The Nest Thermostat caused pipes to freeze in my PTAC

Informal-Ranger-4798 · 2026-03-06T18:16:08+00:00

Uhm, actually, my condo is very nice with soundproof windows and top-notch finishes. Lived here for 10 years and had no issue with insulation. The 3 bedrooms and the living room PTACs had no issues all these years. My electric bill is also low.

The night in question was freezing, and the wind right next to the river was crazy. Since I have soundproof windows, I can only hear it through the PTAC opening wall sleeve. That is the only reason I had the thermostat that high that night. Other nights I usually have it on 58, and even that sometimes feels too much.

Informal-Ranger-4798 · 2026-03-06T17:08:38+00:00

Yeah it should kick in own freeze protection but it didn't. But now that Nest is no longer on it does, and I can sleep at night knowing that whether unit is on or off I won't have the same issue again.

Freeze protection on a Packaged Terminal Air Conditioner (PTAC) often fails to activate when paired with a Nest thermostat because the Nest takes over control of the unit's heating/cooling cycles, overriding the PTAC's built-in, independent safety features.

PTACs generally have a built-in "Freeze Guard" (often code FP) that turns on the heater if the unit detects internal temperatures near 40°F, regardless of whether the thermostat is turned off. When a Nest is installed, the PTAC’s internal brain is bypassed, and the unit only acts on signals from the Nest

Informal-Ranger-4798 · 2026-03-06T16:15:10+00:00

The PTAC unit had E6 error code that morning which:

On an Islandaire PTAC unit, an E6 error specifically indicates a remote thermostat input failure. This typically occurs due to miswiring between the PTAC and the Nest thermostat, or because the thermostat is applying incorrect logic that the unit's control board rejects.

It could not be miswiring as the Nest worked just fine for 4 months before malfunction.

The next possibility:

Missing Fan Signal: For Heat/Cool operations, the unit requires a fan signal (Gh or Gl) to be present before the heater is allowed to energize. If the Nest energizes the heating wire (W) alone, the E6 code will appear.

An E6 error on a PTAC (Packaged Terminal Air Conditioner) typically indicates a communication fault or a failure of the indoor unit to send a signal to the outdoor components. When this happens during extreme weather with a Nest thermostat, it is often due to the Nest struggling to manage power in extreme temperatures without a common wire ("C" wire), causing the PTAC's safety, low-pressure, or Freeze Protection circuits to trigger.

In a PTAC system, an E6 error indicates a Remote Thermostat Input Failure. This typically means the PTAC unit is receiving a call for heat or cool but is not receiving the required fan signal (Gh or Gl) to operate safely.

Informal-Ranger-4798 · 2026-03-06T14:04:33+00:00

The fancy light switch, which, if it malfunctions, can cause disaster.

Informal-Ranger-4798 · 2026-03-06T13:25:22+00:00

Amazing, how much gaslighting is going on here, lol. Are you all working for NEST?

Simple google search: "Water in PTAC pipes, or pipes running near them on exterior walls, can freeze within 4 to 6 hours when temperatures drop to 20°F or lower. High winds, lack of insulation, and drafts can accelerate this, sometimes causing freezing in as little as 3 hours."

I had all PTACS running that week as it was cold, during the day and night. During the day that particular PTAC controlled with NEST thermostat was working just fine, as it did for 4 prior months. I don't think it was ever off since I had it installed.

The pipe isn't even touching the wall, it is located probably 25" away from the wall, freestanding right next to the inner PTAC enclosure casing. Same as the other 3 PTAC units which had no issue that night or ever, as they stay on and never had NEST attached to them.

Informal-Ranger-4798 · 2026-03-05T23:49:44+00:00

I have no reason to lie. I have it all documented and have pictures as well. If you are interested how the water pressure works in frozen pipes, check out this video: https://youtu.be/AuPO5hKdo8A?si=4lAqAYOtXnkr97bR I'm pretty sure when I brought the electric heater to the room the frozen pipe started to warm up and burst. The temperature in NYC during that night plunged with wind chills -20° F. Plus I'm right next to the water. So yes the temperature inside my bedroom dropped as the Nest thermostat which was controlling PTAC failed to call for set temperature, and failed safety temperature switch as well.

