On Friday, August 1, 2014 7:54:14 AM UTC-4, wrote:
Ok here is the logic

The manufacturer probably specified a 50 amp breaker to reduce trips during the startup inrush. You all know an a/c has a large inrush current.

Now if you are using a 50 amp breaker you MUST use #6ga or larger wire to be safe and meet code.

I'm surprised it took this long for someone to post this, which is
wrong. Breakers for equipment with motor loads are not sized like
a circuit for receptacles or a heater. It's perfectly permissible to
have a 50A breaker on an #8 gauge wire for an AC. The overcurrent
protection is in the eqpt and it's rated for that installation.

I agree with Gfre, whoever wrote that manual, wherever they are located,
(China?), doesn't know what they are doing. Proof that they don't is
clearly demonstrated by them calling for 3 conductor cable, while they
really mean 2 conductor plus ground. Another very curious thing that
I've never seen before, look at what goes from the outside unit to power
the evaporator unit(s) that shown in the posted link. And in the spec
they call that 4 conductor. What they are showing looks like 3 conductors
plus ground, all used. So, what they are clearly showing is a
240V only connection coming in to the outside unit, then a 240V connection
*with neutral* leaving it to power the evaporator(s). That seems *very*
strange to me.... It seems like they have established their own neutral,
unconneced to the service neutral, going to the other units.
Any thoughts Gfre?

Regarding the conductor sizing, I agree with Gfre. The spec sheet says
26A min circuit ampacity. The rated power input is 4600W max. Based on that,
10g would be sufficient. Does this thing have backup resistance electric
heat by any chance? I doubt it because it's not in the spec sheet. If
it were my install, I'd go by the rating plate. At 26A, I'd just bump it
up to 8g, 2 conductors. If anything, I'd say the big honking cable with
an extra unused conductor is more likely to draw an inspectors attention,
because it looks odd and likely a DIY.


In most places this should have a permit. Why not write down what's on the
eqpt tag and take that, the manual, and the spec sheet and go ask the
inspector?




The breaker and wire size must match to be safe.

Wrong.




But it does seem the directions were confusing re the number of conductors needed.

6-2 is three total conductors, 2 that carry current and one safety ground.



Mark

And wrong again. 6-2 is TWO conductors, plus a ground. The ground is
*not* a conductor.