Electrical Questions

Existing situation: The wiring in the garage dates from the 50s or 60s. There is a breaker box with a two 15A breakers that feeds the plugs and lights. There is one duplex receptacle that is wired for 240V - it's hooked up to both hot wires from the two breakers. The rest of the 120V plugs, etc. come off one of the breakers. The other breaker is not currently used.
The 240V plug was taped over - I previously didn't even know it was live. I would like to get access to a 240V circuit. However, I am concerned about the (existing) apparent mixing of 120 and 240 circuits.
Questions: 1) Is is permissible to run 120V and 240V circuits off the same pair of circuit breakers - if they are ganged together? 2) If breakers are ganged together, and one leg is overloaded, are they both supposed to trip? I performed a little test: a) with the two breakers separate, an overload (120V) visibly trips one breaker - the handle moves to the off position. b) with the two breakers ganged together, the same overload internally trips the same breaker, but the handles don't move, and the other breaker remains live. Is this proper behavior? Turning the breakers off, the on again resets the tripped breaker. 3) Do breakers 'wear out' or degrade over time? One reason I want a 240V circuit is I'm experiencing nuisance tripping when running my table saw under load. Is it possible that the breaker is just tripping prematurely? 4) Should I just leave the the whole existing mess alone, get an upgraded power drop, main panel and add 240V circuits? This option is MUCH more expensive...
I was looking for the NEC online, but it looks like I have to buy a copy, or see if the library has one...
Thanks!
--
JeffB
remove no.spam. to email
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
1) No. The 240 should be on its own breaker with no circuits 110 tapping off of it 2) a)Yes,if you have 2 seperate breakers for a 240 circuit, one will trip if overloaded. b) If I am understanding you correctly, the ganged breaker handle
does not move when tripped. I would say you have a defective breaker. 3) Yes breakers do wear out over time. Federal Pacific breakers are known to be defective. If you have this panel,change it. 4) What is the rating of the subpanel in the garage? If its at least 40A you should be ok. Just re-wire the sub-panel so the 240 plug is on its own breaker and the 110 circuits on there own breakers.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
JeffB wrote: <[...]

240V circuit

load. Is

Is your table saw ok with running at 240V? Not being a motor expert, I would assume that it would need to be wired for a particular voltage.
How about removing the ill-conceived 240V circuit, replacing the unused 15A breaker with a 20, and wiring a new 12-gauge circuit dedicated to the table saw?
You could make the new breaker a pair of half-height 20's so you'd have room for a new circuit in the future.
Chip C
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"3) Do breakers 'wear out' or degrade over time? One reason I want a 240V circuit is I'm experiencing nuisance tripping when running my table saw under load. Is it possible that the breaker is just tripping prematurely?"
Yes, they do wear out over time. Usually it manefests itself in the form of not tripping as fast as it used to or not tripping at all. The previous reference to Federal Pacific was incorrect, their two pole breakers are infamous for not tripping. This person is experiencing nusiance tripping. Big difference!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
There are two relatively inexpensive ways to do this: First is to get half sized circuit breakers, which would allow you one double pole for the saw and two single poles for the other stuff. The second is to replace the sub panel with a four circuit panel and get one double pole full sized breaker for the saw and two full sized breakers for the other stuff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
i dont know about the rest, but, you CANT run 120 and 240 on the same circuit. i had the same setup at my house.

with
the
breakers. The

I
the
circuit
both
breaker
trips the

live. Is

tripped
circuit
load. Is

power
expensive...
or see

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No.
Yes.
That's good.

That's bad.

No. Kinda defeats the purpose of ganging them together, doesn't it, if they don't *both* move when *one* is tripped?

Yes, they do wear out, particularly if subjected to repeated overloads.

You could get a pair of half-height duplex breakers; that would enable you to run two 120V and one 240V circuits in the same physical space as the two 120V breakers you now have.

Yeah, they don't make it available for free. The library is a good bet; lots of bookstores have it; and they're up for sale on eBay all the time too.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for all the quick replies and good information!
I've looked even further, and the main C/B panel has NO ganged breakers - i.e. no 240V circuits. The little box in the garage is apparently taps off of a pair of 40A breakers that feed a subpanel in the house. Everything in there is 120V circuits. I wonder what the dryer plug (it's dead now) was ever connected to? What it looks like to me is that I really don't have a way to properly wire any 240V circuit. And no, there's no space left in the main panel. Will I be able to find breakers that fit into a 50 year old panel?
The saw motors can easily be switched to 240V - which is what I'd really like to do. But my best choice, without spending lots of money, may be to get a couple 20A plugs in the garage. Or are there slow-blow circuit breakers designed to handle motor current startup loads?
--
JeffB
remove no.spam. to email
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
JeffB wrote:

breakers - i.e.

of a pair

there is 120V

connected to?

properly wire any

be able to

really like to

a couple

designed to

Sounds like you've quite the to-do list, electrically. All very do-able.
Doubtless the dryer shared some other pair of breakers that it shouldn't have.
The only way to find out if you can get breakers for your old panel is to phone around to find out, or take a breaker to stores to see if they have one like it.
Each subpanel *really* should be fed off a dedicated pair of linked breakers in the main panel. As should the dryer and range.
I believe circuit breakers *are* considered slow-blow relative to fuses; their internal mechanisms are twofold, with an electromagnetic part that trips immediately on high overload, and a thermal part that trips after a sustained moderate overload. I don't know if they've always been like that.
For sure your most likely immediate fix is to find a 20A breaker for your current panel (and if any breakers are still on the market for it, a single full size 20A will be) and wire a 20A circuit.
Chip C Toronto
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

With fuse panels, you're supposed to use "time delay fuses" (aka "fusetron fuses") for motors.
Circuit breakers respond to overloads like fusetrons do. They've been like that for a very long time. They've had to be like that, because "one mode" (bimetallic strip) are too slow for abrupt high fault current overloads, and would tend to self-destruct, yet, you want CBs to be reusable.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.