Ice on the liquid line filter

[Acrisoft]

Hi

After installing a new ar conditioning SPLIT, there is ice on the liquid line filter. What can it be ?

Moisés

[frank]

Is it only on the filter?

Where abouts is the filter installed?

Is it a seperate filter that you have installed or is it part of the outdoor unit?

[Acrisoft]

Sorry the guy gave me wrong information.
According to him It's the liquid line valve that is frozen and the pressure is 56psi and 7ºc
Moises

[frank]

Frozen at 7C??

Doesn't make any sense.

[chilliwilly]

The liquid line valve from the receiver?

Is the valve fully open and is there a column of liquid in the sight glass?

[Brian_UK]

Most splits now-a-days do not have a liquid line as such.

Expansion is done mainly within the outdoor unit and continues along the line set.

What are the ambient conditions ?

[chilliwilly]

I thought the expansion started at the evaporator (indoor unit) via the TXV, and along the suction line :confused:

Are you refering to a back to back/package unit?

I had a similar problem once when pumping a system down. The TXV needle valve was set to have a bleed/equalising position, and the service valve on the liquid line from the receiver wasn't closed tight enough due to it being seized. The resulting effect was the compressor sucking a partial vacuum in the evaporator, and partially through the liquid line via the bleed effect of the TXV. Then in turn the liquid from the receiver expanding through the faulty service valve, and causing partial frosting of the service valve and sweating of the suction line.

Maybe the same here, either that or they might have a small leak on the liquid line connection to the receiver.

[coolstuf]

Expansion is done in the outside unit, so Brian is right, no liquid line as such, in standard ac split systems. I think the Japanese started this, to dodge the subcooled liquid problem, amongst other things. Sorry , a bit off topic.

[chilliwilly]

:off topic:
Please don't take this the wrong way.

But I'm confused and worried now, is there a new type of refrigeration system that works with a different principle, that I've missed out on? Please enlighten me if I have missed out on it.

If expansion of the liquid takes place inside a condensing unit, then surely the split is in heating mode and the condensor is now an evaporator. The system mentioned is just an aircon split, no mention of a heat pump.

If it was expanding in the cooling mode, then surely the liquid would be starting to boil off in the condensor coil, and the pressures would be way off scale. And you would never get rid off the bubbles in the sight glass.

This would be similar to being short of refrigerant, plus any pressure control would be tripping out all of the time. And there would be a constant hiss at the TXV due to gas passing through it, and not enough liquid.

[Brian_UK]

Few single splits have TXVs in them, they use cap lines.

Check a few line diagrams.

[monkey spanners]

:off topic:
Please don't take this the wrong way.

But I'm confused and worried now, is there a new type of refrigeration system that works with a different principle, that I've missed out on? Please enlighten me if I have missed out on it.

If expansion of the liquid takes place inside a condensing unit, then surely the split is in heating mode and the condensor is now an evaporator. The system mentioned is just an aircon split, no mention of a heat pump.

If it was expanding in the cooling mode, then surely the liquid would be starting to boil off in the condensor coil, and the pressures would be way off scale. And you would never get rid off the bubbles in the sight glass.

This would be similar to being short of refrigerant, plus any pressure control would be tripping out all of the time. And there would be a constant hiss at the TXV due to gas passing through it, and not enough liquid.

Cap tube or exv is in the outdoor unit the small pipe is effectivly part of the evaporator or an expansion line if you like, thats why in modern splits both pipes are insulated.
No drier is fitted in the field or sightglass for that matter. These systems are critically charged like a domestic fridge.

Jon :)

[chilliwilly]

You live and learn, I have missed out on a new method of piping up a line set. Its been over five years since I fit a split. And they were second hand two year old Mits units charged with 410a, and had TXVs in the AHU.

I knew you insulated both lines for heat pumps for obvious reasons, so whenever Ive looked up at any line sets any where I just assumed they were heat pump configured. Assumption in this case being the mother of kcufup!

Question.

If the splits are critically charged and have cap feeders, won't they have limited cooling capacity and have cooling problems regarding environmental conditons and varying heat load?

If not TXVs then I'll assume their AEVs? otherwise how would you adjust the superheat setting from outside?

[lawrence1]

Most splits have one capiliary in the outdoor unit which partly expands the refrigerant and aslo one in the indoor unit which completes the expansion process...i would say the cause of ice is gas shortage but no idea why he say he has a drier icing up,never see a drier on a wall split.

[langy]

Sounds like refrigerant shortage.
( some systems get a slight frost on the condensing unit liquid line valve, when first ran/commissioned, until pressures balance out)
Is it pre charged? Is the charge correct for the pipe run?

[DC5-T]

it can be a restriction but most likely a refrigerant issue under/overcharge....

[frank]

it can be a restriction but most likely a refrigerant issue under/overcharge....
How would an overcharged system lead to icing on the drier at +7C?

[joshuatan]

In Malaysia you can commonly find manufacturers use capillary tube installed after the condensors in the outdoor unit. You can open the outdoor unit and see if there is a coil of capillary tubings just before the 'liquid' service valve. The piping will be cold as well so you will find both to be cold instead of 1 warm and 1 cold as usually found in units with txv's fitted.
I have checked that the pressure is normally around 100 psig and you should not have a filter drier fitted!!
Both pipes also need to be insulated. Please note that it is used extensively from about the range of 8000 to 22000 btu/hr. cooling capacity units