Cold box window A/C not blowing cold air anymore!?

Old 04-24-19, 11:24 PM
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Question Cold box window A/C not blowing cold air anymore!?

Hi all,

I built a cold box in my garage, in the summer of 2017, for winemaking.

I'm using this Ink-Bird temp controller:

With this window A/C:

I went with this set up so that during crush, I can get the window A/C to cool the box down to 50 F. And, it worked just fine for 2017 and 2018. I didn't want to shell out the ~$350 for a coolbot.

Today was the first day of the 2019 warmer season (northern CA) I was going to use the A/C to keep the box cool. The filter on the front of the A/C unit (which is in the interior of the cold box) is clean. There is no water dripping from the unit. There is no ice. The fan is set to Auto.

This is the current situation:

Garage air temp is 86 F, as registered by the A/C units temp probe that is on the outside of the cold box in the open air of the garage.

The Ink-Bird registers 75 F inside the cold box, and the shut off lower temp is set at 68 F. In this scenario, since the outside temp is registering at 86 F on the A/C unit, and the inside is at 75 F, cold air should blow until the inside reaches 68 F.

When I power on the A/C unit, at first the fan blows. As expected. Then after a minute or so, I can hear the compressor kick in, as expected. This all is familiar as this is how the set up has run for most of the summer/fall of 2017 and all of the warmer months in 2018. Without issue.''

Now, however, there is no cold air, only the fan recirculating the 75 F air inside the box.

What could be the cause, since working just fine last year?


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Last edited by PJmax; 04-25-19 at 01:45 PM. Reason: resized pictures
Old 04-25-19, 09:28 AM
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Sounds like that A/C has lost it's refrigerant charge. Your best bet is to buy a new one. I'm also surprised a window A/C is getting that box down to 50 without the coils freezing over.
Old 04-25-19, 11:52 AM
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Thanks for the reply Tom, I appreciate it!

I'm guessing it hasn't had an ice problem due to the fact that it only runs for ~10 minutes per cycle with between 15 - 20 minutes in between depending on garage temp. Maybe it's the higher garage temps that also help to keep it de-iced?

After running less than 2 years, I'm a little surprised I would have lost it's refrigerant charge. It was run at 50 F for only a few weeks, for 2 crush seasons (2017 & 2018), the rest of the time it spent the other 7 - 8 months running around 65 F (we drink everything stored in here within 2 years), with the winter months turned off.

I guess that ~month of pushing it to 50 F really consumed the refrigerant fast.
Old 04-25-19, 01:29 PM
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Air conditioners don’t consume refrigerant while running, and don’t need fillups every so often. They use a sealed system. If the system is out of refrigerant there’s a leak.
Running that cold probably killed the unit. As they aren’t designed to run that cold.
Old 04-25-19, 01:41 PM
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There really isn't any way for you to cause the refrigerant to leak out. It comes down to poor quality coils and less than satisfactory solder connections. This is a common problem with inexpensive window units and dehumidifiers.
Old 04-25-19, 03:51 PM
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Thanks for the replies guys! Much appreciated.

Looks like I'll forgo the 50 F temps during crush from now on (no more cold press soakings), and just keep the next unit no lower than 65 F.
Old 05-04-19, 01:38 PM
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One problem with low return air temperature is that liquid can get back to the compressor.

The other - no defrost control.

You need refrigeration equipment to do this properly.

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