Assorted AC questions - running lines for future work

I'm closing in a room that has a chase located next to the chimney. I want to run lines for a future central air system while the wall is open. There's a crawl space below, marginal access on the second floor and good access in the attic where the air handler will be located. I picked up a 50' 3/4" & 3/8" line set which will work with the anticipated 2 or 2.5 ton 2nd floor load.
My questions: - I don't see how I'll be able to run the line without having at least one or two cuts/couplings. I've read silver brazing is better than sweating the joints. How critical is the difference?
- Is flux a problem with making connections in a refrigerant line? Alternatives?
- I'll be pulling a 12/3 line for the unit and to provide an additional circuit in the attic. What wire should I pull for the AC controls?
- I've never pulled such a large line. With electrical I use a fish tape. Can I use that to help pull the insulated copper? Any tricks to keep the insulation from hanging up and getting ripped?
Thanks.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If its not a stand up attic with stair step access (not a ladder) your repair guy will hate your guts... not to worry about him though, he will just all the grief to your bill...with a smile.

yes that works

Best by a massive margin is run it without any cuts solders or brazing..those cause oxide inside the tube and that oxide seeds nasty chemistry into your system and shortens its life significantly..if you do braze run a dry nitrogen purge through the line when you do it.... 15% silver brazing rod is best, called silflos in most stores is best, you need an oxy actytlene torch for that.. over 1500 degrees to work well.
dont flux the joint, the acid gets into the tube that way and seeds bad chemistry in the operating system.

Use an oxy/ actylene flame, get it neutral, then open the oxygen valve slightly to get a faint 'feather' on the flame..test it on a tarnished penny... when its right the penny will turn bright copper under the flame..if its wrong it will darken or soot will show up...

Run 10-2 with a ground... you dont need 3 conductors for a single phase system...you will get about 2% less voltage drop on a hot day when the voltage is low anyway... 12/2 would work though for 2.5 tons but its skimping. (the charts are irrelevant to whats best for your system, the charts are for fire safely purposes, the NEC is part of the national fire code)

In buildings less than 3 stories you dont need conduit inside the walls... for ac in those cases run romex. where it goes outside run the romex into a box..then run rain tight conduit outside to the condensing unit etc.
Phil Scott Mech/ Electrical contractor since 1210...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

PS... one caveat.. best is to avoid soldering. the 2 ton unit will have a 5/8" suction line probably and a 1/4" liquid line. so if there is a miss match you will have to solder.
also if the evaporator coil is above the condensing unit the fat suction line you are showing will work just fine, and advantage actually... if the air handler / coil is below the condensing unit, the fat suction line can pose 'oil return' problems if its much of a rise... if thats the case bend a slight trap into the bottom of the riser on the larger line. a riser over 10' should be avoided.. especially if you end up with an oversize suction line as you are showing in the event of the 2 ton unit (size also dependent on the efficiency of the unit, check all that out...with the smaller unit, which should be fine the 5/8" suction line is a lot easier to bend,. you can avoid all the soldering.
bending trick,, try to arrange bends to match the way the tube is already coiled...bending it sideways or backwards is more difficult.. you can rent a lever arm tube bender for that though.
Phil Scott

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Phil Scott wrote:

Hey Phil. If I run the refrigerant and power/controls lines so it's all ready to go for him, that should make him smile, too. The attic is technically a stand up with a flight of twist stairs to get you up to the third floor/attic. Unfortunately the attic storage space will all go bye bye when the evaporator and ductwork are installed.

There has to be soldering at the ends in any event, right? The nitrogen purge (sounds like a visit to the proctologist) with the meticulous soldering/brazing seems a little involved. Can the connections be done another way? Flare fitting perhaps?

Okay, sounds good. Why an advantage?

It's not, so no problem.

Have the 3/4", opened the box, rather not return it. So it sounds like for a smaller unit, 2 tons, the 5/8" is preferred, but the 3/4" is an advantage (to be specified). Net plus or minus?

I have a bender floating around somewhere. It's just a question of finding it at the right time. It looks like I'll need at least three, maybe four people to pull that line in one piece, assuming I can cut adequate holes in some tight locations.
I should make it clear that it's very doubtful that I'd be doing the system installation, so I'm not looking to make more work for myself. I'll hire a contractor in a few months or few years when the project goes ahead and let him worry about all of the connections and such. The driving force is my desire to not have to open up walls down the road. I hate cutting into my own work. Really.
So with that in mind, can I just cut the line set, pull two sections and leave access to the mating ends for the sub's connection a few months from now?
Is there a specialized cap of some sort to facilitate pulling of the line set? Is there something like a Fernco fitting with a loop in the end to which the pulling line could be attached? I'm concerned that I'll rip the crap out of the insulation as I'm pulling the line.
BTW, I could link you to some pictures of the project, 3D CAD files, if you're interested.
thanks again
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Phil Scott

