Academic Question

tried giving yo a greenie Charley bit I guess I can’t.

A very easy answer is that the manufacturer of the A/C says not to, while I have never seen such instructions in the freezer manual. I know that’s not the answer you’re looking for; I suspect you’re asking why the manufacturer says not to, and I’m sure some HVAC techs will tell us eventually.

By the way, I was at a monster mansion 10 days ago that had two 2006 cooling condensers installed, both by Carrier. I had the opportunity to browse the installation/user guides while I was waiting on some folks to show up. Interestingly, these two guides said not to operate the condensers if the outside temperature was 50°F or lower (note that it doesn’t say anything about “within the last 24 hours,” which has never been a recommendation by any manufacturer that I’ve been able to find in 30 years).

I’ve been using 65°F but I shall now have to reconsider that, or at least have a good written explanation about why I’m still using 65° instead of 50°F. I’m sure I can come up with something next time there’s a cooling condenser (I only see them at about 25% of my inspections) and it’s cold outside.

I thought that was what I did???

The major concern about an A/C unit in low ambient temps without crank case heaters is the fact that Freon Migrates to the coldest area of the system which happens to be the compressor where the oil is stored. When you start the compressor that has liquid freon mixed with the oil, the liquid freon can and will damage the valves in the compressor and will also cause the oil to pump out of the compressor. I can go on and on about this but am trying to keep it simple.

BTW refrigerators only have oz.s of freon V/S pounds in a A/C unit and do not have liquid migration as they are not a split system. There has to be two areas with different temps in order to have liquid migration.

I think you did. Unfortunately, that is what sometimes happens when one responds to the first post in a thread without reading all the other posts. It gets really bad when the thread gets to be 30 pages long. My apologies.

I like RR’s first answer:

A very easy answer is that the manufacturer of the A/C says not to.
Sounds like the answer I got from my Dad growing up. Because it says so. Or because I said so.

Try that answer on your next client that ask why you did not test the A/C:D

I knew better than to ask my Dad those three letters W-H-Y was very observant had 5 sisters and 2 older brothers that saw the back of his hand for that very reason. :shock:

yea i dont know what the hell i was talking about, i was talking to my brother at the time and he is going to school for refridgeration…sorry guys (im still learning, apparently he is too)

I have seen so many freezers outside like that, actually ive seen a few in the middle of a yard, but as long as the compressor and all isn’t bothered and protected from the elements it should be ok, right?

Adam: As long as you are willing to learn nothing wrong with that. As stated earlier in this thread you have no major concerns with liquid freon in the compressor on a free standing refrigerator compared to a split system A/C due to the ambient temp. Perhaps I can explain this differently. Take a warm home in the winter time at say 72 degrees and the outside ambient at 20 degrees. Freon in the lines and the A-Coil because of the 72 degrees is being pushed outside to the condenser which has lower pressure effecting the freon because of the 20 degrees outside ambient. This in reality is like overfilling a pot with water the liquid has to go somewhere and in the case of liquid freon it overflows into the compressor and with the freon being a different viscosity than the oil the freon lays on the top of the oil and if you start the compressor the liquid freon is discharged through the valves taking the oil with it. Compressors are designed to pump freon vapor not liquid.

With a refrigerator in a cold garage there is no major temp difference effecting the freon circuit and the total arrangement of the compressor, Evap, and condenser is arranged different than a A/C unit.

Also, freezers normally maintain about 0 degrees F, so if the garage temp is above 0, then the evaporator coil is still the coldest part of the system, just like in air conditioner on an 80 dgree day. If the garage temp is below 0, then the freezer thermostat will be satisfied without the compressor running at all.

Jim King

So what happens if you have the thing turned off during the winter, then on one of the coldest days, say around 0 degree (for whatever reason) you turn it on, even tho oil doesnt freeze it would have a different consistanty(right?) so at that point couldn’t the motor seize up like a car that hasn’t been cranked on in a while?

Sorry, I can’t answer tyhat one! The discussion is getting too “academic” for me now.

Jim King

LOL, what’s wrong with that? help a future brother HI out!!!

