Electric question

[Wacki]

The previous owner of my house ran an office out of the basement and had used a tandem breaker to provide two-20amp/120v outlets for laser printers. These were run using a 3-wire plus ground wire to a 4 outlet box, with the two outlets on each side belonging to it's own 20a circuit. I know the two hots in the outlet are from the different hot buses (sorry I don't know the terminology) via multimeter, I read 250v across the two hots in the panel.

My question is, can I use these two outlets and a "special" wiring configuration in a control box to apply 240v to an element that's rated at 4500w (18.75a) or 3500w (14.58a)?

I figure the 4500w element may be too big, but is there any reason I could not do this for the 3500w element?

I actually already have a 30a 240 outlet for brewing, but I was wondering if this could supplement power for a rims/hlt heater so I could multitask....

Thanks in advance for any insight!!

 

[satph]

You have a Multiwire Branch Circuit.

A tandem breaker provides two circuits with one phase of power. Since you're getting both phases, are you sure you don't have a double pole breaker? (see here.)

Also, what's the gauge of the wire?






http://www.ecmag.com/section/codes-standards/article-210-branch-circuits-1

 

[AnOldUR]

If the breaker is 20 amp, it's probably 12ga wire and I really doubt it's a double pole breaker if it's feeding two separate 120 lines. What you could do is install a double pole breaker in your panel and use the existing wire to a single 240 volt receptacle. The trouble is that you would need another circuit for any 120 volt devices in the area.

 

[Wacki]

Sorry, I should have been more specific, the breaker in place is a dual tandem breaker (again, sorry for terminology). So the "laser printer" hot wires come from the independent top and bottom of the dual-tandem breaker. The middle is a double throw that goes elsewhere in the house.


Maybe the pic helps? I'm referring to the bottom two breakers...and the two laser printer lines I'm referring to are switched off.

Thanks for the responses!!

 

[Wacki]

Also, I'm 99% sure it's 12g wire, I'm just not at home to verify.

 

[AnOldUR]

I'm not an electrician, but something looks wrong there. Two tandem breakers with the center poles being joined to make a 240 volt circuit is ok, but the outer two on each breaker would go to separate 120V lines. I'm not sure what the red wire going to the bottom is feeding. I can't think of a reason that wouldn't be a black wire feeding a 120 volt circuit. Which of those 4 bottom wires (two black, two red) are going to your location?

edit:
Maybe the top black and the bottom red of those four are the circuit you're referring to, and the center black and red go to a 240 volt circuit leading somewhere else?

 

[Wacki]

The top and bottom are encased in a 12/3 plus ground wire that goes to a 4 outlet box, with the two outlets on the right/left each getting one of the hots. This gives me two dedicated outlets on each 20a line.

I didn't wire that part, but nothing seems inherently wrong, you can have multiple feeds going to the same box, afaik.

 

[Wacki]

AnOldUR,
I believe your edited comment is correct, sorry for my poor explanation!!

 

[AnOldUR]

OK. Just read the text at the bottom of your picture. It's what I said in my edit above. Nothing wrong with that.

The bad part is, from what I know, it will be difficult to get another 240V circuit from that if there isn't any other potential in your panel.

 

[AnOldUR]

Toward the top of your picture there are two 20 amp breakers. With a tandem set-up there, like the one at the bottom, you could still feed the existing circuits with the outer connections and use the center 240V for your brewery by moving the existing wires up to it.

edit:
Or you could use a double pole 240V breaker up there for your brewery and move those wires down to where the others are now.

 

[Wacki]

The problem I see with using those two 20a lines is that they are not on a common breaker/switch, otherwise I don't see any issues with creating a two plug special control panel to put those two hots to a 240v outlet to have more capacity for another 240v element.

 

[Wacki]

Toward the top of your picture there are two 20 amp breakers. With a tandem set-up there, like the one at the bottom, you could still feed the existing circuits with the outer connections and use the center 240V for your brewerey by moving the existing wires up to it.

