Using a 30amp double pole breaker with 10-3 I understand if 30 amps is exceeded on either hot wire both will trip. But how about say 25 amps on both hots, a total of 50amps @120v. I guess I'm trying to figure out if by splitting 240v into two 120v circuts whether both circuts combined can't go over 30amps, or if you have two circuts of 120v with 30amps each giving a total of 60amps @ 120v. I hope I'm making sense!
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30amp @240v = 60amp @120v ?
- Thread starter bluenorth
- Start date
G
Guest
yes that's correct bluenorth. 30 amps at 240 is good for 60, 120 volt amps. You've got it exactly correct.
Do bear in mind that 120 volt receptacles are sold in the 15 amp, and 20 amp versions: so you will wind up, breaking it down to 4, 15 amp receptacles.
Note: the ''Do bear in mind.." paragraph originally read, ''Do bear in mind that 120 volt receptacles are sold in the 15 amp, and 20 amp versions: so you will wind up, breaking it down to 4, 15 amp receptacles, or 3, 20 amp receptacles..."
but doing it that way, would involve something uncommon: which would be to split that third, 20 amp receptacle into two, discretely fed, plugs, with the upper one fed by one line, the lower plug fed by the other, and that receptacle being labled ''10 amps max per plug'' - because if you didn't split the load that way, you'd flip one of the breakers.
This does get done but it's uncommon and the answer as given wasn't crystal clear so I amended it to reflect the more common, simpler layout for clarity.
4/19/08
Do bear in mind that 120 volt receptacles are sold in the 15 amp, and 20 amp versions: so you will wind up, breaking it down to 4, 15 amp receptacles.
Note: the ''Do bear in mind.." paragraph originally read, ''Do bear in mind that 120 volt receptacles are sold in the 15 amp, and 20 amp versions: so you will wind up, breaking it down to 4, 15 amp receptacles, or 3, 20 amp receptacles..."
but doing it that way, would involve something uncommon: which would be to split that third, 20 amp receptacle into two, discretely fed, plugs, with the upper one fed by one line, the lower plug fed by the other, and that receptacle being labled ''10 amps max per plug'' - because if you didn't split the load that way, you'd flip one of the breakers.
This does get done but it's uncommon and the answer as given wasn't crystal clear so I amended it to reflect the more common, simpler layout for clarity.
4/19/08
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Y
yamaha_1fan
-KiNgMaKeR- said:
do you mean 30 amps at 240, not 20?
G
Guest
yamaha_1fan said:
ya typo
G
Godless
So this means that I can replace one 30amp 240v breaker with four 15amp 120v breakers? I have a 200amp main panel with 60Amps coming into a garage box with two 15amp 120v breakers and one 30amp 240v breaker. I thought that I could only replace the 30amp 240v breaker with two 15amp 120v - four would solve a lot of problems 
(sorry to thread hijack, but I think we are in the same boat trying to paddle to the same spot...)
(sorry to thread hijack, but I think we are in the same boat trying to paddle to the same spot...)
G
Guest
yepppers; what bluenorth said, if splitting each circuit's worth of current, is something you're wanting.
Y
yamaha_1fan
what size breaker is that sub-panel (garage-box) feeding off? You may want to check the wire size feeding that sub-panel as well. That is ultimately what is going to decide what you can do there in the sub panel. Also the physical amount of slots in the sub-panel.
There may be more slots available, they may just be covered with metal tabs.
Remember that sub panel is limited by the size of wire going to it from the main panel. Under the limit you can create any combo you want.
There may be more slots available, they may just be covered with metal tabs.
Remember that sub panel is limited by the size of wire going to it from the main panel. Under the limit you can create any combo you want.
nothing to see here... 
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no way to edit the guy quoting me below haha
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dontstepongrass said:
....because changing the voltage doesn't change the amount of power drawn, only how it is drawn.
touche. damn i was stoned before. misconstrued the info. just cause P=IV meaning half the current would be drawn but then multiplied by twice the voltage = the same # of watts. damn.
yamaha_1fan said:
listing to man that know's....... watch you input wire thats the key
also make sure it is in fact 220 30amp i was looking at one last week and all it was was 2 x 110v 15amp lines but there ran like 75 feet cutting them down to 10 amps each....
who ever put it in should have just ran orange cords from home depot not romex lmao
G
Guest
Bluenorth's question was crystal clear: with a 10/3 feed, can a 240 be successfully split and used, essentially as is, according to classic Ohm's law voltage/amperage relationships: the answer to that is ''Yes.''
