refrigerant line freezing 1

[rpl3000]

I have a (hopefully) simple question about the central air system in my condo. When I run it for a long time the refrigerant line supplying the heat exchanger freezes up. I suspect that this might be normal for days when it is a bit humid. I have the vent in the basement taped off so all of the cold air heads up into the house. I checked the condensate pan and drain, seems ok. The compressor, fan and everything outside the house seems ok too.

So my question is why is the line freezing? Should I insulate the indoor line? I'm not sure if the whole line is uninsulated or just the short section near the handler. I'll check later. Should I unblock the basement vent to let the air in the basement cool (and dehumidify)? Is is possible that the heat exchanger in the air handler is clogging up and not flowing properly? The unit is very old, 1983 Carrier with a Payne horizontal air handler.

Any help is appreciated. Thanks.

 

[MintJulep]

There are two heat exchangers in the system. Could you be more precise in identifying what line is freezing.

 

[rpl3000]

I'm refering to the heat exchanger inside the house. The line inside the house at the air handler is freezing.

 

[IRstuff]

Is this a new phenomenon?

TTFN
faq731-376

 

[IRstuff]

As a general rule, the lines coming through the wall of a house is typically insulated

TTFN
faq731-376

 

[MintJulep]

One line in, one line out.

Most likely it's the suction line that is freezing, and the cause is low charge, although low air flow could also cause it.

Alternate cause is that you taped off a return vent, not a supply vent.

 

[rpl3000]

I dont think its a new thing. I've just been using the A/C more lately and noticed it.

The taped off vent is a supply vent. I also replaced the filter. If the air flow is low then it would be from the heat exchanger assembly impeding the air (or something else in the ducts that I havent found). The flow from the vents in the house seems normal.

Low charge might be a suspect given the age of the system (1985 installed).

Suction line freezing - Is this the line returning to the compressor? So lack of refrigerant causes low pressure in the line.

Are there contractors today who recharge R-22 systems?

 

[MintJulep]

Yes, it's still possible to recharge an R-22 system.

A good contractor will actually make an attempt to find and fix leaks first. A less good one will just add some juice.

Might have them clean the coil too. You could do that yourself, but it's a messy job.

 

[MTES93]

MintJulep nailed it I believe. Typically a 'frosting' suction line is indicative of a possible frosting coil. Nearly all of the time this is due to a low charge (lower than normal suction pressures/temperatures) or low airflow.

Agree, clean the coil. It is amazing what can pass thru a cheap filter and a damp cooling coil can turn ordinary dust into a rather impressive coil coating!

The suction line will be the larger of the two lines.

 

[rpl3000]

I think this is solved. It was the larger diameter of the two lines that was frozen.

Thanks all for the help. I'll try and clean the cooling coil. Maybe contact a contractor about a recharge / leak check.

 

[Shophound]

Don't forget about the blower wheel. A system that has been in place since 1985 is dirty, even with normal filter changes and good housekeeping.

 

[berkshire]

I had one of these last year,
The customer had removed the return air filter because the airflow was diminished on the unit, he also owned 3 cats.
The suction line was frozen solid at the outlet from the air handler to the compressor inlet.
Opening the unit found the internal air filter plugged solid, and bending up at the sides, the blower wheel covered in fluff, and cat hair, and the air passages through the coil just about impassable.
About 2 hours of cleaning later, the unit was running just fine with no need for a re charge.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor