Fujitsu iceing up.

[N.Lewis]

Hi everyone.
Fujitsu split air con Mod:AOY36ACF3L:
Indoor evap is heavaly iced, checked cond on roof also ice on suc pipe back to accumilator, for now have turned unit off to defrost, have not connected guages until defrost is complete, will then run system to check..Any ideas why so much build up of ice??
Unit is cooling security control room with quite a bit of kit in there as well as personel, outdoor unit does have thermostat for defrosts, is it worth increasing num of these also..
Thanks in advance..

[paul_h]

1) Lack of airflow, ie ductwork/filter/fan not correct
2) Short of refrigerant
3) Set too low a temperature
4) control system fault (thermistor, tx valve etc)

These apply no matter what system you're looking at. It's usually one of these that causes indoor coil ice up

[airefresco]

Could it be something similar to what was happening in this thread http://www.refrigeration-engineer.co...ead.php?t=5926 (scroll down a bit)

[Thermatech]

If the outdoor unit continues to cool even when the indoor coil has ice on it then the coil frost prevention function is not operating or the unit has no coil frost prevention mode.
Typical problem when low air humidity in the occupied space such as computer rooms.
1/Confirm with equipment supplier what the coil frost prevention mode specification is.
2/ Measure the RH & WB on coil conditions to see if the unit is operating within the manufacturers indoor temperature limits.

[N.Lewis]

Thanks guy's, unit short of gas..

[philjd26]

hi

my thinking of short of gas is a low temp after expansion and icing up at the start of the evaparator and then coming back on the suction warm resulting in high discharge...i have never come across a system short of gas icing back to the compressor....this to me would be blend incorrect i.e 407c or filter/fan/coil problem anyone agree?

rgrd phil

[Brian_UK]

The thing with a/c low gas charge is that the evaporator starts to ice up and reduce the airflow over the coil.

The liquid within the frozen section then moves along the coil to find somewhere to boil off. Eventually the whole coil is blocked solid and the evaporation now continues along the suction line and accumulator.

If it isn't a gas shortage then it can also be a stuck compressor relay running the motor when the evaporator fan is off.

[Jase]

Compressor relay comes to mind. Especially on ye ole fujitsu's

Jase

[paul_h]

Compressor relay comes to mind. Especially on ye ole fujitsu's

Jase

Only the small ones with the comp relay on the indoor PCB. Not larger ones like this aoy36.