Then there was Mueller.

Harvey Ramer

Saturday I went out to trouble shoot a Milk Cooler. There was a lot of ice forming on the bottom of the bulk tank and the compressor was running abnormally long. I put on my gauges and yes, it is low in Freon. I charged it appropriately. I ended up with normal condenser p/t for the ambient conditions and about 3° superheat at low load condition, (bulk tank @ 36°). That is what they want, a flooded evap to alleviate thermal stress on the cooling plates on the bottom of the tank. The condenser is a unique setup. I had to noodle over it a bit till it made sense. Starting at the compressor, the discharge line first passes through a free-heater (water heater with a desuper-heating coil in it), then it makes it's way back to the condensing unit and enters the condenser which has standard fan head pressure controls. Once it exits the condenser, it passes through a "suction line accumulator heat exchanger = aka SLAHX" and then on to the TEV. Through the TEV and on to the evap plates and then back to the SLAHX and back to the compressor suction port.



The TEV threw me for a loop at first. It is designed to maintain a specific subcool 10° at the condenser. In this manner it is possible to keep the condenser operating at maximum BTU output regardless of ambient conditions or evap loads. This is important because milk needs to be cooled quickly and the milk that is already in the tank should not be allowed to warm up during consecutive milkings.



So that's all good. Here is the problem. 245° to 250°  comp discharge temp. It didn't seem to vary much with the suction line temp. Granted, the suction line picks up some heat going through the SLAHX but I was measuring temps both before and after to get a better feel for things. The comp is a Techumseh AGA5568EXN. That is a H/Back Pressure Air Conditioning compressor. I did notice the compressor's nominal capacity is about 9k BTUh higher than the max output of the evap, which occurs at the max rated influx of warm milk.



I will attach Pics. <a href="https://www.dropbox.com/sh/p871yhxaodphd8z/AAAc1VEK8ZCVUv1XFik4dPjna">https://www.dropbox.com/sh/p871yhxaodphd8z/AAAc1VEK8ZCVUv1XFik4dPjna</a>



Oh, and I did find 2 leaking service ports which account for the low charge.



Harvey

Techman

Bulk Milk Coolers

Those are an interesting breed of refrigeration units. You are getting a nice variety over there in Pa. land. Its kinda hard to make a decision w/o having those P/T's to judge by. The comp is a 6HP, 68,000btuh @ 45* Saturated Freon in the Evap Coil. What is the TD of evap temp vs milk temp? At 36*f milk temp the evap temp is what? Lets say a 10* TD ,so with 26* Saturated Freon Evap Temp ,the comp will put out only 50,000 btu's  ,or so. With a 15*TD ,36* milk the comp will put out only 45,000 btu's. Got acid? Got moisture? Got the settings on those Head Press controls? Got the number of additional Milkings. Copeland has an AEB # AE-1242-R2 on Bulk Milk and RSES (SAM) has a thing on Bulk Milk Section #38.I liked the people that come with those coolers, the Farmers

Harvey Ramer

Morning Terry!

Doesn't have a S/G. I need to replace the high and low side service valves. Same time I do that I plan on replacing the drier and adding a S/G.



The unit uses R-22. The condenser settled in around 108° @ 78° ambient. The evap never really settled down completely. One snapshot I took was with the condenser temp as previously stated, evap temp @ 23°, 3° SH before the SLAHX, and about 51° refrigerant temp @ the suction port of the comp. Discharge temp registering @ 245°.



Harvey

Techman

Milk Cooler

Hay Harvey, another cool one. Cool! What kind of enclosure is that cond unit in?. Is there a cond air "short circuiting" situation going on ?That's a lot of rust on the SLAHX. Two cond fan motors ,two cond fan motor controls! With the system running I think there should be a little bit of moisture on the SLAHX, especially w/ a 2-3* SH. . Just as a "check to see" thing. How fast can you get a replacement TXV, from who? Can you Rustolium that accumulator and Insulate it? Got a cond fan motor? Got the start and run components handy? LOLOLOLOLOL! Welcome to refrigeration, parts and parts and parts.Got a book started yet? A book w/ all of the comp/cond units MN# &SN# that you now have w/ the info of the cond fan motor, the start& run caps and the start relay. Then you have to cross reference what is in your units with what is supposed to be in those systems!! You'll be surprised, I think!

Harvey Ramer

Supprised yes!

Did a little research on this critter. It is supposed to have a 5HP comp!!! Not a 6! Also I  must take my SH readings at the suction port on the comp, (3°- 4°) after the SLAHX, not before. That means the evap will be completely flooded which is what they want. That means I'm still undercharged and a little more Freon should help bring the discharge temp down some. I am not expecting normal levels.



I ordered the replacement service valves. The parts don't come through the normal channels. I deal with a Dealer/Service company who buys direct from the manufacturer. That is how it is, the dairy equipment service industry is sewed up. They give me a healthy discount on parts though and I had a great conversation with one of their technical guys named Jim. They are fully stocked and can get me anything I need!



Good point on the SLAHX. I have Rustoleum and an insulation blanket that's begging for a home.



I particularly enjoy working on Dairy Equipment. On average the systems (not just refrg.) are more complex and interesting than the normal humdrum ;-)



Harvey

Techman

Humdrum ?!?!

Lol here Harvey!. You have been doing refrigeration for how long now? And you already have HUMDRUM systems? LOL. I really, really like the variety of stuff that the "R" part of our trade brings! And humdrum does suck !

You should know the SH of the TXV/evap AND the SH going into the comp. I'm sure Mueller doesn't want 2-3* of SH going into the comp, considering the SH from the  suction accumulator.Tecumseh would be upset, for sure! What info is on the cond unit nametag? What affect does the slightly larger comp have on the overall system?Suction, head, SH's and discharge temp?? There is only a 7,000 btu difference between those two comps! Maybe , someone wanted a slightly quicker pulldown , maybe the farmer was "overloading" the system by not watching his  Milking ammounts? Is he aware of the 2nd or 3rd Milking requirements? Or , the larger comp was all that was available at the time? Most of those parts are "common" parts and readily available thru a regular supply house.Cross check the $$ of the "specialty" vs "regular" supply house for the caps and relays ,cond fan motors, etc. The TXV is probably an O.E.M. part.

One farmer to another, Hay Joe,call this Harvey guy , he's a little anal but he fixed my Milker and he had the parts with him, saved my butt ( $$$$)again, he did!