I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

The instructions in each box say that I will need to use a 220v
circuit with "amperage according to local code".

Both rooms are next to each other and I'm wondering if instead of
fishing two wires, I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

46erjoe wrote:
Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.


Nope

In article , 46erjoe wrote:
I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

The instructions in each box say that I will need to use a 220v

220, or 240? It makes a difference. If the heater is rated 2000 watts at 220V,
it will produce almost 2400W at 240V -- which is almost certainly the
voltage that you actually have in your house. And never mind the installation
instructions. Look at the rating plate on the heater.

circuit with "amperage according to local code".

You'd have to talk to a local electrical inspector to find out what your local
code is.

Both rooms are next to each other and I'm wondering if instead of
fishing two wires, I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?

Under the National Electrical Code, 10/2 is limited to 30A overcurrent
protection (breaker or fuse), and continuous loads (such as electric
resistance heating) are limited to 80% of the overcurrent rating -- which
would be 24A for a 30A breaker. 24A at 240V is 5760 watts; your heaters total
3500, so one 10/2 30A circuit will be just fine.

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point

NO. First off, that's a Code violation: connecting conductors in parallel is
not permitted. Second, even if that was allowed, that would take care of only
*one* of the two conductors in the circuit anyway. What about the other one?
It would still be 12ga. And don't even think about doubling up the white and
bare wires -- you could wind up making the case of the heater live.

However, if the heaters are rated 2000 and 1500 W at 240V, you don't need a
30A circuit anyway, and you can use 12ga wi 20A * 240V * 80% = 3840 W,
which is adequate for the heaters you have.

OTOH, if they're rated 2000 and 1500 W at 220V, and you run them on 240V, then
you will need a 30A circuit, because the heaters will produce almost 20% more
power: 2380 and 1785 watts respectively, for a total of 4165 watts -- too much
for a continuous load on a 20A circuit.

This is why I asked above if they're rated at 220V or 240V. It does matter.

and then painting the red wire with black marker pen to indicate power?

That would be unnecessary -- red is assumed to be power anyway -- but as noted
above, it's a Code violation, and it's not safe.

I hate to waste wire with the cost of copper these days.

It's come down quite a bit since June. It's still more than double what it was
two years ago, but I saw 250' of 12/2 NM at Home Depot last week for $67...
and just a few months ago, it was over $100.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

46erjoe wrote:

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

Well I can't think of a violation if you would cut the black or red wire
at each end, or cap it, but not use it in any part of the circuit. I am not
sure about that however. Of course you would not have 10/2 you would have
12/2.

Best bet is to find someone with extra 10/2 and work out a trade.


--
Joseph Meehan

Dia 's Muire duit

On Fri, 08 Dec 2006 18:25:10 GMT, "Joseph Meehan"
wrote:

46erjoe wrote:

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

Well I can't think of a violation if you would cut the black or red wire
at each end, or cap it, but not use it in any part of the circuit. I am not
sure about that however. Of course you would not have 10/2 you would have
12/2.

Unless you're only serving one device,
2 12-AWG wires 240V apart at 20Amps will deliver more
watts to the other end than one 10-AWG wire
at 120V and 30Amps.

And the 12-AWG will probably even fit on the screw-terminals.

In article , "Joseph Meehan" wrote:
46erjoe wrote:

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

Well I can't think of a violation if you would cut the black or red wire
at each end, or cap it, but not use it in any part of the circuit. I am not
sure about that however. Of course you would not have 10/2 you would have
12/2.

Yes, and that might in and of itself be a violation, as I explained in an
earlier post -- he might *need* a 30A circuit.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article , Goedjn wrote:
On Fri, 08 Dec 2006 18:25:10 GMT, "Joseph Meehan"
wrote:

46erjoe wrote:

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

Well I can't think of a violation if you would cut the black or red wire
at each end, or cap it, but not use it in any part of the circuit. I am not
sure about that however. Of course you would not have 10/2 you would have
12/2.

Unless you're only serving one device,
2 12-AWG wires 240V apart at 20Amps will deliver more
watts to the other end than one 10-AWG wire
at 120V and 30Amps.

