Cooler with additional heat load.

[pedersrg]

Hello everyone I am very new to refrigeration work having been an electrician i am basically clueless. I am wondering if someone can tell me what negative affect a large heat load would have on a 28 degree cooler. We are using ammonia as our refrigerant to bring a large cooler to 28 degrees with a suction pressure of 24 psia and some maint. personel were having trouble cooling their vacuum pumps so they cut two 2ftx2ft holes in our cooler wall instead of fixing their cooling water problems. I have a basic understanding of pulling the moisture out of the air to cool the area but how would this small room with a temperature of 100 degrees F and a RH of around 95% affect frost build up and general system operation.

[US Iceman]

...maint. personel were having trouble cooling their vacuum pumps so they cut two 2ftx2ft holes in our cooler wall instead of fixing their cooling water problems.


Good grief... The way some problems are solved.:eek:

Those holes will allow a lot of moisture and warm air into the cooler and can cause more frost issues within the cooler itself.

Take their saws away from them....:D

[pedersrg]

So can I expect needing more defrost cycles? The current software we use to control our defrost schedule only allows 4 per day and we currently do one every six hours due to a high traffic of product in and out of the cooler. Will the cooling effect be diminished and what type of cost can I present to management to ensure this doesn't happen again?

[nh3wizard]

Yes your cooling capacity will be reduced, and your defrosts will need to happen more often. At 24 lbs you have a liquid temp of +10 degrees. What is the temp outside the box? Whats the possibility of the guys getting their vacuum pumps working correctly, it would be cheaper to fix that problem than to live with the problems of cutting holes in the walls.

[pedersrg]

Outside the box the temp is kept at 75-80 degrees but the room where the vacuum units are housed is over 100 degrees. The units have been fixed by yours truly a water cooled unit doesn't cool well with out water. Funny thing about pumps they pump nothing if you don't have them turned on. The room still has problems they grossly undersized an exhaust fan by using what was already in place to save a couple hundred dollars so there is no air flow. I just don't think they realize how much their quick fix will cost by having to increase hot gas defrosts.

[US Iceman]

...to save a couple hundred dollar...


The owner will probably pay 10-20X that amount or more because of what was done! Besides, as nh3wizard correctly points out with the suction pressure you are running the impact to the compressor energy waste really adds up.



Will the cooling effect be diminished...


Yes, maybe by a substantial amount!



...and what type of cost can I present to management to ensure this doesn't happen again?


see above...

I don't intend to word this too strongly but... what happened here should never happen.

[frank]

our defrost schedule only allows 4 per day and we currently do one every six hours due to a high traffic of product in and out of the cooler.
Same thing I guess, 4 x 6 hours = 24 hours.

You have 2 problems here.

1) the temperature needs to come down
2) the humidity needs to be reduced.

Item 2 above is a function of item 1, however, if you need to reduce humidity more than temperature, you need first to address the humidity control by over cooling and then reheat to control temperature.

A large load on the evaporator will increase cooling time/pull down time.

[US Iceman]

Same thing I guess, 4 x 6 hours = 24 hours.

You have 2 problems here.

1) the temperature needs to come down
2) the humidity needs to be reduced.

Item 2 above is a function of item 1, however, if you need to reduce humidity more than temperature, you need first to address the humidity control by over cooling and then reheat to control temperature.

A large load on the evaporator will increase cooling time/pull down time.

Or, you could re-install the insulation and vapor barrier and reduce the air flow through the hole!:p