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KSSS42QJT00 - Proper Refrigerant Charge - How to verify/measure?


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#1 cb20777

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Posted 07 July 2013 - 03:35 PM

I've been working on repairs to my Kitchenaid refrigerator (see http://appliantology...?hl=ksss42qjt00 ) and have become puzzled by the related topic of figuring out how to determine if the amount of refrigerant charge is too low, too high, or just right.

 

I have the following tools that would seem applicable:

  • Manifold gauge
  • High and low service ports (high is Schrader valve on the dryer, low is bullet piercing valve on the process port stub)
  • IR thermometer
  • Recharge adapter with "conceptually" calibrated gauge (i.e. too low, too high, nice, and something else as ranges).  This little gizmo screws on top of a small R134a container and also into the low service port.

I also have an evacuator pump, as well as a small digital scale, which I'm hoping NOTto have to use.

 

What I'm missing is the process for determining the proper amount of refrigerant.  In theory I could evac, then recharge using the scale to determine if the 6.7 oz requred had be inserted.  But that seems like overkill, and further is not really useful as a way to spot check given the suspect very slow leak in the system.

 

Are there any quantitative measurements and procedures I could use to figure this out?  I assume there must be, I just haven't been able to find them.



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#2 jumptrout

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Posted 07 July 2013 - 03:45 PM

Well,if you do not want to do it correctly,you are only guessing anyway.

The guessing way would be to charge to a low side PSI of 5.



#3 cb20777

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Posted 07 July 2013 - 03:46 PM

Oh yes, this might be relevant.  After coming home from vacation to a warm freezer, I eventually (after some false starts), recharged the system (while obviously slugging the compressor since I had the refrigerant bottle upside down - DOH!).  Anyway, the freezer is now nice and cold - YEAH.  But I was monitoring the high side pressure and after a day it changed from the 130-160 PSI range to around 250 PSI.  I freaked out thinking I had too much refrigerant and/or maybe the capillary tube was blocked by freezing water or other bad stuff I introduced.

 

So I drained some of the charge at the low process port.  I as surpised to get a few cc's of greasy water (or very very thin oll) along with the warm vapor.  After this the high pressure was more consistent (around 150 PSI).  I also replaced the failed condensor fan.  The unit is currently behaving nicely (hard ice cream!).

 

So I am left with many questions.  What was that thin oily stuff anyway?  Was removing it good bad or indifferent?  How do I check the charge?



#4 jumptrout

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Posted 07 July 2013 - 03:52 PM

The thin oily stuff was oil and other contaminants in the system.

There may also be a high side restriction.

A 134a refrigerator system running correctly would be about1-5 low side psi and 105 or so on the high side.



#5 cb20777

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Posted 07 July 2013 - 04:03 PM

Thanks for the response.  Let me expose more of my ignorance:

 

Low side Pressure:

 

  • When you say (for example) 5 PSI on the low side, is that 5 PSI above standard atmospheric pressure, or 5 PSI over a full vacuum?
  • Secondly, I assume this is when the compressor is running (since when it is not the pressure tends to equalize between the low and high side) -- Am I understanding this correctly?
  • I seem to remember when I had the manifold gauge hooked up that the compressor pulled a vacuum on the low side (and the gauge switched from PSI(g) to measuring inches of mercury (I guess to avoid negative numbers of something -- it seemed odd until I realized this must be a common convention in the industry).  How eactly does this relate to the recharging process, or was this vacuum simply a side effect of far too little refrigerant in the system?

"The thin oily stuff was oil and other contaminants in the system"

  • Does that mean that letting it flow out was a GOOD thing?  Or is the oil something that should be replaced at some point?

Thanks for your help!!!






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