aquasanj

[aquasanj]

Hi, i have query about a roof top APAC reverse cycle air conditioner serving busy grocery shop. we have set it to run on heating as the shop gets too cold with the refrigerated display counters.

Temp set to 22 degrees, shop temp is close to 19 degrees.

It trips out on high pressure now and again
Its a R22 unit and running pressures are within limit i.e 68 lp,240 hp PSI.

All filters are clean, indoor and outdoor fans are running and, running currents are within nameplate ratings.

Air flows are good with no restrictions in duct work.

Any assistance will be highly appreciated guys.

cheers

[Yuri B.]

What degrees superheat is of the gas leaving the evaporator?
If you reduce the air flow through it (close fully fresh air intake?), pressures will drop.
If not, part of refrigerant need to be evacuated off of the system (as too "extrreme" the operation mode is - heating during hot whether)

[aquasanj]

What degrees superheat is of the gas leaving the evaporator?
If you reduce the air flow through it (close fully fresh air intake?), pressures will drop.
If not, part of refrigerant need to be evacuated off of the system (as too "extrreme" the operation mode is - heating during hot whether)

thanks Yuri,

The fresh air intake is fully closed via servo controlled dampers and the system works on an economy cycle system whereby if outdoor temp exceeds 32 degrees, outside air dampers open and the compressor and out door fan go off and now the indoor fan recirculates the outside air.

I had feeling that during defrost (de-ice) cycle, the pressure might be rising above the 360 psi cut out which is factory set and tripping it. probably the de-ice control sensors or the
de-ice time out circuit may need checking???

Of course it has to be monitored to confirm my doubt.

cheers buddy

[Gary]

240 PSI is way too high with 19C air entering the indoor coil.

Assuming you are right about the indoor airflow being good, I'm guessing air in system or overcharge.

[mad fridgie]

What is your ambient (out side temp)?

[aquasanj]

hi,

ambient varies from 28-32 degrees per weekly average the system apparently has never been charged and came factory pre-charged

thanks

[mad fridgie]

hi,

ambient varies from 28-32 degrees per weekly average the system apparently has never been charged and came factory pre-charged

thanks

Simply the unit is not designed to heat in this ambient temp, your evap duty is to high, thus your condensor is to small (high discharge pressure)
Install CPR or slow the out door fan speed down.
Why do you not install an enthalpy heat exchanger and just introduce fresh air (reduces entering moisture)

[aquasanj]

thanks buddy,

hmmmm.. just a thought, if we assume the indoor fan coil to be small, i would expect the liquid line to be warmer than usual and in fact it is normal.

[Gary]

thanks buddy,

hmmmm.. just a thought, if we assume the indoor fan coil to be small, i would expect the liquid line to be warmer than usual and in fact it is normal.

"Normal" is an opinion, not a temperature measurement.

In order to see what is wrong we need actual temperature and pressure measurements.

Specifically, we need to know the high and low side pressures, the temperatures of the air entering and leaving both coils and the liquid line and suction line temperatures. Without real numbers all we can do is guess.

[aquasanj]

Noted with respect dear sir.

will visit site and revert with the info

thank you

[lowcool]

its possible that the outdoor tx valve may have shut down.
whats the back pressure?