Denco unit L.P trip

[N.Lewis]

Hi guys, working on a denco under floor aircon, unit is tripping on L.P, which would suggest low refrigerant, put guages on without comp running, both low and high side balanced out at 100psi, activated contactor manualy and suc went below Opsi diss also down to zero, removed any refrigerant left in system and charged with 7bar O.F.N, leak checked every joint and nut on system no leaks found while unit is in this poorly condition am going to change drier and clean out filter on t.e.v, any other suggestions would be welcome. thanks.

P.S system has had nitro in for about hour and a half and guages show no loss at all...

[paul_h]

A few things, it's hard to get data when the post is written like a story, you need paragraphs and line breaks when you are stating observed pressures and temperatures.
Sorry if I'm wrong but from what I could understand you said HP went from a static 100 PSI, down to zero when you ran the system?
Systems only short of refrigerant don't have the HP going down when you start the system, let alone going all the way down to 0psi

Also 700kpa isn't much to leak test with, I always leak test with the same presuure that the HP could be in normal running conditions. I've found heaps of leaks that others couldn't using that method and a bit of soapy water.

[N.Lewis]

I'll keep my story telling for my daughter next time then, would have thought 7bar was adequate press, will boost it up some more and re-chack..Cheers.

[nike123]

Hi guys, working on a denco under floor aircon, unit is tripping on L.P, which would suggest low refrigerant, put guages on without comp running, both low and high side balanced out at 100psi

That just shows you that you have refrigerant in system.

activated contactor manualy and suc went below Opsi diss also down to zero,

There is no chance that both suction and discharge reads 0psi after you read 100psi initially. This reading you could get only if you connected both gauges at low side of circuit.

removed any refrigerant left in system

How much did you recovered and what is required refrigerant charge for that unit?

and charged with 7bar O.F.N, leak checked every joint and nut on system no leaks found while unit is in this poorly condition am going to change drier and clean out filter on t.e.v, any other suggestions would be welcome. thanks.

P.S system has had nitro in for about hour and a half and guages show no loss at all...

You should pressure test it with higher pressure (maximum allowable working pressure) and also introduce some small amount of refrigerant in it and then test it with electronic leak detector.
Then you should record temperature of surrounding and after 6h check pressure in system.

[frank]

I assume that the system is operating on R22.

Increase your OFN pressure to 375psig (25bar) and leave it on test for 24 hours, then check your gauges for any pressure drop.

Sometimes when you can't find a leak under OFN pressure test , it could have been the schraeder cap that was leaking but now doesn't show up as your gauge line is making a good seal.

[N.Lewis]

Thanks for all replies, paulh and frank, increased ofn to 25b found pin prick leak on cappilary line going into pressure control valve which was behind L.P/H.P switch, Happy Day's

[Brian_UK]

Might also suggest that your HP reading was perhaps downstream of a solenoid valve which didn't open when you manually pushed the contactor in.

[TRASH101]

As Brian says most Denco downflow units I`ve seen have a liquid solenoid and remote condenser. I am still concerned how you managed to pull a vac at suction and discharge . Did you measure at the service valves on the rotalocks. You may have more than a leak to worry about

[crit71]

Simply put, if you just pushed the contactor in, then the solanoid wouldn't have been energized, if your HP guage was connected down stream of the solanoid then your basically reading the same pressure as your LP side.
Pressure test.
Repair leak.
re pressure test.
Vac.
Recharge and run under on demand of controls.

Chris.

[Denco Technical]

I can concur if you just "push" the contactor in the liquid line sol valve will not be energized.

Very confused re the high side?? did you have the gauges on the same side of the system?