So what's your point here? The OP has 240V heaters. The notion of a 120V 30A
circuit was never being discussed.


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Basic Electricity 101: current flows in a circuit, and needs to return back
to the source (in this case let's call it a breaker box) along a 10 gauge
wire as well. Thus, by "clamping" red and black together you get a heavier
conductor only in one direction (from the breaker box to the load) but still
have a light conductor in the return path. You would need to start with 12/4
and "clamp" 2 pairs together to do what you want.

Smarty


"avid_hiker" wrote in message
ups.com...

46erjoe wrote:
Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.


Nope

In article , "Smarty" wrote:
Basic Electricity 101: current flows in a circuit, and needs to return back
to the source (in this case let's call it a breaker box) along a 10 gauge
wire as well. Thus, by "clamping" red and black together you get a heavier
conductor only in one direction (from the breaker box to the load) but still
have a light conductor in the return path.

Right so far...

You would need to start with 12/4
and "clamp" 2 pairs together to do what you want.

But that's a violation of the National Electrical Code.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

061208 1139 - 46erjoe posted:

I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

The instructions in each box say that I will need to use a 220v
circuit with "amperage according to local code".

Both rooms are next to each other and I'm wondering if instead of
fishing two wires, I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Derating the 20 gauge wire to 80% would be 16 Amps.

Don't even think about paralleling the wiring. If the voltage drop is
severe, then consider running two of the 3-wire cables -- one for each
heater.

On Fri, 08 Dec 2006 16:39:24 GMT, 46erjoe
wrote:

I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

You need to know the Full Load Amps. If you have the specs for the
heaters it should be listed. If it is less than 16A then you can use
one 20A circuit with number 12 wire.

If it is more than 16A, I think you are required to use 2 circuits.



The instructions in each box say that I will need to use a 220v
circuit with "amperage according to local code".

Both rooms are next to each other and I'm wondering if instead of
fishing two wires, I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

No, but you can use 12/3 without connecting the white to anything.
(cap it. don't cut it)

In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...

Derating the 20 gauge wire to 80% would be 16 Amps.

You mean 12 gauge / 20 amp, of course.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article , Terry wrote:
On Fri, 08 Dec 2006 16:39:24 GMT, 46erjoe
wrote:

I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

You need to know the Full Load Amps. If you have the specs for the
heaters it should be listed. If it is less than 16A then you can use
one 20A circuit with number 12 wire.

If it is more than 16A, I think you are required to use 2 circuits.

Two 20A circuits, yes -- but he'd be just fine with one 30A circuit.
[...]
you can use 12/3 without connecting the white to anything.

Maybe he can, maybe he can't -- see my other posts in this thread discussing
the voltage at which the heaters are rated vs. the voltage in the OP's house.
He said the installation instructions say to use a 220V circuit -- suggesting
that the rated output of the heaters may be based on an input of 220V. But
it's likely that his actual supply is 240V, and at the higher voltage the
heaters would draw enough current that he can't put both of them on a single
20A circuit. Two 20A circuits would be fine regardless, as would one 30A.


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

On Fri, 08 Dec 2006 16:39:24 GMT, 46erjoe
wrote:

I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

The instructions in each box say that I will need to use a 220v
circuit with "amperage according to local code".

Both rooms are next to each other and I'm wondering if instead of
fishing two wires,

If you need to fish two wires, fish a rope or wire or strong string,
like nylon, and use it to fish each of the two electric wires. You can
use a snake to fish the string. The string only has to be twice as
long as the distance you are fishing it, so you can pull the string
back and forth and not lose the end at either end. And you can
sometimes fish in stages like an inch worm.

I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

So don't waste it. Give it to someone who needs it. Give it to a
friend or a store that sells the stuff.

