HP cutout

[old fitter]

Have a five ton scroll compressor with a reed style hp manual reset about 3 inches down the discharge line. The idle compressor starts and pops the saftey in about 2 seconds. Reset and restart the compressor and all is ok, no trip. Water cooled and there is no problem with head, suspect that the startup pulse, maybe laden with liquid takes out the safety, Anybody?

[centrifugal tech]

I would can that type of swicth and get good adjustable pressure swicth with cap tube penn johnson mechcanical type

[duke of earl]

I would relocate the switch to the liquid line.I'm not an advocate of placing them on the hot gas line with recip compressors. Scrolls don't have the pulsations that recips do but I would still relocate it and see if the problem goes away.

[enart9591]

What has changed? Has this machine always done this? How old is the machine?

[maxster]

before a restart remove the 2 wires tape them together,then put on OHM meter on the HP and start the comp. if you see a bounce on the meter after the compressor starts up change the switch.

[old fitter]

They say this unit has done this since orig install, 1997. I see the switches have been changed, and the water reg valves backed all the way out, but what occures is not high head. You can have your hand on the discharge line and it doesnt even get hot in the two seconds it takes to trip. Again its when the compressor has been down, then 2nd stage calls, compressor starts, then hp trips, falsly.

[roc service]

Take the HP switch out of the equation. Bypass the wires and leave it that way. See if you get the call back. This seems like bad advice but most residential units with 5 ton scrolls don't have high or low pressure protection devices. Why do you need one on this application? Let the compressor internal overloads be the protection.

[ej45]

Originally posted by roc service
Take the HP switch out of the equation. Bypass the wires and leave it that way. See if you get the call back. This seems like bad advice but most residential units with 5 ton scrolls don't have high or low pressure protection devices. Why do you need one on this application? Let the compressor internal overloads be the protection.

because it is water cooled, refrigerant reliefs on some units are at 300 lb

[roc service]

Your answer was not really the reaction that I expected when I told him to bypass the HP control. I figured everyone would freak out when I gave him that advice. Except of course for Maxster "When in doubt, jump it out. LOL. Although your right and the unit is indoors and the refrigerant relief blowing off would not be good thing. He could wire the control circuit to have the lead #1 compressor trip the #2 if there was a water problem external or internal to the unit. This is just in effort to see if it's a control problem with the #2 HP cutout.