Problem with communicating AC

2 years ago

last modified: 2 years ago

I recently had a whole house generator installed at my house. Right after it was installed, my Ruud communicating AC system was showing an error on the thermostat, "Call for Service". When I clicked through for more details, it just said call for service with no indication of what was wrong. The AC appeared to be running totally fine - it was hot outside and the house was staying totally cool. I called the generator installation company and they told me they didn't know anything about it and that I should call an AC repair company.

I called a local AC company that has a good reputation. The technician seemed very inexperienced and was struggling to figure out what was going on and was constantly on the phone with "lead" technicians, asking for help. He said he checked the error codes on the condenser unit and it indicated that the run capacitor was bad. He removed the run cap and tested it and said he confirmed it was bad (the reading was a low number), and he then installed a new run cap. This seemed to fix the error on the thermostat screen but then the blower wasn't coming on and he concluded I have a bad blower. He said I needed a new blower for $1200. As we were doing the paperwork, the blower came on. I told him I wanted to hold off on replacing the blower since the blower was running and it seemed to be working fine before he got there (except for an error notice on the thermostat).

Soon after he left the unit was having a new problem - communication problems appearing on the thermostat screen. It was randomly showing a screen saying "Air Conditioner Found" and then "Air Handler Found" and "Searching". And then it would show a screen saying "Communication Error". And then shortly after that the screen of the thermostat would look totally normal like nothing was wrong, and the unit would run fine. And this communication searching would just keep repeating every hour or so. But the AC was working and the house was cool (I live in Miami where it's still hot during the day).

Now, a day later, there is a burnt smell in my house. The AC unit is not coming on. The air handler appears to be trying to come on (it's vibrating at times) but the condenser unit outside is not coming on. The communication is re-setting almost constantly, saying "Air Conditioner Found" and then "Air Handler Found" and "Searching". Then the thermostat looks normal for a short time, and then starts searching again. Could communication re-setting problems and burnt smell be caused by a bad blower? Is it possible that the technician who installed the new run cap broke something by installing the wrong run cap? Would an incorrect run cap cause communication problems and ultimately lead to a burning smell and the system failing to run?

Thanks!

Featured Answer

HU-867564120

2 years ago

Re: Could communication re-setting problems and burnt smell be caused by a bad blower? Is it possible that the technician who installed the new run cap broke something by installing the wrong run cap? Would an incorrect run cap cause communication problems and ultimately lead to a burning smell and the system failing to run?

IMO, no, no, and no.

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Comments (8)

sktn77a
2 years ago
It sounds like the generator install has caused a problem with the HVAC circuitry that you "tech" is unable to diagnose. Disconnect the generator from your home grid and see if anything changes. If is doesn't, leave the generator disconnected and get the HVAC fixed.

Then start all over again!
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Austin Air Companie
2 years ago
last modified: 2 years ago
I recently had a whole house generator installed at my house. Right after it was installed, my Ruud communicating AC system was showing an error on the thermostat, "Call for Service".

But you don't mention how old this Ruud communicating AC system is?

This may just be a freak coincidence / or the new generator may be interferring in some way. Communicating systems operation depend on good connections from communicating thermostat to furnace to outdoor AC unit. Probably just as bad or worse would be to use a nest thermostat on a traditional system... well unless you're trying to generate more work for your company a few years later..lol. What do you mean my nest is bad it's practically brand new?

It sounds like the AC system is old enough to have a defective run cap... at least 3 to 5 years old or older. Less than 3 years? power surge problems would be my guess.

The furnace blower to this machine is likely ECM or variable speed DC inverted motor. The generator *may* have inadvertently caused power surge at your home. That said... even without a home generator you could suffer a power surge. So trying to blame that on a generator install would be quite pointless. Power surges are known for shorting run caps, there's other reasons they fail too.

I've never seen a ECM or variable speed DC inverted motor spring back to life after being declared broken, so either this is due to communication problem or? Is merely speculation, I wasn't there. The burning smell if I had to guess came from said blower motor. (whatever it is ECM or varible speed) -- if that happened after? likely internal problem of blower motor, possibly brought on by power surges.

