Liquid Line Insulation

[goldpau]

Hi all,

Had a general look through on past posts and some people recommend insulating both refrigerant lines whilst others say you only need to insulate the suction line and not the liquid line - we have always insulated both as its Ac and thats what I was taught.

Going to be replacing some R22 systems next month with new R410a cool & heat systems and aim to re-use pipework (its the correct size), suction lines are all insulated but none of the liquid lines are insulated, was just going to insulate them but for 4 of the systems the pipework runs through an area which we cant get to (one section is above plasterboarded ceiling & another section is under the floor) & main builder doesnt want us doing 'too much damage'.

So I know that by not insulating this section of liquid line there will be a slight reduction in performance (not really a big deal as system is slightly oversized anyway as calcs show it needs 6.2kw and we are installing 7.1kw systems) but will we have any other problems?

One of our guys mentioned the liquid line will sweat (condensation) when the system is used in cooling mode and this will damage the plasterboard ceiling & thats why it needs insulating but one of our other guys said no it wont the old system was a cooling system and the liquid line wasnt insulated and didnt sweat and looking at the ceiling theres no damage so he has a point.

Any other thoughts? Are we just looking at a slight drop in efficiency thus performance or will we get a condensation problem? (struggling to see how we would get a condensation problem as the old systems havent had a condensation problem but Im open to others thoughts)

Cheers

[frank]

If your expansion device is on the outdoor unit - as is the case on most A/C split systems, then the 'liquid line' isn't really a liquid line, it is part of the evaporator and contains low temp liquid/flash gas, and so it needs insulating to prevent it absorbing heat prior to the coil.

[martinw58]

on new ac the pipe will sweat ad pos frost so will need insulating

[Mick13]

as frank said, it depends where the refrigerant is metered. if it is metered from the outdoor unit, on cooling mode the liquid line will contain low temperature saturated refrigerant that will condensate, and will start to boil off prematurely before the evaporator, resulting in a loss of performance and energy. on heating mode in the same situation the liquid line will contain subcooled liquid and should be slightly above ambient temperature.
if your expansion valve is in your indoor unit, on cooling the liquid line will contain the subcooled liquid and on heating it will contain the lower temperature saturated refrigerant, and will condensate.

some systems have 2 expansion valves, one in the indoor unit and one in the outdoor unit, the indoor unit one acts as the expansion valve on cooling, and the outdoor one acts as the expansion valve on heating. this can be done with 2 tx valves with check valves passing the refrigerant around them when they arent in use, or they may use accurators or which are designed to only meter refrigerant in one direction. in this case the liquid line always contains subcooled liquid refrigerant, so it doesnt really need to be insulated.

this may be why it wasnt insulated before.... u dont really see that around much anymore with new units, with the presence of inverters on the market with electronic expansion valves.

[still learning]

it may sound like a daft question, but have you run a acid test on the old equipment( did it work?) it would be a shame to put new kit onto old contaminated pipe work . was it pressure tested?
if the pipe works contaminated or leaky the builder will have to open the pipe run areas to run in new pipe as the possible leak may be anywhere in your exisiting pipe runs .

[nevinjohn]

If your expansion device is on the outdoor unit - as is the case on most A/C split systems, then the 'liquid line' isn't really a liquid line, it is part of the evaporator and contains low temp liquid/flash gas, and so it needs insulating to prevent it absorbing heat prior to the coil.

Why is that ac manufactures now a days consider having expansion tube in outside unit itself?

[FreezerGeezer]

Noise levels.

As for re-using the old R22 pipe: are you sure it's rated for R410a pressure? If not, I'd be replacing it. If you use pair coil it makes it easier as it's pre-insulated. Not as neat as hard drawn though.

[question mark]

hi mate, i have been taught and have read that 410 works on higher pressure then other refrigerant and also it has thicker diameter pipe and special flaring tool. so how can you use r22 rated pipes for 410 system may result in future leaks.

[Tayters]

Why is that ac manufactures now a days consider having expansion tube in outside unit itself?

EEV is outdoors so you don't get as much noise indoors from the refrigerant boiling off.

Cheers,
Andy.

[r.bartlett]

hi mate, i have been taught and have read that 410 works on higher pressure then other refrigerant and also it has thicker diameter pipe and special flaring tool. so how can you use r22 rated pipes for 410 system may result in future leaks. If you ever get to rip out a 410a split cut the evap tube and compare that with the copper pipe thickness of the interconnecting. You will see the copper tube we use is much thicker than any copper the split manufacturers use. Reusing old R22 copper is a very effective way of installing and will not incur any issues