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

More on soldering... some units have tube connections that must be soldered.. the hot set up for that is 'stay bright silver solder' the kind I am talking about is available only at refrigeration wholesale houses as a rul, it comes in a roll, has a silver content, is soft, and needs the matching flux, it melts and flows very well at 400 degrees or so...all that tends to preclude oxidizing the inside of the tube...its very strong and wont corrode with age...it flows well.
If you go that route, sand the tube with the sand cloth you buy at the refrig wholesalers, other sand cloth has resins on it that screw things up totally... then wipe the flux onto the tube end and fitting with a paper towel, leave no excess.. fit then solder..that works great..dont over do it.. heat the fitting not the tube. a propane torch is good for that. you can avoid the use of dry nitrogen that way.
then if you need need air purge directions for the fit up tube post on that issue... it should be covered in the directions or they are advising you to use a vacuum pump to get the air out of the lines before you open you new line set to the system. thats important.
Phil Scott

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The diameter of the pipe is dependant on DISTANCE and tonnage. You estimate the tonnage, but what about the distance? Call someone in your area and get a quote for the a/c. And what size of lines they would run. I insulate after installing and all silver soldering is finished and a vacuum verifies all is well. I use mule tape and AT LEAST one other person to pull in the line set. Harder situations some time it is 2-3 other guys for a short period of time. I work to NOT have couplings in the lines.
Why run 12 -3? You do not need a neutral for a condenser and most air handlers. Are you sure 12 is big enough? Controls are dependant on what your doing. High end stuff I do I use 9-12 wire, never less than 7 wire for the controls. Way to easy to have more than enough than less. But then again I buy control wire on 1000 foot spools.
Soldering WILL get ya in trouble maybe not right away but it will fail. Silver solder is the only way to do it correctly. Also the ends need to be welded shut.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SQLit wrote:

I have gotten some estimates, and received much conflicting advice as to whether the high velocity systems would work in this particular house. The load estimates (no calculations were done) were in line, so that's where the tonnage came from. The distance I alluded to (sorry, should have spelled it out) was the 50' lineset. It's going to be right in that ballpark, a few feet shorter at the most.

I can see the advantage to doing it that way. Unfortunately access would make insulating the line almost as difficult as pulling it.

I can see the obvious advantage and would love to have an unbroken line for a bunch or reasons. However, the route this line takes, while fairly direct and with only two turns, is beyond tight. It seems that pulling the line set down from the attic will be the easiest as I can lay out a fairly long stretch to start to straighten it.

Not any more. My electrician said the 12 was fine, that most units are 110 now, and it wouldn't be a problem. I'll look into it some more.

Hmmm. Same electrician said a 5 wire was plenty, as that's the maximum number of wires he's seen.

Explain that welded shut bit, please.
I have a friend that used to be in the business, and used to be a jeweler. He's the brazing master. Maybe I'll have to twist his arm to come over and get his hands dirty for old times sake.
Thanks for the input.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Get a small rope or fish tape...insert rope or fishtape into the 3/4 copper with a knot on the end or bend small section of the fishtape out about 90 degrees......bash the end of the 3/4 copper closed so that the rope or fishtape wont pull out......tape or wire tie the 3/8 line and thermostat wire to the end of the 3/4 copper...wrap the end of the 3/4 copper that will be pulled thru first with duct tape so that the end of the insulation doesnt hang....pull lineset up cut off end that you have ruined and seal with plastic cap or something....If I was gonna leave it for any length of time I would braze caps on to both ends of both lines and put a schrader type access fitting on one end.....then charge with nitrogen and leave the nitrogen in there....just a few psi...enough to let you know if a nail or anything has gone thru the line after the wall or chase is closed back up.
~:>
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If there is absoluely no way to run the lines without having to make any joints in them, then silver solder is a must. If you use anything else, including flare fttings, you are just begging for trouble. Pressure test the lines afterwards just to be safe, so just in case there is a leak at a joint, it can be located and repaired while still accessable. Also, in pulling the lines, be sure to carefully unroll the lines. DO NOT try to pull them off from the edge of the roll, like stretching a coil spring. You are guaranteed to kink them if you do. I have had more than one helper do that, when I told them to feed me the lines as I pulled them into the attic. I could have strangled them. Best bet-- do not try to run them by yourself, and get a good dependable helper. You are not real clear as to the electrical you are talking about running. Is this for a gas furnace in the attic? If so, a 20 amp circuit with #12 should be fine. Or are you talking about a line for the outside unit? If so, do yourself a favor and run at least #10. Good luck Larry
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

If you have to ask all of these questions then you should not be fucking with it. Ther are so many things you need to know in order to keep future problems at bay that one could probably not post them all here. Good luck with all that.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Al Moran wrote:

I am not fucking with it, I'll be running a line. The specifics are the reason I posted - to gather information beforehand. Standard procedure, no?
I've checked on a couple of manufacturers' web sites and the 3/4" works, but the 3/8" may be a little large. I know a smaller size would minimize the charge, but how much difference does that actually make?
So if the sizing is okay, and besides me putting a hole in the pipe, the only future problem I see is the question of contamination. That's where I am, and I'm open to suggestions and comments.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I would run a conduit or two for the electrical and cap them. Let them run the wires through them when they install the A/C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.