Low Temp Skid on Med Temp Cooler,,, Mechanic going bald!!

[SamRock]

I got a call from a customer about walk in cooler at one of her stores.

We get to the site and its a Singer system from the late 70s but looks to be in good shape for 30+ years of use. The head master valve was wide open stacking refrigerant.

Indoor coil info

Make Singer
MN: HDC150-1
SN: 18-00916
The TXV was stamped R500 with no other markings
As per HeatCraft 15000 BTU 25*SST/10*TD "Evap is for cooler only as it has no heaters"

Outdoor unit

Make Singer
MN/SN Tag missing
Hand written tag on unit said R507
Compressor Copeland EADB-0200-CAB
Compressor is low temp R22/502 with 67000 BTU @ -25* evap / 105* cond

Before starting work box temp was at 50*F
Suction 60psi SH 70
Liquid 345psi SC .78

Shot off to supply house picked up a new

1 - Sporlan Head Master OROA58058ODF
1 - Emerson TXV HFE1RC 12000 BTU Med temp r404A
2 - POE oil
1 - Liquid Dryer
1 - See All
1 - Start cap
1 - Run cap

Back to customers store and do the good deeds. System started up and ran fine with below stats

Indoor Unit

28* Evap Air Discharge temp
36.5* Evap Air Return temp
19.8* TXV Dist tube 1
13.2* TXV Dist tube 2
21.8* TXV Dist tube 3
19.5* TXV Dist tube 4
26.8* Suction line temp
108.4* Liquid line temp
23* Evap surface at inlet
26* Evap surface at outlet
33* Box temp at stat
71% RH

Outdoor Unit

85.2* Condenser Air inlet W/ 86% RH
91.9* Condenser Air outlet
48.7psi Suction
26.4* Suction SH
11.2* SC @ Receiver outlet
7.6* SC @ Condenser outlet
282.9psi Hot Gas
23.5 Compressor SH
128* Compressor Motor end temp
102.5* Condenser face inlet temp
93.5* Condenser face outlet temp

At time of shut down

30* Box temp
10.6* SH @ Condenser
47psi Suction
281psi head

Cycle time
18min off
24min on


All was good until I put the cover back on the terminal box of the compressor, the next run cycle got about half way through and the thermal protector kicked out the compressor. I pulled a new one from the truck popped it in and the same thing 14min into the on cycle it kicked out on thermal. The compressor is pulling 7.84A and only shuts down with the cover installed...


Thanks for any input given.
SR

[Magoo]

low temp system at medium temp application would be overloading compressor windings/current draw after extended run times. The klixon protector is being cooled by having terminal cover off . Fit a crankcase pressure regulator and limit actual compressor suction pressure. Better to replace compressor for a medium temp range.

[SamRock]

just to add

104.2* LLT @ condenser outlet
101.9* LLT @ receiver outlet
40* RGT @ compressor


Compressor listed for

Evap/Cond -25/105
RGT/LIQ 65 / 105

I wonder if I up the SH so that it in the 20s when the unit hits the off cycle if the problem will subside, Is the motor passably getting over worked from the colder RGT. I did not record the SSH when the overload tripped but I will check this first thing in the morning.

[SamRock]

low temp system at medium temp application would be overloading compressor windings/current draw after extended run times. The klixon protector is being cooled by having terminal cover off . Fit a crankcase pressure regulator and limit actual compressor suction pressure. Better to replace compressor for a medium temp range.

Missed your post when I put the last reply in, I was off in the data sheets and had the bing moment! but I think I was on the same track that you stated.

I would love to replace the whole unit but customer does not want to spend the money.

[SamRock]

Fitted the unit with a CPR, Overload issue went away. Box pull down time is longer I just left the store and it was at 40* will check temp in the morning.