I'm running a 220 VAC line in my home to power a high power RF amplifier in my ham shack. I'm pulling a 12/3 with ground so I can branch off both 120VAC legs and create 2 additional outlets in the ham shack. I'm beginning to wonder though if this is allowed by NEC. I have a double pole 220 breaker and I realize that if one leg is shorted, it will pull the other out as well. This is acceptable. What say you guys?

 

I doubt if it'll pass inspection running other 120vac recpts off the 220Vac recept.
Sorry... But I'll be the first to admit I'm NEC ignorant.
When I remodeled an old home, It seemed what was logical was not permitted by NEC and what was permitted by NEC was forbidden by local city codes.. I just let the electrician deal with the building code ****'s...


Now for my real question..., What kind of big amp are you running? three Eimac 8877's with Peter Dahl transformers?

K.

 

With out opening an NEC I can tell you that it isnt meeting code. You will probably never have a problem with it either. The NEC is ment as a minimal and that is why the local regs were harder to meet. My biggest complaint about the NEC is that it is written by fire fighters. Heck I know how to use a garden hose but I dont try to put out burning bldgs.

 

Im away on vacation right now so I'll have to look up the article and section of the NEC that addresses this but from what I recall this is specifically allowed. With the 12/3, if you use a 20a double pole breaker you are ok. In fact there are duplex receptacles made that have both 240v and 120v receptacles present on the same yoke. The only real requirements for this are that the continuity of the grounded (ie neutral) conductor not rely on the device, in other words you have to use pigtails... and that both hot legs of the circuit are simultaneously disconnected.

Like I said I dont have the book with me right now but if I remember it is in article 210 Branch Circuits, specifically check the part about multiwire branch circuits. Its within the first few articles and should mention something about a multiwire branch circuit being allowed to serve both line-to-line (a 240v load) and line-to-neutral loads (a 120v load) if the breaker opens all ungrounded conductors of the multiwire branch circuit simultaneously.

If someone doesnt get it before I do Ill get it here in a day or so.

 

Does it meet code?
Depends on your local laws.
Locally, just about anything is legal for residents to do to homes they own. Past that, if you sell, you have to remove anything that doesn't past NEC 2002.

 

Dave you are right. For some reason I was thinking of a 12/3 extension cord. The section is 210.4 in the code book. 210.5 goes into the wires need to be clearly marked in color or tag at each end and also labled at each fixture. You will also need a breaker that disconnects both phases at once as stated.
I think a beter approach would be to pull in a larger gauge wire into a cheap panel box. From here you can enter it into a main breaker and then make as many branches as you like on there own circuit. This is how I did a famly members shed. Breaker panel was around $25 and breakers were only a few dollers each. Room for expansion is the only way to go.
I dont know what the amp draw is of your ham equipment is but you may want to run a larger wire if you are not going to install another panel box.

 

OK guys, thanks for the replies.

'Rattler, I'm going to be running a pair of 4CX800's. 100% key down duty cycle. It's not a Dahl transformer, so it's pretty heavy! Beautiful amp, made in Bulgaria.

 

Who told you that? The NEC is written by different panels that have jurisdiction over certain sections of the code. The panels are made up of industry people like NEMA and the IBEW. It's published by the NFPA but fireman don't write it.

 

No, but they have to work on the situations that happen when the code isn't followed! Just a retired electrical guy who was also a fireman.

 

COOL! Bulgaria huh? Made the OLD way...lots of iron and lots of copper... What brand is it? something sold for the Western market or a direct Bulgarian import?
Are they regular 4CX800's or something more akin to those Russian power toobs that kick butt?
That'll be just the perfect size for running on that 20amp 220vac ckt...


K.

 

The amp is an ACOM 2000A, and comes with Svetlana GU74b tubes. It's FCC type accepted. Beautifully made with auto-tune and QSK. It'll do 1500+ watts easily. The company is owned by Krassy, K1LZ who is also a fellow club member of the contest club I belong to.

 

Yep! thats them! GU74b's Russians are up on their high power tubes!
Even their eqiv of our venerable 4CX1500's,8877's, etc have quite a bit higher ratings.
I assume since they didn't have US Gov't Mil-spec's to maintain, they were free to improve on them. I assume Eimac could have too, but then they wouldn't meet the replacement parts spec's for the US DoD. After all, hams were a SMALL piece of their market compared to Uncle Sugar.
Sounds like a winner of an amp!

K.

 

Why not just run both a 220v line and a 120v line. Just as easy to run both at the same time instead of running the 220 and then the 120. That way their will be no question that you will be in code.