Mea Culpa? A little accidental nitrogen… and now a burned out compressor

I had an old freezer cabinet extremely low on charge. So I evacuated the system, leak checked nitrogen ~150 psig, pulled a vacuum overnight, held the vacuum for 1 hour, then weighed in the charge per the name plate.

Here’s where it gets uncomfortable for me. In my haste I accidentally introduced some compressed nitrogen. Yes my lines were still hooked up to this. Not much but a little charged in the low side port while the compressor was running. Yes, I know, big OOPS. I was pressed for time and in my haste I did not evacuate, dehydrate, and re-charge. http://hvac-talk.com/vbb/images/smilies/oops.gif

Regardless of this the freezer worked great per the specs. Nearly -10 degrees F in my hot workspace.

Two weeks later. I got the call that made my heart sink. Circuit breaker this unit was on got tripped. Apparently it worked after that but I’m not sure about that. Then it stopped working. The fan blowing on the compressor worked but it didn’t get cool.

So I looked at the unit today. No continuity between Start and Common or Start and Run. So that’s an open start winding. Now take a look at these pics. Looks like some serious overheating going on. See these before and after shots…

<img src="http://hvac-talk.com/vbb/attachment.php?attachmentid=705131&d=1467492169&quot; border="0" alt="Name: BEFORE 2016-06-11 10.35.23.jpg

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So that’s some serious overheating crisping the label. I’m thinking two things…

1. That nitrogen found its way to the compressor and stayed there, not allowing any cooling suction gas to cool. Is this possible? http://hvac-talk.com/vbb/images/smilies/13.gif

2. My other thought is the unit was mis-wired and the start winding stayed energized for far too long. I’m pretty sure I checked the amp draw and it was normal. Could it have been energized for two weeks before failing?

Oh how I wish I took better notes on this before I returned it. Well I just feel horrible about this and now I’m leaving for vacation and can’t resolve the matter quickly.

Please let me know your thoughts.

Attached Images

  

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