True prep table

[nickellhead]

I've been working on older true prep table. The evaporator keeps freezing up. I've replaced the cap tube with same size and length and dryer. Ive brazed in access fittings on high and low it's a R134a system. The thermostat went bad on it also so I replaced it. Then I've replaced the evaporator fan too. At start my cabinet temp was 80 degrees. My ambient 95 degrees. My suction was 17 degrees and head 250. Any help would be appreciated!

[VTP99]

Looks like a restriction with that hi of head pressure. Of course if your condenser is plugged you would get the same result.

[nickellhead]

I overcharged it about 4-6oz to get suction up. I'm wondering if I need to shorten length of cap tube to raise suction pressure. It ran good for a week but now froze up again.

[VTP99]

What's the nameplate charge say ?

[nickellhead]

11oz. It's a True TSSU 48-12

[VTP99]

Pull the charge and weigh in the exact amount. Your overcharged.

[nickellhead]

When I first weighted it in my suction was at 3-4psi. That's why I overcharged. Shouldn't my suction on a refrigerator with 134 be around 25 psi?

[VTP99]

On a hot pull down it can go low at first.

[VTP99]

Shouldn't my suction on a refrigerator with 134 be around 25 psi?

Well at 26 psig your coil would be 30* add a 10* TD and your at 40* air temp.

[2sac]

134a I like seeing 16-19psi on the suction side. Your head is way too high.

[nickellhead]

When I weighted it in I let it cool down but suction pressure nor head changed. It stayed at 3-4&160ish. And it took cabinet forever to get down to 38 degrees. I just don't understand how it's freezing up when I have it overcharged? I'm wondering also if maybe new thermostat is acting up. The probe goes into a well inside middle of evaporator. I've always seen the probes clipped on outside of evaporator. here's a pic of the top of the evaporator.

[VTP99]

What was the head pressure when you first weighed it in ? With a cap tube and no receiver the only place the extra refrigerant could go to was the condenser. This would reduce your condensing surface area. And yes the temp. control cap tube belongs in that well. Take a closer look at the condenser coil to be sure it is clean.

[2sac]

Does this unit have pans on top? If so, are they keeping pans in it overnight or just a cover? Need to keep pans in it.