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Post by allan on Aug 2, 2014 0:31:52 GMT
I am beginning to understand what jhigdon has been preaching about DR machines. These machines have a very common problem of restricted float needles due to the accumulation of black crud around and on the needle seat. This crud restricts the refrigerant flow volume which in turn reduces the available draft cooling of the windings and then the windings overheat and fail. I plan on doing a complete restore of my recently failed DR3 and am studying a donor DR 3 to learn as much as possible before starting the project. This is a set of pics for the DR3 float and a close up view of what happens as they stop up from the crud which I understand is caused by bad chemistry between the SO2, Moisture, Cotton windings and Heat. The first pic is a shot of slicing off the inlet tube exposing a plugged disc type strainer like the one I found in the check valve assembly  |
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Post by allan on Aug 2, 2014 0:46:03 GMT
More pics of the strainer. This is the first disc strainer i have run across in a monitor top liquid line. The CA's and CK's that i opened have had rolled up strainers slipped up into the liquid lines. Gotta put some thought on how to thoroughly clean one of these strainers with it in place and float fully intact! Got some ideas but still searching for a really good solvent to cut the stuff   |
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Post by allan on Aug 2, 2014 0:46:46 GMT
More pics to follow of the actual needle and seat
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Post by allan on Aug 2, 2014 0:55:56 GMT
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Post by allan on Aug 2, 2014 1:02:08 GMT
It's really interesting to me that the crud is only around the seat opening. Notice the rest of the float tank bottom is reasonably clean. And this stuff is very hard and bonded tightly to the steel in this area. |
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Post by allan on Aug 2, 2014 1:06:21 GMT
 A close up view of the DR float from the manual. Entire base appears to stay wet and flooded with SO2 but crud concentrates only around needle and seat |
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Post by jhigdon2 on Aug 2, 2014 2:32:54 GMT
Those are some really good pics. That black crud is really a menace in those things. Most if not all of the DR units I've seen, are restricted in some way with that stuff. I have wondered if removal of the whole float chamber and hot tanking it would be the thing to do.
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Post by coldspaces on Aug 2, 2014 2:33:23 GMT
Must be either drawn to the seat area from the flow of refrigerant or some other kind of attraction(magnetic?) Great pics, got me wondering if my formally stalled dr2 could have a strainer problem. May just be more crud moved into the seat and is plunging it.
Have you tried any modern coil flushes such as RX-11 or Deversitech's coil flush?
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Post by allan on Aug 2, 2014 2:44:02 GMT
Must be either drawn to the seat area from the flow of refrigerant or some other kind of attraction(magnetic?) Great pics, got me wondering if my formally stalled dr2 could have a strainer problem. May just be more crud moved into the seat and is plunging it. Have you tried any modern coil flushes such as RX-11 or Devesitec's coil flush? Have not tried any flush yet. Tried ether and gumout carb cleaner without much success. Auto forums mention hot water and simple green. Gonna give that a try. |
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Post by cablehack on Aug 3, 2014 23:33:09 GMT
I'm starting to wonder if the blockage problem is something inherent with SO2 over time, and will the Scotch Yoke machines start suffering from it in a few years. Or, is there something unique to the DR that causes it?
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Post by allan on Aug 4, 2014 2:10:04 GMT
I'm starting to wonder if the blockage problem is something inherent with SO2 over time, and will the Scotch Yoke machines start suffering from it in a few years. Or, is there something unique to the DR that causes it? From what I am now understanding about the DR I have to agree with jhigdon. It appears that these compressors are prone to winding overheating which starts the chain reaction that produces the gunk that plugs the seats. After that it just gets worse since lower refrigerant flow through the system due to a partial clog causes the winding to get even hotter. Their windings are totally cooled by refrigerant draft over them. Surely a rebuilt unit placed into service in a conditioned space will have a good chance at a long life |
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Post by birkie on Aug 4, 2014 4:06:19 GMT
The CK is oil cooled, so they probably don't exhibit the same kind of chain reaction
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Post by coldspaces on Aug 4, 2014 4:14:46 GMT
The float is not gonna be an easy thing to clean all the gunk out of. Especially if they all have a strainer at the inlet, doesn't help if you are back flushing to have the strainer there. The coil flush would have to be able to dissolve the gunk to flush it out.
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Post by allan on Aug 4, 2014 14:31:32 GMT
The main issue is finding something that will break the crud down. Flushing won't be so bad since the liquid inlet line to the float chamber will be cut and loose between condenser and float. And the leaving liquid feed line will also be cut and open
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Post by ChrisJ on Aug 4, 2014 14:32:34 GMT
Another possibility, what about Acetone? That usually breaks stuff down really good.
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