air conditioning

[airconadam]

hi fellas iam new to this website and to this game really iam still training and been doing this for about 3 years now and done an nvq 2 but all it is when ihave been to air con units the suction side in the outdoor unit has frozen up solid and ful of ice upto the compressor now i have heard a number of engineers saying that its low on gas just add some, but others say its not the case but also irecently rechared a system with 3kg of r22 which is the exact charge of the system when i started it up the pressures were fine and all working fine but sometimes i can go to the unit and it be froze up and other times its not with no change in pressure so any help would be gratefull thanks alot guys

[Brian_UK]

Hi Adam and welcome to the forum.

The sort of problems that you describe can be due to a number of things but a lot more information is needed before an answer can really be given.

What make/model of unit

Suction temperature
Superheat
Discharge pressure
Subcooling
Expansion device
State of fan/filters/coils

One problem that used to occur with some of the older R22 units was that they were designed for the Far East and simply froze up in the UK climate; still worked though

[lana]

Hi there,

As Brian said we need more info.

One thing I clear for you about the frost. Seeing a suction pipe frozen up doesn't mean that liquid is coming back to the compressor. It might be because the suction line is cold, so the moisture in the air is frozen on it.
You can check the followings :
Measure superheat. If it is zero or very low then you might have a liquid flood back problem.
If superheat is normal and still you see the frost then it is from the moisture in the air.
Measure sub cooling. If it is low so the refrigerant charge is low. If sub cooling is OK then the refrigerant charge is OK.
Again I repeat what Brian said: measure everything then decide.
Hope this helps.
Cheers

[cameron.e]

hozit friend it sounds like it is over charged with refrigerant if it is a cipillary flow control if it is an expansion valve the super heat will need to be set correctly also check the air flow across the evap

[airconadam]

hi guys thanks alot for the quick replys ihave got a few details for you here it is a daikin r125fj7w1 and its a split with a above ceiling indoor unit fancoil the suction pressure is 4 bar and the discharge 16 bar iwent to this unit today just to have a quick look at it and the frost was just a tiny bit when i rubbed my finger across it it went but then half hour later it was thick again also i have seen this quite often on other makes and models not just his one i just thought it might of been something simple but then again what is simple in this game thanks alot adam

[airconadam]

sorry guys the fans and coils on indoor and outdorr are all very clean no problems here regards adam

[lana]

Hi Adam,

I assume it is R22.

If suction pressure is 4 bar(g) then this means that evaporating temperature is just about 0°C which is low for an air conditioner. This is why the frost is building up. Probably the evaporator coil has some frost on it.
There is a low pressure fault. Check the followings :

1- Lack of refrigerant.
2- Expansion device problem or blockage.
3- Any blocking in the liquid line, like filter or ...
3- Evaporator. Fan is working properly, any frost on the evaporator, Air filter , ...

The first three make the superheat to increase and the last one make the superheat decrease.

Hope this helps.
Cheers

[airconadam]

yes r22 ihave spoken to daikin and checked these pressure and they say they are fine so now that has confused me the indoor unit (evaporator) is not freezing up thanks adam

[lana]

Hi adam,

I said probably.

How can 0°C evaporating be OK for an air conditioning ? Think yourself.

I would like to add something. You said that the thickness of the frost changes. This means that the suction pressure fluctuate. I suggest that you monitor the readings for a longer period to see the changes. This would point out the problem.
cheers.

[Brian_UK]

How can 0°C evaporating be OK for an air conditioning

Actually Lana that is about normal around here, superheat brings it back up 8-10K.

We tend to dehumidify and the units don't always run that hard.

[airconadam]

thanks lana as you can see ihave only been doing this for just under 3 years and apprieciate all your help but ihave always been tought and shown that 4 bar or just over is perfect all your help is well apprieciated thanks adam also this unit has had 3kg of r22 which is the correct amount of refrigerant for the pipe run etc thanks

[airconadam]

thanks brian was geting worried there for a minute thinking ihave lost my mind especially after not long finishing my nvq level 2 and now on my level 3 thanks alot you guys but still why do alot of units do this ihave seen one unit froze upto ther compressor and on the side of the compressor it looking like a snowman it was that bad thanks again adam

[lana]

Actually Lana that is about normal around here, superheat brings it back up 8-10K.

Hi Brian,

If the superheat was OK and the suction gas temperature was say 8°C then there would be no frost. Only sweaty pipes and compressor suction. If there is a frosted suction or compressor then the suction gas temperature is around or below 0°C. This is the whole idea of superheat.
Cheers

[wombat]

Adam

What is the room temperature?
Also the air on and off the coil?
Is there adequate air flow?

[airconadam]

hi wombat iwill get this info asap thanks but i remember checking the ducting that comes of the fan coil and the dampers to ensure they were open and air flow thanks again will post back asap

[2434rick]

Check your superheat and subcooling check filters ect, keep to the basics then work from there hope this helps 2434rick

[mohamed khamis]

hi wombat iwill get this info asap thanks but i remember checking the ducting that comes of the fan coil and the dampers to ensure they were open and air flow thanks again will post back asap

Hi airconadam

I suggest that u check the position of the TXV it may be placed wrongly or in a warm position that means the TXV open widely more than required. In turn, the evaporator is overfeeded by the liquid refrigerant causing the flooded back phenomenon in ur system. Othewise, ckeck the TXV it self may it is stuck opened by debris becus u mentioned it is sometimes the ice is formulated and sometimes no....so me think u have movable blockage......thank u

best regards

[Sledge]

Hi Adam,

I assume it is R22.

If suction pressure is 4 bar(g) then this means that evaporating temperature is just about 0°C which is low for an air conditioner. This is why the frost is building up. Probably the evaporator coil has some frost on it.
There is a low pressure fault. Check the followings :

1- Lack of refrigerant.
2- Expansion device problem or blockage.
3- Any blocking in the liquid line, like filter or ...
3- Evaporator. Fan is working properly, any frost on the evaporator, Air filter , ...

The first three make the superheat to increase and the last one make the superheat decrease.

Hope this helps.
Cheers

Also check the head pressure. A low head pressure will result in a low back pressure

[analog]

Also check the head pressure. A low head pressure will result in a low back pressure

As will an overcharge of refrigerant. Common rookie mistake. Everyone's looking for that 60 and 225.


I've seen kids dump 30 pounds into a 6 pound system.


As these other chaps said, airflow, metering device, etc.