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Home > Archive > Electrical Engineering > May 2007 > electrical short in barn?
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electrical short in barn?
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| o.k. hear I go. I no longer have electricty in my barn. A brief history that
leads up to this post, I had my old barn re-decked, re-shingled last fall.
I started noticing about a month later my lights would dim and or go out
completly then come back on again.
Now the lights will not come on at all.(just outlets and light bulbs in barn
no heavy equipt). When I test voltage at 220 switch coming into barn, 110v
on each side is o.k.
with all fuses off. but when I test voltage again with fuses turned on I get
a drop of 90v on 1-side and 40 to 50v on the other, I've tried different
fuses as far as 1-off, 1-on etc,etc. When I test a outlet for power I get
90v.
Any ideals would be very helpful, thanks.
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| SparkyGuy 2007-05-08, 1:25 pm |
| > but when I test voltage again with fuses turned on I get
> a drop of 90v on 1-side and 40 to 50v on the other, I've tried different
> fuses as far as 1-off, 1-on etc,etc. When I test a outlet for power I get
> 90v.
This is one of those situations that without being there hands on (well,
insulated-glove hands on (c: ) it's near impossible to diagnose.
But, if you're measuring ~90v at the service input to the barn with "fuses
on", and you're not blowing any fuses, I'd say you have a wiring problem *in*
the service connections or *prior* to the service connections to the barn.
Check back to the source all connections and wires.
Might be time to call an electrician...
Good luck,
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| Daveh wrote:
> o.k. hear I go. I no longer have electricty in my barn. A brief history that
> leads up to this post, I had my old barn re-decked, re-shingled last fall.
> I started noticing about a month later my lights would dim and or go out
> completly then come back on again.
> Now the lights will not come on at all.(just outlets and light bulbs in barn
> no heavy equipt). When I test voltage at 220 switch coming into barn, 110v
> on each side is o.k.
> with all fuses off. but when I test voltage again with fuses turned on I get
> a drop of 90v on 1-side and 40 to 50v on the other, I've tried different
> fuses as far as 1-off, 1-on etc,etc. When I test a outlet for power I get
> 90v.
> Any ideals would be very helpful, thanks.
>
>
Loose connection, construction activity damaged
the feed to the barn, or nail penetrated the wiring.
Ed
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| phil-news-nospam@ipal.net 2007-05-13, 9:25 am |
| On Tue, 8 May 2007 12:52:38 -0400 Daveh <dholmes@computer-systems.com> wrote:
| o.k. hear I go. I no longer have electricty in my barn. A brief history that
| leads up to this post, I had my old barn re-decked, re-shingled last fall.
| I started noticing about a month later my lights would dim and or go out
| completly then come back on again.
| Now the lights will not come on at all.(just outlets and light bulbs in barn
| no heavy equipt). When I test voltage at 220 switch coming into barn, 110v
| on each side is o.k.
| with all fuses off. but when I test voltage again with fuses turned on I get
| a drop of 90v on 1-side and 40 to 50v on the other, I've tried different
| fuses as far as 1-off, 1-on etc,etc. When I test a outlet for power I get
| 90v.
| Any ideals would be very helpful, thanks.
There is a broken connection coming in. You are most likely reading a
phantom voltage with a very high impedance digital voltmeter. When the
wiring is extended longer (fuses on, as you say), the voltage drops due
to the need for more charging current to feed that wiring. This phantom
voltage is a small amount of capacitively coupled charge voltage due to
one wire very close to another.
It is not a short. If it were a high current short, the fuses would blow.
If it were a low current short (wire touching earth for example) then the
voltage would not be pulled down so much to prevent lights from working.
Test voltages with very low power loads connected, such as an electric
clock or a small gadget wall wart transformer. Or connect small wattage
lights and see what you get for voltage readings across a range of load
wattages. Repeat these measurements on both sides of the system where
you were reading 90V and 40-50V respectively.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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