DAIRY CABINET PROBLEM

[bunglebear]

I had a call out to diagnose a fault with a dairy cabinet not maintaining temperature. The case thermostat is reading 15 degrees C, it should be around 2 or 3.

There are two hermetic pots. The refrigerant is R404A, and the suction pressures are 40 psi and 80 psi on each circuit. The compressor head has a temperature of 105 degrees C on the 80psi circuit and 55 degrees C on the 40psi circuit-the first one is way too hot. The discharge temp is also very high on the first circuit. When the unit goes to defrost the standing presssure on the first circuit is 95psi (but there is alot of heat in the compressor and lines) and 75psi on the other circuit. During the defrost cycle the cabinet temperature actually falls !!. When the defrost ends the compressors start up, and the first one does not pull down by more than 5-6 psi. The condenser inlet pipes are at 55-65 degrees C, and the outlet is 27 degrees C, but the dT across the condenser(air cooled) is only 4 degrees C.

As there are no service valves on the rig I can't try and pull a vac on the compressor to test the valves. The suction line measured before the compressors are at about 20degrees C or so- way too high. I had a listen to the compressors-using a screwdriver blade against them, and the hot one that is not sucking down sounds noticeably different to the other.

My thought is that the first compressor has bad suction valves-hence the lack of pull down, meaning that the refrigerant in the evaporator is boiling at nearly room temperature, and also as a result the condenser is not condensing properly etc etc.

If anyone else can give an opinoion, I would appreciate it.

Kindest Regards
James

[icemeister]

First off, I must ask.....When did you folks in the UK start refrigerating the milk? ;)

Seriously, I see from your profile that you reside in the UK. It's cool to talk to a fridgie from across the pond. Is this a single dairy case with two independent refrigeration systems with two evaporators?

It's apparent to me that the first compressor has broken valves with the pressures involved.

Are these cap tube fed evaps or TXVs? Were the condensers clean or dirty when you walked into this? POE oils and high discharge temperatures are not kind to capillary tubes so you may want to add a new cap tube to the shopping list when you go to pick up a new compressor.

While you're at it, fit up some service valves so the next poor bloke that comes along will have something to work with. ;)

[bunglebear]

Hi Icemeister

Very Funny!!

Actually it isn't as cold as people thinkk in the UK. Yesterday the temperature was 30 degrees C(86F). Most of our buildings are air conditioned. Even though we are on the same latitude as parts of Canada, our climate is warmer because the atlantic jetstream pushes the cooler air away to the north and misses us. We don't have snow or ice in the winter, but it can be quite wet.I work for a US based company so am always back and forth over the pond. I just got back from Dallas TX. I'm probably giving it another two years here then will have to give in to the company's demands to move to the states. Here in the UK gasoline is the equivalent of $6 a gallon, and everything else is really expensive-anyway enough about the UK.
Yes it is a single dairy case. It has a large single evaporator, with each compressor running one side- one side is colder than the other-as you would expect. They are cap tubes, and the condenser is very clean-so I know a blocked condenser has not done the damage by causing high head pressures. I'm probably fitting service valves anyway-to make my life easier.
Out of interest-what's the situation over there for technicians employment prospects.
Just remember though I have the posh accent to go with it
LOL !!!

Regards
James

[icemeister]

Originally posted by bunglebear
Out of interest-what's the situation over there for technicians employment prospects.

For market refrigeration techs? Well let's see now........Freezeking2000 just left a spot in Connecticut a month ago, R12rules has been on the job in Austin, Texas for a couple of months and his company has openings (with low pay :(), Outlaw481 quit his spot a week ago (I don't know where) and I heard that a local tech working for Winn-Dixie here in Florida just got canned for doing a side job at a Quickie-Mart.

See, there's lot's of opportunity over here. :D

BTW, how did you make out on your supermarket site visit yesterday, the one with the parallel racks (or as you Brits say, compressor packs)? Customers will often go for a fixed-price, simple monthly inspection contract.......a preventive maintenance type of deal with any repairs done on a T & M basis. Anything above that you're sticking your neck out

[Edited by icemeister on 06-15-2004 at 06:41 PM]

[bunglebear]

Icemeister

Sorted out the supermarket rack, one of the cases not maintaining temp. Simple enough problem, just had to get the evap fans to stop on defrost, and give the whole thing a check over. Wasn't nearly as bad as I expected-don't know what the fuss was about. It's all stable now.

Contract for service- well it's for once a month visual check. Any repairs, call outs recommendations will be extra. There's no way I was committing to a fixed price for the whole lot.

Reason I asked about employment was that eventually I have to leave the UK (sooner rather than later), because I've had enough of it for various reasons. The company I work with are in Waco TX, but I don't want to be limited to Waco, but if I make the move which I think I will it will be to the southern USA-right now I'm developing the UK sector for them, for I guess the next 3 years or so, but perhaps want to be away from here before then-that's why I asked about employment. I could go out to Australia, but have a long lasting affinity with the USA, besides I can't go anywhere without being told "I love the accent"-don't know why !!

What is low pay ???

Regards
James

[icemeister]

Originally posted by bunglebear
What is low pay ???

Check out this thread: http://hvac-talk.com/vbb/showthread.php?threadid=52637

[bunglebear]

In the UK, the average is £10 per hour-about $17.
The cost of living here is much higher. Gasoline $6 per gallon. 3 bedroom house about $300,000. The average guy makes about £25,000 or $40,000 + overtime for a 40 hour week. The wage seems about the same- the difference is in our cost of living-and income tax is nearly 40%.

Anyone want a British fridgie ??

[R12rules]

Ook-Ook-A-Choo Sir .... now I see WHY our Nation's ForeFathers left the Crown!

[NedFlanders]

yeah , 6 dollars a gallon for fuel. I keep telling people we don't have it so bad yet.

[bunglebear]

Anybody with any sense would get straight out of the UK. The USA is like my second home. Everytime I'm over there I wish I was able to stay on, on the airplane back here it's depressing.

No you don't have it nearly so bad at all. Spend six months here and I guarantee that you won't be able to get back home soon enough. As soon as my job here's finished off, I'm off.

[Freezeking2000]

Yea I guess it isnt so bad here in the good ol'USA!

[gerryboy00]

viva America!

:D

[bunglebear]

OK stop making me feel even worse !!!