City Multi heavy icing on suction and reduced heating performance.

[Collie]

Hi guys,

Having a problem with a City Multi PURY P500YGMA.
Unit has 12 indoor units, 2 BC's.

There was complaints of poor heating performance in the areas being fed by the slave BC. Checked the outdoor unit and found the system running but the suction heavily iced up and the evaporator slightly iced up. PAR27 controllers showing "DEFROST" frequently also.

Units seemed to be working fine up until two weeks ago when the ambient dropped dramatically from about 14 degrees to 5-6 degrees celcius.

I read somewhere that sometimes the LEV's (not sure which one) can open and bypass the indoor coils and therefore flooding the suction returning to the compressor? am I right or way off? could LEV 3 in the slave BC be faulty? or the temp sensors controlling it?

Any thoughts guys?

thanks in advance

Collie

[Airconking]

Is the gas charge correct? If that's ok then it's probably going to be an LEV in the bx box that is faulty and letting liquid flood back down the suction.
How bad is the frosting? Is it rite back to the comp?

[stufus]

Throw the dip switch on the outdoor board to increase the target discharge temp,can't remember it off hand ,and carry out a full system LEV reset.
Run all units in test cooling and heating alternately and check coil temps ,keep an eye out for wrong branch address's
Cheers
Stu

[AbsoluteWDJ]

In full heating mode. Measure the common suction pipe temperature (between four way valve and accumulator) and have a pressure gauge on the low side. Calculate the suction superheat. If this is low then it is possibly LEV3 valve issue if it's high then it's possible short of refrigerant. On these systems it good to have the piping schematic and service manual to gather data off the SW1 switch. Fault finding isn't always a five minute job! Good luck.

[Don Erb]

What should the superheat be

[Thermatech]

Dont forget in heating mode the suction pipe is an extension of the outdoor coil as the LEV 3 in the master BC is the expansion valve for the liquid to flash off & return back to the outdoor unit coil.

For general poor heating performance SOG or locked LEV3 at the BC are the prime suspects.
If your not sure try changing the LEV 3 motor head first as it is easy & cheaper than recovery of the refrigerant charge.