I damaged my bathroom sink years ago -- by letting water sit in it for
days or weeks, under a sponge iirc. I thought that a porcelain sink
could hold water for months or years, but maybe my steel and enamel
sink isn't the same as porcelain. So insteaad of going to a good
plumbing supply store, I bought a replacement at a big box store that
is meant to mount on top of the counter instead of underneath, like
the original. Last night I found one that one of my neighbors has
thrown away, and it is a perfect match, and it's in perfect
condition.**

So I'm going to give away the sink I had bought. The store that I
bought the sink from is out of business, 8 years ago, Hechingers, so
I'm going to find a plumbing supply store and give it to them. I was
going to buy a new sink from them, that actually fit, and maybe try
and get some money off for giving them the sink I bought, but now I'll
just give it to them.


**Even the faucets, and the drain pipe and stopper control rod beneath
the sink I found are in perfect condition. And shiny clean. The
faucets are just like mine, so they and the sink are almost certainly
original, which means 27 years old. I don't know how anyone could be
so clean. And there aren't many people here anymore who were here
even 15 years, so it must have been two families in a row who were
clean.

Even then, have any of you ever polished the metal strip behind the
drain which raises and lowers the stopper, or even the drain pipe? I
didn't think one was supposed to clean those parts.

061208 2234 - Doug Miller posted:

In article , indago wrote:

Derating the 20 gauge wire to 80% would be 16 Amps.

You mean 12 gauge / 20 amp, of course.

Ooops! Yes...


Maybe he should check his line voltage to be sure...

On Sat, 09 Dec 2006 03:38:22 GMT, (Doug Miller)
wrote:

In article , Terry wrote:
On Fri, 08 Dec 2006 16:39:24 GMT, 46erjoe
wrote:

I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

You need to know the Full Load Amps. If you have the specs for the
heaters it should be listed. If it is less than 16A then you can use
one 20A circuit with number 12 wire.

If it is more than 16A, I think you are required to use 2 circuits.

Two 20A circuits, yes -- but he'd be just fine with one 30A circuit.
[...]
you can use 12/3 without connecting the white to anything.

Maybe he can, maybe he can't -- see my other posts in this thread discussing
the voltage at which the heaters are rated vs. the voltage in the OP's house.
He said the installation instructions say to use a 220V circuit -- suggesting
that the rated output of the heaters may be based on an input of 220V. But
it's likely that his actual supply is 240V, and at the higher voltage the
heaters would draw enough current that he can't put both of them on a single
20A circuit. Two 20A circuits would be fine regardless, as would one 30A.

I am still not sure I follow your explanation. It is true that there
are more than one application for 220V 240V and even 208V, but is it
not true that all homes are designed to be 220 nominal?

I am not sure how buying anything for a home would be designed for
anything else?

The op says 220V and I am sure that he got that from the box. Why
would a home owner assume they had more than 2 choices?

I am also not sure why you would be able to go to a 30A circuit. While
it is true that using a 30A circuit would be more than adequate, I am
unsure that is it permitted by the code. (I hope someone can cite the
section)

In article , Terry wrote:


I am still not sure I follow your explanation. It is true that there
are more than one application for 220V 240V and even 208V, but is it
not true that all homes are designed to be 220 nominal?

No, not really -- utility supplies have been 240V for quite a while now.

I am not sure how buying anything for a home would be designed for
anything else?

The op says 220V and I am sure that he got that from the box. Why
would a home owner assume they had more than 2 choices?

The point is simply that if the heaters are rated for so many watts at 220V,
when installed on the 240V supply that the OP almost certainly has, they will
draw more current -- enough more that they cannot both be used on the same 20A
circuit. If their rated output of so many watts was rated at 240V, then they
can both be used on the same 20A circuit.

I am also not sure why you would be able to go to a 30A circuit. While
it is true that using a 30A circuit would be more than adequate, I am
unsure that is it permitted by the code. (I hope someone can cite the
section)

Why would it not be permitted? The breaker is there to protect the *wire*, not
what's attached to it. Look: you probably have an electric can opener in your
kitchen. It's plugged into a 20A circuit, even though it's about a 1amp
device. So what?

