HP switch malfunctioning

[sendhilkmar]

Hi ,
I have experiencing HP switch (cartridge type) erratic tripping issue with our AC units. This switch is Schrader pin type and has a cut out pressure of 30 bar. When we tested the unit by partially blocking the condenser , the HP switch initially tripped at 445 psig and reset at 300 psig then tripped at 350 , 270 psig. The switch was installed in a liquid line after condenser. What would be the problem? It is happening almost in all the units

Regards,
sendhil

[Rob White]

.

The pressure in the liquid line after the cond will be
the same (or very near) as the pressure on the discharge.

I personaly though would have them conected to the discharge
from the compressor to the condenser.

If you have erratic readings from all of them perhaps it is more
to do with the hydrolic effect of subcooled liquid than it is to
do with the switches them selves.

Could you move just one or two and run them in the discharge
pipe and then compare the results.

Regards

Rob

.

[sendhilkmar]

Thanks Rob for your suggestion. I am visiting the site next week and will try some trails with discharge line and liquid line

Regards,
sendhil

[Tesla]

Hi Sendkilkmar
If I had suspect HP safeties on several units I would be checking the device it's self romoved from the system, set up with a nitro bottle and set of gauges. If the result is not as stated (435psig) + or - the error% or value it is the sensor. It may have been ok when it came out of the factory but with time and use they become unreliable. This is the only sure way to test & know for sure the HP safety is working. Like you did it will need 3 tests - cut out & cut in. If it proves ok when tested directly with nitro then the problem is likely answered by Rob in the above post, or it could be affected by temperature.