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.
- 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?
- 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?
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
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.
Mech/ Electrical contractor since 1210...
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
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
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
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.
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
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.
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.
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
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.
I am not fucking with it, I'll be running a line. The specifics are
the reason I posted - to gather information beforehand. Standard
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.
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