As a matter of fact, if the rated output of the OP's heaters was determined at
220V instead of 240V, and he puts them both on a single 240V circuit, the Code
*requires* that circuit to be 30A *minimum*.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

On Dec 10, 10:58 am, (Doug Miller) wrote:
In article , Terry wrote:

I am still not sure I follow your explanation. It is true that there
are more than one application for 220V 240V and even 208V, but is it
not true that all homes are designed to be 220 nominal?No, not really -- utility supplies have been 240V for quite a while now.



I am not sure how buying anything for a home would be designed for
anything else?

The op says 220V and I am sure that he got that from the box. Why
would a home owner assume they had more than 2 choices?The point is simply that if the heaters are rated for so many watts at 220V,
when installed on the 240V supply that the OP almost certainly has, they will
draw more current -- enough more that they cannot both be used on the same 20A
circuit. If their rated output of so many watts was rated at 240V, then they
can both be used on the same 20A circuit.



I am also not sure why you would be able to go to a 30A circuit. While
it is true that using a 30A circuit would be more than adequate, I am
unsure that is it permitted by the code. (I hope someone can cite the
section) Why would it not be permitted? The breaker is there to protect the *wire*, not
what's attached to it. Look: you probably have an electric can opener in your
kitchen. It's plugged into a 20A circuit, even though it's about a 1amp
device. So what?

As a matter of fact, if the rated output of the OP's heaters was determined at
220V instead of 240V, and he puts them both on a single 240V circuit, the Code
*requires* that circuit to be 30A *minimum*.


I admit I don't know, but I would think instead of going to #10 and a
30A circuit you would be required to run 2 seperate 20A circuits if the
total load exceded 16A.

I would also assume that you would take the the only two choices you
would have. Either the equipment would be 110 or 220. Why would they
sell something that was not the common voltage for the home?

Taking 240V instead of 220V the current would be less and not more.
This would be 14.6A

I do understand that if you use somethign designed for 220V and it is
infact 240V the current would be more, but can't see that being the
case something designed for a home.

I wish the OP woud chime in and give any more information he could give
on the heaters, like maybe the Full Load Amps.

Doug Miller wrote:
In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...

Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied. Same for
the 1500 watt heater. The resistance stays the same. Only the amps
and volts are variables. The higher the volts, the lower the amps.
Indago's calc was correct, as he figured it on the (worst case) lower
voltage. One 20 amp circuit is sufficient for both baseboard heaters.

volts500 wrote:
Doug Miller wrote:

In article , indago wrote:


If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...


Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied. Same for
the 1500 watt heater. The resistance stays the same. Only the amps
and volts are variables. The higher the volts, the lower the amps.
Indago's calc was correct, as he figured it on the (worst case) lower
voltage. One 20 amp circuit is sufficient for both baseboard heaters.


If it's a pure resistance element, then no, that's not true. The
*RESISTANCE* stays constant; watts and amps increase with volts. V=IR
and all that. Of course I know we're talking about AC circuits here so
that will only be an approximation, but you get the general idea.

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

In article . com, "Terry" wrote:

I admit I don't know, but I would think instead of going to #10 and a
30A circuit you would be required to run 2 seperate 20A circuits if the
total load exceded 16A.

Why? Is there some reason you think it would not be acceptable to attach a 16A
load to a 30A circuit?

I would also assume that you would take the the only two choices you
would have. Either the equipment would be 110 or 220. Why would they
sell something that was not the common voltage for the home?

Residential electrical supply in the US and Canada hasn't been 110/220 for
many years -- it's 120/240 and has been for a long, long time. Doesn't stop
people from referring to it as 110 and 220, obviously, but that's not what it
is.

My point was this: the OP referred to installation instructions that said
(according to his post) to connect the equipment to a 220V circuit. Maybe that
was just a mistake on the part of the OP and the instructions really said
240V, or maybe they really said 220V like he said -- and if *that* is the
case, that the manufacturer really said 220 and not 240, it's quite possible
that the rated output of the heaters is based on their output at 220, and not
at the 240 that the OP certainly has in his house. And the distinction is
important because if these heaters were rated at 240V, then they can both go
on the same 20A circuit -- but if they were rated at 220V they cannot.

Taking 240V instead of 220V the current would be less and not more.
This would be 14.6A

Wrong.

