[doc havoc]

Can anybody help with sizing capillary tubes for two Matsushita compressors? It's a long story, but this is a class project and the compressors were pulled from refrigerators, oil changed, and new unit being built from scratch. Converting from R-12 to R-134a. Targeting a -10 degree evap.
Model #1: CB120L26
LRA: 15.1Amps

Model #2: DA66L11RAU6
LRA: 11.3Amps

I've been to the Panasonic web site and to the J/B Ind. web site but to no avail. Also put in a call to Matsushita but they were of no help. Thanks for any info.

 

[doc havoc]

As long as we're on this topic, can you tell me what a model number on a comnpressor out of a Dixie-Narco vending machine means? Compressor model # is E5187A2170G20. This is part of my previous post. Thanks

 

[R12rules]

I had an old neighbor, may God rest his soul. That dear man was around doing this work when Seal Units Parts Company was just starting out.
If anybody would be able to give you a heads up, I would say it would be Supco.

If this doesnt help, post back and I'll dig around with you. We'll figure this out.

 

[doc havoc]

Thanks Dichlorodifluoromethanerules. I'll let you know.

 

[R12rules]

Thanks Dichlorodifluoromethanerules. I'll let you know.

That's funny! That's the first time anyone here has called me "by that name"!

Keep me informed. Maybe I can learn a lesson myself in reseach preceedures with this adventure.

By the way, have you searched for the manufacturer using the Thomas Registry? They list ALL manufacturers. And perhaps The News would have a referance for them in their yearly directory. I dont know if your a member of their listing.

You might consider e-mailing someone over there at The News and making inquiry.

[Edited by R12rules on 10-07-2004 at 12:46 PM]

 

[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

 

[Dad]

Isn't it true that if you have the HP and refrigerant type and know the evap temp target you can calculate the Cap?

You can find it starting on page 30


http://www.supco.com/images/1 HVAC Section.pdf

 

[doc havoc]

Danfoss Engineer, yes we do change all the tubing. 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?

 

[doc havoc]

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.

 

[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

 

[R12rules]

Mr. Danfoss,

What is your recomended method for removing the oil from a pot compressor.

In another thread, I aproached a NuCalgon rep at a wholesale house. He had some very interesting advice given him from the factory tech support person he phoned on my behalf.

....Something about drilling tek screws down the side of the can until oil squirts out....

Those stiff plastic tubes will not always insert into the service port.
It is not always practical to "tip" the condensing unit in order to remove the oil either.

I have even heard advice that we are to leave things be unless the compressor should be replaced.
Replaced either because the POE oil is contaminated with moisture or replaced due to ineffecient compressor.


Shux, if it was up to me, I'd just weld in a short piece of tubing from the base of the compressor and have it extend out to where a field service tech could un-screw a 1/4" flare cap, attach a service hose and pressure the oil out into a measuring cup.

What's six or eight inches of tubing going for these days?
And how long would it take to punch just one more hole into a steel housing?
And what would be the added expence of just one more weld onto the side of a pot compressor?

Honestly, we in the field could pretty much care less about those low side ports you factory people pinch off near the top of the cans.
In most cases, we simply leave them alone and ignore em'.

If you gave us one we could use ... I imagine everyone would be buying your particular brand of compressor rather than the others .... simply because they were serviceable!

We love service-able!


Any comment? Thanks

 

[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