No power to thermostat after power outage

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  #1  
Old 06-05-19, 07:25 PM
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No power to thermostat after power outage

Hello, so we had a power outage for about 1 hour due to a storm and after power was restored, I noticed both thermostats (up and downstairs) had no power, blank display.
Our house was new construction roughly 2 years old. There's a Goodman air handler outside and furnace inside.

Here's the checks I've done:
1. Circuit breaker, everything is "ON" and I flipped the switches for AC and furnace to Off then On again. Nothing was tripped.
2. Checked all GFCI in house, none of them was tripped.
3. One of the thermostat takes backup batteries, so I put new batteries in. Display was back but I knew it probably still won't work, and it didn't. Set to Cool and lowered temperature, nothing happened to the AC unit outside. I set it to Off then.
4. Checked the AC unit power box outside (the one attached to the siding), there's no fuse in it. I pulled the switch and put it back to reset it. Didn't really help.
5. Checked the drain pan in attic and it was completely dry.

I'd appreciate any help. The system is relatively new so hopefully it's nothing major?


Thanks in advance!
 
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  #2  
Old 06-05-19, 09:35 PM
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Welcome to the forums.

Unclear what you have. Two thermostats for two furnaces with split A/C systems ?
Two thermostats for one furnace with split A/C and some type of zoning system ?

Hard to help without knowing exactly what you have. Pictures are always a big help.
How-to-insert-pictures.
 
  #3  
Old 06-06-19, 04:08 AM
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Thank you Pete.

I think it's two thermostats for one furnace and one controls downstairs and one for upstairs. So i think it's some type of zoning system.
I'm a newbie to AC systems so hopefully I got it correct.

What pictures should I take?
I did more research online and someone mentioned a fuse inside the air handler, I will check that as well shortly.
 
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Old 06-06-19, 05:04 AM
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Update:
Checked the fuse in air handler, appears to be OK.
Opened up the AC unit outside and everything look normal. With power connected, I carefully pushed the "switch" thing in with a screwdriver (saw this from one of the youtube videos) and the AC unit started right up.

So something is not working between the control board in air handler and the thermostats?

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Last edited by PJmax; 06-06-19 at 07:01 PM. Reason: resized used pictures/added labeling
  #5  
Old 06-06-19, 06:03 AM
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Update:

I went up to the attic again to test the fuse with a multimeter and it is not blown.

The control board in air handler has a constant red led when power is turned on - google told me that it means the control board is getting power and operating?

I'm really lost what else could be the problem then? And is caused by simply a power outage?
 
  #6  
Old 06-06-19, 07:46 AM
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Update:

Checked the zoning control unit, HoneyWell HZ311. None of the lights was on even though the furnace is on and the control board has constant led.
27V between R&W, R&G, R&Y on the EQUIPMENT section - i guess this means power is coming to the HZ311?

0 between R&C, W, Y or G on the THERMOSTAT sections.

Do I need to replace this HZ311 panel?
 
  #7  
Old 06-06-19, 06:08 PM
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Usually there is a separate transformer running the zone panel. It connects as shown in the picture below. You may have to follow the wires from R and C to find it.

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  #8  
Old 06-06-19, 06:37 PM
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I do see them going way beyond the furnace where the attic floor is filled with the white insulation stuff...
If I remember correctly, there's no reading when I checked between this R&C. Only reading was from the EQUIPMENT's R and W/G/Y.

I guess I could try to trace it, if so, what should I be looking for?
So it could be that the transformer is bad, not necessarily this control panel?

Hmm, wait is it the one inside the air handler's bottom compartment (in the picture I attached)?

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Last edited by PJmax; 06-06-19 at 07:04 PM. Reason: resized picture
  #9  
Old 06-06-19, 06:55 PM
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Bingo. You have located the wayward transformer.
Check it at the transformer. If no voltage.... the transformer is fried.
 
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Old 06-06-19, 07:00 PM
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Thanks! So basically get a voltage reading between the 2 terminals shown in the pic (facing outwards), with the power ON I assume and do I need to "close" the security switch on the left while doing this?
 
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Old 06-06-19, 07:04 PM
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Yes.... the safety switch must be held/taped in.
 
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Old 06-06-19, 07:34 PM
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Just checked. 27 V from the transformer.

I also found another one behind it, and that measured 27V as well...
I double checked the POWER's R&C terminal and there's no reading at all when power ON and the air handler's door put back.
 
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Old 06-06-19, 08:17 PM
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Then you need to trace the wire from the transformer you circled to the zone board.
You may have an A/C float switch for overflow protection. That could possibly be inline and tripped.
 
  #14  
Old 06-06-19, 08:27 PM
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Hmm, let me go up there and check tomorrow morning.. There is a pvc looking thing with text safe-t-switch or something like that.

OMG yes I unplugged it and put it back in and now it's ON!
So there is a little bit of water in there, not too much but definitely there's water, should I do something about it?
 
  #15  
Old 06-07-19, 09:37 PM
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Sometimes when tripped from high water they get stuck. The key words here are "high water".
You need to check and clean your primary drain as it has backed up enough to trigger that float.
 
  #16  
Old 06-08-19, 04:17 PM
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Will do.
although isn't it too coincidental that this happens at power outage? It appears to be working fine all along...
 
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