So you’ve got some quotes for a new air conditioner. One says you need to purchase a new refrigerant line set – the copper pipe that runs from the AC’s indoor unit to the outdoor unit. Another quote says you don’t need to replace the line set. That contractor says you can reuse the line set you already have.

Who should you believe?

Before getting into the nitty gritty details, let’s answer the question from the title of this article: Does a new air conditioner always need a new line set? The answer is an emphatic no. A new AC does not always need a new line set.

But sometimes it does.

When our team evaluates whether to keep a line set or replace it with a new one, we make recommendations based on the customer’s goals, line set size, and other site-specific factors.

Size matters when it comes to line sets

This is the main factor when it comes to reusing vs. replacing a refrigerant line set.

When replacing an air conditioner, it’s important to look at the manufacturer’s specification for the line set size. If your old AC used a line set that’s the same size as the one the new unit calls for, then you’re good. You don’t have to replace it with a new one.

Unless, for course, there’s something wrong with it. Like a refrigerant leak.

If a contractor is saying that you need a new line set for your air conditioner replacement, ask them why. They need to be able to point to a size mismatch or some kind of problem with the existing line set in order to justify the installation of a new one.

What if a line set is the wrong size?

Ok, so here’s something we encounter from time to time: an HVAC installation that reused the old line set even though it was the wrong size. Oh, and look! The AC still runs. I guess the size mismatch isn’t such a big deal, right?


An AC might run if the line set is the wrong size, but it almost definitely won’t perform to spec. The refrigerant pressures will be off, and you’ll have a much less efficient system and (probably) frequent repair bills. A wrong-sized line set will also shorten the lifespan of the system. Parts will wear out sooner, and you’ll have to replace the AC before you’d planned to.

This is the sort of thing you see with inexperienced or unscrupulous HVAC contractors who cut every corner. We wish it wasn’t common, but it is.

Other considerations for refrigerant line set replacement

We already mentioned refrigerant leaks. If your system has a leak in the refrigerant line set, you definitely do not want to reuse that line set! Have the contractor replace it with a new one that doesn’t leak.

Accessibility is another factor. If the line set is really short or runs through an easily accessible area, sometimes we advise the customer to just replace it along with the new system.

Line sets that are really long or that run behind walls? Not so much. We’ll always try to reuse those, assuming they’re the correct size for the new system.

Procedures for reusing a line set

If an HVAC contractor is suggesting that you reuse a line set, here’s what you need to make sure they do (seriously, ask them!):

  • Ensure the existing line set is the right size for the new equipment
  • Perform a triple evacuation; this involves flushing the line with nitrogen and vacuuming it out again and again and again
  • Properly charge the line set with new refrigerant and check the pressure; we hold it in a pressure check status to make sure there are no leaks

You’ve got to do all of this stuff if you want to reuse a line set and not experience any problems. It’s not just about matching the sizes – although your contractor does need to do that. It’s about ensuring that the line set is clean, free, and clear before charging it with new refrigerant and commissioning the new system.

Comparing AC replacement quotes for your home?

If you live in Metro Atlanta and are considering a new air conditioning system for your home, give us a shout! Our team works closely with homeowners to determine the right size and type for their new AC. We also go through a rigorous pre-installation process to ensure you’re getting the best possible system for your home.

And yes, we’ll reuse your existing line set if it’s the right size and doesn’t have any problems.

Just give us a call at (404) 994-2229 today or fill out the form below!

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