walk in freezer not going into defrost

[royd2]

what would cause my compressor to keep runing while in defrost , this is a pumpdown system. changed time clock twice still same problem

[mattt787]

did you have your gages on the system if it was pumping down you would see the low side drop and the high side would go i know this might be basit but if that does not happen the liquid line secanord might not be closing

[ar_hvac_man]

bad pump down solenoid or low pressure cut out. have to put your gauges on it to know which. contactor could also be welded closed.

dont just throw parts at it, troubleshoot it.

[royd2]

so if my low pressure control doesnt go off on low pressure my compressor will continue to run preventing my defrost from coming on ?

[supertek65]

contactor stuck?

[ar_hvac_man]

so if my low pressure control doesnt go off on low pressure my compressor will continue to run preventing my defrost from coming on ?

If your clock is energizing the heaters youll be heating and cooling at the same time.

[royd2]

thanks ar. i am posting this after the fact as i tried to tell the senior tech to check solonoid and pressure cut out. i quess what i am asking is if my compressor never shuts off my time clock will never allow my defrost heaters to come on correct?

[supertek65]

defrost timer de-energizes ll solenoid valve and then compressor will run until pressure switch opens.

[ar_hvac_man]

thanks ar. i am posting this after the fact as i tried to tell the senior tech to check solonoid and pressure cut out. i quess what i am asking is if my compressor never shuts off my time clock will never allow my defrost heaters to come on correct?

Compressor shutdown doesnt initiate defrost, your clock does. Your compressor could continue to run while your heaters are energized.

[royd2]

ok but does the defrosters come on instantly ?

[royd2]

ok thats what i thought so we need to check our elements and solonoid and pressure cut out then.

[royd2]

could a bad defrost termination switch also cause my heaters to not come on ?

[ar_hvac_man]

Put guages on it. Turn the clock to initiate defrost. Watch gauges. It should pump down. If it pumps down and doesnt shut off, your contactor is stuck or your low pressure cutout is bad. If it never pumps down, ll solenoid is bad. OR its wired wrong.

[royd2]

idk somehow reading hotter temp than actual

[ar_hvac_man]

You need to follow those steps i listed then worry about wether your heaters are coming on or not.

[royd2]

ok thanks thats what we will try

[supertek65]

[royd2]

i will post back tomorrow, thanks again

[jpsmith1cm]

Compressor shutdown doesnt initiate defrost, your clock does. Your compressor could continue to run while your heaters are energized.

This is not necessarily true.

Many times, the electrical circuit to the condensing unit is only large enough to run the compressor OR the heaters, but not both.

Thus, there is often an interlock so that the compressor must cycle off before the defrost heater contactor can energize.

[ar_hvac_man]

I agree. I dont see them often but there are systems set up and wired that way. No offense to the OP but hes obviously lost(we all were at some point) so I posted what I felt he needed to tackle first.