230v or 240v outlet?

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  #1  
Old 12-06-12, 04:29 PM
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230v or 240v outlet?

There's a heavy-duty outlet in my garage that I'd like to use for a construction heater. The cover plate says 230 volts 15 amps BUT my main panel indicates the service is higher. There are two circuit breakers for that line. Each breaker is rated for 20 amps and the electrician who installed the panel wrote on the index "240v outlet in garage."

Can I prudently assume the supply is 240v and up to 40 amps? Construction heaters seem to require 240v and 20 amps.

Is there anything special about replacing the current outlet with one rated for 240 and 20 or 40 amps? (I've replaced lots of 110 outlets)

Thanks
 
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  #2  
Old 12-06-12, 05:15 PM
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Voltages are nominal; 220, 230 and 240 are all the same although the actual voltage is more likely closer to 240 (or even a bit higher) that it is to either 220 or 230. Likewise, what you refer to as 110 volts is in reality much closer to 120 volts.

The double pole circuit breaker IS 20 amperes at 240 volts. You do NOT add the individual breakers together.
 
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Old 12-06-12, 05:22 PM
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There is no 230V residential service here or in Canada nowadays, but there used to be. The old designation crops up from time to time. You have a 240V circuit.

Each breaker is rated for 20 amps and the electrician who installed the panel wrote on the index "240v outlet in garage." Can I prudently assume the supply is 240v and up to 40 amps? Construction heaters seem to require 240v and 20 amps.
Assuming that you are referring to each half of a two-pole 240V breaker, that is a 20A breaker. The protection is not additive.

If the conductors for this circuit are 12AWG, as they should be, and if the receptacle that's there now is only rated for up to 15A and that's not enough to match the heater's requirements, you can prudently and safely replace it with one that's rated for 20A without having to replace the breaker or the wiring.

What does the heater require?
 
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Old 12-06-12, 05:26 PM
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I've replaced lots of 110 outlets
Doubtful. The general purpose receptacles in your home are 120 volts.

There are two circuit breakers for that line. Each breaker is rated for 20 amps and the electrician who installed the panel wrote on the index "240v outlet in garage."
Then you have a 240 volt 20 amp receptacle. The twenties aren't added together they are simply the level of protection on each side of the 240 volts.

Can I prudently assume the supply is 240v and up to 40 amps?
No, its 20 amps as explained in the preceding paragraph.

Construction heaters seem to require 240v and 20 amps.
If their full load amps is 20 you would need a 30 amp breaker.

Is there anything special about replacing the current outlet with one rated for 240 and 20 or 40 amps?
For anything more then 20 amps you would need to replace the type of receptacle, the wire to it, and the breaker so better to just run new. Of course if it really was intended as a 15 amp receptacle then the wiring may not be adequate even for 20 amps.

echo, echo, Bill
 
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Old 12-06-12, 05:35 PM
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echo, echo, bill
.
 
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Old 12-06-12, 06:08 PM
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When I was a kid, I remember all electrical appliances said "110V". Then after that, for a while I would see 115V. Now it's 120V. Have the utilities actually been increasing the voltage or have we always been getting 120V?
 
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Old 12-06-12, 06:34 PM
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I just got done wiring a 460 volt motor on according to the nameplate. It is wired to 480v.
 
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Old 12-06-12, 07:14 PM
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Many things made today are still listed as 110 volts.

Back in the 1960s the voltage at our house was between 117 and 121 depending on just what time of day the measurement was made. There was a 50 kVA transformer hanging on the pole in front of our house.

In my current home the voltage is 121.15 volts. There is a 50 kVA pad-mount in my front yard and I think it serves three or perhaps four other houses.

The "480 volt" service at the historical museum where I volunteer is about 504 volts.
 
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Old 12-06-12, 08:09 PM
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When I was a kid, I remember all electrical appliances said "110V". Then after that, for a while I would see 115V. Now it's 120V. Have the utilities actually been increasing the voltage or have we always been getting 120V?
The utilities have been increasing and stabilizing the voltage to meet their original goal of 120/240V.
 
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Old 12-08-12, 03:09 PM
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Thanks for the replies. Specs for the heater I'm looking at are:
-- 240 volts
-- 20 amps
-- 4800 watts

It would be the only device on that circuit and would probably not be used a lot.
 
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Old 12-08-12, 03:27 PM
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That heater requires a minimum of a 25 ampere circuit. Since 25 ampere circuit breakers are less common for residential panels it means that you probably need a 30 ampere circuit breaker AND in either case (25 or 30 ampere CB) #10 wiring to a 30 ampere, 240 volt (250 volt) receptacle.
 
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Old 12-08-12, 03:45 PM
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That would be a 6-30 NEMA receptacle (6-30R) and a 6-30 NEMA plug (6-30P)
 
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Old 12-08-12, 05:47 PM
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Thanks all. Sounds like it's too much trouble unless an electrician happens to be working on my road and has a few minutes to spare. I would not try to replace a circuit breaker myself. Thanks again.
 
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Old 12-08-12, 05:55 PM
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It would be great if all you had to do was increase the breaker size......however you would need that electrician for several hours to increase the size of that wire.
 
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