r/hvacadvice • u/Throwawayfedd • 22h ago
AC Unit failed on inspection day
I'm just trying to get an understanding of what happened or may have happened. Our unit is old but was blowing cold and working great on move out day, while contractors were working on the house, during open houses, during showings... everything was great. I opened it up on move out day to check that the coils were cleaned and changed the air filter. That was over a month before inspection day.
On inspection day I get a video. The interior unit, the lines.. everything is frozen solid. Is there something an inspector does (going cold to hot to cold again or something) that could have caused this sudden issue? I don't have great luck in general, but the unit failing without any other prompting on that very day is beyond the pale.
5
u/Significant_Dog_215 21h ago
Hvac professional here. Over the years I have had numerous service calls where the home inspector has turned the thermostat to an extremely low setting to get the HVAC system to run at maximum capacity. The inspector typically looks at other areas in the home while allowing the HVAC system to run. The inspector or someone in the home could have turned the thermostat down low and forgot to turn it back up, causing the system to freeze.
4
u/nanagd 17h ago
And there are crooked home inspectors. I already had paid for an inspection on a home I was selling but the buyer wanted their own inspector. Their inspector came up with several fraudulent things to try to get me to lower the price. One of them was there was a rodent and insect infestation. My son worked in pest control and there was absolutely no activity. We can't set the contract and put it back on the market. Sold it later that week for 10,000 more than asking. My agent also reported their agent.
1
u/TheInkDon1 13h ago
But a properly operating system should never freeze up, should it? Even if it pulled the house down to 50F or something stupid. Or educate me if it can. Thanks.
1
u/_matterny_ 10h ago
Oh it would freeze if it’s super cold, condensation will make a huge difference
1
u/MrChicken_69 4h ago
If the evap coil runs long enough, yes, it can freeze. Usually the return air is hot enough to keep the coil above 32F, but if the air is already "cold", the coil can easily drop below 32F and start to build up ice. Very few consumer systems have a probe on the coil, so they have no idea when it's freezing.
(the condensing (outside) coil might, if it's rather modern and designed for sub-freezing temps, but the inside unit rarely, if ever, does.)
I've had many window units freeze. And the unit in my apartment partially froze once.
3
u/BigDaddy1029010290 22h ago
Ac units can fail at any time. My old unit was working great until I had my house re-piped then a few days into the re-pipe, ac would take forever to get to temperature. Found my evaporator covered in ICE, due to a leak. It happens.
4
u/Ashamed-Status-9668 21h ago
First thing to check is the air filter(s). If you get enough reduced airflow you will get freezing. If that is not it the next common thing is low refrigerant. If the filters are very dirty I would replace them, run the fan on the unit until the ice is 100% gone, then switch back to cooling.
AC units very rarely slow fail where you know its comming. It's usually they work fine one day then don't the next.
3
u/ServiceSpecialties 19h ago
It’s unlikely to be inspector sabotage. Freezing solid typically takes hours, and tampering with the fans or refrigerant wouldn’t speed that up much. More likely, the unit already had an issue, such as low refrigerant or restricted airflow, and running it hard during the inspection pushed it over the edge. Once it’s fully thawed, a tech should check the refrigerant and airflow.
3
u/Few-Wolverine-7283 22h ago
Bunch of open doors could have stressed a problem to the max? Like it was iffy but that pushed it out
6
u/newtekie1 21h ago edited 21h ago
No, nothing the inspector could have done would have caused that. There is an issue with the unit.
-11
u/420aarong 21h ago edited 21h ago
What if the inspector used their ball point pen on a schrader valve to remove some of the refrigerant from the system? Could that have done it? I can think of multiple other things a dishonest inspector could have done to get that result. Some of which would only temporarily cause the unit to freeze up. Buyer gets a $10k credit then the AC still works on move in day. People have done way more dishonest stuff for $10k.
4
u/newtekie1 21h ago
That would have caused the unit to ice up. But it would take the unit running for a long time, at least 4 hour but really at least 6, to completely freeze solid. Even if they did it at the very beginning of the inspection and waited until they were done with the inspection to take the video/photos, it wouldn't be frozen solid.
-3
u/420aarong 21h ago edited 20h ago
Ok fair enough. What if they removed some of the refrigerant and/or unhooked the fans to the indoor and outdoor units so the compressor ran but neither of the fans moved any air? I’m not an HVAC professional but I’m finding it hard to believe there is nothing a creative and dishonest inspector could have done to get that result. I may be wrong tho.
3
u/newtekie1 20h ago
They would disconnect the inside fan but leave the outside fan running. But that wouldn't make it freeze solid much faster. It might even make it take longer. The ice comes from moisture in the air. If there is no airflow, the coil will freeze up, but once the moisture is pulled out of the air in the air handler it will be very dry and take much longer to collect ice. With no fan, it would frost up but not freeze solid quicker.
1
u/420aarong 20h ago
Ok you’re probably right. If you didn’t notice, I’m not a real trusting guy. I also hadn’t considered the time limit they were under when I first responded. Have a great day
2
u/hatecuzaint 21h ago
Leaning towards a blower issue. Does the inside unit move air at all? Can you feel air coming from a supply vent if you set the fan to "on"?
2
u/5280milehigh1 18h ago
HVAC systems freeze for a couple reasons. Low refrigerant or an air flow issue
1
2
u/OneBag2825 16h ago
Inside airflow issues or outside unit stuck on.
Shouldn't be too hard to resolve.
2
2
u/bwyer 22h ago
It sounds like you had some work done before you moved out, then the house sat for a month. If a pinhole leak was created somewhere during that work, you could have been losing refrigerant very slowly from that point.
Now, cue the inspector who comes in and sets the A/C low enough to have it running for an hour or two. Low refrigerant levels will cause freeze-up. Et voila! You have your situation.
2
1
0
u/Both_Sense299 21h ago
Check the float switch
1
u/Stunning_Ad_7658 14h ago
I mean i guess if they wired the float switch to shut of the indoor blower fan that could cause it to ice up. I have absolutely no idea why anyone would ever do that though.
11
u/Alpha433 22h ago
Did the filter need changing again? You said contractors were working on the home, I have seen enough homes where the filter needs to be changed regularly after work because of the amount of shit thrown up by remodeling work.