mitsubishi puh5yksa

[al]

I'm looking at an r22 ducted unit, tripping on high discharge pressure, on start up gets to 30b, if left running drops to 24b, condenser clean and both fans running flat out. Unit drawing 8.5a, nominal rating is 7a,(3 phase).

Found faulty bypass solenoid from discharge to liquid line, removed gas and replaced, same symptoms.

suction into unit is 5c(5.2b),Liquid line temp out of condenser is:33c(24b), liquid pressure from service valve is 8b,

Suction out of 4 way valve is also 5c(if this was passing would this be higher?), discharge temp is 90+, i reckon it's a blockage but before i pull and replace every component in the line would anyone have a more scientific explanation??

i've seen mention of a strainer out of the condenser but can't find its location, i reckon it's got to be on the outdoor as if it were further downstream it would just pump down?

Changing unit to heating leaves pressures the same.

thanks

al

[Thermatech]

Suggest remove side corner panel & measure liquid temp through the 2 distributors & 2 capilary coils which bypass the 2 heating mode expansion devices.
Then the strainer.

Sometimes I find it helps to use 2 sets of gauges on the outdoor unit to help find blockages.
Then you can monitor the pressure at both S & L service valve & also discharge & suction at the compressor.

After the capillary tubes you have pre expanded liquid so pressure should be slightly lower at liquid line service valve.
Make sure in heat mode you have good liquid line pressure to make sure the blockage is not at the indoor unit.

[al]

Thanks Therm,

where exactly is the strainer, i have the individual distributors coming back to the manifold then into the check valve/capillary assembly, does it expand in the outdoor before heading to the indoor?

temps on the distributors and at the liquid line after the service valve are at 25c, i'll check heating mode later tomorrow, customer would like me to narrow it to outdoor or indoor!!

al

[AbsoluteWDJ]

Just a thought. I've on a couple of occassions looked at a condensor coil and thought it was clean but when actually hydrocoiled it and rinsed, I've found it to be the opposite. Have you tried a condensor coil cleaner yet?

[al]

Absolute

thanks for the input, if this was the case wouldn't the liquid line temp be way higher?

al