On Sunday, May 29, 2016 at 10:23:36 PM UTC-4, Diesel wrote:
trader_4
Sun, 29
May 2016 14:45:19 GMT in alt.home.repair, wrote:


Like Gfre said, a resistance heater isn't going to increase it's
current draw because there is some additional resistance in the
circuit. It's like saying a light bulb will burn just as bright
with a rheostat in the circuit to dim it, because it's going to
pull additional current to compensate for the lower voltage.
Put additional resistance in the circuit and the total current
goes down, not up. And the difference here, the resistance in
that wire is negligible.

That isn't what I'm saying at all. I'm saying that the further out
you go with 12/2 (or any wire really, it just depends on the
thickness of the wire, the power you started with, and how far you're
actually going), the less available voltage you'll have at the end of
the run.

The less volts you have, the more amps you'll need to make up the
difference to get the desired wattage.


The heating element looks like a resistor. There is no magical making
up. Take a simple circuit with a voltage source V and a resistor of
value R1. The current is V/R. Now add an additional resistor in
series, R2 that represents the resistance of the wire in our system.
The current is now V/(R1+R2), which is less than the current of V/R1.

Like Gfre said, if you look at a heating element, if it's rated for
two voltages, the power output is stated lower at the lower voltage.





Also, the 10/2 isn't going to be near capacity at any time, either.
even if he has them all going on high at the same time. The 12/2
however, will be depending on the amount of heaters going and their
setting(s).

going by Ugly:

7.9 volts lost 12/2 at 100ft
4.97 volts lost on 10/2 at 100ft


IDK what parameters they used. I worked out the
actual numbers, it's very simple and the voltage drop due to the
resistance in the wire is only 2.7%, at 20A, for 100 ft of #12.
Why no reply to the actual math? Here it is again:

The resistance of 12 gauge wire is .0016 ohms per foot.
100 ft, you have .16 ohms. At 20A, that produces a voltage drop of 3.2V .
There are two conductors so double it, 6.4V. It's a 240V circuit, 6.4V
drop from 240V is just 2.7%, not 5.6%.







240-7.9=232.1 on the 12ga
240-4.97=235 on the 10ga

1500/232.1=6.5 amps *rounded up*
1500/235=6.39 amps *rounded up*

And that's due entirely to distance with no loads present on the line
yet.


No idea what you're even doing here, no loads? yet 1500?


100ft on 12/2 according to my 2014 edition of Ugly's electrical
reference is a net loss of 7.9 volts at the end of the run, with no
load present, yet. At 125 ft out, the loss increases to 9.8 volts.
And, obviously gets worse from there.


Again, the resistance of #12 is .0016 per ft. The math has been
presented above, the voltage drop at the full 20A is just is just
6.4V, which at 240V is just 2.7%. Even using your higher number,
which is probably coming from using some high temperature, you still get
a voltage drop of only 3.2%. There is no 125 ft, he said the run is under
100 ft.

And you say this is with no load present yet. That's incorrect too.
This is with the MAX load the circuit is rated for, the full 20A.
With no load, there is no voltage drop period.




OTH, the 10/2 wire loses 4.97 volts at 100ft and 6.21 volts at 125ft
out. I'd rather get as many volts to the device (heaters) as is
realistically possible.

Then use #8, #6, etc. Same argument can be made there. It does nothing
in terms of safety or proper operation of the heater.



The closer I can get to their expected input
voltage, the less amps they'll require to do their jobs. The more
heat I'll get (which is obviously the point here) and the less power
I'll use doing it. A win win win.


You're really confused here. The heater does not magically adjust to
draw more amps. Take this to an extreme. If I put just 24V across those
heaters, following your logic instead of drawing 14A at 240V they would draw
10 x 14A = 140A? It doesn't work that way.



To do anything less is only costing me more money and time in the
future. The 12/2 is going to heat up a bit more under various
conditions than the 10/2 ever thought about doing, even if all
heaters were on at the same time, on HIGH. Over time, the 12/2 wire
will degrade due to heating/cooling cycles that the 10/2 won't have
experienced. As it degrades, it's own resistance will increase.


BS. If that was the case, no electrical inspector would approve it.
You have one, Gfre, telling you that it does meet code and citing NEC
to back it up.



Another side effect of running the wire warm/possibly hot to the
touch

More BS.


at near full load over a period of time is that the connection
points and terminals in the panel and the heaters will also become a
little 'warmer' than they would if they'd been powered from the 10/2
line and pigtailed to it with a short 12/2 run.

A random internet posting is your cited source of information?

Uhh, no. I remembered it was 100ft or so off hand as the general rule
of thumb, but didn't remember how much voltage was lost as a result.
I've also got various NEC books and my 2014 edition of the yellow
Ugly electricians reference book. It's where the voltage drop figures
I used today came from, actually.


And even using those numbers, the voltage drop at the full 20A circuit
rating is just 3.2%. At the actual load, 14.6 amps, it's just 2.3%,
so again there is no problem, no hot wires.


That's right, just use 12 gauge which NEC says is perfectly fine.
You're the one throwing all kinds of FUD in and using incorrect
calculations.

Just to clarify, the calculations I provided in this post aren't FUD,
unless you're able to dismiss the yellow Ugly electrician reference
book.

Show us where Ugly's says it's a violation of NEC, unsafe, etc to wire
the circuit on a #12.


I haven't seen any 240volt baseboard heater wired with a 12/2
in sometime, actually.


That depends entirely on what the rated capacity of the heaters is.
And if you're that familiar with heating elements you should know that
there ones that are rated for either 240V or 120V and that at the lower
voltage they put out LESS power, they don't magically adjust, pull
more current, to put out the same power they do at 240V.



I think the last time I actually observed that
was with a trailer. Alas, they're built with heavy consideration on
cost. IE: as cheap as you can get away with. I don't work like that,
I don't offer advice with that in mind first and foremost.

If it were me, writing only for myself, I'd spend the extra money for
the heavier gauge wire and use the 12/2 wire for pigtailing off of it
into the heater units. I've already explained why I'd run it in this
manner. No real point in doing so again.


Which again implies that this is destined to fail, when of course it's
not.