Godless asked for a second verification of what we'd said: that a 30 amp 240 can be split to give 60 amps of 120 volt power.
The answer to that, is "Yes."
This garage is discussed in another thread. In it, Godless says the feed for the garage is 60 amps; then goes on to say the internal rating for the garage is 70 amps.
Here, the assumed same, detached garage, is discussed, referencing 15 amp circuitry.
The other thread is Here
The presence of a 200 amp main panel is a clue to a well planned installation with proper load dispersement. The separated lighting, power, and heater circuits imply a properly planned installation; this could also be an indicator of good contracting which thoughtfully included, for future usage, a spare neutral for the 240 volt circuit, in case it were ever split; but it's not a guarantee.
The discussion of a 60 amp garage feed, with a 30 amp 240, and two, 15 amp 120s, downline is in perspective with proper design, and the previous mention of two 20 amp circuits is assumed to have been in error previously, corrected here.
The first thread made mention of an existing neutral for the 240 volt circuit. That neutral, may or may not be, in fact, in place. Godless needs to get a look at the feeds to that 240 volt circuit.
If an un-used neutral is in place alongside the two hot lines for that 240, then he's sitting pretty. If not, one must be added.
That neutral is to be kept isolated from the body of the garage breaker boxes; and, from the bonding bus to which the grounds are attached.
Wire size is the lesser of concerns for this potential conversion. The presence of the proper neutral is the primary real, crucial consideration. The system shows every hallmark of having been properly designed and installed. Any functionality already in place remains unchanged with the conversion of the 240 to 120. Current, isolation, bonding, all remain identical.
The only pertinent question to the viability of the conversion resides in the presence of a neutral; which if found, will be found to be of the proper gauge.
Godless asked for a second verification of what we'd said: that a 30 amp 240 can be split to give 60 amps of 120 volt power.
The answer to that, is "Yes."
This garage is discussed in another thread. In it, Godless says the feed for the garage is 60 amps; then goes on to say the internal rating for the garage is 70 amps.
Here, the assumed same, detached garage, is discussed, referencing 15 amp circuitry.
The other thread is Here
The presence of a 200 amp main panel is a clue to a well planned installation with proper load dispersement. The separated lighting, power, and heater circuits imply a properly planned installation; this could also be an indicator of good contracting which thoughtfully included, for future usage, a spare neutral for the 240 volt circuit, in case it were ever split; but it's not a guarantee.
The discussion of a 60 amp garage feed, with a 30 amp 240, and two, 15 amp 120s, downline is in perspective with proper design, and the previous mention of two 20 amp circuits is assumed to have been in error previously, corrected here.
The first thread made mention of an existing neutral for the 240 volt circuit. That neutral, may or may not be, in fact, in place. Godless needs to get a look at the feeds to that 240 volt circuit.
If an un-used neutral is in place alongside the two hot lines for that 240, then he's sitting pretty. If not, one must be added.
That neutral is to be kept isolated from the body of the garage breaker boxes; and, from the bonding bus to which the grounds are attached.
Wire size is the lesser of concerns for this potential conversion. The presence of the proper neutral is the primary real, crucial consideration. The system shows every hallmark of having been properly designed and installed. Any functionality already in place remains unchanged with the conversion of the 240 to 120. Current, isolation, bonding, all remain identical.
The only pertinent question to the viability of the conversion resides in the presence of a neutral; which if found, will be found to be of the proper gauge.
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G
Guest
Stop Guessing-Start Reading
Google: [http:/www.en.allexperts.com/q/Electrical-Wiring-Home-1734/15A-vs-20A-follow.htm] for factual information.
Also: [electrical-online.com]
Hope this helps in CLARIFYING the Q.
TyStik
Google: [http:/www.en.allexperts.com/q/Electrical-Wiring-Home-1734/15A-vs-20A-follow.htm] for factual information.
Also: [electrical-online.com]
Hope this helps in CLARIFYING the Q.