I would not have a problem restarting a refig at any temp within the garage no matter how long it had been off. The freon measures in Oz’s most all of the newer models have the condenser mounted in the bottom of the unit near the condenser fan motor. The compressor sets the same level or a little higher. There would not be enough liquid freon in the condenser in the idle mode to back up into the compressor. You should think of freon in its two states, liquid and vapor. I have observed in the past, people moving refrigerators and laying them down on their sides and then powering the unit right back up after they uprighted the unit this causes more damage than any thing else you can do as it allows the oil to move from the compressor. The unit should be stood upright for approximately 1 hour before applying power to allow the oil to drain back into the compressor.

  1. Refrigerator compressors are differant than A/C compressors.
    I will not go into this. They are piped differently internally.

  2. Refrigerant migration occurs in an A/C because the compressor is out in the cold and the house is warm. A reefer compressor is always on the warm side ,even if it is below zero in the garage. If it is 0 and it’s a refrigerator it won’t run anyway.

3.As Roy said, capacity suffers in the freezer when operated in low ambient conditions, but the load drops in the cold environment and it’s not noticed.

The condenser design in a reefer is not as efficient as an A/C’s and can tolerate low ambient conditions better. You can run an A/C in the winter if you modify the condenser system.

Russel, The Carrier unit claiming 50 degree limits is not about starting the unit in the winter. It is about system design. When the ambient goes below 50 (for that unit) the indoor coil will freeze (unless modified with a low ambient kit). I would not change your SOP.

Aren’t reefers very hot on one end and about 98.6°F on the other end? :margarit:

But there is a significant difference between 50°F and 65°F (and I know some inspectors use 60°F). Although I’m capable of talking or writing a very good answer to a Client who reads my disclaimer about not operating the compressor because it was 59°F outside, then reads the user guide on his brand new Carrier unit that says you can safely operate it down to 50°F outside, then asks me why I didn’t operate the unit since it was 59°F outisde, others might not be quite as good with words as am I.

I’m probably going to stay with 65°F but put in a disclaimer similiar to what I have for recessed lighting fixtures poking their rear ends up into the attic and covered with insulation.

Just depends on if it had been floating in a urinal;-)
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That is why I expounded on Charlies post. There are differant reasons for these temps.

If you called Carrier and asked if you could start their A/C in Bangor, ME today (@50 degrees) and it has been off all winter, with the power off, I think you may get a differant answer.

The 65 degrees is a made-up number. It has no specific significance. Nothing happens below 65 (like ice forming at 32F).

But then they may tell you to go ahead.
Their unit may have a scroll compressor that has no valves or crankshaft to be damaged. It will make one heck of a noise, but will not be damaged when oil gets in the head of the compressor.

Just stick with your SOP.
The reason for not inspecting is not the temp. It is your opinion (& sop) that damage may occur therefor you don’t have to. I do not stress “old equipment” in the winter, even though it is the equipment that needs to be tested the most.

Actually, it’s not my opinion. It’s the opinion of several manufacturers who, like Carrier, put the information in their User Guides. I’ve seen 65°F many times, never 60°F, and, now, 50°F once. As with everything I do, if it’s good enough for the manufacturer, it’s good enough for me, and if it’s not good enough for the manufacturer, then it’s not good enough for me. When I was setting up my company, my attorneys looked at industry-wide SOPS from CREIA, ASHI, NAHI, HIF, and FREA; legal statutes and case law which affect my business; and the 78 home inspection reports that I had in my possession at that time.

I do occasionally adjust my onw business SOP when new laws take affect, or new court cases create case law, or technology changes, etc. In this case, Carrier appears to have come up with some new technology that will cause me to rewrite my disclaimer when the temperature is colder than 65°F and there is a compressor present. Since 65°F is still the industry standard, I shall continue to use that, but caution requires that I take into account that at least one manufacturer is now using 50°F for at least one of its products, especially since I don’t know what all the other manufacturers are currently doing. New information should also give rise to new industry-wide SOPs when necessary; it might not be necessary at this point, but readers should be cautious nonetheless.

My Bad:twisted: Operated one today with a outside ambient 48 degrees;) I have observed outside ambient at 65 degrees in the middle of August:shock: Lordy mercy what do I do then???

I haven’t read any manufacturer’s directions that include the month, just the temperature. :margarit: