safely pulling 110V off a 220V circuit

Thread Starter

oley55

Joined Feb 6, 2016
2
I have a 220V water pump located approximately 150 feet from the house. The exterior grade direct bury romex type feed has a black, white, and bare copper. I would like to create a 110V outlet in the pump house.

Can I use the bare copper wire as my neutral going back to my service panel and create a new ground by clamping off the well casing, or is my only legitimate option to run new four wire romex back to the house?
 

Robin Mitchell

Joined Oct 25, 2009
819
Firstly you should hire an electrician. This type of work needs to be notified to the local building regs.
Secondly, you would use a transformer to drop the voltage to the desired level.

The bare copper will most likely be CPC (earth). The black will be neutral and the white will be line (to my knowledge).
Again, you need to hire an electrician.
 

dl324

Joined Mar 30, 2015
9,317
Your location would help. I'm assuming you're in the US...

Don't think it can be done unless you have neutral. The 220VAC coming from my panel only uses 3 wires; both sides of the split phase and ground. There is no neutral. You can't use ground to get 110VAC; neutral and ground can only be connected at the distribution panel.

Any exterior outlet needs to be protected by a GFCI.

As mentioned earlier, you should hire an electrician to make sure it's done according to code.
 

MaxHeadRoom

Joined Jul 18, 2013
19,385
Instead of a new 3cond and Gnd, the cheaper way may be would be to use a 240-120v control transformer and connect one side of the secondary to earth conductor, you then take the neutral directly off of this connection.
The earth/neutral connection has to be done directly at the secondary terminal.
This is a common method in control circuitry.
Max.
 

tcmtech

Joined Nov 4, 2013
2,868
Yes you can. On your present three wire 240 volt feed the bare copper wire would be considered both the common and earth return line so technically if you are using it as the common and supplying a independent solid earth ground to the well casing four the fourth line you could use it for 120 volt loads and be within NEC code compliance.

Three wire 120:240 feeder lines are used everywhere. In fact there is a high probability that your whole house and any outbuildings you have are fed by three wires with a local earth grounding rod system at the main entry point of each structure acting as the fourth earth ground line.
 

Lestraveled

Joined May 19, 2014
1,946
On the 110 Vac circuit, how much power do you need? If it is just a few amps, then a transformer would be very reasonable, and very legal. Look on EBay for used step down transformers.
 

Thread Starter

oley55

Joined Feb 6, 2016
2
If I decide to install new wiring (and it for sure won't be direct bury), what size would be appropriate for that long a run? I'm guessing by the time I get all the way back to the breaker panel, I'll be close to 180 feet. Will 10/3 with ground suffice?
 

dl324

Joined Mar 30, 2015
9,317
If I decide to install new wiring (and it for sure won't be direct bury), what size would be appropriate for that long a run? I'm guessing by the time I get all the way back to the breaker panel, I'll be close to 180 feet. Will 10/3 with ground suffice?
If you're asking these types of questions, you should be hiring an electrician.

Code specifies gauge for current capacity. I not aware of any length restrictions; but, I'm not an electrician...
 

tcmtech

Joined Nov 4, 2013
2,868
If I decide to install new wiring (and it for sure won't be direct bury), what size would be appropriate for that long a run? I'm guessing by the time I get all the way back to the breaker panel, I'll be close to 180 feet. Will 10/3 with ground suffice?
Depends on what the load is.
 

tcmtech

Joined Nov 4, 2013
2,868
It is illegal now to use a ground wire as a neutral in NEC/CEC.
Max.
If the line was installed before the rule change then it is grandfathered in as legal which I suspect that it had to have been since with the new codes that pump line would have had to have 4 wires to pass inspection.

Also given that he refers to the structure as a pump house not a well head has me believing that that there is a small structure or building of sorts ans the three wire line set going there now is the primary power feed which if had been installed some time ago has it's own exemptions relating to how power was fed to it and how it can be tapped into.

Sometimes getting things done by code is less about the codes and more about the grey areas and exemptions to the codes. ;)
 

Dodgydave

Joined Jun 22, 2012
8,568
How much current are you using,will determine the voltage drop per meter,

as a rough guide use 10amps per mm2 cable, so if you want to use a 10amp breaker, use 1mm2 cable,
20amps breaker use 2.5mm2 cable,.
 

MaxHeadRoom

Joined Jul 18, 2013
19,385
I suspect that it had to have been since with the new codes that pump line would have had to have 4 wires to pass inspection.

.
A 3wire installation is allowed, L1-L2 and GND.?

What is the expected load on the 120v outlet? Lighting?
If I were faced with the task of providing a new run of that length, for the cost and time involved I would tend to use the control transformer method.
Max.
 

tcmtech

Joined Nov 4, 2013
2,868
A 3wire installation is allowed, L1-L2 and GND.?
I don't know your most recent Canadian codes but here in the US a three wire (two live one common/ground) line system is standard practice in residential single phase systems.

When I moved my old trailer over to a different part of the yard so that I could start on the new house project all that was required for the ~350 foot run was standard 4/0 three conductor aluminum cabling with a minimum of two 8' ground rods at the house end for the 4th line earth ground.

Same with my work shed I just put in last summer. All that required was a 4 ga three wire aluminum feeder with a ground rod at the building to meet code.

To my knowledge the only place that 4 wire service with independent common and ground lines are needed in residential environments is for higher powered indoor household appliances that require two circuits for 240 volt power like electric stoves, clothes dryers, central heating and AC systems.
 

Lestraveled

Joined May 19, 2014
1,946
All that required was a 4 ga three wire aluminum feeder with a ground rod at the building to meet code.
In typical residential construction, the power company only brings in 3 wires, L1, L2, and neutral. The ground is established at the site with a ground rod or UFER. I think the issue here is if it is legal to use the bare ground wire in Romex as a neutral.

Also I don't think "grandfathering" works exactly how you say. The way I understand grandfathering is they can't make you change it if the rules change. But, almost always, if you change/modify it then you must make it meet current code.
 

bwilliams60

Joined Nov 18, 2012
1,231
Be careful with L1-L2 and neutral being the only wiring. Newer houses are using PVC piping and the grounding rod we used to use no longer exists (tied into plumbing. In this case you need to be careful where you are "grounding" to.
 

dl324

Joined Mar 30, 2015
9,317
The way I understand grandfathering is they can't make you change it if the rules change. But, almost always, if you change/modify it then you must make it meet current code.
That's the way it works here. When my well pump was replaced, they upgraded my electrical to meet code; and registered my well with the state (who "owns" all water rights).

The more I think about it, the more I think the company replaced my pump, pipes, and check valve when all I needed was a new check valve. Live and learn...
 

tcmtech

Joined Nov 4, 2013
2,868
You are aware don't ask don't tell applies to more than the military right? :rolleyes:

That's the way it works here. When my well pump was replaced, they upgraded my electrical to meet code; and registered my well with the state (who "owns" all water rights).
I just replaced the deep well submersible pump (~200' down) on dads well two weekends ago do you honestly think we told anyone about it who would care? :rolleyes:

As far as the authorities that be are concerned that well still has the windmill and pump jack on it from back in the 1030's or 1940's when it was drilled as a livestock well. :p
 
Top