Refrigeration Troubleshooting

[Hudson Force]

Here's the scenario: After having a suitable operating Technautics "Cool Blue" system for ten years, I found the need to replace the Compressor and associated modules as one unit (Danfloss w/fan, control module, etc.). This was a simple task requiring six connections (12VDC power +&-; thermostat +&-; and Aeroquip fittings for R134a to and from cold plate). Connections tested and secure,- coolant fully charged and not leaking; cold plate frosting and all apparently operating properly.

Here's the problem: The temperature remains suitable in the refrigeration section (ca 4cuft) vented from the freezer side (ca2cuft) as in the past. Most everything remains frozen in the freezer side; however, melt water does accumulate at the bottom of the box from added ice that partially melts)

Possible Solutions: 1- I'm sure I could alter and improve the the lid seal, but this remains the same as it was during the former good function of the freezer. 2- I'm considering that the insulation of the box has degraded due to water seeping from the box into the insulation. Access to the outside of the insulated box is very limited to check for temperature or condensation. I'm thinking of drilling a test hole to detect water and then plug and repair. 3- The newly replaced Technautics unit has a selection switch to control compressor speed that was not present on my older unit. I can increase the compressor speed and consume more amps that were formerly required. 4- My R134a volume is judged by looking for air bubbles in a sight glass which doesn't seem very accurate. Could I have too much or too little coolant. 5- I can't imagine any problems occurring on the cold plate side,- 'thermostat works, no leaks....

So, what are your thoughts? What other possibilities am I missing?

[Paul L]

Are you using the manual thermostats that comes with the unit or the optional elect tronic one? I have found it much easier to dial in the cold plate and the on/off range with the electronic one.
If you use the directions with the Coolblue the fill amount should be pretty accurate. Use a flashlight at an angle to get a good view of bubbles.

[Hudson Force]

I do have the "manual" thermostat and was not aware of an option for an "electronic" thermostat. I have to admit that I don't understand the difference. I manually select the adjustment of my electrically connected thermostat. I'll need to look at the Technautics options. I don't have my manual with me, as I am away from my boat for this week, but I believe the directions stated that the R134a should be added to achieve "minimal" bubbles. Are you saying that the proper condition would be NO bubbles? Thanks for your reply.

[Paul L]

You fill till the bubbles stop, then wait something like 5 or 10 minutes and check for additional bubbles. Have measured the holding plate temp?

[Hudson Force]

Originally Posted by Paul L

.......... Have measured the holding plate temp?

No I have not. Should a read the temperature from a frost removed area near the center of the cold plate? I also recall another complication to add to the mix. After installation I noticed the Schrader valve that is not the one designated for filling with the R134a had a minor leak. I poked at the center pin, with hope that it would seat properly, and tightened the brass cap. A soapy water spray indicated that it was not leaking. I do not know if this schrader valve leak was stopped at the valve or with the tightened cap. The cold plate is certainly below freezing due to it's frosted surface, but what temperature range should I expect?......and Paul, would you suggest that the final proper state would be infrequent small bubbles or absolutely no bubbles in the sight glass? Thanks...

[daddle]

Check that the thermostat probe, if any, is attached the same as before. Mine goes to a clamp on the holding plate.

A few bubbles is okay. A sight glass is actually a fine way to judge the fill. The other is that after running for a while (normal temps and such) the frost line on the return tube should be somewhere after the holding plate, but before the compartment wall.

[Paul L]

As said above, a few small bubbles os OK. You might call Tang at Technaitocs, he id Good at walking people through issues. There are small O ring gaskets in the Scchrader gable connections that cam get offset and damaged
I had a small that would leak out over 3 or 4 months. Replacing the O ring fixed it
My plate gets down to low double digits or bight single digits F.

[Hudson Force]

Thanks for the ideas. This gives me some clear goals when I get back to my boat.

