BM23 Not Cooling Enough

[zachriggle]

I'm having an issue with my BM23 not cycling enough. It will cycle and chill the evaporator fins just fine (thermometer probe reads "LL" -- below 32°). Within about half an hour, the evaporator coils are back up to 57°, as is the rest of the interior. Turning the thermostat control all the way to 10 does not affect this.

Here's some photos...


I can only get a glass of water inside to chill to about 55-60°F, depending on which of three thermometers I use.

[THE ICEMAN]

I'm having an issue with my BM23 not cycling enough. It will cycle and chill the evaporator fins just fine (thermometer probe reads "LL" -- below 32°).

Are you saying that the unit is cycling on & off or runs continuously?

Within about half an hour, the evaporator coils are back up to 57°, as is the rest of the interior. Turning the thermostat control all the way to 10 does not affect this.

Here's some photos...


I can only get a glass of water inside to chill to about 55-60°F, depending on which of three thermometers I use.

When the unit gets up to 57° is the compressor running?

Some possibilities...
You have a temperature control that has a spread between on/off that is much too wide. In that case you would need a new control. Be careful turning the control as cold as it goes. All that does is make the compressor run continuously & will freeze up the coils thus cutting off the airflow. Typically a setting of 4 to 5 is normal.

If the compressor runs continuously then you might have refrigerant problems, i.e. low on refrigerant. Also, I believe that vent hole shown in the pics should have a tube running to your tower to keep the lines cold all the way up to the faucets. At the very least, the vent should be covered, the air in the evaporator should flow down the back, not out the front.


THE ICEMAN

[zachriggle]

The compressor turns on for about 10-ish minutes, then turns off. It doesn't turn on again for about an hour.

The previous owner says he put it on 5 and it cooled just fine. I set it to five vs. ten and didn't get any difference in performance. I have no reason to distrust him, since I met him at his place of work and had his phone number, etc. Even assuming the entire unit was completely broken and disheveled, the six cornies, 5lb Co2, four-tap tower, and four Ventmatic faucets that I got would completely cover the $750 price.

I pulled the house out to show the fins rather than pull off the evaporator housing.

Given that you think it's a temperature controller in this scenario, how hard is it to replace -- and whats the process?

I can see what looks like a temp probe on the front of the evaporator -- would that have to be replaced too?

I don't believe it's a refrigerant issue, as the evaporator fins get down below 32° as I said before. I also *hope* it's not, since I believe this unit uses a now-unavailable refrigerant.

[THE ICEMAN]

If the unit had been sitting for a time without running before you got it that could have caused the control to 'stick' a bit due to corrosion.

It's not that tough to replace a control. The only tough part is getting to it sometimes, they don't always give you a lot of room to work.
First unplug the unit of course, take the cover loose & then take off the wire connectors from the control. Then slide the control's capillary tube out of the tube along either the front or the back of the evaporator (it varies on different models) & then carefully insert the new capillary tube where the old was. Re-connect the wires (it does not matter which wire goes where) & button it up.


THE ICEMAN

[zachriggle]

I've added some photos of my temp controller that I pulled here.

I've read elsewhere on the forum that I can bypass the thermometer by shorting out two wires. I'm assuming these are the black wires that go into the back?

Edit: Turns out yes. Bypass the temperature control and it kicks in. After pulling out the unit, I see this information:


RANCO TYPE A 30
VAC 240 OR LESS // FLA 20 // LRA 80


(Other side)


P?502-48A5?
A30-3620
6-75-6


(? means a symbol I can't read)

From what I can find online, Ranco A30 is the type of thermo-controller. The A30-3620 is obsolete and has been replaced with A30-263. Does this follow, Mr ICEMAN? You've been so good so far, thanks! Seems like you really know what's going on with these units.

[zachriggle]

New temperature control is installed. The sensor probe is a good bit longer than the other one, but I don't think that'll be an issue. The refrigerator seems like it's running much more frequently now (which is good, since it wasn't cold enough before) and if I stick a digital probe into the evaporator fins, the temperature at which the compressor kicks back in is around 45° instead of 60°. I also got a real NSF-approved refrigerator thermometer. The refrigerator has been on for a few hours (granted, I was opening it every half hour or so to look ^_^) but it looks like it's currently cooled down to the high 40's. My "meat thermometer probe in a cup of water" from before now reads 52-54°, where before it never got below 57° -- so there has been some improvement.

Hopefully it'll get down to chilling temperature overnight -- when I can't open the thing anymore to mess with it. Fingers crossed.

Assuming that the issue isn't fixed, and the new Temp Controller *isn't* the solution, what else would cause the unit to cool, but not cool enough? To cover the status briefly, the inner fan is always running, the outer fan runs when the compressor is on. The compressor gets lukewarm, the condenser coils get a bit warmer. The evaporator coils get down below 32° (as low as my meat probe goes). New temperature controller.

[zachriggle]

I also noticed this in the back (below). There's a metal strip that covers the power and refrigerant line that runs from the bottom to the top of the unit. There's about a 2" diameter hole that these go through, which doesn't look like it has any real way to seal the cold air in or otherwise insulate this section. It's also one of the paths of least resistance for the airflow from the cooler fan. Might this be where the cold air is going to?

[THE ICEMAN]

If you feel cold air coming from the hole, seal it. Originally they are sealed with silicone or permagum.


THE ICEMAN

[zachriggle]

I've got some expanding latex foam, but I'm a bit concerned about how much it might expand and fill some of the evaporator fins.

FWIW, I didn't feel an actual draft so much as was feeling around the units for cold spots, and while the top-rear of the unit would be colder than the rest of it (that's where the evap. is), the area around that entrance and the metal strip itself was much colder.

I'll give it my best go to seal it up carefully.

[zachriggle]

The unit now cools to about 42° (according to the refrigerator thermometer in the unit), and 45° liquid temperature from the second glass poured. As I understand it, this is *acceptable*, but not ideal. Again, this is on the "9" setting.

I've also noticed the the unit cycles fairly frequently. Timing it for a few cycles, it seems to consistently cycle 3 minutes on 8m30s off. Does this sound right? As I understand it, that's not out-of-line for the duty load (35%). Ambient temperature is 75°.

Anything else anybody can think of? I hate to ask, but I'd really like to get this thing down to 38°!

Thanks :-)

[THE ICEMAN]

Take a close look at the evaporator coils while it has had time to run & cycling. Reach up behind the coils & see if you can feel any ice buildup. It would most likely show up on the left side as you look at it from the front. If you are finding an ice buildup you could quite possibly be low on refrigerant. This would mean you have a leak in the system. You would need to contact a company that works on those units & not just an A/C company to confirm this.

While I work on those units all the time, it is still difficult to diagnose something remotely. There are a lot of possibilities & having the ability to see something & put your hands on it will speak volumes.


THE ICEMAN