R22 Split With Frozen Suction Line

[AC noob]

Hi guys,

So i have a 3kw R22 split system, at the outdoor unit the suction line is covered with frost.

The suction pressure is 300kpa (-5 degrees) and the liquid line is just sweating.

The indoor unit is putting out 6 degrees of air. All coils are clean and no blockages.

Is this a sign of over charged or under charged?

thanks

[Mick13]

it is a sign of a lack of airflow over the indoor coil, in my opinion, without looking at the job.

[AC noob]

it is a sign of a lack of airflow over the indoor coil, in my opinion, without looking at the job.

Filters were clean and there is plenty of air flow over the coil.

It's obviously flooding back to the compressor and into the indoor. So is it over charged or under charged?

[frank]

Filters were clean and there is plenty of air flow over the coil.

It's obviously flooding back to the compressor and into the indoor. So is it over charged or under charged?

Just because the suction line is frosted doesn't automatically mean that it is 'flooding back' or that the charge is wrong.
A lack of indoor heat onto the coil can cause this, such as low air flow or a cold room (set point below equipment design conditions)
To determine if you do have liquid flood back you need to measure your suction superheat.
Frost on the pipe just means that the pipe temperature is below freezing point

As you are a noob, do a search on the forum for 'Refrigeration 101' which is a good thread explaining the basics

[r.bartlett]

Filters were clean and there is plenty of air flow over the coil.

It's obviously flooding back to the compressor and into the indoor. So is it over charged or under charged?

What do you understand by the term 'flooding back'?

[AC noob]

What do you understand by the term 'flooding back'?

liquid enterting the compressor instead of vapour.

[AC noob]

Just because the suction line is frosted doesn't automatically mean that it is 'flooding back' or that the charge is wrong.
A lack of indoor heat onto the coil can cause this, such as low air flow or a cold room (set point below equipment design conditions)
To determine if you do have liquid flood back you need to measure your suction superheat.
Frost on the pipe just means that the pipe temperature is below freezing point

As you are a noob, do a search on the forum for 'Refrigeration 101' which is a good thread explaining the basics

Ok thanks for that.

but answer me this. If you had a frosted suction line, would you be inclined to say that the unit is under charged or over charged? With the pressure being 300kpa (-5 degrees)

I had the set poiint at 18 degrees which was as low as the controller went. And i got 6 degrees of air from the indoor coil.

[Mick13]

i would be inclined to say NEITHER.
dont be so quick to assume that all problems are related to the gas charge.

from what u have said, i dont think your problem is either an undercharge or an overcharge.

you are not absorbing enough heat through your evaporator coil, likely caused by a lack of indoor coil airflow.

with the unit off, get a torch and shine it up inside the indoor unit and tell me if the fan barrel is dirty. a dirty barrel will result in a lower airflow, a low suction pressure and a low superheat (exactly what you are describing). Check the coil also, a dirty coil can cause the same problem.

if it was undercharged your suction line would be much warmer and not icing up, resulting in a high superheat.

an undercharge can only cause an iced up suction line after a long period of running, after it has iced up the indoor coil, and as ice acts as an insulator, it causes the refrigerant to stop absorbing heat and hence brings the superheat down.

[frank]

Do you know how to measure your suction superheat?

[install monkey]

if you say your indoor coil is clean- is that the surface is clean- get some compressed air on it, also check the indoor fan blade, as dirt can build up on the scroll causing restricted air flow

[redroge]

What make is it.
What is the head pressure.
Has it got head pressure control.