Refrigeration troubles!

[davedottcom]

One of my customers are having a problem with their ice machine and walk in cooler. They both "Freeze-up" after short losses of power. The momentary power outages are a regular occurance here in Florida. (Almost daily)
After one occurs the owners have to adjust the thermostats on the units (Turn the temperature- UP) for almost 2.5 hours until the compressors will re-start.
What can be done to stop this from happening?
Dave

 

[wayne123]

Re: Refrigeration troubles!

Either talk to the power co. or get the customer to buy an automatic transfer switch and a generator.

 

[tony_psuee]

Re: Refrigeration troubles!

Dave,

In addition to Wayne' suggestion I would add contacting the compressor manufacturer about the restart issue. If the compressor is shutting down without being able to unload it may not be re-starting on power return because the pressure is to high. Dealing with that will not resolve the power loss, but may allow the compressor to come back on line sooner.

Tony

 

[davedottcom]

Re: Refrigeration troubles!

LOL, I'm not looking for a way to stop the power outages!!! I'm trying to figure out why the 2 compressors wont kick back on until 2.5 hours after the fact.
Tony, what you said sounds like it makes sense, I'll try to contact the manufacturer and ask them how to lower the pressure to allow for the restart.
Thanks, Dave

 

[wayne123]

Re: Refrigeration troubles!

Dave, when you say "Freeze up" are you refering to the coils freezing up or are you saying that the compressors won't start back up? I may have misunderstood the question. When the power returns is the voltage correct? This is very strange. I have worked around refrigeration equip. for a long time and I have never heard of this before. It is possible the the compressors are locked out because of high head pressure as Tony says but when the compresso cuts off the pressures should equalize.

 

[davedottcom]

Re: Refrigeration troubles!

Wayne, what I meant by freeze up was that they will not begin to work again until they seem to "Warm-up". the coolers are usually set for about 34 degrees and after any brief power outage they have to adjust the t-stat to about 55 degrees and after about 2 hours they start back up.
I already tested the voltages (Under Load) and they are both around 127 V. Unfortunately an "Outage" nevers happens when I'm there! I've already tried replacing & moving the S.P. breakers to different phases, but that didn't stop it. Also, the coolers are fed from 2 different panels.
I guess the problem lies in the pressure system, which I am not familiar with! What regulates the high pressure?
Dave

 

[hbiss]

Re: Refrigeration troubles!

Doesn't sound like an electrical problem. Can you duplicate it by killing the breaker?

I would contact the refrigeration service company, I think this is their ball game not ours.

 

[lrollo]

Re: Refrigeration troubles!

Sounds to me the compressors just wont restart under head pressure and even turning the thermostat up to a higher temp wont do anything to relieve that. Maybe look into a UPS system for the refrigeration unit. I didnt know they even made large UPS's but I recently installed one on a 10 hp 3 phase 208 volt airplane hanger door at the Air National Gaurd which needed to open in case of a power outage to get their jets out of the hanger.

 

[big jim]

Re: Refrigeration troubles!

Sounds like compressor "flooding" or high head pressure. The solution is likely in the refrigeration side - check valves, bleeders, or the like. The addition of a "hard start" capacitor may give the motor enough oomph to overcome high head pressure but if it is a flooding issue, they will have to wait untill the freon evaporates. Compressors will not sucessfully pump liquid. Many refrigeration systems have a delay start timer to prevent them from trying to restart immediately after a power failure. Another option that would reduce the wait time is an external crankcase heater. You should work with a refrigeration guy on this problem.

 

[hurk27]

Re: Refrigeration troubles!

Sounds like a case of the units being over charged. And or a bad start/run cap or relay on the compressor in any case it does need a certified HVAC man to work on it as the federal government has put the clamps on anyone being able to buy parts that go on a cooling unit that uses freion

 

[steve66]

Re: Refrigeration troubles!

Sorry, I hit reply instead of edit. See my post below.

Steve

[ November 06, 2003, 09:08 AM: Message edited by: steve66 ]

 

[steve66]

Re: Refrigeration troubles!

Originally posted by steve66:
[QB] My 2 cents worth:

I am somewhat suspicious that there is even a problem. You said an outage never happens while you are there? So you have never seen the units not restart? How did the owners find out that turning the thermostat up to 55 fixes the problem? Maybe turning up the thermostat up to 55 is why the compressor doesn't start for 2 hours. Maybe there is a short time delay for the head pressure to drop after an outage, and the owners just weren't patient enough. So they start screwing with everything, and then 2 hours later when the thing restarts, they think they have magically fixed it by turning up the thermostat and waiting 2 hours.

Also, it sounds like a job for the HVAC people. However, if you are determined to get to the bottom of this, take the previous advice and shut off the breaker. Turn it back on and wait patiently (don't let the owner screw with the thermostat either.) You may find things aren't just what the owner said or thought.

Steve

P.S. Sorry for the rant.

 

[jgriffin02]

Re: Refrigeration troubles!

Not sure what freeze up means but the unit should have some sort of short cycle protection timer installed to keep it from short cycling. Depending on the compressor, it may not have enough hp to start into head pressure situation.

 

[etszap]

Re: Refrigeration troubles!

Sounds about the time required to de-ice from a low freon or filter problem. Delay timer is a necessity.
By the customer setting the thermostat up, it keeps the compressor from compounding the problem.