Take the case of a resistance heater that emits 2000 watts at 220V. It draws
2000 watts / 220 volts = 9.09 amps. Now calculate the resistance: 220 volts /
9.09 amps = 24.2 ohms.

Note that the resistance is a physical property of the heating element, that
does not change no matter what voltage is applied to it.

Now push 240V across that same 24.2 ohm resistance.

240 volts / 24.2 ohms = 9.92 amps.

A similar calculation applies to the 1500 watt heater.


I do understand that if you use somethign designed for 220V and it is
infact 240V the current would be more,

Isn't that exactly the opposite of what you said in the previous paragraph?

but can't see that being the
case something designed for a home.

Maybe you're right -- but assuming that, without proof, could be dangerous.
Which is why I cautioned the OP to check the rating plate to see whether the
heaters were rated at 220V or 240V.

I wish the OP woud chime in and give any more information he could give
on the heaters, like maybe the Full Load Amps.

Simply knowing what voltage they're rated at is sufficient.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article .com, "volts500" wrote:

Doug Miller wrote:
In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring
a
30A circuit because...

Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied.

That is *not* correct.

The *resistance* stays the same. Increase the voltage, and you increase the
current. Increase the current and voltage, and you increase the power even
more.

Suppose you have a 10ohm resistance heating element. Operate it at 220V.
V = IR
I = V / R = 220V / 10 ohm = 22 amps.
E = VI = 220V * 22A = 4840 watts.

Now operate the same element at 240V:
I = V / R = 240V / 10 ohm = 24 amps
E = VI = 240V * 24A = 5760 watts.

Same for
the 1500 watt heater. The resistance stays the same.

Right. The resistance stays the same. But the power output changes with
voltage.

Only the amps
and volts are variables. The higher the volts, the lower the amps.

False. The higher the volts, the *higher* the amps.

V = IR

Increase V while holding R constant, and I goes *down*??? Hardly.

Indago's calc was correct, as he figured it on the (worst case) lower
voltage.

Wrong. The worst case would be figuring it at the higher voltage.

One 20 amp circuit is sufficient for both baseboard heaters.

Not if they were rated at 220V but operated at 240V.

If they were rated at 240V, yes -- but that's the whole question here, isn't
it? The installation instructions cited by the OP apparently referred to
installing a 220V circuit, which raises the possibility that they heaters were
rated at 220V and not at 240V. Operating them at a 9% higher voltage than that
at which they were rated will cause them to draw 9% more current, and deliver
nineTEEN percent more power, than rated.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

061210 2113 - Doug Miller posted:

In article .com, "volts500"
wrote:

Doug Miller wrote:
In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but
his
service is actually 240V (as is very likely), the currents will be almost
20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring
a
30A circuit because...

Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied.

That is *not* correct.

The *resistance* stays the same. Increase the voltage, and you increase the
current. Increase the current and voltage, and you increase the power even
more.

Suppose you have a 10ohm resistance heating element. Operate it at 220V.
V = IR
I = V / R = 220V / 10 ohm = 22 amps.
E = VI = 220V * 22A = 4840 watts.

Now operate the same element at 240V:
I = V / R = 240V / 10 ohm = 24 amps
E = VI = 240V * 24A = 5760 watts.

Same for
the 1500 watt heater. The resistance stays the same.

Right. The resistance stays the same. But the power output changes with
voltage.

Only the amps
and volts are variables. The higher the volts, the lower the amps.

False. The higher the volts, the *higher* the amps.

V = IR

Increase V while holding R constant, and I goes *down*??? Hardly.

Indago's calc was correct, as he figured it on the (worst case) lower
voltage.

Wrong. The worst case would be figuring it at the higher voltage.

One 20 amp circuit is sufficient for both baseboard heaters.

Not if they were rated at 220V but operated at 240V.

If they were rated at 240V, yes -- but that's the whole question here, isn't
it? The installation instructions cited by the OP apparently referred to
installing a 220V circuit, which raises the possibility that they heaters were
rated at 220V and not at 240V. Operating them at a 9% higher voltage than that
at which they were rated will cause them to draw 9% more current, and deliver
nineTEEN percent more power, than rated.

