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JoeFL77 05-09-2008 08:49 PM

Line set size for Central AC
I am trying to determine the size of the line set I should intall for my central AC. Presently, I have a water to air AC system that I will be replacing with a normal AC system. I bought a used (1998) 10 SEER Trane XE 1000 3 ton system for a 2000 sq ft house in Melbourn FL. I am considering installing the Trane system and later upgrading to a high SEER r410A system later. The line set run will be 85 feet. I beliieve I should install a 1 1/8 suction line for the 3 ton unit. At least I believe if I install a new 16+ SEER system with a 85 ft run it will rrequire a 1 1/8 inch suction line. Since copper is so expensive I was hoping to reuse it when I switched from R-22 to R410A with the new system. So the question is: Can I reuse the line set? is 1 1/8 the prpoer siz for the new system? I don't know the brand of the new system but since it will be a 3.5 to 4.0 ton system with a 85 ft run I think the 1 1/8 size would be correct.
Any thoughts?

bervin306 05-10-2008 12:16 AM

I hope this doen't come off the wrong way but why would you buy a used 10 year old system. If the system was not properly sealed it will be nothing but a problem for you. Also why was the person selling it?

Your also saying you have a 3 ton and will be upgrading to a 3.5 or 4 ton. I would sugest that you have a system properly sized based on you home by doing a load cal on it. A undersized or a oversized system you will not be happy with and it will not work as designed.

The used system that you bought is an r-22 system. You can not just replace it with 410a. The line set will have to be flushed with chemicals to remove the oil. And the indoor unit would have to be replaced as well because the indoor coil will not work with the new referigerant.

As far as the line set 85 feet is pretty long is there a another place you can locate the equipment for a shorter run. The size would be based on how long of a run and how much of a lift there would be. It should be all in the manual.

So in my opion it would be best to do it right the first time and install new equipment and live worry free for many years.

coolmen 05-10-2008 11:29 AM

7/8x 3/8 is what you need 3 to 4 tons. Why on earth would you buy a 10 seer r-22 set up when 13 seer is the norm with r 410a???????? You are going about it all wrong just because you think you gott a good deal on a out dated piece of shi*. and you are looking at your house from across the street to determine your size a/c ,yah right
do a load calculation and then start from there. do it your self the right way not the wrong will pay more later and may not be comfortable. and remember bigger is not better. some day the old r22 will need service and wil cost you lots

JoeFL77 05-11-2008 08:01 AM

More Information
I presently have a water to air air conditioner in the attic. It is 25 years old and there has been a poorly constructed 600 sq ft addition. The unit is 2 tons and it barely keeps up, well it doesn't realy. A gentleman did a load calc for me and can up with 3.5 tons. There are a lot of variables that may be incorrect because of the age of the house and the construction.

I built a closet under the center of the duct run to install the air handler.

I have two choices for the location of the condenser. Just ouside the bedrooms is only about a 30 foot run. The electric run would be about 100ft but that is probably easier than the lline set. I am concerned about the noise. The house is 2X4 frame with vynl siding and seems to transmit noise. The single pane windows may not help either. I was going to put the condenser on the other side of the house with the 85 ft run and a 20 ft electrical run.

We don't use the AC that much. Just when company visits or just for a break once in a while. I bought the used unit as an experiment to validate the load calc. I was going to use it for a year or two to check the size and replace it with a new 410a efficient system. I got EPA certifide and have the equipment including a recovery machine. I may have a contractor install the new unit. With a unit, copper and electricity in place I thought the install may be a bit cheaper. That in why I want to put the proper copper in place for the planned new unit.

I plan on loosing my job in a few months so I don't want to ring up that big bill just yet. I was hoping to get by for a year or two and nurse that old machine along.

So, I was hoping the line set size was somewhat generic and I could install it first with the old system and use it for the new system which would be chosen in the future.

The install will be a standard central Florida. Condenser outside, run lines up into the 8 ft high attic and then down into a closet in the center of the house.


bervin306 05-11-2008 02:41 PM

well it seems like you have already made up your mind. You need to understand that you are making a big mistake. Would you put a used 10 year old engine and transmision in your car?

Trust me I have over 10 years in the field. You will be paying more in the long run and will not be comfortable. If noise is an issue the new equipment is so much quieter then that the boat anchor your looking to put in.

Oh and just because you have an epa card that only means you can read and take a test that has nothing to do with servicing and installing HVAC. It is really going to stink when you get all done installing everything and you go to turn it on and find the compressor locked up.

Well good luck

Do it right don't do it twice

JoeFL77 05-21-2008 09:23 AM

Thanks for all the advice and help!
Thanks for all the advice and help! I start project and at some point either finish it or decide to have a professional do it. Doing the first part gives me the knowledge to choose the right professinal.

So I found a great contractor that will be installing a Amana 4 ton 2 stage 18 SEER heat pump in my house.

Thanks for all your help, without it I would be making the wrong decision.

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