True ice cream dipping cabinet

[hvacskills]

Thanks. Just to verify the performance check you mentioned in Post #1, at 20#/220# (-16F/97F) the Danfoss Coolselector2 program shows 8.2 amps, just what you said.

Attachment 803687

I've always put a lot of confidence in performance chart results, enough so it would convince me not to simply replace the compressor when nothing else appears to resolve the problem. If there's going to be "one last try" with one of these types of jobs where nothing seems to improve matters, let the performance data be that last try, not the cost and bother of a new compressor.

In the end, these headbangers sometimes need to be brought into the shop so you can fiddle with it in your time. It's certainly of no use to the customer as it sits now.

are you able to calculate some BTU numbers of the compressor vs .042 x 10 ' capillary vs TXV ?

[icemeister]

are you able to calculate some BTU numbers of the compressor vs .042 x 10 ' capillary vs TXV ?

For cap tube sizing, I use the Tecumseh program: http://boxload.tecumseh.com/SelectCapTube.aspx

This compressor at -27F/99F has a capacity of 0.179 tons or 2148 Btuh. Based on that and 89F liquid temperature and 36" heat exchange length, I get 66" of 0.042" cap tube would be required.

This program has always given me sizes that work from the start with no fussing about.

[hvacskills]

For cap tube sizing, I use the Tecumseh program: http://boxload.tecumseh.com/SelectCapTube.aspx

This compressor at -27F/99F has a capacity of 0.179 tons or 2148 Btuh. Based on that and 89F liquid temperature and 36" heat exchange length, I get 66" of 0.042" cap tube would be required.

This program has always given me sizes that work from the start with no fussing about.

think OP may want to look into capillary tube length

question ..... 1/4 ton TXV ... is that while the valve is modulating within it operating temperature range or at full flow ? question being suppose the sensing bulb is not cold enough to start metering the valve closed and is still wide open ?

even if not 1/4 ton looks slightly large and might explain the lower head pressure if it was wide open

[icemeister]

think OP may want to look into capillary tube length

question ..... 1/4 ton TXV ... is that while the valve is modulating within it operating temperature range or at full flow ? question being suppose the bulb is not cold enough to start metering the valve closed and is still wide open ?

even if not 1/4 ton looks slightly large and might explain the lower head pressure if it was wide open

The 1/4 ton is the nominal rating of the valve at its standard conditions. The conditions for a specific application will be different and so the valves flow capacity will vary accordingly. Since when a valve is selected the closest valve capacity will most always be a little greater than the required capacity. the valve will tend to feed wide open to its max flow capacity if above the design conditions but modulating if it's at design temperature.

A higher suction and condensing temp during pulldown with a TXV as compared to a cap tube would be expected. A TXV with an MOP, pressure limiting powerhead would be somewhere in between.

If the compressor capacity is sufficient, one would expect the box temperature to pull down to design within a reasonable time. When it doesn't and all else look good, you have a problem which may be difficult to find, but often has a simple explanation.

[hvacskills]

The 1/4 ton is the nominal rating of the valve at its standard conditions. The conditions for a specific application will be different and so the valves flow capacity will vary accordingly. Since when a valve is selected the closest valve capacity will most always be a little greater than the required capacity. the valve will tend to feed wide open to its max flow capacity if above the design conditions but modulating if it's at design temperature.

A higher suction and condensing temp during pulldown with a TXV as compared to a cap tube would be expected. A TXV with an MOP, pressure limiting powerhead would be somewhere in between.

If the compressor capacity is sufficient, one would expect the box temperature to pull down to design within a reasonable time. When it doesn't and all else look good, you have a problem which may be difficult to find, but often has a simple explanation.

that is why understanding how and why refrigerant is supposed to act / re act within a system is important

[icemeister]

that is why understanding how and why refrigerant is supposed to act / re act within a system is important

However it's those little things you overlooked or dismissed that are behind you. That's why they often bite you in the butt.

[hvacskills]

However it's those little things you overlooked or dismissed that are behind you. That's why they often bite you in the butt.

if too long of a capillary tube was installed and refrigerant was added to raise the lowside pressure to be somewhat reasonable for the box temperature I would expect to see a noticeably elevated highside pressure

[drage93]

Finally got in contact with customer. Still sits at 25F. I am going over there tomorrow to see what going on, I will report, customer is interested in new compressor.

[hvacskills]

Finally got in contact with customer. Still sits at 25F. I am going over there tomorrow to see what going on, I will report, customer is interested in new compressor.

catch all of your readings ....

lowside pressure
highside pressure
superheat
subcooling
ambient
box temperature
compressor amperage

what length / size cap tube did you install ?