On Thu, 16 May 2013 09:25:32 -0400, bilfre wrote:

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.
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