using a 240v heater on 120v, wattage and.....

Heat/AC, electrical, lighting, flooring, design, construction, photos...

Moderator: Team

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sat Dec 11, 2010 8:22 am

Hi guys
When i plug an ~1200w heater 240v, into 120 what are the watts?
looks to be ~58 ohms.
Also, if i cheat, and plug into one leg of 2 different outlets, i get 240v, but i would lose the protection of the circuit breaker, correct?
Thanks! I know just enough to be dangerous :lol:
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

Keith Morganstein
Guru
Guru
Posts: 5024
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: using a 240v heater on 120v, wattage and.....

Post by Keith Morganstein » Sat Dec 11, 2010 10:35 am

Matt Gruber wrote:Hi guys
When i plug an ~1200w heater 240v, into 120 what are the watts?
looks to be ~58 ohms.
Also, if i cheat, and plug into one leg of 2 different outlets, i get 240v, but i would lose the protection of the circuit breaker, correct?
Thanks! I know just enough to be dangerous :lol:
volts x volts / resistance = watts

58 ohms at 240 Volts is 993 watts. 58 ohms at 120 is only 248 watts

If the heater has a 240V fan motor, forget about it.

You can use two outlets, but they need to be one from each side of the panel (both legs) or it will only be 120V. Test it with your voltmeter before connecting. You will still have some circuit protection, but only one breaker may trip. Don't forget the ground.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sat Dec 11, 2010 2:49 pm

Keith
Thanks!
ohms law. years ago i called the power company, and nobody there could do the calculation or give the formula! So i'm very grateful for your help. i will write that down.
So i learned to use the house meter. Just tested it on 120v and got 300w net (was 418total, was 118 heater off).
I'm in the ballpark now.
i'm ordering some surplus baseboard heaters 750w 240v for the garage etc. only $7.99 each. on 120v good for warming my shoes! only 188w then. Another rule i just learned is 1/4 the watts for half the voltage.
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

User avatar
MadBill
Guru
Guru
Posts: 12624
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: using a 240v heater on 120v, wattage and.....

Post by MadBill » Sat Dec 11, 2010 7:31 pm

I expect the operating temperature of the heater element will be a factor also. The higher temperature at 240 v. will radiate more infrared, which helps heat the skin, Vs. just the air.. :-k

How about running 240 v to the garage? Of course once it's in you'll be using it for welders, bigger compressors, etc..
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sun Dec 12, 2010 6:43 am

MadBill
i've got a unique detached garage that i designed myself. has 3 16' doors
part of it is a DRIVE THRU to a rear exit.
but, with the workshop it looks like an apartment.
every year the inspector tries to figure out what i'm doing. they think i must have illegal aliens in there i guess. :lol: it has 100a service but only 2 240 outlets. 1 for my 60gal comp. 1 50a for who knows what.
i've had to return previous heaters as i don't like the smell. my new heat pump in the house, has no emergency heat strip, as the smell on the old one was so bad, i had to open the windows, which reduces heating efficiency :lol:
so i'm hoping at 1/4 power i can warm my feet, but,maybe not. Here in Fla it doesn't take much heat to make a big difference. Only 10-20 days a year does the garage get below ~50F.
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

User avatar
MadBill
Guru
Guru
Posts: 12624
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: using a 240v heater on 120v, wattage and.....

Post by MadBill » Sun Dec 12, 2010 8:41 am

There's probably some gizmo that would switch off power to the 240 v. heaters when the compressor fired up and turn them back on when it stopped, to avoid overloading the circuit...
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

Keith Morganstein
Guru
Guru
Posts: 5024
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: using a 240v heater on 120v, wattage and.....

Post by Keith Morganstein » Sun Dec 12, 2010 8:49 am

MadBill wrote:There's probably some gizmo that would switch off power to the 240 v. heaters when the compressor fired up and turn them back on when it stopped...

A simple relay set-up would accomplish that. Simple circuit and a few dollars of parts.When the comp motor kicks on, the relay would open and turn off the heaters. Still, a spare 50A or even the compressor circuit should have PLENTY enough amperage to handle a few 240 V baseboards. You will disappointed in the performance of 120V. No reason to over-think it.

Keith Morganstein
Guru
Guru
Posts: 5024
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: using a 240v heater on 120v, wattage and.....

Post by Keith Morganstein » Sun Dec 12, 2010 9:52 am

Keith Morganstein wrote:
MadBill wrote:There's probably some gizmo that would switch off power to the 240 v. heaters when the compressor fired up and turn them back on when it stopped...

A simple relay set-up would accomplish that. Simple circuit and a few dollars of parts.When the comp motor kicks on, the relay would open and turn off the heaters. Still, a spare 50A or even the compressor circuit should have PLENTY enough amperage to handle a few 240 V baseboards. You will disappointed in the performance of 120V. No reason to over-think it.


BTW, 1200W, 240V heaters only draw 5 amps each.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sun Dec 12, 2010 10:46 am

i think i could cut a plug in half and use that 50a outlet. But 188w on 120 should keep my feet warm.
.
in the 60's my aunt remodeled and gave me a 1953 240v heater that i've been using that works great on 120v (300w).
don't underestimate 300w! in NJ my cat loved to sleep on it, it is flat glass 16x24".
anyway i tried it on the side of my bed, and it is too large and a little hot, so i'm going to try 188. My heating pad is 50w on HIGH, i use medium. u guys r heating a room, i'm heating just me.
.
a guy once rigged a microwave oven, door open, so it could heat him in his shed with the shed around ZERO. he was well done when they found him :lol:
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

Keith Morganstein
Guru
Guru
Posts: 5024
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: using a 240v heater on 120v, wattage and.....

