Damaged Line Repair - DR3 dual pig evaporator...

So it's time for a little follow-up on this!

After the line repair, this DR3 was placed on a D2 cabinet (very small compared to its correct cabinet) for a test. The control is missing a part necessary for the overload breaker functionality to work, so for safety, I placed an RO41 relay/overload device in series with the cord.

It took a while for the frost line to equalize between the two evaporators, but it eventually did. For about a day, everything was just fine - the unit was cycling and maintaining temperature well.

Then one fateful morning I walked out to my shop to begin the day, just like any other. While turning on the lights and getting ready for the day, I heard the DR3 kick in, run in a very "labored" manner for about 10 seconds, and trip.  Fearing the worst, I looked at the Kill-A-Watt meter and watched the current at the next startup. It was over 18 amps. The start-relay stayed engaged, buzzing angrily until the overload tripped. As a test, I pushed the relay down with a plastic object during the next start attempt. It dropped the current draw down to about 9 amps, which is still Very Bad. This was not the beginning of a good day, I tell you. 

Thinking about the way the DR3 motor works, with the transformer / capacitor system for start and run, I wanted to eliminate this is a possibility. By placing paper between the "run" contacts for the wire going to the capacitor box, I was able to eliminate all possible action of this device while the motor was running. After making a start, and pushing the start-relay down, the start contact was open and the run contact was blocked by paper.  The compressor ran normally, with about 3.2 amp draw.  This was a big relief, as it seems the capacitor-transformer device was what failed - not the motor winding.

I deconstructed the capacitor box by baking it in an oven, to de-pot the tar from the components.

As the tar was draining away I noticed that the capacitor film was exposed without any sort of metal can around the capacitor. It was just the foil windings of a capacitor placed in there, and covered with tar. Amazing this lasted so long.

The parts after depotting. Capacitor remains....

Transformer, capacitor, and the bin of tar.

During the initial disassembly, before depotting - there was moisture and rust evident on the bottom of the tar. It seemed that moisture had seeped into the capacitor box. It's very likely this managed to get to the capacitor film and dielectric; thereby causing it to fail and arc over from one foil plate to the other.

To verify the compressor was still OK, I rummaged some capacitors.

The tall one is a 35uF vintage capacitor for a run cap. The smaller one is a modern 80uF capacitor used for a start cap. this is too small, but it works for a test Should have about a 100 to 125uF for start.  With this configuration, the unit ran again, but uses less amps than before.

The DR3 was placed in service and allowed to run and cycle for a couple months, with a few periods of shutdown while I was out of town. It ran flawlessly. 

Time for some more appropriate capacitors...

The larger cap is a Titan HD 35uF run cap; and the smaller, Bakelite capacitor is a 100uF start cap. I used scraps of door gasket to make padding so the caps could not rattle; as well as welded a support bracket to the base of the capacitor box. The RO41 is not used to start the compressor. It is only used as a redundant overload breaker.  The transformer to the right is the heater boost transformer, to give the voltage needed for the higher wattage heater. All this will be covered up with the original capacitor box.

The control wiring. I placed heat-shrink labels on the circuits to make it easier to work with.

From a distance, you can see the layout of the components better.

As shown previously, I installed a low-side service port to assist with troubleshooting and charging. Through this port it was evacuated and charged with approximately ten 10-ounce cans of R152A. during the charging, there was an issue with noncondensable gases collecting in the float. About 3 or 4 times, I had to purge the float chamber via the Schrader port installed at that location. The first purge became necessary early in the charging process. The next one about 10 minutes later. The next about an hour later; and the final one about 3 hours later. Each time, refrigerant flow was immediately re-established. After the last purging, the same day as the charging, the system has not required any additional purging. The temperature was in the mid 80's during the repairs. It has also been operated while the night time temps were in the 40's or even high 30's. So I believe the NCG issue is sorted.

So it won't be long now, this one will be on its way home for the second time!  We'll hope it has a smoother ride the second time around LOL!

Sincerely,

David