evaporator ice and compressor overheat

[andy1967]

I have been asked to look at a Sharp AH A249E split cooling a server room. The evaporator is icing and the compressor overheating. When running Ok an example of temperatures is the off coil temp at 11deg/C and the return air at 25deg/C. Would undergassing or overloading due to additional equipment in the room be likeley causes. I am of an electrical background and could do with some pointers before calling in a AC engineer or questioning the capacity of the system as I suspect extra equipment has been added to the room.
Cheers !

[icecube51]

when the evap is icing then there is too much refrig in the system. check whit the manifold for pres & temp.
posibilyti ; blocking or tube bent in the suction line ?

frozen capilair ?? water in the sytem.

just a few guesses:eek:

Ice

[Peter_1]

when the evap is icing then there is too much refrig in the system. c
Ice, in my opinion, this is not true. When you overcharge, then you will see frosting on the tubes to the compressor - not on the evaporator - with capillary systems not with EEV's like nowadays AC systems.
Overcharging increases LP

[nike123]

I have been asked to look at a Sharp AH A249E split cooling a server room. The evaporator is icing and the compressor overheating. When running Ok an example of temperatures is the off coil temp at 11deg/C and the return air at 25deg/C. Would undergassing or overloading due to additional equipment in the room be likeley causes. I am of an electrical background and could do with some pointers before calling in a AC engineer or questioning the capacity of the system as I suspect extra equipment has been added to the room.
Cheers !


First check that filters are clean and that fan is at high.
11°C/25°C looks good. Is that readings for unit who is icing or it is for other unit.

[wambat]

Visually inspecting the condition of the evaporator coil will help in determining if the system:
Is low on its refrigerant charge;
Has poor or no airflow across the evaporator coil; or
Has a problem defrosting. A system low on charge may show some icing on the evaporator coil, and overheat the compressor because of high SH, however, it will normally only be at the inlet of the evaporator coil from the outlet of the metering device. The icing will normally be contained to this area as opposed to the entire coil being iced up. A completely iced evaporator is normally the result of either inadequate defrosting or little or no airflow across the coil, or a dirty evaporator. I would not suspect an over charge wirh a TXV system and if it was a cap tube system with an overcharge a hi head pressure would be more then likely which would result in lower then normal SH and a wet suction temperature but a cool compressor. :cool:

[andy1967]

The temperature readings are from the unit that is icing.The icing is light but spread accross the evaporator. The filters are clean and the evaporator looks clear and there is good airflow through the unit. The system has been working fine for some time and there has been no charge added during that time.
Thanks for your help.
Andy

[Brian_UK]

Perhaps a difference in description here...

Is it icing as in blocking the coil with ice ?

or

is it frosting the fins of the coil ?

[wambat]

The temperature readings are from the unit that is icing.The icing is light but spread accross the evaporator. The filters are clean and the evaporator looks clear and there is good airflow through the unit. The system has been working fine for some time and there has been no charge added during that time.
Thanks for your help.
Andy

Now it sounds to me as if you are running a lighter load or the control is set too low

[Pooh]

My
thoughts are short of refrigerant, low suction pressure/ evaporating temperature and high superheat point to short of gas. Blocked filter would result in low suction pressure and low superheat so frost back would be seen. Overcharged would result in high suction pressure / evaporating temperature and low superheat so also frost back. High load would result in high suction pressure / evaporating temperature and high superheat but no frosting on the coil.

Only obvious is short of refrigerant but without fitting gauges and taking temperatures I am only guessing.

Ian

[Kh1971]

Hi,

As Nike123 Said , I have this problem before and I think it is dirt you have to clean the system first before doing any thing else

[andy1967]

Ive checked everything electrical and all that I can and your sgggestions but no joy. So passed the job to a refrigeration engineer. Cheers for your help

[nike123]

Ive checked everything electrical and all that I can and your sgggestions but no joy. So passed the job to a refrigeration engineer. Cheers for your help
Good decision! :p