Post by Keith Morganstein » Sun Dec 12, 2010 11:22 am

Matt Gruber wrote: anyway i tried it on the side of my bed, and it is too large and a little hot, so i'm going to try 188. My heating pad is 50w on HIGH, i use medium. u guys r heating a room, i'm heating just me.
I strongly discourage you from fiddling with any heater for use in a house especially when sleeping. The fire department will find you crispy.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sun Dec 12, 2010 12:46 pm

Keith Morganstein wrote:
Matt Gruber wrote: anyway i tried it on the side of my bed, and it is too large and a little hot, so i'm going to try 188. My heating pad is 50w on HIGH, i use medium. u guys r heating a room, i'm heating just me.
I strongly discourage you from fiddling with any heater for use in a house especially when sleeping. The fire department will find you crispy.
So u think a residential baseboard heater is unsafe? :lol:
I thought this was a wise upgrade(from a heating pad).
Not that i disagree, i shut off the central heating at nite, as they are notorious for setting the house on fire as u sleep. Like, the blower motor windings fail, smokes and sometimes sets the house on fire. Once i had the start capacitor fail, but during the day, i noticed it right away. But i don't run it at night, because guys that do, don't always get to tell the tale! I hope no one here runs a forced air heater when they are asleep!
I had a smoke detector installed in the attic, but the high temps gave false alarms, so there in NO detector in my attic anymore!
To me, a 750w baseboard, with no moving parts, at 188w is about as safe as i can think of. But, if u have a better upgrade, do tell!
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

Keith Morganstein
Guru
Guru
Posts: 5024
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: using a 240v heater on 120v, wattage and.....

Post by Keith Morganstein » Sun Dec 12, 2010 2:24 pm

Matt Gruber wrote:
Keith Morganstein wrote:
Matt Gruber wrote: anyway i tried it on the side of my bed, and it is too large and a little hot, so i'm going to try 188. My heating pad is 50w on HIGH, i use medium. u guys r heating a room, i'm heating just me.
I strongly discourage you from fiddling with any heater for use in a house especially when sleeping. The fire department will find you crispy.
So u think a residential baseboard heater is unsafe? :lol:
I thought this was a wise upgrade(from a heating pad).
Not that i disagree, i shut off the central heating at nite, as they are notorious for setting the house on fire as u sleep. Like, the blower motor windings fail, smokes and sometimes sets the house on fire. Once i had the start capacitor fail, but during the day, i noticed it right away. But i don't run it at night, because guys that do, don't always get to tell the tale! I hope no one here runs a forced air heater when they are asleep!
I had a smoke detector installed in the attic, but the high temps gave false alarms, so there in NO detector in my attic anymore!
To me, a 750w baseboard, with no moving parts, at 188w is about as safe as i can think of. But, if u have a better upgrade, do tell!
I feel properly installed electric baseboards, wired according to electrical code are quite safe.

What really alarms me is any type of haphazard or kludged wiring or installation, operating outside of design parameters etc... inside of the house while sleeping. That is just plain foolish and dangerous.

Electric baseboards are cheap enough brand new. Get one at the voltage you wish to run with proper thermostat and install it according to code.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sun Dec 12, 2010 2:42 pm

Found a new 240v plug in my junk drawer, so i'll be using that in the garage. 750w OK there.
.
Ordering a 5amp breaker with rocker switch, trips at 6.75a for my bedroom, will go into a code box. BR does have a smoke detector.
.
Nobody makes a 40" ~200w baseboard heater! The heaters i'm buying are NEW surplus. They have thermal protection.
NO thermostat means 1 less thing to fail and start smoking or worse.
.
Nothing wrong with running a resistance heater on 120 instead of 240. After doing this for 40 years, i'm not going to worry about it. If anyone else is worried, they should call an electrician!
.
Thanks for the replies! Make sure u all have a smoke det. in your BEDROOM that WORKS!
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Wed Dec 22, 2010 3:50 pm

Heaters came today! New in MARKEL factory cartons. Made in Johnson City, Tennessee. Looks to be worth many times the surplus price of 7.99.
Very nice. I'm testing 1 right now. 73 ohms about 200w on 120v. Have it at the side of the bed. Back of it is cool to the touch. It deflects heat only out the front, up the side of the bed, not underneath the bed. Guard is ~95F, while heat pours up thru the slot. Feels nice! Can't burn shoes or socks, but maybe a place to warm them.
.
But it is 74F today in FLa! So will have to wait for some cold.
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

Matt Gruber
Guru
Guru
Posts: 1496
Joined: Fri Mar 19, 2010 7:32 am
Location: near Daytona Beach FL

Re: using a 240v heater on 120v, wattage and.....

Post by Matt Gruber » Sat Jan 01, 2011 8:35 am

i wish i had these 20 yrs ago!
basebed heaters.
1 heater good down to ~45F (i shut the central heat OFF at night).
2 good down to ~35F.
3 heaters tested to 29F, maintains 69-70F using only 600w That(at 12 cents per kwh) is just 7.2 cents per hour for 3 heaters TOTAL! How does that compare with your heating costs?
gave #3 to m&d as they have a cold spot in their LR. They use it every cool day on 120v.
Ran cable in garage for 240v switched outlet . Heater rod does not get red even on 240v. Decent warmth at workbench in 40F garage. 750-800w at 240v
Very good for those trained in basic wiring, but not for those that don't have experience.
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

Post Reply