On Sat, 02 Aug 2014 10:36:24 -0400, email@example.com wrote:
Skin effect doesn't even begin to have any effect in residential or
normal commercial wiring. I know code does not require upsizing for
stranded wire - I never said it did. I said, generally one should use
one size heavier flexible cord than one would use for solid permanent
wiring. I stand by that. Flexible cable is submitted to a lot of
flexing which will eventually compromize some strands, increasing the
resistance. It is a good idea to use one size heavier cable than
"required", particularly when running close to the design current
limit for the cord.
In general practice, MOST people use a cord that is AT LEAST one size
too SMALL for the load.
On Saturday, August 2, 2014 3:58:37 PM UTC-4, firstname.lastname@example.org wrote:
You have your outside AC units swinging around in the breeze up
there in Canada? Around here, they *are* installed with permanent
wiring, not cords. And the cord reference is in the same lame
drawing, that was obviously written by a buffoon. They confuse
conductors with grounds and call for a 4 conductor cable. As I
already said, even if you allow that they really mean 3 conductors,
plus ground, it's still wrong. The drawing only shows two hots, ie
a normal 240V AC connection. So, following that, we should get a
big old honking 6 gauge 4 conductor stranded "cord". Then leave two
conductors unused. Then let;s call the inspector over and see how he
Or we could use two #8 THWN stranded run inside liquidtight. Actually
per the eqpt label, you could use #10, but since the 26A is close to
the max for #10, I'd bump it up.
It is a good idea to use one size heavier cable than
Cable? Cord? Which is it now? Better rip out all your 14 gauge that's
on 15 amp breakers, make it 12 gauge.
In general practice around here, people don't install permanent,
outdoor AC eqpt with cords. And I've never seen a 3.7 ton AC unit
on #6 anything, cord, stranded, solid, etc.
On Sat, 02 Aug 2014 15:51:59 -0400, email@example.com wrote:
Continuous is 3 hours in the NEC.
It is really not even a factor here. The "minimum circuit ampacity" is
an engineered value based on that particular piece of equipment and
takes into account all applicable factors.
In this case a 10 gauge copper wire will fulfill that requirement.
On Saturday, August 2, 2014 4:01:14 PM UTC-4, firstname.lastname@example.org wrote:
Except of course that the manufacturer did not say #6 or any gauge on the
UL label. Nor have I ever seen gauge on a similar label. The governing data
on the eqpt label is the 26A, if he chooses to follow that. The manufacturer
stated #6 gauge in the install manual, which was obviously written by a buffoon, because they don't understand the difference between conductors and
grounds. The install instructions say that it's to be installed with
4 conductors and then they show only a 240V connection, no neutral, just like
you'd expect with any other air conditioner. So, following that, even
after correcting it to 3 conductors, plus ground, you'd have an extra
wire that goes nowhere. Would you follow that too?
That 3.7 ton AC would have to be the most inefficient piece of crap ever
made to need #6. It would be so inefficient, it couldn't meet the min
SEER required today. It also states in the spec that the rated input power
is 4600 watts. 4600 watts = 19 amps. There is nothing there that comes
close to needing 6 gauge wire.
On Saturday, August 2, 2014 5:06:41 PM UTC-4, email@example.com wrote:
We don't have access to the UL listing spec. All we have are the eqpt
rating plate and one page of the install manual. That one page, was
obviously written by a complete buffoon. They call for #6 and in the
diagram call it a cord. How many outside AC condenser/compressor units
have you seen installed on cords?
And then they call for 4 conductor cord. Lets take that literally too.
So, we have 4 conductors and a ground? WTF? OK, whooops, I guess
they really meant 3 conductors plus ground. So we get a big honking
#6 cord, with 3 conductors plus ground. Whooops! They only show two conductors actually used, ie like you'd expect for a 240V AC unit. So
I guess the extra one is for good luck, but heh, they said to do it
righ? In other words, whoever wrote that manual, proably in China,
didn't know WTF they were talking about.
On the other hand, we do know the unit is rated at 3.7 tons. That
the rated input power is 4600 watts and that the eqpt label says the
min circuit ampacity is 26A. All that says #6 is nuts and that 10g
would suffice. Since 26A is close, I'd go with #8. And I would not
use a cord, which I don't think would even pass code here. I'd put
THWN, #8, 2 conductors plus ground, inside liquidtight. The OP as
always, can do as he chooses.
On Saturday, August 2, 2014 6:28:45 PM UTC-4, Doug Miller wrote:
Agree with you except for the above. The "min circuit ampacity" is 26.
The rated load amps is 19. It also says the rated input power is 4600W.
Clearly it's running closer to 19 amps, not 26. The exact current is
going to vary based on the exact conditions present at the time. But all
that is taken into account when they spec'd the min circuit amps at 26.
The unit is only 41K btu, ie 3.7 tons. It's impossible for a unit to
need #6, if it drew that much power and only produced 3.7 tons, it would
never meet the min govt SEER standards.
It's obvious whoever wrote that manual made several mistakes. If it were
me, I'd use #8 and a 50A breaker, which is consistent with the unit label
and be done with it. I suggested previously that if this needs to be
permitted, the OP could take the relevant info to the inspector and ask.
I for sure would do one of the above before I installed it with #6, using a
*4 conductor *cord*, because the lame manual says so.
On Sat, 2 Aug 2014 22:28:45 +0000 (UTC), Doug Miller
If the AC unit runs at 26 FLA for 3 hours and 1 minute on the hottest
day of the year, it is over 80% and "continuous" by code, so the wire
needs to be derated to 80%., meaning it needs a larger cable.
On Saturday, August 2, 2014 7:23:06 PM UTC-4, firstname.lastname@example.org wrote:
You're confused again. The 26 amps is not FLA, it's the spec for the
minimum ampacity of the circuit. The rest is the wire size that will
support 26A. You're taking what was already calculated by engineers
and applying factors on top of the factors they already applied when
they did the UL listing.
On Sat, 2 Aug 2014 22:31:25 +0000 (UTC), Doug Miller
If the AC runs for 3 hours and 1 minute without shutting down at 26
amps, a #10 cable is undersized for the application.
That is according to your interpretation of the code.
Is it inconceiveable that this air conditioner could run for over 3
hours at a time???
If this AC can run for more than 3 hours without shutting down,and it
draws 26 amps, it requires #8 cable. If the rating label states it
requires a #6 cable, it requires a #6 cable to meet code.
I don't pretend to know WHY the manufacturer specified a #6 cable,
when according to code a #8 would be adequate. My only GUESS is it had
something to do with the specification that the unit was to be
connected with stranded cable (I believe that was part of the original
post) - in which case the premises wiring could be #8 and the flex
cable be #6.. The specification was 3 conductor # 6 flexible cable,
and the OP misread that to be NMD or NMW6-3 + ground from the service
panel to the unit.
That's MY take on it.
On Sat, 02 Aug 2014 17:06:41 -0400, email@example.com wrote:
The U/L listing is on the label per the marking guide and relevant the
number I saw was "minimum circuit ampacity 26 amps".
I really would not pay much attention to anything else. This is the
number provided by the engineer, not some tech writer who's first
language is probably not English..
On Sat, 2 Aug 2014 22:35:00 +0000 (UTC), Doug Miller
I thought the OP said the label on the unit gave the circuit
requirements and the cable specification. I could have misread that.
My reader does not make it easy to go back to previous posts in a
thread, so I'm going by memory.
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