Low Superheat Eror

[Meer Abdulrehma]

Hi! This is my first time

Have a situation where we have a Trane chilled water system it runs for about 2mins and the unit switches of eror displays Low Superheat. The superheat setting is 3.5 , Evap ref pressure is 1640 Kpa cond pressure 860. have tried checking the unloader does not energise, but when i set to test the compressor it energises. any advise.

[goshen]

hi it sounds like either your sensor needs replacing or u have crossed wires unplugg the sensor and check the reading this should put u in the right direction

[NoNickName]

And how much is the superheat actually?

[Lowrider]

From the readings he gave, most likely negative!!

So indeed chech that the wires are hooked up correct. If they are, you can check them by measuring the resistance. @ 25 dgr C they should have a resistance of 10k Ohm. They are NTC's. If they are off, you will have to change the one in the suction pipe and the one after the EXV, they are a pair and matched!

[NoNickName]

How do you know it's negative, without knowing the suction temperature?

[frank]

And how do you know that you do not have a Low Superheat problem?

Is it a shell & tube evaporator? has it been cleaned recently? Is the water flow correct?

So many reasons for Low Superheat - it's too easy to blame the sensor.

[ptsac]

can you confirm that the evap pressure is reading 1640kpa. If the sensor is reading that pressure then low superheat will always show. Check your pressure transducers as Lowrider says.

[NoNickName]

Guys, superheat is calculated by subtracting the evaporating temperature from the suction temperature.
We don't have the suction temperature, therefore NO ONE can affirm whether superheat is low or not. And NO ONE knows the evaporating temperature from the pressure unless the poster says what refrigerant is used.
Stop talking nonsense. Go do your homework. Chapter 1. Fundamentals.

If anything is wrong, the condensing pressure CANNOT be lower the evaporating pressure. The poster probably swapped the two pressures.

[ptsac]

Guys, superheat is calculated by subtracting the evaporating temperature from the suction temperature.
We don't have the suction temperature, therefore NO ONE can affirm whether superheat is low or not. And NO ONE knows the evaporating temperature from the pressure unless the poster says what refrigerant is used.
Stop talking nonsense. Go do your homework. Chapter 1. Fundamentals.

If anything is wrong, the condensing pressure CANNOT be lower the evaporating pressure. The poster probably swapped the two pressures.

Perhaps the original poster would clarify the pressures. However even if the readings have been swapped 8.6 Bar would be a high evaporating pressure for 134a R22 or R407c. We do know however that the suction superheat as seen by the controller must be less than 3.5c. With the information supplied we have had to take a guess. Those pressures would lead most to suspect a faulty pressure transducer. Less accusations of people talking nonsense please.

[Lowrider]

You are all right, but judging from his statement he is working on a Trane screw chiller with a UCM-CLD controller which has one temperature sensor in the condensor, one temperature sensor directly after the EXV and one in the suction line, per circuit. The superheat is calculated from the difference between the one after the EXV and the one in the suction line. If the reading shows 1600 kPa it's most likely that the sensor is at fault!

[goshen]

hi all been there done it fixed it
it is as i said before probably faulty sensors just as lowrider agrees
wish u all a good week

[NoNickName]

So you've gone to Kenya for fixing it?

[goshen]

hi there ,not that far away though!!!!!!!

[Meer Abdulrehma]

Hi Guys

Thanks to all of you for all the ideas, when got the first message from goshen went and checked found had miswired sensors the one after the expansion valve and the one in suctiion pipe. and the unit kicked with out any probs and is running well.

[Shibhrac]

Some problems could be solved in a professional manner and faster than typing my paragraph. In short we should make all our efforets before we ask the experts

[goshen]

happy to be of service!:)

[toughquestion]

sorry guys its just driving me crazy, perfect super heat, duct work sized wright, delta t only 10 degrees. liqued line 330psig temp 93 i belive middle curve, 410a suction line not to sure if press is ok 130pisg please help