u/Sensitive-Hamster-14

One morning, we discovered that the heat pump was shut down. The worst part was that the main circuit breaker had tripped.

We checked the compressor motor—it was fine. The refrigerant pressure in the system was sufficient. We tried turning it on, but the circuit breaker tripped the moment the compressor motor attempted to start. It became obvious: the compressor had left us without saying goodbye.

We ordered a new one and dismantled the old one.

We found oil in the receiver, so we drained, washed, and dried it. There was also oil in the suction accumulator, which was trickier. We drilled a small hole (5mm) in the bottom, drained the oil, tapped the hole, cleaned, and dried it. We screwed a bolt into the hole, heated it up, sealed it with silver solder, cleaned it, and painted it with zinc primer.

We checked the operation of all valves. We decided to replace the mechanical TXV with an electronic one. We ordered it and soldered it in. We built an additional box for the EEV driver and installed electronic pressure and temperature sensors. We spent a week doing a "ritual dance" trying to integrate the EEV controller with the heat pump controller. Eventually, we settled on a simple scheme: simulating a mechanical TXV.

The new compressor arrived. We lifted it and installed it (just the two of us, by the way). We replaced all the filters and moisture indicators. We vacuumed the system and charged it to about half volume. We started it... it ran very quietly with very low power consumption (low current). We shut it down.

We started thinking...

We systematically ruled out all the inexpensive parts. Three days later, only one option remained—the same thing that caused the previous compressor to fail: the 4-way reversing valve was stuck in an intermediate position. It was a direct bypass from discharge to suction, with all the resulting consequences.

We searched online marketplaces for this valve without success. We eventually found one, looked at the price... and decided to go disassemble the old one instead :)

It was built very solidly: brass, precision honing, thermal welds. It turned out there was a thin layer of carbon buildup. We struggled to knock the plunger out, but we cleaned it, applied some oil, and it slid back in like it belonged there.

We reassembled everything, vacuumed, charged, and started it. Then came the EEV tuning. It wasn't without its quirks and mistakes, but everything ended successfully. It is running now.

In the top-left corner of the board, it literally exploded and burned out.

This is a PCB from a old large Ballu AC unit.

No schematics available. No markings.

This cone-shaped (pothead/funnel) is used for paper-insulated lead-covered (PILC) cables. It's filled with an insulating compound to prevent oil leaks and keep moisture out of the paper insulation. A tru piece of indastrial history that's still in service.

Someone installed this hot water system a long time ago.

Those look like PEX-AL-PEX pipes to me.

Toyota corolla 2012

Feel free to pick his technique apart - he could use the feedback.

The electric guitar was given to us 15 minutes before we went on stage.

Apple