electrical question

[randy41]

i have a small greenhouse that i use for starts. it's heated with a small electric heater that is fed by a 220 line. the plate on the heater says it draws 23 amps. it is connected to a 30 amp breaker at the box. the cable is 10/3 (i think).
could i tap off this line at the receptacle in the greenhouse and have a 110 receptacle in there? i don't care if it is up to code, i just want to know if it would work.

 

[ray66v]

It probably is not 10/3, it is probably 10/2, with the third wire being a bare ground wire.

It would be unlikely they would have run a neutral wire, which you would need to have 110 volts. Because, a 220 volt heater would not need it.

If they did for some reason run 10/3, which means there would be 4 wires in the cable, you could in theory, have 110 volts coming off of that.

 

[randy41]

the "they" is me and i will check to see if its 10/3 or 10/2.

 

[kennyd]

So this greenhouse has it's own breaker panel?

Technically-you could get the 120v from the 240v heater line, but not only is it against code it very unsafe.

 

[deepNdirt]

How long use of wire and size wire is important to the green house? it would be best you used a small 30/40/50 amp panel box and and split from there using a 15 amp breaker for the 110/115v circuit, or if you know enough about what your doing you could use a disconnect box to split from,

 

[MikeD74T]

Randy, YES it will work, NO it's not to code nor particularly safe. MikeD74T

 

[LD1]

I would net do it even if it is 10/3. But yes it "can" be done.

Problem being that the 10/3 wire is rated for 30A and you are protecting it with a 30A breaker. It is "in theory" possible if you pull a 110 leg off, that you could be running more than 30A on the one leg and still the 23 on the other and the breaker NOT trip. It depends on the type of breaker though. I think most of them will trip if either leg sees more than 30A. But I have seen DIY jobs before where TWO 110 breakers were used and NOT pinned together. (that is what the little hole in the switch is for).

 

[Iplayfarmer]

How long use of wire and size wire is important to the green house? it would be best you used a small 30/40/50 amp panel box and and split from there using a 15 amp breaker for the 110/115v circuit, or if you know enough about what your doing you could use a disconnect box to split from,

This is the idea I like best. Basically you'd be installing a subpanel in your greenhouse. Run one double breaker for the heater and a 15 or 20 amp single breaker for the 110 volt outlet.

I have no idea about the code, but I can't see how this would be unsafe as long as the following conditions are met...

-The breaker in the main panel is sized to protect your wire (I.e. a 50 foot run of 10 awg needs a 30 amp or smaller breaker. See this calculator)

-Your sub panel is properly grounded.

-Your wiring within the greenhouse is up to snuff.

I'm happy to be educated otherwise if there are some specific safety concerns to wiring a subpanel in the greenhouse.

 

[Transit]

If you have lights than you have 110-120 volts. As for code, if any thing ever goes wrong kiss your fire insurance by-by.

 

[Craig Clayton]

This is Canadian Electrical advise, assuming the greenhouse is close to you main panel /house because I did not gather that your 240 V feeder was a long run simply pull in a new 120 V 15amp 14/2 feeder and mount your receptacle on the wall. I presume it will have to be a under ground installation so bury as per code with NMW in 1" poly at 15" min. but deeper is always safer and not against the code.
I know how to do it with a transformer but I am not going there.
Craig Clayton

 

[randy41]

the cable is 10/2 and the suggestion to install a sub-panel in the greenhouse seems to be the easiest solution. do you guys think the frost free hydrant i have in the greenhouse would be a suitable ground?
i did all the wiring in my house so i have electrical work experience. how would i use a disconnect box to do this that is different than using a sub-panel? is it wired the same way but the equipment is cheaper?

 

[ray66v]

I believe I already answered these questions.

If you have 10/2, 220 volts, you have no neutral wire. Unless your planning to run one, you should stop.

Whatever your using for a sub panel, needs to have the grounds, and the neutral wires isolated from each other, rather than connected, (bonded), together as they are at the main panel.

The only thing considered a suitable ground, is a properly driven, (as per code in your area), ground rod.

 

[tommu56]

I believe I already answered these questions.

If you have 10/2, 220 volts, you have no neutral wire. Unless your planning to run one, you should stop.

