True Manufacturing food prep table refrigeration issue

3450BB · February 15, 2015, 11:28:31 PM

I have this True TSSU-72-18 food prep table that I have changed the compressor, a Tecumseh AKA4460YXA, and it's not cooling, the evaporator gets over 130F. The low side pressure is 60psi on R134A but it should be at 140psi according to the rating plate. I have it charged to 15oz, 5oz over the 10oz on the plate. I have a feeling its the dryer, there is loose fine material in it. I may also have to change the line set. Anyone worked on capillary tube fridges?

viking · February 16, 2015, 04:14:00 PM

Something doesn't jive. 130F evap? 134A at 60# is 62F. 134A at 140# is 107F.
You sure we're talking evap and not condenser? Can you post high/low pressures, superheat and subcooling?

3450BB · February 16, 2015, 05:28:10 PM

I'm talking evaporator. Temp taken with infrared temp gun. I can only measure low side as there is no high side connection for gauges. Your right about the 140PSI is 107F, that's what it should be on the low. There has to be a blockage in the capillary tube from the shot dryer. The new line set and dryer are on the way from RG Henderson in Mississauga, should be here on Wednesday.

viking · February 16, 2015, 07:14:31 PM

There's absolutely no way 140# evap pressure can be correct. If you are reading nameplate it probably indicates test pressure.
Also if you have 60# evap pressure (which is too high) its not possible to have 130f evap temp. (unless maybe compressor is installed backwards?)

I think you need to re-check. I usually avoid using the infrared for critical measurements. Best to strap a sensor to the suction line.

Again something doesn't jive.

3450BB · February 16, 2015, 11:29:14 PM

The first image is of the rating plate. The second image is of my gauge of the low side connected to the service valve while operating the compressor. I have not run the compressor longer than 15min to avoid undue stress on it.

viking · February 18, 2015, 09:33:53 PM

I believe the pressures on the nameplate are max. pressure ratings not operating pressures.
Need more than one pressure to tell the story. I don't dought your evap pressure is 60# but that is too high. I believe you should star by weighing in nameplate charge. You may just be overcharged. 140# evap. is NOT going to be operating pressure.
Can you at least get superheat leaving evap?

3450BB · February 27, 2015, 11:22:47 PM

I replaced the shot drier. Vacuumed the system to 520 microns, held for 20min. I then charged the system to 10oz as per the rating plate. I ran the unit for 30 min, had frosting on the lower part of the condenser. The evaporator was at 27C and getting warmer. I think the lines are reversed. Unfortunately I'm not equipped to measure super heat. In the photo, the suction is at the king valve.

viking · February 28, 2015, 08:39:49 AM

Kinda hard to tell from the picture but based on everything your saying and if I'm seeing the picture right, I think the compressor is installed backwards.
It looks like the suction is piped to the condenser.

Got a closer look at the pic. Definitely the compressor is piped backwards.

mrbean · February 28, 2015, 10:57:42 AM

Quote from: viking on February 28, 2015, 08:39:49 AM
Kinda hard to tell from the picture but based on everything your saying and if I'm seeing the picture right, I think the compressor is installed backwards.
It looks like the suction is piped to the condenser.

Got a closer look at the pic. Definitely the compressor is piped backwards.

yes yes

3450BB · March 02, 2015, 08:01:19 AM

The prep table works. The suction line was installed to the discharge of the compressor by error on my part. I re piped the discharge so it enters the condenser, then to the dryer and then to the capillary tube. I installed the suction to the king valve port. I vacuumed the system to 320 microns, it held at 520 microns for 20min. I then charged the unit to 10oz. Its working great now.

viking · March 02, 2015, 06:52:54 PM

Right on. Thanks for letting us know the outcome