house wiring voltage drop

[bilfre]

Suspected a wiring problem at a friends house where her computer and
monitor fed via a UPS is connected. The UPS sounds it's alarm
sometimes when there is no apparent reason. The outlet in question has
120v no load and 110v with a 1500 watt load. At my house voltage only
drops from 120v to 115 volt under the same 1500 watt load. Just
wondering if this much voltage drop (10v @ 1500 watts) is excessive and
does it warrant further investigation of the friends wiring? I only
tested the one outlet at the computer so plan to go back and check some
others.

[Plai...@yawhoo.com]

That voltage drop is excessive. The National Electric Code specifies
a drop of no more than 5% from the breaker box to the furthest outlet
at full load (Note that a 1500 watt load is about 85% of full load).

Checking the drop at various points from the breaker box to the outlet
supplying the computer is a good idea. The faq at
http://www.psihq.com/iread/faqvolt.htm also has suggestions.

PlainBill

[bilfre]

On 2013-05-16 16:17:16 +0000, Plai...@yawhoo.com said:

> That voltage drop is excessive. The National Electric Code specifies
> a drop of no more than 5% from the breaker box to the furthest outlet
> at full load (Note that a 1500 watt load is about 85% of full load).
>
> Checking the drop at various points from the breaker box to the outlet
> supplying the computer is a good idea. The faq at
> http://www.psihq.com/iread/faqvolt.htm also has suggestions.
>
> PlainBill

Hi PlainBill,

Thanks for the response and the link. I will go back to my friends
and look for the problem. I suspect there is a loose connection at one
end or the other since it seems to be intermittent. Checked my own
wiring with same load and only had a 4 volt drop.

billfre

[hrho...@sbcglobal.net]

On May 16, 8:16 pm, bilfre <nob...@nowhere.ca> wrote:

> On 2013-05-16 16:17:16 +0000, PlainB...@yawhoo.com said:
>
> > That voltage drop is excessive.  The National Electric Code specifies
> > a drop of no more than 5% from the breaker box to the furthest outlet
> > at full load (Note that a 1500 watt load is about 85% of full load).
>
> > Checking the drop at various points from the breaker box to the outlet
> > supplying the computer is a good idea.  The faq at

> >http://www.psihq.com/iread/faqvolt.htmalso has suggestions.

>
> > PlainBill
>
> Hi PlainBill,
>
> Thanks for the response and the link.   I will go back to my friends
> and look for the problem.  I suspect there is a loose connection at one
> end or the other since it seems to be intermittent.  Checked my own
> wiring with same load and only had a 4 volt drop.
>
> billfre

Your own experience is more typical. 10 V is excessive. Aluminum
wiring??? I would be careful not to keep the load on continuously
just in case there is some heating somewhere in the walls. P = IV =
20 x 10 = 200Watts, probably not enuf to start a fire but just in
case!!!

[amdx]

I could have started a fire in my home a few years ago.
I plugged a couple of chest freezers into an outlet with out trouble
for a couple of years. One evening I smelled a burned plastic smell in
our living room. I could not isolate it before I didn't smell it. A week
or three passed and the smell recurred, this time I moved a TV away
from the wall and found the plug was hot and slightly deformed. The
outlet was also hot.
I removed the paneling and found the wiring looped through this outlet
on it way to the one I plugged the freezers into. The connection to the
outlet was poor and caused the heating with the extra current going to
the freezers. The heat over time had caused the 35 year old outlet to
pretty much crumble during removal.
So, I guess I would say, make sure that most of that voltage drop is
NOT at one outlet.
Mikek

[Plai...@yawhoo.com]

With standard wiring practices there are several outlets in this run
of wire. The most likely point for a problem is at the point an
outlet or switch is connected to the wire. IF you can determine
intermediate points along the wire run, the best approach is to
determine if the majority of the drop occurs between a pair of
outlets.

Someone else gave a wattage - they miscalulated. The TOTAL power
dissipation for the drop is about 125 watts - still a sizeable amount.
The EXTRA dissipation is about 75 watts. One approach would be to
hook up the 1500 watt load, then carefully check outlets to see if any
feel warm. If no suspects are identified, wait 15 minutes or so (with
the load still present), then repeat.

PlainBill

[Fred McKenzie]

In article <201305162116512010-nobody@nowhereca>,

Billfre-

Also look for evidence of a poor neutral connection. When that happens,
voltage will divide according to the load on each line. If that were
the case, ten volts drop at a high current load could cause a ten volt
rise across the other line-to-neutral circuit.

Five or ten volts doesn't sound like a serious problem, but a poor
neutral connection could get worse with age.

Fred

[bilfre]

On 2013-05-18 03:59:39 +0000, Fred McKenzie said:

> Billfre-
>
> Also look for evidence of a poor neutral connection. When that happens,
> voltage will divide according to the load on each line. If that were
> the case, ten volts drop at a high current load could cause a ten volt
> rise across the other line-to-neutral circuit.
>
> Five or ten volts doesn't sound like a serious problem, but a poor
> neutral connection could get worse with age.
>
> Fred

Fred,

Thanks for that tip, I think it may be the problem here. I went back
and tightened the screws on both leads at the outlet and at the hot
side on the breaker. One screw at the outlet tightened maybe a quarter
turn. This brought the voltage drop down from 10v to 7v. Still over
the 5% specified by code. I also put a voltmeter on another outlet in
the same room that was on a different breaker. When I loaded the
outlet that had the 7v drop, the voltage at the other outlet went up a
couple of volts from 120v to 122v and I wondered, what could cause that?

Then you posted about the poor neutral and I thought about the 2v rise
I had measured at an adjacent circuit. Then remembered that I did not
check tightness of the neutral wire connection in the panel. Think I
will go back again and make sure the neutral wire is good and tight at
the panelboard. Maybe that is why it is still over the 5% drop spec.

Does this make sense?

[tuinkabouter]

Measure the drop at the breaker too.

[cottto...@yahoo.commy]

My experience with an open or loose neutral wire, is that the problem
is usually outside of house. The problem is usually with the electric
company's wiring. Call the electric company. They usually don't charge
to check their equipment.

[bilfre]

On 2013-05-25 21:49:15 +0000, cottto...@yahoo.comMy said:

> My experience with an open or loose neutral wire, is that the problem
> is usually outside of house. The problem is usually with the electric
> company's wiring. Call the electric company. They usually don't charge
> to check their equipment.

The problem is only at one wall outlet inside the house. Please
explain how it could be caused by a problem outside the house. .

[Fred McKenzie]

In article <2013052711075876283-nobody@nowhereca>,

Bilfre-

This problem exists somewhere between a power company transformer and
where the neutral connects in your breaker box.

When I had the problem, I called the power company. Their man checked
the transformer, but said I would have to hire an electrician to fix my
end of the circuit. While he had the meter removed, he went ahead and
tightened the connection there, which solved my problem.

Fred