I have three wall-mounted a/c's running off one outside unit. Just this week, when I'm running two of them, the large line going to one of the units builds up white frost quite heavily at the condenser unit, and then for about 7 to 8 feet after. Everything is working fine however. They still cool great. Any reason for concern?

 

The large lines are supposed to be insulated.

 

Check air flow at all units , inside and outside .

Try setting the indoor fan on all units to high speed .

Check the discharge air temp on all 3 indoor units .

Is the condenser cycling properly ? Or slowing down / speeding up as demand is satisfied ?

Who installed the system ?

And , yes , both lines are suppose to be WELL insulated . As ar the service valves where the lines connect to the out door unit .

God bless
Wyr

 

The lines are insulated, however near the condenser unit there are a few spots where it has broken down a bit and you can see the refrigerant line itself.

Airflows are good everywhere, that's what has me puzzled.

The condenser has two fans on it, and they appear to be going on and off as demand is needed.

 

Re-insulate them VERY Well . Keep them as air tight as you posably can . Might put the silver tape over the top of the insulation to protect from sunlight .

I bought a roll of " cork insulating tape " to go over the exposed service valves . They were sweating profusely .

https://www.johnstonesupply.com/stor...ords=cork+tape

God bless
Wyr

 

Insulation of that line is not the problem. The temperature of that line should never go below 32F, You need to check on something else. May want to call a tech to check on charges or other possible causes.

 

I have never seen the smaller high side line between the air handler and a condensing unit insulated.

Why would that be important?

 

Joe, many mini-splits are heat pumps and the reversing valve along with the expansion valves (or capillary tubes) are contained in the condensing unit. This means that the two lines going to the inside unit actually change function between liquid and vapor lines and THAT is why they are both insulated.

 

Yes , I read the capillary tube is in the condenser unit . So , in the cool mode , the liquid line is down stream of the cap tube . Which means it will be cool / cold & will readily absorb ambient heat .

Some may or may not use an electronic expansion valve . in stead of a cap tube . I do not know .

I insulated the service valves / fittings on the condenser unit . I did not want them dripping water & possibly corroding . I also did not want to loose any of the " cold " , that I could prevent . I paid for that " cold " .

In heat pump mode , I guess they may both get hot ? Do not know . In that case , I still want them both very well insulated .

But , you are correct . With traditional cool only , low SEER A/C , the liquid line gets hot . The more heat it looses between the condenser and the A-Coil , the better .

Mo 13 SEER central unit , the liquid line never gets more than warm . I would think , the newer / higher SEER units would be even more so .

I have read that it is recommended , on those , to insulate both lines if they pass through a hot attic , for a significant distance . To keep the liquid line from absorbing heat .

My lines run under the house ( pier and beam construction ) . So that is not much of a consideration .

God bless
Wyr