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lees8110
14-01-2010, 09:30 PM
Hi all,

I attended a call to heating not working in an office today, a Mr slim split, the outdoor coil has a iced up quite alot, I dont suspect the unit is low on gas but I didnt notice it defrost while I was there either. The ambient temp was around 0 degrees.

Does this sound like a blocked coil? Or does it sound more like a defrost problem? I am back on the job tomorrow as today was just a quick visit before I left for home so havent carried out any tests as yet. Just thought I'd pick your brains on here first to help me out a great deal.

Cheers Guys

DEVIL
14-01-2010, 09:43 PM
It sounds like a low gas problems, but it you'r shore it's not that the problem you might have problems with the temperature readings, or the sensors not making good contact

wilt
14-01-2010, 09:45 PM
did you put gauges on and check charge this is normal in winter for the coil to ice up but not completly

lees8110
14-01-2010, 09:52 PM
No this is next step really, I just took the cover off and had a quick check for oil patches ect on the pipework, for signs of a leak, It is iced up quite badly, how often does the defrost cycle on these units? is it hourly?

thebigcheese
14-01-2010, 09:54 PM
mate wouldnt set my sights on a gas leak straight away. with weather like weve been having it may just be on full heating too long etc

check the simple things first

lees8110
14-01-2010, 10:06 PM
Yea this was my thought to, I was jus expecting it to of defrosted befpre it got as bad. I will give the coil a thorough check first once all the ice melts!

DEVIL
14-01-2010, 10:19 PM
mate wouldnt set my sights on a gas leak straight away. with weather like weve been having it may just be on full heating too long etc


A quality unit won't have the problem for "full heating too long" ,and it's a Mitsubishi not made in China (no offense the them).
It should be able to work as long as it's needed, the only problem that might be is for the wind, or water dripping on the unit from somewhere.

Widemouthed no pressure and making shore all temperature sensors at their place it's difficult to say.

And if the ice isn't uniform (big diff) it's for shore a low gas problem

lees8110
14-01-2010, 10:27 PM
"And if the ice isn't uniform (big diff) it's for shore a low gas problem"

Thats a good point, The ice is uniform, so this would indicate even temperature in the coil which would point away from low charge really?

DEVIL
14-01-2010, 10:52 PM
That would point away but you need to confirm it with the pressure because it's just a rule of tomb not fail safe.

And in this case i stick with the temperature sensors not managing to feel that the unit is icing up (excluding the pressure transducer because is almost never happening)

Buzzant
15-01-2010, 06:38 PM
Check to make sur it's not cause by water dripping from the roof or gutter then freeze up it happened to me but i had a good 2 inches thick ice in the buttom of the outside unit that blocked the dripping hole.

Melted it with warm water, i'v put a cover over the unit without blocking the flow of air and everything is ok now.

Buzzant
15-01-2010, 06:43 PM
i'v put a cover over the unit without blocking the flow of air and everything is ok now.

Of course it already had a cover but i put a plastich sheet over it so water slip instead of freesing up on the cold metal.

Buzzant
15-01-2010, 06:46 PM
here is a picture except i cut it a bit more in the back so it does not interfer with the flow

http://img42.imageshack.us/img42/7302/img6222o.jpg

cadillackid
22-01-2010, 04:24 AM
one of my units had this issue.. outside air-temp thermistor was bad.. it was reading 60 degrees f all the time no matter what the temperature was.. stupid chinese unit will NEVER defrost if ambient temp is above 55f.. even though 3 temp sensors on the coil were -20 f it still wouldnt defrost.. might want to check the ambient air temp sensor...
-Christopher

lees8110
03-02-2010, 03:23 PM
Just to confirm, this unit was not low on gas hooked the gauges up and have good pressures, unit now heating fine (raised ambient temperature)