High superheat

[ewart]

I am having problems with a system consisting of two evap. they are cooling quite well but they are like 100feet away from the compressor. At the compressor i am having high superheat and the compressor is running at a high temp. What would be the solution for that porblem? increasing the horsepower of the compressor would be the right thing?
Ewart

[Brian_UK]

Can you not move the compressor closer to the evaporators?

[monkey spanners]

If the refrigerant is getting more superheat in the suction line, can you improve the insulation?

[Paul J]

yes the pipes should be insulated, 100 feet isn't that far really, what is the superheat from each evap, it could be that one evap is feeding correctly but the other isn't

[mikeref]

Could use liquid injection into the suction line

[ewart]

The lines are all insulated. I like the idea of injecting the liquid but what could be used to control the flow of liquid to the compressor and also it is a pump down system so it would require more controls to prevent short cycling.
What you guys think about increasing the horse power of the compressor and or TXV would it make any sense?

[Peter_1]

Increasing HP of your compressor will make the problem worser (lower TE will result in higher discharge temperatures)
Decrease your SH on the evaps to the lowest possible and allowable, install eventually a suction accumulator (SA) , look like Paul J said if one is not running with too high SH, and if you can't control it, install a TEV (start with a small orifice) injecting its liquid to the inlet of the SA and the bulb of the TEV on the outlet. Take the liquid after the normal liquid line SV (you use pump down you said) or install a second SV in the liquid line of that TEV so that it closes together with the normal SV.

[joe magee]

What do you consider high superheat? Whats the return gas temp? Is this unit charged properly? Is it sized properly? Is this a new unit? Pipe size correct? both evaps have high superheat? Did you try to open the txv to lower superheat? On and On. Look at basics first before you get fancy.

[Sandro Baptista]

Also check the pressure loss on the suction line. If the tube and/or valves have a small DN a big pressure loss will occur and generate more superheat.
Also see if the suction filter is not clogged. Can you check de suction pressure just at outlet of the aircooler? Compare it with the suction pressure ate the compressor.
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[NoNickName]

Move the TEV bulb and the equalisation pipe just before the compressor suction. You will benefit from a higher refrigerant titration in the evaporator as a side effect. Basically you would be treating all SH as useful SH.

[Sandro Baptista]

Move the TEV bulb and the equalisation pipe just before the compressor suction. You will benefit from a higher refrigerant titration in the evaporator as a side effect. Basically you would be treating all SH as useful SH.

NoNickName,

I understand your general idea but I think it's not possible to move the bulb and the equalization pipe to so far of the valve. We are talking about of 30meters of distance.

The SH wouldn't be useful SH. The line superheat will continue to be a "waste"...but of course, because the evaporator will now be better feeding with refrigerant (so it would be nearly saturated at the outlet of the evaporator) the SH will be lower at inlet of the compressor.

[NoNickName]

I understand your general idea but I think it's not possible to move the bulb and the equalization pipe to so far of the valve. We are talking about of 30meters of distance.


Of course, sorry. But you can still evaluate the unuseful SH and reduce the evaporator SH accordingly.
Or in case of EEV, move the sensors further away possible.

[Sandro Baptista]

Yes, I also agree.

[yorkman_gr]

a good solution is to add in your system a suction accumulator,that way u can low your SH and u will have also oil return to your compressor

[kssoin]

a good solution is to add in your system a suction accumulator,that way u can low your SH and u will have also oil return to your compressor
Hi,
You mean a vessel like a cylindrical cannister that is found on rotary compressors. How do you size such an accumulator?
Regards
Kssoin

[joe magee]

The original question was a high superheat issue. Why all the fancy answers? Liquid injection,moving the bulb add an accumulator etc. He never even posted what his superheat was. To him high superheat might be 10 degrees. There is not enough info to give him a defined answer. Lets get back to basics.

[Subzerohero]

Could use liquid injection into the suction line

Sporlan Y10 valve is a great way to inject liquid

[Goober]

Well said......Joe magee

[brazzy wind]

I agree with Joe Magee

[mikeref]

EWART, you disappeared, It would be nice to see a result for contributions made? Besides, i unfortunately have a job comming up where refrigerant lines have to run 150 feet to an open drive.. mike.

[shieldcracker]

The original question was a high superheat issue. Why all the fancy answers? Liquid injection,moving the bulb add an accumulator etc. He never even posted what his superheat was. To him high superheat might be 10 degrees. There is not enough info to give him a defined answer. Lets get back to basics.

I know I am new to this forum, but I agree with Joe. There is a tendency here to overshoot the basic principles and trouble shooting techniques. Do not assume everyone that is posting here is an expert or try to dazzle the less knowledgeable readers.

[radekklimat]

High superheat indicates a small quantity of agent or poorly regulated expansion valves.
Everyone should be regulated separately from the measurement of superheat on the suction pipe just behind the radiator

[ironmen]

I'm fully agree with joe.well i believe a well designed and well built installation a balance is made with the respective capacities of the evaporator and your txv to maintain a good superheat.if this two is incorrecttly size it wont work.start with the basic it could be anything.more info its better

[Leonado-dance]

Hello everybody!
I'm a new member on this web, and i'm a new RE too!
Please to meet you on web to share any imformation about major and job!
Thanks a lot!

[coolxpert7]

Err, what's going on at the evaporator end superheatwise? If there's an issue there it will manifest itself all those miles away at the compressors!

[coolxpert7]

What, with a 100ft of suction line? Then you're just extending the evaporator, recooling ambient & depriving the process!