110 outta 220

[randy41]

i have a little greenhouse with a 220 line going to it for my electric space heater. but i'm thinking of getting heating mats for some onion seeds i want to start in february. the mats call for 110 so i'm thinking of tapping off of one of the 220 legs. anyone see any problem with that plan? i guess i wont have the correct breaker protection. alternatively i could just rewire the line at the breaker box and then rerewire it when i want to use the space heater in march.
so what do you think?

 

[MrJimi]

Here is your answer..
Totally Illegal !!
It will work, but not SAFE
Do yourself a favor and DON"T do it
Do it right and to code
It WILL burn you in the butt later and not worth it
Jim

 

[kennyd]

Yeah, doing it the way you suggested would not be safe.

What kind of wire is feeding the 240v to the greenhouse? If you have 4 conductors, ( two hots, a neutral, and a ground) you could wire up a small sub-panel to safely get your 120v. Also what amperage breaker is on the circuit now?

 

[MossRoad]

Have a proper 220v sub panel installed at the greenhouse with a 220V breaker for your space heater circuit and a couple 110V breakers for other circuits. Since it is outside and in an area with water and dampness, you should also make everything GFCI protected.

 

[ultrarunner]

Back in the days when I worked in the machine shop for a large Manufacturing Plant all of the small (under 16" swing) lathes were powered by 220 3 phase circuits.

Attached to each lathe's power disconnect was a small metal junction box with a screw in Edison base 20 amp glass fuse and a single outlet cover to provide 120v for illumination. OSHA inspected the plant regularly and the 120v taps were never an issue.

My Grandparents 220v electric range has 2 120v outlets... one is on a timer and the other outlet is powered all the time.

Just my observations

 

[gordon21]

Mossroad has the plan you should use. It will be code compliant and cost less than $120. A small sub panel with one 220 breaker for the existing heater and four extra 120v breakers. Use the GFI breakers. They are only a few dollars more.

 

[randy41]

what about one of those european voltage converters?

 

[midlf]

Back in the days when I worked in the machine shop for a large Manufacturing Plant all of the small (under 16" swing) lathes were powered by 220 3 phase circuits.

Attached to each lathe's power disconnect was a small metal junction box with a screw in Edison base 20 amp glass fuse and a single outlet cover to provide 120v for illumination. OSHA inspected the plant regularly and the 120v taps were never an issue.

My Grandparents 220v electric range has 2 120v outlets... one is on a timer and the other outlet is powered all the time.

Just my observations

You cannot get 120v off of a 220 3 phase circuit (unless it is the very rare "red leg delta" system). Most likely the 120 was tapped off the machines control power transformer. Typically the control power transformer has the machines supply voltage as the primary and 120v as the secondary.

The range has a 15 amp fuse on it and the outlet circuit is connected to one hot and the neutral. Ranges no longer are allowed to have outlets. Too many burned cords.

Mossroad has the best answer.

 

[RobJ]

i think i remember something about this in another forum i visit. you can do it but the safe way is to run a neutral back to the main. but if you are doing that you can run another line. all depends if the current line is underground, above ground, etc.

good luck,

 

[BillyP]

Why can't he do as he suggested when he said "i could just rewire the line at the breaker box and then rerewire it when i want to use the space heater in march."?

Just rewire at the breaker box with a 110 breaker and change to a 110 receptacle. As long as the wire is of sufficient size to carry the amp load, I don't see the problem?

 

[kennyd]

Why can't he do as he suggested when he said "i could just rewire the line at the breaker box and then rerewire it when i want to use the space heater in march."?

Just rewire at the breaker box with a 110 breaker and change to a 110 receptacle. As long as the wire is of sufficient size to carry the amp load, I don't see the problem?

He could.

 

[VA_Joe]

Back in the days when I worked in the machine shop for a large Manufacturing Plant all of the small (under 16" swing) lathes were powered by 220 3 phase circuits.

Attached to each lathe's power disconnect was a small metal junction box with a screw in Edison base 20 amp glass fuse and a single outlet cover to provide 120v for illumination. OSHA inspected the plant regularly and the 120v taps were never an issue.

My Grandparents 220v electric range has 2 120v outlets... one is on a timer and the other outlet is powered all the time.

Just my observations

That's because it used to be okay to run a small amount of current on the ground of a range circuit to power the clock-timer, lights, and other small draw accessories. This practice was recently (10 - 15 years ago???) banned by the NEC. You now need to run a separate neutral wire (i.e. four wires vice three). The reason is that current through a wire induces voltage. If someone was to touch the range chassis while also touching some other grounded appliance they could receive a very mild shock. Most of the time this induced voltage would be so low as to not be dangerous (or even perceptable by human). The problem is that if by chance the clock-timer or some other accessory had a fault and drew too much current - there is a chance that the chassis ground could be high enough to be deadly.

I suggest making sure that you have a valid neutral (and ground) if you plan on tapping 120 volt off the existing circult.

My two cents.

VA_Joe

 

[randy41]

I need to look at what I have at the box...its been many years since I first hooked it up...but I'm pretty sure I have 3 wire w/ground going there now.

thanks for all the responses.

 

[Soundguy]

I assume this was also how the 120v cooling fans ran on old buzzboxes??

Soundguy

That's because it used to be okay to run a small amount of current on the ground of a range circuit to power the clock-timer, lights, and other small draw accessories. This practice was recently (10 - 15 years ago???) banned by the NEC. You now need to run a separate neutral wire (i.e. four wires vice three). The reason is that current through a wire induces voltage. If someone was to touch the range chassis while also touching some other grounded appliance they could receive a very mild shock. Most of the time this induced voltage would be so low as to not be dangerous (or even perceptable by human). The problem is that if by chance the clock-timer or some other accessory had a fault and drew too much current - there is a chance that the chassis ground could be high enough to be deadly.

I suggest making sure that you have a valid neutral (and ground) if you plan on tapping 120 volt off the existing circult.

My two cents.

VA_Joe

 

[midlf]

If the buzz box had a neutral then yes. If it had a ground, no. The only code exemption that used to exist where you could cheat a 120v load onto a ground was for electric ranges and electric dryers. Both of these are no longer allowed. Most likely the transformer on the buzz box has a centertap for the fan if the fan is 120. It would be easier for the mfr to use a 240v fan, but I'm not familiar with the old buzz box.

 

[randy41]

Well I finally got around to doing this this morning. It's in the 20's and windy out but it's in the 70's in the unheated greenhouse.
So I just replaced the 2 pole 30 amp breaker in the main box with a 20 amp single pole one. The wire turned out to be 2/10 w ground so that worked out fine. I also replaced the 220 receptacle in the greenhouse with a 110 one. A little screw turning and wire stripping (needed to wrap the wire around the receptacle screws) and now I can start my onions.
I was also pleasently surprised at how well the 220 receptacle has held up in a sometimes very damp location.