[Trish the Fish]

Hi, I'm new to the forum and want to add my 2 pennies. When you were checking for bubbles in the sight glass was the compressor running on high speed? It not, run it on high speed and check the sight glass again, if you see lots of bubbles add refrigerant, if you don't see any bleed a little refrigerant out (slowly) until you see a few. You can fine tune the charge from there.

Good luck, Mike

[Hudson Force]

Originally Posted by Trish the Fish

............... When you were checking for bubbles in the sight glass was the compressor running on high speed? It not, run it on high speed and check the sight glass again, if you see lots of bubbles add refrigerant, if you don't see any bleed a little refrigerant out (slowly) until you see a few. You can fine tune the charge from there.

Good luck, Mike

I'm still not back to my boat to test these ideas, but "Trish the Fish" is confirming my earlier thought that too much refrigerant (no bubbles) can be a problem as well as too little (many bubbles). I had not considered that the view of the bubbles would be easier with the higher speed of the compressor. Maybe not "easier",- I'd assume the rate of flow would simply increase the number viewed over time. I'll be ready to test these ideas Sunday.

[Paul L]

On the Technautics I believe the flow control is done by the control value on the evaporator. This how it differs from tbr other vendors.

[sailalibi]

I also have a cool blue with problems. My compressor runs all the time! It cools (and freezes stuff next to the holding plate) but I see NO bubbles in the sight glass. When I added 134a (about 1 can) still no bubbles but then I got 3 flashing led lights and a lout sounding compressor. I drained off some freon ant he flashing stopped as well as the noise but still no bubbles. Also when I push in the low side fill valve (shrader?) I hear no hissing. Any ideas?

[Richard Kollmann]

Question: I drained off some Freon refrigerant the flashing stopped as well as the noise but still no bubbles. Also when I push in the low side fill valve (shrader?) I hear no hissing. Any ideas?

Yes, After sorting through several thousand emails and forum posts for my new forum the most expensive and extended boat refrigeration outages are caused by someone tampering with refrigerant. I just posted on my Forum sections on Too Much and Not Enough Refrigerant. Only one out of twenty so called service technicians know what they are doing on these small Danfoss compressor systems.

Depressing low pressure fill valve with compressor running is like shooting yourself in the foot as pain of no refrigeration may last throughout the cruising season. When someone says you need a new compressor 999 times they are wrong now the gun went off again and shot the other foot if compressor is replaced..

If you are positive compressor runs continuously problem of poor cooling is not electrical. On a Cool Blue a wide range of refrigerant volume is possible and still maintain good performance because of refrigerant receiver tank’s extra storage capacity. With a warm holding plate’s way oversized Thermo Expansion Valve (TEV) wide open to maximum flow large bubbles will be present in sight glass. When plate solution cools TEV will start reducing its orifice size and begin to reduce refrigerant flow. As refrigerant flow slows sight glass liquid will be more condensed with fewer and fewer bubbles. If compressor runs long enough plate solution will freeze hard like a rock and excessive liquid refrigerant will back up into receiver tank. It there is too much for receiver to hold excessive refrigerant will back up into condenser reducing systems overall performance. By tapping on froze plate with a large coin you can tell if plate is completely frozen. Now when condenser’s cooling medium’s air is warmest and plate is frozen will sight glass be completely clear. If condenser cooling air is cooler then small bubbles in glass will still indicate a correct charge.

There is a big difference in refrigerant charge volume between a TEV and a Capillary tube flow control device system that all other small refrigerators have. A Cool Blue unit can tolerate a variance of 3 to 5 ounces of refrigerant while ½ ounce change plus or minus will affect a Capillary tube system’s performance.

[Greggegner]

My issue with cool blue was fixed when I got a programable thermostat and found the correct position for the thermocouple. It was to large in diameter to fix in the tube on the cold plate. If the plate is getting cold then the compressor is not the issue. Also make sure the box is not empty.

[Hudson Force]

'just a note for closure of my problem,- Technautics walked me through some diagnostics and then replaced my compressor unit under warranty. Now I'm back with a very cold, very quiet, and low amp use freezer/ refrig.