Refrigeration

Status
Not open for further replies.
cschmid

cschmid

Senior Member
Location
Northern cold country
had a couple of service calls to a mom and pop meat processor..they have a freezer unit display case style..the compressor is located on the roof and the condensing unit is located directly below the compressor in the freezer unit..on hot days it will trip out once..on days it is just mild to cool it is okay..there was a slow leak on the refrigerant so the refrigeration man put this substance in it to stop the leak..Now I believe it is over heating due to lack of cooling capacity..the refrigeration guy has them believing it is a electrical problem..I have checked everything I can think of you guys have any Ideas..i have never been there while it is tripped and the amp readings are from 8 to 11 amps..I have no idea how big the compressor is but we installed the condensing unit couple years back..all wiring looks good..
 
How about table 310.15(b)(2)(C),could it be the ambient temperature causing your problem??
310-15 (C)Also mentions conduits exposed to sunlight on rooftops..maybe this is causing your problem...?
 
I agree with the others and focus on the breaker, if it was not the problem it likely is at least part of the problem at this point.

cschmid said:
Now I believe it is over heating due to lack of cooling capacity.
Click to expand...

Put that thought aside, if the electrical side is OK, that compressor should able to run forever without tripping the breaker.

If the system is low on refrigerant there is a low pressure cut off. But the compressor spins easier with less pressure.

If the pressure is to high the compressor will draw to much current but most also have high pressure cut out.

The compressor itself will have thermal overloads (I assume this is sealed motor compressor unit)

After replacing the breaker I would check to see if it has been short cycling. If for some reason the thermostat or the wiring to it causes a short momentary drop out of the compressor it may trip the breaker as the compressor tries to restart against the remaining pressure.
 
Last edited:
By the way you really have to pin down the ratings on the tag.

The breaker may well be undersized, don't forget the rules are different for motor loads, even if it is wired with 14 AWG it may need a 30 amp breaker.
 
I did not think about the short cycle..I have checked the paragon defrost-o-matic timer and it is working correctly..I have replaced the breaker..I megged out the conductors..the starter (relay) is quite old but appears to work properly and is not all wore out..I have checked out the condenser and every measures alright but if the hockey puck sensor for the defrost temp was bad I would of thought it would be regular in its actions..the condenser is a BOHN unit made by heat craft..if you want to see how it works..

It happens during the day when it is hot out but it does not happen everyday..last week it happened 4 times the week before 5 times it just started doing this 3 weeks ago..granted it has been 10 years or so since I wired the whole thing in..

It is rated for a 20 amp breaker..
 
Last edited:
iwire said:
By the way you really have to pin down the ratings on the tag.

The breaker may well be undersized, don't forget the rules are different for motor loads, even if it is wired with 14 AWG it may need a 30 amp breaker.
Click to expand...
thats also a good point. the breaker might be too small for the compressor
 
It has ran since last Friday without a problem..I will ask Bud the refrigeration guy about the short cycle but neither one of us has been there when it has tripped out..I was trying to figure out how I could monitor it so i could get some kind of data to work with..
 
You mentioned it's running load is "8 to 11 amps".

That being the case I find it surprising that it calls for a 20 amp breaker. Often the breaker will be far above the RLA.

Not saying it's not possible just odd.
 
What kind of defrost does it have, electric heaters ? or hot gas?

Also, if there are any doors on this unit, they might have heat tape on them.

When it gets hot outside, the unit will probally 'sweat' more and may have a

pump to discharge the water, it may even be freezing the evaporitve coils

and making the fans work harder, and increasing the load.

Or it's a bad breaker like everyone else suggested.
 
iwire said:
You mentioned it's running load is "8 to 11 amps".

That being the case I find it surprising that it calls for a 20 amp breaker. Often the breaker will be far above the RLA.

Not saying it's not possible just odd.
Click to expand...

side-note that doesn't help with the problem, but, I'm suprised it calls for a "breaker" at all. 90% of those type units I've seen state "max FUSE"
with no provison for breakers.
 
benaround said:
What kind of defrost does it have, electric heaters ? or hot gas?

Also, if there are any doors on this unit, they might have heat tape on them.

When it gets hot outside, the unit will probally 'sweat' more and may have a

pump to discharge the water,
Click to expand...


Some good points there, I am used to those items being on separate circuits but they certainly can cause shorts. :)
 
stop-leak???

stop-leak???

Hello,

A number of us are cross-trained in air-conditioning/refrigeration. A few points to consider:

1. stop-leak is not widely accepted in the profession.

2. most techs can diagnose a power-circuit problem.

3. air-flow restricted by dirty fins and/or dirty fan blades are suspect.

Of course, other things can be involved, but the tech should have documented all of the pressures and temps. In other words, the problem may not be the equipment.

YHS
 
lets see it has electric heaters on it..2 elements one on the coils and one on the pan so it will drain..it has two sensors on it one to kick the heaters off and the other to start the fan..i talked to the manager and ask him to watch it and tell me what he could about the consistancy..he says when it happens it happens with in 5 minutes of the defrost cycle..so I am going to go over and remove the covers and do a physical check on the elements and then order the parts up and replace the hockey puck sensor(thermal cutout switch)..this is on a display freezer where you walk up and service yourself..and the employees can walk in behind and take the storage and refill the display..

edited..I know the stop leak is not good practice..the guy doing the refrigeration is a semi retired guy..closest refrigeration guy outside of him is 100 miles..
 
Last edited:
I havn't heard where the panel is located. Is it outside? Is there alot of heat radiating from nearby breakers? I've been victim to nuisance tripping from heat alone.
If it runs fine on normal days, this may be the problem. Try giving the breaker a little breathing room, or move it next to breakers that don't have so much load.
 
cschmid said:
lets see it has electric heaters on it..2 elements one on the coils and one on the pan so it will drain..it has two sensors on it one to kick the heaters off and the other to start the fan..i talked to the manager and ask him to watch it and tell me what he could about the consistancy..he says when it happens it happens with in 5 minutes of the defrost cycle..so I am going to go over and remove the covers and do a physical check on the elements and then order the parts up and replace the hockey puck sensor(thermal cutout switch)..this is on a display freezer where you walk up and service yourself..and the employees can walk in behind and take the storage and refill the display..

edited..I know the stop leak is not good practice..the guy doing the refrigeration is a semi retired guy..closest refrigeration guy outside of him is 100 miles..
Click to expand...

i would replace the defrost termination stat/thermo-disc
next i would replace the compressor start relay and capacitor
 
Last edited:
Status
Not open for further replies.
Top