Condensation on a/c line set.

[jgerwitz]

Can anyone explain why the small un-insulated freon line, going from the coil in my oil furnace to the compressor unit outside, is dripping wet with condensation? The water is dripping onto my drop ceiling creating stains. What can I do to fix this? Is there a problem with the system?

Thanks in advance,
Jeff

[jdenyer]

The smaller uninsulated line is the liquid line, if it's sweating that means the liquid is boiling off in that line, undercharged probably, could be low head pressure due failing comp? Call for service and have someone check it out, and make sure they charge by superheat or subcooling, which method depends on the type of metering device.

[tlcartman]

is this happening with the unit running in cooling mode, the heating mode, or off.

[jgerwitz]

This is happening while running in the heating mode in the winter MD climate.

[aircooled53]

Need to have unit checked by professional. But, for now try and get some insulation 3/8" and cover the line from evaporator to where it goes through the wall.

[tlcartman]

insulating the pipe will be the cheapest fix

[trane]

Jeff, I am very interested in your problem if its anything like whats happening with a couple of our units. Is your unit a A/C only and not a heat pump? When this drips, is the outside unit off?

[bornriding]

Is the coil for the oil furnace in the attic with the lines.
In other words, is the cooling coil above the refrigerant lines. Or do they go up from a closet type furnace & coil, into the attic ( or overhead space ) ?

[jgerwitz]

I believe the unit outside is a/c only and has been off since the end of summer. The A-coil in the furnace is in the basement below the freon lines. I can insulate the line, however, will that only cover up a real problem?

[trane]

Is this a new A/C unit and is the furnace in a basement?

[tlcartman]

Originally posted by jgerwitz
I believe the unit outside is a/c only and has been off since the end of summer. The A-coil in the furnace is in the basement below the freon lines. I can insulate the line, however, will that only cover up a real problem?

there is no real problem. the condensation is coming from the migration of refrigerant caused by the changing temp of the evaporator coil. other than insulating the line, the only other option is installing a solonoid valve on the liquid line. when your furnace runs it acts like the flame on an absorption system.

[bornriding]

Yes, insulating lines is just temporary cover-up to possibly save ceiling until proper repair is made. At least that what I took it to be.
You have puzzling problem. I'm sure many are trying to help solve it.

Does the return air being drawn into your system going through the cooling coil first and then the funace, or is the air going through the furnace before it goes through the cooling coil ??

[trane]

Originally posted by tlcartman

Originally posted by jgerwitz
I believe the unit outside is a/c only and has been off since the end of summer. The A-coil in the furnace is in the basement below the freon lines. I can insulate the line, however, will that only cover up a real problem?

there is no real problem. the condensation is coming from the migration of refrigerant caused by the changing temp of the evaporator coil. other than insulating the line, the only other option is installing a solonoid valve on the liquid line. when your furnace runs it acts like the flame on an absorption system.

Can you explain why I have two systems exactly the same and only one is doing this? So far the factory techs can't tell me what is causing this.

[Special Ed]

Puzzling problem, indeed, especially if it's a furnace with an A/C. I can't see any reason for the liquid line to collect condensation in heat.

Now, if it is a heat pump it's a different matter entirely.

[tlcartman]

Originally posted by trane
Can you explain why I have two systems exactly the same and only one is doing this? So far the factory techs can't tell me what is causing this.

i have ran across this problem more than once. in the off cycle the refrigerant goes to the lowest point, in this case the coil in the basement. when the furnace comes on it heats the indoor coil up raising the pressure, and forcing the refrigerant back to the outdoor unit. the refrigerant passes backwards through the metering device causing the gas to flash. i have seen it happen on a cap tube system, with an orifice (not enough pressure to shift piston), and once with a txv that didn't close completely. as for why you have one that does it and one that doesn't, without seeing them i don't know. i have seen the problem made worse due to outside air being tied into furnace return.

[trane]

No outside air and these are frosting from the outside wall in. Right now we have the valves closed until the factory comes up with a solution. As soon as you open the valves the liquid line gets ice cold with the furnace and A/C both off.

[tlcartman]

for the refrigerant to move you have to have either a temp difference or a pressure difference, other wise the liquid will settle at the lowest point. if it settles on the evap coil in the off position, then when the heat comes on it will be driven outside. as the evap cools it will return to it.
is yours frosting only from the wall, or does it go all the way back to the service valve? if only from the wall, and the outdoor temp and humidity are the same as the basements, it sounds like there is a restriction where the line passes thru the wall.