"RicodJour" wrote in message
oups.com...
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.


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.





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.

yes that works



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?

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.


- Is flux a problem with making connections in a refrigerant
line?
Alternatives?

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...


- 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?

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)




- 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?


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...



Thanks.

R