Copeland scroll compressor

[Steve Wright]

One of our service techs said he had a high pressure (HPC) tripping at 275# (18.9 bar) when the HPC was set for 425# (29.3 bar). The system is R-22.

He said the cause was flood back causing scroll plate separation then the reverse flow of the discharge gas to the compressor caused a hammer effect on the HPC causing it to trip.

This problem occurs specifically as the fan cycle control (FCC) cycles on with with FCC bypassed there is no problem.

Other info: 65# (4.4 bar) suction, 275# head, 2* (1.1*C) superheat, 12* (6.6*C) sub cooling, no rapid equalization as if a pop-off goes off, this is a new 7.5 ton condensing unit on an existing air handler w/TXV, Copeland Compliant Scroll.

I know the 2* (1.1*C) SH too low taking action to rectify that, Replacing the Air Handler like we should have done to start with.

I'm not bitting on the hammering of the HPC, I believe there is some type of restriction in the condenser or its outlet that he is not seeing.

Any ideas or conformations?

Has any one heard of plate separation (compliance) causing a situation like this?

Steve

[Peter_1]

Is it possible to place SI units between brackets please?
This is very difficult to read for SI readers.

[Dan]

This problem occurs specifically as the fan cycle control (FCC) cycles on with with FCC bypassed there is no problem.

Hi Steve. This is very odd, indeed. Are you confident that there is a relationship between cycling the fans ON and not OFF? I would put a tee at the high pressure control and see what the gauges say.

I cannot help but think that your problem will disappear as soon as you get your superheat under control.

[Steve Wright]

Hey Dan

No i am not confident of that relationship tripping HPC vs FCC on however the problem went away when we stopped the FCC from cyling.

I think there is a restriction at the outlet of the cond and that is what the FCC looks at.

When we change the air handler I'll cut in a tee.

Steve

[Steve Wright]

Peter

That is a good idea do you know a quick source for conversion to SI, is there one on this site?

Steve

[Josip]

Peter

That is a good idea do you know a quick source for conversion to SI, is there one on this site?

Steve

Hello Steve,

for me this one is the best:

http://ns.winsite.net/bin/Info?2156

but you can choose:
http://www.katmarsoftware.com/uconeer.htm
http://www.sporlan.com/unitconverter.htm

Agree with Peter_1, quys please put in brackets SI values

Best regards,

Josip

[Dan]

I think there is a restriction at the outlet of the cond and that is what the FCC looks at.

What is the High pressure safety control looking at? If there is a restriction at the outlet of the condenser, wouldn't the FCC see the same pressure as the high pressure safety control?

[Lc_shi]

transfer to SI

HPC 275 ---18.9bar
425----29.3bar

suction 65---4.48bar
head---18.9bar

SH=1.1K
SC=6.6K

if offer a sketch of control of FCC and HPC, it's better to know the problem

rgds
LC

[Steve Wright]

Dan

I'm thinking the liquid line is at a much lower pressure than the condenser pressure.

The HPC is at the inlet of the condenser and the FCC is at the outlet of the condenser.

I will let you know what I find.

Steve

[Steve Wright]

Many Thanks to Josip and LC for SI conversion.

Steve