Whatever your using for a sub panel, needs to have the grounds, and the neutral wires isolated from each other, rather than connected, (bonded), together as they are at the main panel.

The only thing considered a suitable ground, is a properly driven, (as per code in your area), ground rod.

I second the vote you are setting your self up to get shocked
Electrician for 30 years
tom

 

[hitekcountry]

I strongly recommend you not violate the electrical code, It is very much designed around safety. I've seen things that were done that do work but that are very unsafe. It isn't hard to do the job correctly.

 

[ray66v]

I second the vote you are setting your self up to get shocked
Electrician for 30 years
tom

It's nice to have someone agree.... for a change.

 

[Iplayfarmer]

I have to concur with the others if you have 10/2 wire. There's no good way I know of to wire it without a neutral. Like Hitekcountry suggested, there are ways that will work, but it's not a good idea. Your options at this point are...

1) Follow Craig's advice and run a whole new 120 volt line to your greenhouse. (I'd recommend using 12 gauge wire so you have the option of a 20 amp circuit.)

2) Run new 10/3 wire and do the subpanel idea.

3) Re-configure your heater to 120 volt and run the whole circuit out there on 120 volt. (This depends on how much heat you need and whether your heater is convertable.)

If it were me I'd just run the extra wire for a separate 120 volt circuit.

 

[ruralNearDallas]

I have a similar situation running to my barn. We ran 10/3 with ground in UF. I would have run 6 or 8, but we got a great deal on the 10/3.

We will be putting a panel out there, soon.

We also have a 30A breaker protecting the UF and the barn.

Remember, the breaker protects the downstream equipment.

One issue you will have: I can't find a 110V receptacle that will accept 10 guage wire. You will need a pigtail or something to convert.

Also, each leg (not technical, but I am going to talk color) will allow 30 amps. That means the red will do 30 and the black will do 30. If the heater is really drawing 23 on 220, then both the red and black are already using 23A. Note that the label is for the maximum, not what it truly does.

That means you can have two 110V circuits that can supply 7A per--assuming the heater is running and drawing 23A.

Also, I certainly agree with the other posters who like the sub panel idea.

Also, I agree with the person who said that sometimes appliances are expecting to be protected with a 15A breaker, so they could burn up using your original plan. Solution: buy an inline (comes in various ways including power strips and extension cords) 15A breaker.

I hope I helped.

By the way, I am planing to go with the flexible conduit with wire already in.

 

[ray66v]

One issue you will have: I can't find a 110V receptacle that will accept 10 guage wire.

My understanding is, you can't legally put 30 amps, to a normal 20 amp duplex receptacle.

However, I do occasionally use #10 wire on them, I have never seen a receptacle that would not allow a #10 wire on the screw terminals. Which is the only way you should wire one.

 

[mmurphy]

It's nice to have someone agree.... for a change.

There is others who agree with you.

My question is, why not run another circuit to the green house?

 

[tommu56]

I have a similar situation running to my barn. We ran 10/3 with ground in UF. I would have run 6 or 8, but we got a great deal on the 10/3.

We will be putting a panel out there, soon.

We also have a 30A breaker protecting the UF and the barn.

Remember, the breaker protects the downstream equipment.

One issue you will have: I can't find a 110V receptacle that will accept 10 guage wire. You will need a pigtail or something to convert.

Also, each leg (not technical, but I am going to talk color) will allow 30 amps. That means the red will do 30 and the black will do 30. If the heater is really drawing 23 on 220, then both the red and black are already using 23A. Note that the label is for the maximum, not what it truly does.

That means you can have two 110V circuits that can supply 7A per--assuming the heater is running and drawing 23A.

Also, I certainly agree with the other posters who like the sub panel idea.

Also, I agree with the person who said that sometimes appliances are expecting to be protected with a 15A breaker, so they could burn up using your original plan. Solution: buy an inline (comes in various ways including power strips and extension cords) 15A breaker.

I hope I helped.

By the way, I am planing to go with the flexible conduit with wire already in.

as long as it is 10/3 with ground (4 wires) and on a double pole breaker this is OK.
If you put it on the same leg the neutral could be loaded with the sum of the total current.
After seeing many neutrals burnt up after some one rearranged the panel and put both wires on the same leg I always recommend separate neutrals.

tom