Adjusting superheat on multiple evap units

[dkemper]

What is the best technique to adjust the superheat on a multiple evaporator unit?

Should I close off the solenoid valve for one evaporator and adjust the valves when they are the only one supplied with refrigerant or is it best to adjust and balance the expansion valves with both supplied with refrigerant?

It seems to me both techniques have issues.

If each is adjusted separately, the compressor becomes over capacity for the single evaporator.

If both are left running, I'd think it be quite the challenge to balance the real pressures and refrigerant flows through the different valves since the settings on one would effect the overall pressures in the entire system.

I think I'm tempted to start with each valve isolated from the other and once close, then balance them together.

I guess I'm asking, what is the best practice?

Thanks!

Win

[lana]

Hi there,

I assume you have multiple evaporators connected to one compressor.

First of all the piping (suction and liquid) become very important. If piping is not correct then adjusting one TEV will effect the others.
If piping is done correctly then there is no problem. You can adjust the valves separately which gives the proper super heat for that evaporator.

The correct piping arrangements are given in ASHRAE Refrigeration Handbook chapter 2.

I have done this with three evaporators with one compressor for -40°C rooms. There were 12 rooms.
11 of them had correct piping and there was no problem. One of the rooms suction pipe was done wrongly. When one TEV was adjusted then the other two were messed up.

My suggestion is the piping. Check them first then try to adjust the TEVs. If piping is not correct then it will be a waste of time with no success.

Cheers

[dkemper]

Lana,

Again, many thanks. I've ordered up a copy of the handbook.

Win