Line Size for replacement


Old 07-14-06, 05:02 PM
Thread Starter
Join Date: Jun 2006
Posts: 5
Received 0 Votes on 0 Posts
Line Size for replacement


I'm replacing a 10 SEER 2.5 ton HP/handler with a 13 SEER 3.0 ton unit. The lineset runs ~55 ft and is currently 3/4 and 3/8. The new unit calls for 3/4 and 3/8 if 25-50' and 7/8 and 3/8 if 51-75'. The height differential between the HP and handler is about 20'

So technically, I should increase the lineset size. However, this will be a bit of a pain to run up the side of the house, run through the attic, etc.

I think I have the following options:
1 - replace the existing line set with the proper size
2 - use the existing line set
3 - use a combination of old / new

For #3, I am thinking of running the new 7/8 line about 30' under the house (from the HP to the wall where it goes up), then using the exiting 3/4 line up the wall. In the attic, I would again use the 7/8 from the wall to the unit.

Any thoughts on this?

Sponsored Links
Old 07-14-06, 05:12 PM
mattison's Avatar
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,548
Received 0 Votes on 0 Posts
If you're gonna keep any of the 3/4" you might as well keep it all. It will do you no good to only do part of it properly. I don't think you'll lose much efficiency by staying with the 3/4" anyway.

Are you having a pro do the evac and release of the charge ?
Old 07-14-06, 10:53 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,386
Received 0 Votes on 0 Posts

You say the lines are 55 ft. My chart calls for 7/8 and 3/8 for 50 ft on a 3 ton. That dont even count the 90o L's you will have in it. So I for sure would go with your #1. Dont know if they do it there but we bend up a small sheet metal U duct and put that over the line comeing down the outside of the home and paint it.You dont say where you are .If south Id go for a seer of 15
The way fuel cost are going
Old 07-15-06, 08:32 AM
Thread Starter
Join Date: Jun 2006
Posts: 5
Received 0 Votes on 0 Posts
Thanks for the advice. The current 3/4 does not have any sharp elbows. When they originally did the lines, the did a gradual bend to go up the wall, so it is 90 degree bend, but not like a sharp 90 elbow that I've used in plumbing.

I have an HVAC contractor friend that will braze the lines, charge the system and check everything prior to startup.
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: