frozen liquid line

[frostedflake]

greetings to everyone

this time i found an AC multisplit 3*12,000 BTU with 2 compressors, one 24k btus the other 12k btus.

I cleaned condenser and evap, and when checking the superheat (no liquid line service valve)
i found out the superheat was 28k (28 psig R22 at 13ºC, so -15-13=28) normal amperage rating and the liquid line was completely frozen.
the airflow seems to be fine at evap (evap air temp 20ºC) and at condenser (condenser air temp 33ºC)
my guess is that there is some restriction on capilary tubes or that compressor is defective.
once i turned the unit off i watched how the manifold needle went ever so slowly (3 minutes) from 28 psig to about 80 psig on suction line.

I discarded an over/undercharge because i have no current draw and cannot measure subcooling.

what do you say?

i am aware that most recommended is to recover refrigerant and charge according to label weight, but just for the sake of it let's say i already did that and the result was the same.

comments much appreciated

have a great weekend! ;)

[amitsaxena]

Dear , this seems to be a problem of expansion valve as it seems that the your expansion valve opening is restricted. Please change / service the same. Hope your problem will get solved. Let me know if i am right.

Thanks

Amit

[Peter_1]

...AC multisplit 3*12,000 BTU with 2 compressors, one 24k btus the other 12k btus.
....i found out the superheat was 28k (28 psig R22 at 13ºC, so -15-13=28) normal amperage rating and the liquid line was completely frozen.
the airflow seems to be fine at evap (evap air temp 20ºC) and at condenser (condenser air temp 33ºC)
my guess ...some restriction on capilary tubes or that compressor is defective.
once i turned the unit off i watched how the manifold needle went ever so slowly (3 minutes) from 28 psig to about 80 psig on suction line.

I discarded an over/undercharge because i have no current draw and cannot measure subcooling.


Where is the expansion done for each unit?
What sort of expansion?
How can a defective compressor provoke frosted lines?

[frostedflake]

thanks for your prompt responses

the system has no TXV installed since it has capillary tubes at condensing unit.

my diagnose was that freezing liquid line was caused because low compression ratio or damaged compressor valves, since the suction line measures 28psig and a 28k superheat with compressor plate amperage rating.

I came to the possibility that the compressor liquid side valve is not able to pump the propper amount of liquid refrigerant refrigerant to evaporator, causing the liquid line to freeze due flashing gas.

My client refuses to go with the refrigerant recovery and label weight charging, so that's why i turned to your experience for another possible conclusion other than a system obstruction (in which case system cleaning is required) or the weak compressor since this unit has about 8 years of use and no previous service (so client says).

i discarded an undercharge because there's no amp draw and no suction line freezing (although i realize superheat is still high)
i discarded overcharge because then my superheat would be much lower and have too an amp draw.

both condenser and evap air flow seem to be within operational ranges.

thanks for taking the time to read my post.

regards.

[SteinarN]

Seems to be a simple under charge condition. You have low suction pressure and high super heat in a capilary tube system. If the condencer pressure is low and no liquid subcooling then it is definitely low on refrigerant.

[Peter_1]

Frostedflake, You are making false conclusions, SteinarN shares my vision.
Your expansion is in your outdoor unit, so as soon you evaporate below 0°C (aha, that's how much in °F) it will freeze under certain conditions.

If a valve should be broken in the compressor, how it then can pump that low to reach freezing temperatures of your R22. (R22 :mad:) Why should a broken valve provoke flashgas? I don't see any relation amongst those two

If you should have an overcharge, why should this be related to high SH? If you are overcharged, then you should notice a high SC and ran not necessarily pull more AMPs. Depends how much it's overcharged, ambient and how heavy indoor units are loaded.

AMP's is also relative to ambient temperatures, so measuring AMP's is for me a factor which doesn't learn you a lot, especially in a multi application like yours.

If you're undercharged, then you should have a big SH - which you have - but how then you conclude that the suction line should frost with a high SH. Those two can't go together.

If all tree are functioning not the way they performed in the past, then it's undercharged.It's only one, blocked cap tube perhaps or blocked stainer (if mounted)
If it happens on all tree after some time, moisture in circuit perhaps but then SC should normally increase.

[frostedflake]

Thanks so much for keeping track of this post, all your pointers are much appreciated.

but just to clear these two:




"If you should have an overcharge, why should this be related to high SH?"



As I stated above, an overcharge reflects a LOW superheat.




"If you are overcharged, then you should notice a high SC"



Also I posted the fact that this unit has no liquid line service port, so i can't make any SC measurment.
Can I? :o

Other than that I am glad you point out there is no way this system could have defective compressor.
And we do share the possibility of a blocked capilary tube, and i should now look for system undercharge/moisture.

In which case, my costumer still has no choice but to go with the refrigerant recovery, system cleansing, leak checking, pressure testing and weight refrigerant charging. (because then now I can say that if the system is running on that much low refrigerant as it is, then it must have a leak somewhere.)

Being the case that we don't like to pollute, which refrigerant should I replace this sistem with?

best regards.