[engi_nerd]

Nest pretty much says that you and I were doing it wrong.

It worked just fine for heat -- although I later found out that every time it turned on my heat pump it was activating the emergency heat. I tried finding a way to get the unit to be okay with ramping up the temperature over a longer period of time, but that setting was not exposed in their UI. All I wanted was to say "I don't really care what temperature the house is while I'm gone so long as it never goes below 55F or above 80F, but I want you to make sure that when I arrive home at 6PM the temperature has reached the point I set". But...alas, the unit never figured that out. The "learning mode" never actually did anything, no matter what I tried.

Fortunately I was able to get a full refund on the devices from Amazon.

[ckinnan]

We had the same issue last year (professional install), and spent a lot of time working with Nest troubleshooting two different units. Nest either had a mystery incompatibility with a brand new Goodman HVAC or a dirty electrical current was frying the circuit on the Nest. We had to get a dumb thermostat instead, it works fine. :(

[ashark]

I used to own a house equipped with a heat pump, and in heating mode the cheap-o thermostat would display "e heat". Maybe it's just common to use the same control circuit for that, that might otherwise be used for some sort of actual emergency heating device?

It just said "heat" when the furnace was on.

[engi_nerd]

You have a point -- I don't know for sure, but my extremely high electricity bills (even during two relatively mild months) are my reason for believing that the Nest was activating the emergency heat.

EDIT: corrected that whole last sentence. It made no sense.

[ckinnan]

We had the same issue and had a pro service call, in our situation the Nest was calling for emergency heat.

[engi_nerd]

I wasn't willing to pay more money for a professional service call. I was hot and angry and frustrated. I de-installed the units and hooked up the old Honeywells.

[maxerickson]

e-heat is the manual override to use the resistance heater in the heat pump (it also disables the heat pump part of the heat pump). It shouldn't normally be triggered.

I don't know anything about nest, maybe it displays that in other situations.

[maxerickson]

Did your nest ever properly call for cooling?

[engi_nerd]

No. The unit saw that it was not reaching its setpoint, so it kept trying to reach the setpoint. But there is apparently no feedback from this.

Instead of A/C, the unit activated heating. So the temperature kept rising even further beyond the setpoint. So, more heat.

Positive feedback -- exactly what I didn't want.

[maxerickson]

I can see both sides of including detection of improper wiring in the software. It's a nice feature when it works right. On the other hand, it's something new to go wrong that is only helpful in one specific case (that you would rather prevent using some other method).

(I'm presuming enough QC in the manufacturing that improper wiring is the most common trigger of positive feedback)

Have you gone far enough into it to compare how the wires are hooked up on the heat pump side to the nest diagram? Not trying to heckle you about it, it's a puzzle, it must be solved.

[engi_nerd]

"it's a puzzle, it must be solved."

I agree with you. I love solving puzzles, that's why I'm an engineer. But I had to balance solving this puzzle with the ongoing puzzle of maintaining domestic harmony. My then-pregnant-wife insisted I get the system working properly ASAP. The best way to do that was to reinstall the Honeywell -- the system worked properly within 15 minutes. As life circumstances dictated that I was away from home for most of the time -- and we moved a couple of months later, the best solution was to get a refund.

Did I have some wiring wrong? Most likely.

Not to beat my credentials against my chest, or to imply that they mean that I could not have possibly made an error... I have engineering degrees and have done a lot of instrumentation system design work. Figuring out how to wire up strange sensors to an existing system is something I do all the time. If I had this kind of difficulty, what kinds of problems are ordinary people having? Or maybe it just reinforces the aircraft industry joke that "you shouldn't let engineers touch tools, they'll break something".

[maxerickson]

Other people are posting about problems with professional installs on heat pump systems. The two more likely explanations of that are faulty nests and wiring problems. If it's wiring problems, it suggests there may be something that is easy to overlook or misunderstand.