I recently picked up a used BM23 kegerator (Superior branded). I have it set so that the temp of a gallon of water is at 40. I have a corny keg and some other bottled beer in it, so it's pretty full, but not too full (air can still circulate. What I've noticed is that when the compressor comes on, it's on for quite a long time. I've been measuring this weekend and it seems pretty consistent that the compressor runs for close to 60 minutes and then is off for 80-90 minutes. Being on for 60 minutes seems to me to be way too long. I know that measuring air temps isn't that important and that keeping the liquid temp constant is, but what I've also noticed is that the internal air temp ranges from 35 to 46 during the cycles and it's pretty consistent. The compressor comes on when the inside air temp reaches ~46 and shuts off when it reaches ~35. (Should the thermostat allow for such wide swings?) I wonder if the long compressor on time is due to the wide temperature swing and the high of 46 or probably more due to low refrigerant? I've cleaned the coils and the compressor doesn't feel very hot after its been running for an extended period. It's warm, but not so much that you can't keep your finger on it. To make matters worse, somebody replaced the original compressor fan and motor with an axial fan that is quite loud, so when it kicks in, you know it. I'm sure they did this due to the cost of the replacement part (+$100). I'm thinking I should have a refrigeration repair person look at it, but wanted to see what others had for cycle times and also get the thoughts of any refrigeration experts regarding the temp swings. Although, it would seem that it should be able to cool down from 46 faster than an hour. Thanks
How are you monitoring these temps?With door open or with a cabled/remote thermometer? Hows your door gasket? Sealing all around no rips? Hows the tstat probe on the back wall is it strapped in position or hanging free? What number do you have the dial set to on tstat? Please replace with the proper condenser fan motor.I can't see that fan moving the air in a large enough area across the condenser.(This might even be your problem)
The air temps were monitored using a remote wireless sensor. The liquid temps were measured using ainstant read Thermopen. The door gasket seems to be good. There are no rips or tears and no obvious air leaks. Cannot see any light escaping when I place a flashlight in the unit and the room is darkened. The tstat probe is strapped in position along the back wall. The plastic sleeve covers pretty much the entire probe, I believe. The dial is set to about 4.5. The fan seems to push a lot of air, but that style fan seems better suited for evacuating air from a space rather than pushing air over/through the condenser. It seems to have air on the radius, but not in the center. Unfortunately, none of the original mounting hardware remains and the fan mounting bracket seems to be the piece that isn't stocked. I'm planning on ordering the parts (bracket, motor, blades) anyways since the current one is way too loud. Although, neither the compressor nor the lines on the condenser seem to be overly warm. Thanks
@zero_signal Judging by your avatar, it looks like you have one also. Just out of curiosity, when the compressor kicks in, how long does it run for (assuming door hasn't been opened, etc)?
I'm not familiar with a BM23 and will defer to zero_signal for more detailed feedback, but a 60 minute run time seems excess for any type fridge that is pretty full. Your 9 degree differential in air temp should not be a problem, this is the spread I use on my ferm fridge and the wort temp stays pretty steady. To be sure, use your thermopen and measure the water temp at the beginning and end of a cycle. Remember, a keg of beer is changing temps even slower than a gallon of water. For grins, place your wireless thermo in your kitchen fridge and compare the differentials. From your description I am suspecting an inefficient compressor, low refrigerant level, or some type of blocked flow of the refrigerant. You are compressing and expanding the gas (exchanging heat), but at a slow rate. My experience is the condenser coil should be fairly hot (touchable, but no doubt there is some heat transfer). Is your coil exposed on the back or bottom or is it integral to the cabinet? Either way you should feel some real heat from the condenser. I would not worry about the compressor motor not being hot, but would worry that it is a replacement with a wacky fan. Although it won't hurt to try it, raising the temp setting will probably do nothing to correct this. It will raise the temp of the interior (beer, et al) but your run time will probably be similar. Your differential spread should be independent of temp setting.
Ok. That's a good sign that it's not 25 years old. I would work on the fan replacement at this point first. Easy to replace.
Replacing the fan will be a piece of cake compared to replacing the thermostat. I replaced the thermostat last night to see if that would reduce the temperature swing. What a PITA that was. Most of the job was easy, but trying to secure the short ground wire on the back side of the housing was not easy. Perhaps that was modified on mine. Haven't had a chance to check the temp swing yet with the new thermostat. The one that was in there was a 502-194A