TyStik
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G
Guest
Well Ladies, keep shootin' your mouths off--just get'r done!!!!!!!!!!!!!!!!!!!!!!!!!
G
Godless
Ty-Stik said:
I have been doing my homework on this and I think I am getting close here, but I do have a couple questions that I couldn't answer by reading my "complete guide to home wiring" or the links you posted.
Some addl detail and a clarification:
I misspoke when I stated that the lights/outlets circuits were 15a - they are indeed 20a as I originally stated. There wasn't a spare neutral wire going to the 240v outlet. If I take out the 240v30a breaker, I have 3 breaker slots open on the garage panel. I could add 3 120v20a breakers (could use slimlines to add 4 15amp breakers), or I could add a single 120v60a breaker and feed that to a new subpanel.
The existing subpanel is inside a finished wall. The 240v outlet is attached by conduit and is 1.5ft right below the panel. I need to get my new circuits into a new wall I'm building 15feet away from the panel and am trying to figure out the best way to do it. I could through the wall, up to the (currently inaccessible) attic and down into the new wall, but the walls are finished, I suck at drywall repairs and I hate crawling around in a tight, insulation filled attic. Instead, i am thinking of using some kind of rigid plastic raceway. I read through the NEC (National Electric Code) book and it seems like this is acceptable as long as I don't exceed some crazy formula about how much heat can be generated by the wires. Without trying to figure out the formula, I am guessing that 60amps should be fine considering that the 60amp service from the main to the garage is in pvc conduit. Am I being a dumbass? Should I try to figure out the crazy math? Does anyone know offhand? Should I put it in flexi metal conduit instead?
Assuming that there are no issues with the raceway, are there any considerations in the decision between running 4 14/3 cables (interchangeable with 3 12/3) or one 6/3 cable to a new subpanel? I am guessing that it might cost more to run 3 or 4 circuits, but I doubt the cost will be an issue. Any other issues? Any recommendations on the raceway itself? I'm going out to Lowes today to check out my options.
The other question I have is how can I attach the raceway to the box? I am thinking that the easiest thing would be to feed it through the existing conduit down to the 240v outlet, replace the outlet with a box and run the raceway from there. Any other suggestions?
Again, much thanks for all the assistance.
G
Godless
Correction: I mentioned cables specifically, but since I am using conduit/raceway, I should be using separate THWN wires. (plus, the cables I mentioned were wrong - they should have been x/2 instead of x/3 - I forgot that 2-3 is the number of insulated wires) I also think that I will just use metal conduit. Still could use some advice on how to get out of my in-the-wall subpanel.
bluenorth said:
With a 30a double pole breaker the total draw on the circuit cannot exceed 30a. If each hot was carrying 25a the breaker would trip cause you have 50a on a 30a circuit. Remove the 30a 240v breaker and you can add 2 15a 120v. You cannot exceed the main breakers amp rating or it will trip. 60a main means you have 60a available. Need more and you need to upgrade.
I'm not an electrician but, i think you're receiving alot of bogus info here. I will respond to some other posts i think are incorrect based on my knowledge. You should verify whats proper before going further.
-KiNgMaKeR- said:
Statement 1: answer is "no" Each 15a 120v circuit would require the appropriately sized hot,neutral & ground wires. You cannot split the 240v wiring to make 2 15a circuits.
Statement 2: answer is "no" A 30a 240v circuit = 2 15a 120v circuits
The statement referencing the 200a panel. KiNgMaKeR said,"this could also be an indicator of good contracting which thoughtfully included, for future usage, a spare neutral for the 240 volt circuit, in case it were ever split;"
A "spare" neutral? refer to response to statement 1. A 30a 240v circuit properly wired uses the white neutral as the second "hot" no neutral to the buss just a ground. I say disregard any referance to the 240v wiring and the "spare" neutral. It will not be reused in wiring 15a 120v circuits. 30a 240v=#10 15a 120v=#14 guage wire.
KiNgMaKeR said,"The only pertinent question to the viability of the conversion resides in the presence of a neutral; which if found, will be found to be of the proper gauge."
Again, should not exist is not relevant, new cable with #14 wire will contain needed hot, neutral and ground for your new 15a circuit.
If unsure ask an electrician & be safe.
