[danfoss engineer]

I searched through my Matsushita file and couldn't come up with much info. All I found was that a compressor with a very similar model number to your second one put out 735 Btu/h at -10/130.

In this change over are you changing all refrigeration components. I ask because you can sometimes run into problems on R-134a swaps on cap tube systems. As I understand it R-12 and the mineral oil in an R-12 system leave a benign varnish on the inside of the copper tubing and just sits there and does nothing for years. Then when you change over to R-134a you also have to change to POE oil. This oil actually disolves this once benign varnish into solution and then it comes out of solution when the liquid refrigerant starts to become a gas which, unfortunately, is in your cap tube. Therefore resulting in a plugged cap tube. This is not always the case, in fact usually not the case but it does happen and is something you should be aware of when making changes from R-12 to R-134a. We usually tell people with cap tube systems to use one of the many drop-in replacement refrigerants which do not require POE oil just in case.

Danfoss AE

 

[danfoss engineer]

I don't think we do an adequate job of flushing oil out of the compressor though. My last price quote for POE oil was $45.00/gallon so we do tend to skimp on waste. Is there another way to flush oil from compressor? We drain it, measure the amount and fill with new oil. Maybe I'm missing a step?

I thought $45/gallon was absurd until I checked my own price book. Our list price is $333.52/gallon LOL! You'd think we were selling fancy Champagne or something. As for your technique that's fine. Just get as much out as possible by draining it out of the suction port. The little left over shouldn't cause any problems.

Lusker, thanks for the reply. Those charts are the same ones we use in class, unfortunately the lowest HP on these charts is 1/8 HP. One of the compressors in question is only about 735 BTUH at -10 evap. That's smaller than 1/12 horsepower if I calculated correctly.

You can directly convert Btu/h into horsepower but that doesn't give you anything useful. Compressor horsepower was something that was used back when compressors were belt driven by external electric motors. This practice still lingers today but there is no way to directly compare motor horsepower to refrigeration capacity since it depends on the efficiency of the pump. I believe most compressor manufacturers list a nominal horsepower for their compressors that roughly equates to the power needed at air-conditioning conditions. At LBP conditions the refrigeration capacity for the same motor would be greatly reduced. So we at Danfoss would call a compressor capable of 735 Btu/h @ -10 a 1/5 or 1/4 "horsepower" compressor. Since there's no established way of determining horsepower for compressors it's left up to the compressor manufacturers to determine and therefore Danfoss, Tecumseh and Copeland all have slightly different definitions of "horsepower". I know referring to horsepower is still very prevalent today but the correct way is by Btu/h or tons.

Danfoss AE

 

[danfoss engineer]

I honestly don't have much advice. For the fractional compressors just unbolt it and hang it upsidedown until all the oil drains out of the suction port. I know our newer scrolls have an oil drain connection (1/4" flare) that has an internal tube that goes to the sump so all you need to do if put a couple pounds of pressure in the crankcase and it all comes pumping out for you. On the Maneurop compressors you could just simply unbolt the oil sightglass. Most would come out right there and then it's easy to access the sump to get the remaining oil out. Make sure you get a new oil sight glass gasket!

As for drilling holes and such I can't imagine that's ever a good idea. Who knows where those metal bits will end up.

I imagine everyone would be buying your particular brand of compressor rather than the others .... simply because they were serviceable!

Unfortunately I doubt it. Our customers, the OEM's, wouldn't pay for that feature and most don't really consider the compressor a service item. They would also prefer you to just buy a new compressor for obvious rea$on$. In the end though of the millions of compressors we sell there's probably some astronomically small percentage that need to get their oil changed for service reasons.

Danfoss AE