All:

Here is a link to some wiring pictures that may help https://goo.gl/photos/KH7j8srZ2TCGc1u6A

By way of background, I installed an Ecobee3 smart thermostat about three months ago on an older heat pump system (1 stage, with aux heat). The ecobee worked great and I loved it.

Yesterday, I had to have my entire system replaced with (what I was told) was a virtually identical heatpump setup, just 15+ years newer. When we turned the power to the thermostat back on, it would boot up, and then the main screen would say that it was 'calibrating - heat-cool disabled'. According to Ecobee support, this was normal. However, as soon as the Ecobee finished calibrating and tried to call for A/C (whether on its own, or if I force tested the equipment in test mode, which I did several times as a test), the entire thermostat would reboot / reset and start the process over.

The installation contractor said they did not change any of the wiring at the furnace / air handler (i.e., they just set it up the same way it was before), and none of the wires were changed at the Ecobee. So the Ecobee went from working with an apparently identical setup yesterday to rebooting every time the system turned on.

As a temporary solution, I reinstalled our old, but still digital, carrier programmable thermostat that works on similar wiring (requires C, etc.) Oddly, this seems to work perfectly. The A/C turns on when called and the system does not reboot.

The two best clues seem to be (a) the older programmable still works, and (b) the ecobee was working fine with an identical setup as of yesterday. This leads me to believe its not a voltage issue or short, but perhaps something got messed up at the furnace level wires.

Any help would be appreciated. Pictures here: https://goo.gl/photos/KH7j8srZ2TCGc1u6A

 

I would fix the red wire connection at the air handler. I would also check for similar poor connections at the heat pump outside.

It is possible that the newer Ecobee is picking up a short the the older stat didn't.

I have seen this problem when replacing older Carrier equipment with new Carrier Infinity equipment. 2 million Ohms wasn't an issue with the older control but the Infinity control would pick up an error.

 

Thanks!

Do you see a problem with the red wire specifically at the air handler in one of the pictures? I am new to this, so I may need a bit more info than the next guy.

 

It almost sounds like an undersized 24vac transformer.

Do you have a voltmeter ?
Check the 24vac from the red wire to the blue wire with the system in heat mode, off and in A/C mode.

 

The red wire connection that PJ has pointed to looks bad.

I am sure that it is a 40 VA transformer.

 

I do have a voltometer, buy I am not very experienced using it. Do I just take off the wire nuts and then touch one lead to each set of wires and then record the values? The power should be on while I do this I take it?

 

I guess I should start by fixing the red wire connection. Do I just need to make the wires are in the wire nut all the way?

 

The wire nut grabs the tips of the wires.
Remove the wire nut and make sure that the ends of each wire are even.

Orange wire nuts would have been better.

 

OK, I'll give that a try and then try switching back the Ecobee. It may need to be later today, but I will try to post back soon. Thanks for the help!

 

I would see if similar poor connections have been made outside.

 

You can make the voltage checks with your current thermostat.

 

OK, so take the wire nuts off, leave the system on and do the voltage checks, then replace the connections with large wire nuts or push wire connectors, then try switching to the ecobee?

What am I looking for on the voltage readings?

 

Set your meter to the next scale over 24vac.

With thermostat set to OFF..... no heat or A/C what is the voltage ? Should be +/-24vac.
With thermostat set to HEAT... what is the voltage ? Should be +/-24vac.
With thermostat set to COOL.... what is the voltage ? Should be +/-24vac.

See a pattern forming. We are looking for a power drop or loss.

 

Got it, I'll try to post results in the morning

 

Ok, I replaced the two connections with push connectors. That made the voltage testing easy. Results:

Cool: 24.85
Heat: 25.75
Off: 25.45

Does that make sense? If that's normal, I may give the ecobee another shot.

 

Those voltages appear normal.
There is no unacceptable load shown which means the Ecobee stat should work.

When you connect the thermostat..... the voltages at that end should match what you measured above.

 

28 volts would have been better.

Some houses only have 208 volts to them. A wire on the transformer should be moved from the terminal labeled 240 to the terminal labeled 208 when this is the case.

(Though I usually see 22 volts when this is the case)



Have you ever measured line voltage to this or the outdoor unit?

 

So I tried the ecobee again with no luck and the same problems. I was getting the same 25.75 volts at the thermostat as the air handler.

I put the old thermostat back on and it's fine again.

I can't really access our condensor since it's on the roof of our condo building.... I would probably have to get the company back out for that.

Any other ideas?

 

I just got a Refurb unit and will try to install next week after I'm back from vacation. I'll let you know if that solves it. I have a newer furnace fwiw.

 

SOLVED

The new replacement Ecobee3 is up and running. If nothing else works, try RMA.