you have two breakers in your panel..... probably a 2P30 for the outside unit and a 2P50 or so for the inside unit. There should also be a breaker on or near the inside unit. That is what needed to be shut off.

When you changed the stat you touched the C wire to the R.

You'd need to go to the inside unit and remove the side panel where the wiring goes in to investigate. Make sure the power is off to this unit first.

A model number or pictures are going to be needed.
 
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Old 01-12-17, 10:13 AM
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These are from the summer when I changed out the capacitor in the A/C unit. There is a big type pull out fuse/breaker outside which I didnt remove when i did it. I only pulled the circuit breaker for the A/C unit inside the garage.
 
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Old 01-12-17, 10:18 AM
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Those are pictures of your outside compressor.
You are looking for the blower unit inside the house.
 
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Old 01-12-17, 12:34 PM
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hmm, ok, not sure where that would be at all.
I have a Fan/Vent (intake) upstairs. But not sure about anything else in referance to that.

Ill ahve to look all over today and see what else I can find.
 
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Old 01-12-17, 05:29 PM
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There will be an air handler in the basement, a closet or the attic. It's a big box. All metal. The refrigerant lines connect to it as the cold coil is inside of it. The duct work will also connect to it.

It usually has the air filter on the side of it which means that may be pretty dirty.

If you have a return vent in the second floor hallway..... the air handler would be directly above it.
 
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Old 01-12-17, 05:44 PM
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Ok so there is a Lennox G40UHX in the attic. I have some pictures but not sure where to look for transformer/fuse or anything of that nature. Not sure to tell if it has power.
 
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Old 01-12-17, 05:59 PM
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There will be two removable panels. The top one with the louvers is the burner panel. The one below or next to it is the blower panel. Remove the blower panel and the control board will be inside. Look for a 3A or 5A plastic automotive type fuse on it.

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If you haven't changed a filter in a while.... look around for it.

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Old 01-12-17, 06:12 PM
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Alright I found the main panel that pulls off (guess thats not the side I needed) Took a few pictures. The one with the control panel has a little window.. Shows no lights currently.

There is a plug that the whole thing is plugged into, looks like there is power there, and the lights in the attic work.

Is there anything I should be worried about w/ the system currently off? From looking it over sounds like it is gas powered.

Also someone said there should be a breaker or something for this, I am guessing its not labeled or the whole "bedroom" should have been shut off.
 
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Old 01-12-17, 06:13 PM
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It is gas powered. When you open the blower door.... power will be removed from unit.
There will not be a blinking light with a blown fuse.
 
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Old 01-12-17, 06:35 PM
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Ok found the fuse, pulled the fuse, and yep can see blown fuse. Need to get new fuse. Let panels off for now (best practice?). Till I get fuse, this one is a purple fuse with E on it, were can I pick them up?

Next question. Since I dont truely see a breaker for "HVAC" or heating at circuit board, should I power down the whole bedroom?

My breaker box is like
Bedroom 1
Bedroom 2
A/C
Washer
Dryer

And yea I got in way over my head for what I thought was simple.
 
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Old 01-12-17, 06:50 PM
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Just leaving the blower door off is ok.

That is an ATC-3 auto fuse. Available many places especially automotive stores.
Comes in a box of five so there will be spares.

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  #17  
Old 01-12-17, 09:24 PM
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That's not an E, it's a 3. As in 3 amp.
 
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Old 01-13-17, 03:04 PM
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Picked up the fuses, will put them in shortly. Ill cut power again to the A/C not sure if its needed. Anything else when putting in the new fuse?

So I talked to Nest again, and they will not tell me wire configuration cause its considered dual fuel..are they really that hard w/ dual fuel? As you can see from the above pictures thats with the old thermostat to the Carrier A/C and then Lennox Furnace, if anyone has inputs let me know or if its all a hassle I guess I could see how much it costs for a pro, figured since I am this deep in it.

Would never have thought you would pay 250$ for a product then have to pay between 100-300 for install (estimates on the nest site). That is crazy for everywhere i hear its like a 10 min install (mine certainly was not).

Nice thought the E was weird for an fuse, didnt even think in numbers.
 
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Old 01-13-17, 03:08 PM
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I don't think Nest supports duel fuel without an auxiliary control on the equipment.
Personally, as a tech, I don't recommend Nest. There are much better options from Honeywell for less money.
 
  #20  
Old 01-13-17, 03:09 PM
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k, I just happened to have 2 spare 2nd Gen Nests lying around. One seems to work the other might have a dead battery , thats why this whole thing started.
 
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Old 01-13-17, 03:38 PM
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Dave....

Have we confirmed that you do indeed have a heat pump. Your condensor pictures don't support any defrost items or control board. Can you post the model for the outside unit ?

I see you're in Ca. Do you get cold winters ? Can't see the need for heat pump with gas.

The problem with dual fuel is you must shut the heat pump off before starting the gas furnace. The furnace could easily overheat the heat pump causing permanent damage.

No need to shut off the outside unit. Put the fuse in. When you put the blower door back on the furnace will be powered again.

Keep an eye open up there for a replaceable filter. Could also be above grill in hallway.
 
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Old 01-13-17, 03:58 PM
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ill grab a picture in a minute. I dont know anything about a heat pump. Yea live in San Diego....its get cold here like 50's
 
  #23  
Old 01-13-17, 04:10 PM
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K This is the A/C Unit
Its a Carrier cant really see the model number on it though.

38HDR (Model)
 
  #24  
Old 01-13-17, 05:57 PM
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We're coming to the end of the road.

That is a group model number and it shows compact split units and heat pumps in that same package.

38HDR

Did your outside unit ever operate in the winter ?
 
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Old 01-13-17, 06:56 PM
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I think that I have used it to cool the house on some hot days during the summer.

just put the fuse back in btw, and it turned the thermostat back on. Was able to put the heat back on was getting a bit cold in the house (65).

I can turn the heat higher and see if the outside unit turns on right?
 
  #26  
Old 01-13-17, 07:51 PM
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I would doubt setting the heat higher would bring on the outside unit.

My guess is that you have a split A/C system with gas heat.
Not a dual fuel setup with heat pump and gas heat.

Keep an eye on the outside unit..... if you see it on with the furnace..... shut it down.
 
  #27  
Old 01-13-17, 08:05 PM
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I just talked to a neighbor who has the nest installed so at least I know that they are viable (live in a townhouse), so they are pretty much the same build. Everything is back to normal (honeywell thermostat).

Will do, yea I think out side is strictly for the A/C. Never really thought where the heat came from, just always assumed it was a dual a/c heater thing outside. Guess it helps to look around once in a while.

I am glad that it was just the fuse to get everything back and running. Everytime I hear HVAC i dredd some crazy expense (summer my A/C died, after talking to a few folks figured out the issue was the capcitor. Doing it myself probably saved a bunch)

And with everyones help here, probably saved myself again a bit for my own stupidy . Next time learn everything, or just cut power to the entire house
 
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