This is correct, and at this point I would connect a temporary line to the
panel and place the heaters on a bench and turn on the power and check the
voltage and current with a clamp-on ammeter at first surge, and then when
the heater heats up, check the current again to get an accurate measure of
just what would be demanded of the circuit. I am assuming the baseboard
heaters are of the calrod class of heater, and the hotter the element gets,
the more the resistance, and the lower the current.

On Dec 10, 9:00 pm, (Doug Miller) wrote:
In article . com, "Terry" wrote:

I admit I don't know, but I would think instead of going to #10 and a
30A circuit you would be required to run 2 separate 20A circuits if the
total load exceeded 16A.

Why? Is there some reason you think it would not be acceptable to attach a 16A
load to a 30A circuit?


Like I have said, I don't know for sure, but I have it in my head that
if you can limit the load to 15A or 20A then you should.



I would also assume that you would take the the only two choices you
would have. Either the equipment would be 110 or 220. Why would they
sell something that was not the common voltage for the home?

Residential electrical supply in the US and Canada hasn't been 110/220 for
many years -- it's 120/240 and has been for a long, long time. Doesn't stop
people from referring to it as 110 and 220, obviously, but that's not what it
is.

My point was this: the OP referred to installation instructions that said
(according to his post) to connect the equipment to a 220V circuit. Maybe that
was just a mistake on the part of the OP and the instructions really said
240V, or maybe they really said 220V like he said -- and if *that* is the
case, that the manufacturer really said 220 and not 240, it's quite possible
that the rated output of the heaters is based on their output at 220, and not
at the 240 that the OP certainly has in his house. And the distinction is
important because if these heaters were rated at 240V, then they can both go
on the same 20A circuit -- but if they were rated at 220V they cannot.

Taking 240V instead of 220V the current would be less and not more.
This would be 14.6A

Wrong.

Take the case of a resistance heater that emits 2000 watts at 220V. It draws
2000 watts / 220 volts = 9.09 amps. Now calculate the resistance: 220 volts /
9.09 amps = 24.2 ohms.

Note that the resistance is a physical property of the heating element, that
does not change no matter what voltage is applied to it.

Now push 240V across that same 24.2 ohm resistance.

240 volts / 24.2 ohms = 9.92 amps.

A similar calculation applies to the 1500 watt heater.


I do understand that if you use somethign designed for 220V and it is
infact 240V the current would be more

Isn't that exactly the opposite of what you said in the previous paragraph?

but can't see that being the
case something designed for a home.

Maybe you're right -- but assuming that, without proof, could be dangerous.
Which is why I cautioned the OP to check the rating plate to see whether the
heaters were rated at 220V or 240V.

I wish the OP woud chime in and give any more information he could give
on the heaters, like maybe the Full Load Amps.

Simply knowing what voltage they're rated at is sufficient.


My assumption for using 240V was that the OP had made the same mistake
we all do in referring to 110-220 and 120-240 interchangeably. If this
was the case, then the load would be 14.6A. Maybe I didn't say that
too clearly, but that would be my observation. I am sure he got the
wattage right, and I would think that he couldn't buy a heater for the
home if it was truly rated for 220V.

In article .com, "Terry" wrote:
On Dec 10, 9:00 pm, (Doug Miller) wrote:
In article . com, "Terry"
wrote:

I admit I don't know, but I would think instead of going to #10 and a
30A circuit you would be required to run 2 separate 20A circuits if the
total load exceeded 16A.

Why? Is there some reason you think it would not be acceptable to attach a
16A
load to a 30A circuit?

Like I have said, I don't know for sure, but I have it in my head that
if you can limit the load to 15A or 20A then you should.

You seem to be confusing "load" with "capacity". In any event, there is *no*
reason why you could not connect a 16A load to a 30A circuit.
[snip]

My assumption for using 240V was that the OP had made the same mistake
we all do in referring to 110-220 and 120-240 interchangeably. If this
was the case, then the load would be 14.6A. Maybe I didn't say that
too clearly, but that would be my observation. I am sure he got the
wattage right, and I would think that he couldn't buy a heater for the
home if it was truly rated for 220V.

