Floating Condensation/Suction - Electronic EPR/TXV

[georgedvf]

Hello!!

Do you use Floating Condensation when Parallel Compressors Rack is used??? What changes are there to be done in the components of the system???

I've read that when use of Floating Condensation the TXV should be analized to determine if Electronic one is required, and if Floating Suction the EPR should be electronic too to ensure the correct functioning of the control.

Also I will like to discuss the benefits of using this type of control.

Thanks!!

[georgedvf]

OK, I guess not many use the Floating Suction or Floating Condensation...

Any one????

[Magoo]

Best described as a floating accident waiting to happen, when electronics are envolved. One hick-up one broken compressor. All in the name of progress and efficiency.

[georgedvf]

Ok, 1 vote for DO NOT USE IT !!!

Anyone else?

[Segei]

In industrial refrigeration people use floating condensing and suction pressures. Their are good tools to save energy.
TXV has narrow range of operating condensing pressures. So it is not good for floating. EER has wider operating range of condensing pressures.
I assume that EPR is evaporator pressure regulator. I'm doubt that any EPR can be helpful to save energy. It is better if you do not have EPR. To save energy, compressor operating suction pressure should be floated.

[georgedvf]

Thanks Segei. One question: If you don't have EPR how do you manage diferent rooms with diferent suction pressures???

[Dacien]

I used floating condensation and suction.

for example: 404a work the 15 to 20 bar (+25 to +35ºC) Dt 10ºC cop increase 20-30%.

One degree Celsius is a 3% energy savings

0 problems. This installation works with plc.

[Magoo]

PLC's are as good as the programer, functional descriptions from the designer is only half way there. Programers always take short cuts, beleive ME. been there done that with computer nerds.
What is the saying..., rubbish in , rubbish out. I am being polite very unusual for me. [ common comment/ didnt think that would happen or even matter. ] and you have compressor bits scattered on the floor.

[Segei]

Thanks Segei. One question: If you don't have EPR how do you manage diferent rooms with diferent suction pressures???
It depends of the system. In industrial refrigeration we have 2 -3 different separate suction pressures. Each pressure has compressors operate for this particular suction. If you compressors only for low suction pressure, you should have EPR. However, it doesn't matter for efficiency it is mechanical or electronic EPR.

[Dacien]

PLC's are as good as the programer, functional descriptions from the designer is only half way there. Programers always take short cuts, beleive ME. been there done that with computer nerds.
What is the saying..., rubbish in , rubbish out. I am being polite very unusual for me. [ common comment/ didnt think that would happen or even matter. ] and you have compressor bits scattered on the floor.

I am a programmer and refrigeration technician. This is the key for me if you use plc. The first is the safety of equipment.

[georgedvf]

When usign floating condensation pressure, what are the parameters to determine de best condensation pressure??? in other words, where to put sensor, transducers, etc???? what's the logic to determine the best pressure at the time???

[Dacien]

Pressure = Pressure equivalent to temperature (Room temperature + DT)

IF Pressure < P min Then Pressure = P min

Minimum pressure P min is determined by experience, type of compressors, etc.

[Segei]

About optimum condensing pressure.
First you should choose the base line. For air condensers base line is dry bulb temp. For evaporative condensers base line is wet bulb temp. Than you should determine optimum approach. Approach is temperature difference between condensing temperature and base line temp. Criteria of optimum approach is minimum compressor+ condenser energy use. I've done my tests and for evaporative condensers optimum approach can vary from 8 degF to 30 degF. I think it will easier to determine optimum approach for air condensers.