You are correct, but those slots won't allow tandem breakers.

Also, I already have a 30a 240v outlet for the brewery, I just thought I could use these dedicated lines to have an extra 20a 240v outlet for use with a lower watt element for rims/hlt.

 

[ForestGroveBrewer]

You can swap out that breaker with a quad breaker. In essence it has 2 pole joined together in the center and another two pole joined together via bracket for the outside handles. Similar to this picture. You would still be limited to 20 amp due to wire size which is larger enough for the 3500W element.

Note: these breakers are designed to add circuits to panel when you have no space. However, the service conductors may not be large enough to handle the added load. they are sized with the calculated load of the building at the time of construction.

 

[satph]

I don't believe Square-D makes a two 2 pole quad breaker like Forest Grove posted. And you need the breakers to disconnect both breakers simultaneously when you're using them in a single circuit.

I don't know if the current set up is code-compliant. But, if it is, and you have a 20 amp tandem on the other side, could you swap it with the 15amp tandem in the picture? Then you'd have a second set of 20amp breakers next to each other that could be tied together like the pair that's already tied together to convert your laser printer circuits to a 240v circuit. Although I think this would fit, I do not know if it's legal.

 

[Wacki]

Yea, my thought is just that the two lines are there, and (assuming it's all ok the way it's wired) just make a Frankenstein box that has two 120v plugs that go into my existing outlets, and wire those through controller/ssr to a 240v outlet that I could plug a rims or hlt element into so I could operate independent of the boil element.

This way, it's all good the way it's currently wired when everything is unplugged, and when brewing I would just know that both of those outlets are on different breaker switches., if neede

 

[AnOldUR]

You are correct, but those slots won't allow tandem breakers.

Why not? From my experience, any single pole breaker can be replaced by a tandem breaker in the same slot. I've never seen two tandems side by side with a bar joining the inner breakers so that they can be used for 240V, but it looks functional and safe.

The problem I see with using those two 20a lines is that they are not on a common breaker/switch.

Those upper two could be taken out and replaced with one double pole 240 volt breaker that has a common breaker bar. But it would mean purchasing the new 240V breaker and tossing the two old single poles.

 

[Wacki]

Why not? From my experience, any single pole breaker can be replaced by a tandem breaker in the same slot. I've never seen two tandems side by side with a bar joining the inner breakers so that they can be used for 240V, but it looks functional and safe.

Those upper two could be taken out and replaced with one double pole 240 volt breaker that has a common breaker bar. But it would mean purchasing the new 240V breaker and tossing the two old single poles.

Yea, actually tandem breakers can only be used in certain slots, the slit on the back of them is shallower than the regular breakers. I know they won't fit, even with a lot of force , from personal experience.

I really don't want to change or add anything, I thought I might just be able to use those outlets rigged up to get 20a 240v, since I know (and confirmed with multimeter) that I have 240v across those two hots.

 

[AnOldUR]

Yea, my thought is just that the two lines are there, and (assuming it's all ok the way it's wired) just make a Frankenstein box that has two 120v plugs that go into my existing outlets, and wire those through controller/ssr to a 240v outlet that I could plug a rims or hlt element into so I could operate independent of the boil element.

This would work, but it's not a good idea. One side could trip and not the other. Now you have one side hot. If the other side tripped because of some kind of fault, there may be a path for that hot 120V line to follow. Like the ground from the pot itself.


edit:
By swapping the two single pole breakers with a double and swapping the wires with the lower ones, you'd be able to keep your existing circuits and safely use the Frankenstein box you proposed. The only thing would be that when using it as two single 120V circuits, when one tripped the other would also. Not a safety issue, just a nuisance.

 

[Wacki]

Those upper two could be taken out and replaced with one double pole 240 volt breaker that has a common breaker bar. But it would mean purchasing the new 240V breaker and tossing the two old single poles.

This would work, but like I said I already have a 30a 240 line for brewing, I just wanted more power and to do things simultaneously with what already exists.

Thanks all for the comments!!