Just want to start this thread so I can update it as events
We have these Frigoboat systems with Danfoss BD50 compressor
, keel-cooler condensers and flat evaporators. They have been running without any maintenance
worries for 6 years now and we got used to not having to deal with refrigeration
problems. I have sold my gauge set, vacuum pump etc. years ago.
So we were a bit in shock when one box didn't really cool anymore. The compressor
runs but the evaporator just has condensation
, no ice. No sound of moving refrigerant either, so our first diagnosis was a blockage.
Thinking back, this must have been the moment where it all seemed reasonable but from where on it all becomes bizarre.
Frigoboat comes with resealable connectors which have O-rings. You get a whole bunch extra which indicates you're supposed to replace them now and then, although there's no mention on intervals etc. But, it's reasonable that 6 years is too long. I see some oil
residue around them so they must leak a bit which means moist air can enter the system too so an ice blockage is likely.
However, Richard Kohlman, our CF refrigeration
, has repeatedly warned about the keelcoolers so I had some worries, like dirt coming out of them and blocking the lines. Frigoboat does not put a filter in front of the evaporators to prevent dirt to get to the capillary tube.
So, we start monitor
first to see what happens. We find that before the box temperature gets to 10 degrees Celsius, the circulation starts again and the box is pulled down to 5 deg C which is when the thermostat shuts the compressor down. This does not indicate blockage by ice at all because it would freeze again way before the box is down to 5 deg C, keeping the plate just above freezing all the time.
And the next cycle... it works normally again and some time later it starts all over.
We decide to test with the heat gun. We wait until it happens again and point the heatgun onto the evaporator. Refrigerant start flowing immediately. A minute later it stops again and every time we put the heatgun on it starts again: moisture freezing and blocking !!
But for whole periods it just works fine. Could it be blockage from both ice and something else?
After reading some info, I decide to tap the line where it reduces to the small diameter of the capillary tube. It does not start flow so we also use the heatgun and heat the whole plate thoroughly this time while I tap around where the cap tube starts. We also put the system to manual speed and the highest speed setting. My hope was to flush all that blocks out through and from the evaporator so that it has to pass the small filter/drier just before entering the compressor again. The compressor stops with 3-flashes LED meaning overload. This sounds okay as we're heating
the evaporator. I switch the speed control to automatic again and the compressor tries to start every minute or so until all is cooled down enough to succeed. It quickly pulls the box down to 5 deg C and reduces speed to the middle setting. Next cycle it pulls it down very quickly and the controller chooses the lowest speed setting.
This is where it has been sitting for days now, lowest speed setting and quickly pull the box down every cycle without any trouble. It didn't work this efficiently for a long time !
to be continued...