Replace a 36 year old Line Set?

[maddog82]

I need to replace the split system AC in my 36 year old house. The line set is original to the house as far as I can tell. One tech told me he could just flush the lines and there was no need to replace them. Sounds like non-sense to me. What do you pros think?

[I_bend_metal]

I need to replace the split system AC in my 36 year old house. The line set is original to the house as far as I can tell. One tech told me he could just flush the lines and there was no need to replace them. Sounds like non-sense to me. What do you pros think?

If it is REALLY 36 years old.....its the wrong size for your new unit.....replace it!

[subway]

I agree, for a little more cost it should be replaced especially if there are any joints in it. Either way replace it.

[rubberduck]

Replace the lineset. Replacing the lineset should be part of any new install. The guy that suggested flushing the lines is just being lazy. Being 36 years old the lineset is probably not the only thing that needs to be replaced.

New Lineset
New Thermostat & Wiring
New Pad (for the unit to sit on)
New drain piping
Duct work (it is hard to say without looking at the system, but you could probably benefit from new duct work.
New Electrical Disconnect & Wiring Whip

You could get away without replacing all those things. However, if it were my house I would do these things. It will be cheaper to do these things as part of a changeout vs. having to come back and replace them ala carte later on.

[maddog82]

Thanks guys. I'll cross him off the list. I'll replace the suggested items as well.

[beenthere]

If it is REALLY 36 years old.....its the wrong size for your new unit.....replace it!

Thats not true. Lots of old line sets are still the correct size for new systems.

While I prefer to change the line set. It is not actually required in many applications.


OP: Do you know what size your line set is? If so, could you please post it. Along with the size of the new proposed unit.

[beenthere]

Thanks guys. I'll cross him off the list. I'll replace the suggested items as well.
He was not lying to you. Nor is he misinformed. Don't be too quick to cross him off the list.

I'm not saying you should use him. But the line set can be used over.

[the dangling wrangler]

Thats not true. Lots of old line sets are still the correct size for new systems.

While I prefer to change the line set. It is not actually required in many applications.


OP: Do you know what size your line set is? If so, could you please post it. Along with the size of the new proposed unit.

Beat me to it.
I've seen lots of older installs, from back in the day, when people really did try to do it right.
He could be the contractor, that knows his stuff.

[beenthere]

Some 13 SEER 5 ton R410A units have less capacity loss on a 3/8 X 7/8" X 50' (factory listed size) line set then an R22 unit.

Some techs are not aware that R410A is suppose to have a higher vapor velocity then R22 for good oil return.

R22 vertical riser 1000 FPM (From York piping guide)
R410A vertical riser 1250 FPM (From York piping guide)

The application (individual install parameters) determine line set size.

[venting]

I noticed that most suction lines are one size larger for R22 than 410a. For example, a 3 ton R22 would have a 7/8" line and a 410a might have a 3/4" line. Is there any problem with going up one size on the suction line?

[beenthere]

Varies with the individual install application.

No one answer fits all applications.


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[maddog82]

It will be a 4 ton 14 seer R410a unit. I'll have to check the line set size. I have to believe this will be the fourth condensing unit hooked up to this line set if it's re-used.

[beenthere]

It will be a 4 ton 14 seer R410a unit. I'll have to check the line set size. I have to believe this will be the fourth condensing unit hooked up to this line set if it's re-used.
Look at any contract, or written proposal you have or receive.
Does it say 14 SEER condenser?
Or, does it say 14 SEER system?

Matched to the correct indoor unit. A 13 SEER condenser, can reach 14 SEER and or higher. But still use the same line set size as a 13 SEER condenser.

There is a lot more to it, then just what refrigerant is being used.

Post the line set size.
The line set total length.
Condenser above or below indoor unit.
How much height difference.
Brand of equipment.
Model numbers of equipment.

This is the info that is generally needed (and easily gotten) for a contractor to determine what size line set is needed for an install. So a contractor on site, is generally able to better determine what size to use. Instead of us looking through our monitors.

[the dangling wrangler]

Some 13 SEER 5 ton R410A units have less capacity loss on a 3/8 X 7/8" X 50' (factory listed size) line set then an R22 unit.

Some techs are not aware that R410A is suppose to have a higher vapor velocity then R22 for good oil return.

R22 vertical riser 1000 FPM (From York piping guide)
R410A vertical riser 1250 FPM (From York piping guide)

The application (individual install parameters) determine line set size.

That's a good point.
There was a discussion a while back about that.
It surprised me to learn, that sometimes the linesets should be reduced, instead of increased. On the surface, it doesn't sound right.

[beenthere]

It does seem a bit backwards at first. Until you take into consideration the oil return.
And how little capacity you actually loose.

[the dangling wrangler]

Honestly, when I typed that, I was thinking oversized.

[beenthere]

Over sized can be the death of the compressor. Good ole LRA.

Extreme under size can do the same thing.

Better to have good oil return from a size down vapor line and a 3 to 5% capacity loss, then no oil return.