If your communicating system is taking on inference you may need shielded thermostat cable run from thermostat to furnace to condenser if this wasn't done at time of install. That may not be necessary, as the age of the system "may be" contributing to this communication problem.

Finding out a solution to this & other problems really comes down to the skill of the tech.

I service the Katy, Texas area.
mike_home
2 years ago
Does the whole house generator power every circuit in the house including the furnace and AC condenser? If it does not then that would eliminate the generator as the initial cause of the problem. You need an over sized generator to start up an AC condenser and for this reason in most cases the HVAC system is excluded from the generator transfer switch.
Greg
Original Author
2 years ago
last modified: 2 years ago
It's a whole house generator. It's supposed to be big enough to power everything. Not necessarily everything in the entire house at once but it is supposed to work for typical use, and it's supposed to power the AC/condenser. An AC technician came yesterday and said definitively either the thermostat is bad or there is a problem related to the generator installation. The electrician from the generator company had come the day before and checked everything and said everything was perfect. The AC technician said that if a new thermostat doesn't fix the issue, then it's certainly the generator installation causing the problem and, in that case, the control module is the problem, or there is a problem with the high voltage wiring, or they must have messed up the the low voltage wiring related to the AC such as by mixing up wires. Does that make sense?
PRO
Austin Air Companie
2 years ago
An AC technician came yesterday and said definitively either the thermostat is bad or there is a problem related to the generator installation. The electrician from the generator company had come the day before and checked everything and said everything was perfect. The AC technician said that if a new thermostat doesn't fix the issue, then it's certainly the generator installation causing the problem and, in that case, the control module is the problem, or there is a problem with the high voltage wiring, or they must have messed up the the low voltage wiring related to the AC such as by mixing up wires. Does that make sense?

Not really, first you say the unit was having communication error, then the blower was not working, then the blower fired off, then you smelled a burning smell?

Now you say they say it's the thermostat, or it's certainly the generator, how about the control module yeah that could be it. OR there's a problem with high voltage wiring... or they must have messed up the low volt wiring by mixing up wires?

So is the blower working now? The burnt smell what happened with that?

How does someone mix up wires unrelated to what they are trying to do? Does that make sense?

The definition of a "parts changer" is what? It's not that part so it "must be" this part. Maybe they get lucky and figure it out that way? Let us know if they do...

Could it be the thermostat: yes, but that doesn't mean it will be. The thermostat is only one such piece in the network of a communicating system, if the problem is elsewhere? Oh well the thermostat needed to be replaced anyway? maybe, maybe not. How old is the system you still haven't said?

Manufacturers in all their wisdom make these machines that point to problems give clues as to what is wrong, but you still need to "know" how to diagnose a system without these clues. Obviously it sounds to me, that is not the case with whom you've chosen for service.
mike_home
2 years ago
It is possible it is a communicating thermostat failure. However the problems started to occur after the generator was installed and now you smell something burning. Do you know if the electrician tested the generator when it transfer switch was flipped to run the house? Was the AC running when the he did this test?

HVAC techs are not equipped to troubleshoot thermostat communication problems. They would need an oscilloscope to check signal levels. It would be easy to install a new thermostat, but they are expensive. You should ask if you are going to be charged for the new thermostat if it does not resolve the problem.

You should also request a senior tech come to your house. The guy coming up with possible causes does not seem to understand basic electrical wiring in my opinion.
HU-336800582
2 years ago
How old is your system and is it still under warranty (usually 10 years for parts 1 for labor)

I had a similar experience I got an Echo Bee and installed it myself have had great experience with that.

My issue was that FPL has a system that causes really fast brown outs, this is to prevent extended power outages which can be good, however A/C compressors are not designed to turn off and on really fast. They needed 5 minutes minimum if the power went off.

I got an addon for my compressor that forces it to stay off the allotted time if it loses power. and the Echo Bee has a minimum time off setting that you can use to do that as well.

Problem with communicating AC

HU-867564120

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sktn77a

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Problem with communicating AC

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sktn77a

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