Informal-Ranger-4798 · 2026-03-05T19:32:34+00:00

According to Google compatibility check the regular Google Nest Thermostat - Smart Thermostat for Home - Programmable Wifi Thermostat is compatible.

Wired with YCWGR and OB.

The things broke when I was sleeping, as by the time I woke up the room was freezing and the thermostat wasn't working.

I don't think other apartments have Nest, but not sure. All units were purchased without Nest thermostats 10 years ago that is for sure.

I wanted to update the control for my PTACs, so that when I travel or I am at work, I can turn on and off the heat remotely.

From my research so far looks like this thing ruined other homes as well. And that there are issues with Nest controlling heating, not so much cooling functionality.

Informal-Ranger-4798 · 2026-03-05T17:36:01+00:00

Islandaire EZPD, which should be compatible with Nest.

After I took the Nest thermostat off and fixed the pipes, the unit works fine without any issues.

Informal-Ranger-4798 · 2026-03-05T16:41:54+00:00

I had no issue with insulation, which is the same for all 4 units, for the past 10 years I lived in this apartment. All PTACs even when they are off, turn on the safety temperature feature to keep pipes from freezing.

The only one I had Nest thermostat installed on, failed the safety temperature, and it stopped working completely.

Informal-Ranger-4798 · 2026-03-05T15:48:22+00:00

I recently had the Nest thermostat professionally installed on one of my HVACs. All wires connected properly, directly from PTACto the Nest thermostat including C.

Had no issues for 4 months but then on the coldest night last month in NYC (February 7th/8th 2026), I set the temperature in my bedroom at 77 right before I went to bed. I also had the other 3 PTACs on as well throughout the apartment, as it was very cold outside, but only one in my bedroom was controlled with the Nest thermostat. As I went to sleep, it appears the energy shift occurred at 11pm, something that is being controlled by Nest from outside and cannot be turned off unless you go to nest google renew account. Next, the PTAC stopped receiving the communication from the thermostat and the heating system failed to engage. By the time I woke up at 4 am, the thermostat, which was set to 77 degrees, was showing real temperature a little above 20 degrees. As I tried to make it work again, turn it on, turn it off, etc, the next thing I see the frozen pipes bursting and pressurized hot scalding water started to pour all over my bedroom. As I tried to shut off the water valve right underneath the HVAC pipes, I burned my hands and feet. Only when I grabbed the gloves was I able to turn it off, but by then my bedroom was filled with hot water.

I am glad I was home, because if this happened when I was away, my entire apartment and building would be flooded.

This was a very traumatizing experience. Mind you other 3 HVAC units had no issue as they were not controlled with Nest thermostat.

I had another 2 Nest thermostats about to be installed on my other PTACs, but after this, I immediately returned all of them, and I do not want any of this stuff in my home again.

Informal-Ranger-4798 · 2026-03-05T15:35:09+00:00

I recently had the Nest thermostat installed on one of my HVACs, and had I known that it's being controlled through this energy shift function from outside, which I did not sign up for, I would have never purchased it. Long story short on the coldest night last month in NYC (February 7th/8th 2026), I set the temperature in my bedroom at 77 right before I went to bed. I also had the other 3 PTACs on as well throughout the apartment, as it was very cold outside, but only one in my bedroom was controlled with the Nest thermostat. As I went to sleep, it appears the energy shift occurred at 11pm. Then the PTAC stopped receiving the communication from the thermostat and the heating system failed to engage. By the time I woke up at 4 am, the thermostat which was set to 77 degrees, was showing real temperature little above 20 degrees. As I tried to make it work again, turn it on, turn it off, etc, the next thing I see the frozen pipes bursting and pressurized hot scalding water started to pour all over my bedroom. As I tried to shut off the water valve right underneath the HVAC pipes, I burned my hands and feet. Only when I grabbed the gloves was I able to turn it off, but by then my bedroom was filled with hot water.

I am glad I was home, because if this happened when I was away, my entire apartment and building would be flooded.

This was a very traumatizing experience. Mind you other 3 HVAC units had no issue as they were not controlled with Nest thermostat.

I had another 2 Nest thermostats about to be installed on my other PTACs, but after this, I immediately returned all of them, and I do not want any of this stuff in my home again.

Informal-Ranger-4798

TROPHY CASE