KJS wrote:

On Sat, 16 Oct 2004 12:47:03 -0700, Tony Hwang wrote
(in article XUecd.117702$a41.89152@pd7tw2no):


Blackdogs wrote:

Our source of domestic water is a spring. There is a pump enclosed in
a pump house and it operates on 220V. I want to install a filter
system that uses a clock (110V) to control backflushing of the
limestone filter. My problem is, the power to the pumphouse consists
of two hots and a ground, no neutral. What I want to know is, can I
use one of those step down transformers to get 110V to operate the
clock? As near as I can determine from websites describing the
transformers, they are made to be used with 220V european (or
elsewhere in the world) power. Those voltages are a single hot with
respect to ground while US 220V is what it is, with each hot at 220V
with respect to the other hot. Can I use one of these transformers
with US 220V input? I can't see much of any other option rather than
replacing the wiring to the pumphouse which would be beaucoup
expensive (underground wiring) given the distance. Any help is
appreciated.

Hi,
You may have 110 volts acros one leg of hot and ground.
If so tap it from there.
Tony


Blackdogs -

I emphatically disagree with Mr. Hwang's suggestion. You should never use
the equipment ground as a neutral return path. It will certainly "work", but
you have potential touch voltage on the entire ground path (equipment
housings, conduit, etc.) back to the panel. If that path gets interrupted
anywhere by a break or high-resistance connection, you will have a very
hazardous situation. Using the ground in this way is, of course, a code
violation and with good reason.

I am not familiar with the European to US transformers, perhaps another
poster can tell you if they're suitable.

However, you certainly can get a small hard-wired 220V to 110V step down
transformer for your application, but it's not a Home Depot item. This sort
of "separately derived system" is done all the time in industrial/commercial
installations. You end up with a transformer feeding a small panel with a
breaker for the 110V circuit. One of the transformer secondary terminals is
grounded in the panel and you have a "normal" 110V to neutral branch circuit.
It's not hard to do, but the details (particularly concerning grounding) are
a little hard to understand. Depending on how ambitious you are, it may be
better to have an electrician do this.

Whatever you do, please don't use the ground as a neutral.

- Kenneth

Hi,
In this case it's only a clock. It can float.
Enclose in a plastic enclosure or something. Won't even draw much
current.
Tony