I would think that, too -- but when talking about electricity, assumptions can
be deadly dangerous if they prove to be incorrect. The only reason I raised
the issue is that the mention of installing the heater on a "220V circuit"
raises the possibility that the devices may have been rated at 220V instead of
240V, and hence the possibility that they may draw more current than
anticipated when operated at the higher voltage.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

On 10 Dec 2006 17:14:53 -0800, "volts500" wrote:


Doug Miller wrote:
In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...

Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied. Same for
the 1500 watt heater. The resistance stays the same. Only the amps
and volts are variables. The higher the volts, the lower the amps.

What actually causes this to happen? The current through a constant
resistance will increase as voltage increases.

Indago's calc was correct, as he figured it on the (worst case) lower
voltage. One 20 amp circuit is sufficient for both baseboard heaters.
--
15 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"How could you ask be to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

Doug Miller wrote:
In article .com, "volts500" wrote:

Doug Miller wrote:
In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring
a
30A circuit because...

Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied.

That is *not* correct.

The *resistance* stays the same. Increase the voltage, and you increase the
current. Increase the current and voltage, and you increase the power even
more.

Suppose you have a 10ohm resistance heating element. Operate it at 220V.
V = IR
I = V / R = 220V / 10 ohm = 22 amps.
E = VI = 220V * 22A = 4840 watts.

Now operate the same element at 240V:
I = V / R = 240V / 10 ohm = 24 amps
E = VI = 240V * 24A = 5760 watts.

Same for
the 1500 watt heater. The resistance stays the same.

Right. The resistance stays the same. But the power output changes with
voltage.

Only the amps
and volts are variables. The higher the volts, the lower the amps.

False. The higher the volts, the *higher* the amps.

V = IR

Increase V while holding R constant, and I goes *down*??? Hardly.

Indago's calc was correct, as he figured it on the (worst case) lower
voltage.

Wrong. The worst case would be figuring it at the higher voltage.

One 20 amp circuit is sufficient for both baseboard heaters.

Not if they were rated at 220V but operated at 240V.

If they were rated at 240V, yes -- but that's the whole question here, isn't
it? The installation instructions cited by the OP apparently referred to
installing a 220V circuit, which raises the possibility that they heaters were
rated at 220V and not at 240V. Operating them at a 9% higher voltage than that
at which they were rated will cause them to draw 9% more current, and deliver
nineTEEN percent more power, than rated.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.


My mistake, Doug, you are absolutely correct.

volts500 wrote:
Doug Miller wrote:

In article , indago wrote:


If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...


Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied. Same for
the 1500 watt heater. The resistance stays the same. Only the amps
and volts are variables. The higher the volts, the lower the amps.
Indago's calc was correct, as he figured it on the (worst case) lower
voltage. One 20 amp circuit is sufficient for both baseboard heaters.

Wrong! E=IR Voltage = Current * Resistance (or E/R = I) and
P=IE Power = Current * Voltage

Since the resistance effectively stays the same ( not exactly, as the
higher voltage will create a little more heat, raising the resistance
very slightly, we CAN ignore the change for this example ), when the
voltage goes up, the current must also go up for the first equation to
stay in balance. Also, by inserting the first equation into the second,
we get P = E squared / R. So a 2000W heater at 220V has a 0.04132 ohm
resistance. ONLY the resistance can be treated as a constant, as it is
the only physical thing that doesn't (effectively) change. So at 240V,
the POWER becomes 240 * 240 / 0.04132 or approximately 2380W, and the
current will be 9.9A, not 9.1. Since US standard line voltages are
usually closer to 240 than to 220 in real life, using 240 for the
calculations is the safest and most appropriate method. Regardless, as
voltage rises in a circuit, if all physical constructs remain the same,
the current MUST rise, and so will the power.

All of this goes out the window in other countries, power grids, etc.
Take with a grain of salt, as this was based entirely on the laws of
physics, and we all know that science is completely out of favor in the US.

Husky