[RFI] Motor starting and UPS

[Bill Vehe]

Dave Robbins  last comment on a faulty neutral is something worth 
considering.

My home was built in the middle 60s when aluminum wire was frequently 
used from the pole all the way to the main breaker. One day at dinner 
time I noticed the lights over the kitchen table got brighter when the 
electric skillet went on. This did not make sense, so I started 
investigating. Tests that I conducted on the neutral wiring indicated 
the problem was not in my home.

So I called the power company and they found a faulty connection where 
the aluminum drop was connected at the pole. Now to be fair that was 60 
years ago, so you are not likely to find aluminum wire as the problem. 
But as Dave pointed out a faulty neutral can cause problems. Consider 
this, if you have some resistance in the neutral from your power panel 
back to the power Co. transformer, then it is likely you will have the 
same voltage drop regardless of which side of the 120 volt distribution 
you connect your pump to.


Bill Vehe
W9ZJ
email w9zj at arrl.net



On 11/21/2020 12:05 PM, k1ttt.dave at gmail.com wrote:
> It will depend on the ups and the amount of the dip.  I am surprised a circulation pump would draw enough to drop the voltage that much, usually they are relatively small.  Is the ups on the same circuit as the pump??  Assuming they are on the same circuit have you checked for loose or corroded connection from the breaker to the pump and outlet??
>
> When you say the sdr is powered from the computer, is that via usb?  Or off one of the other power supply voltages internally??  Usually usb is pretty well regulated by itself so again it would surprise me that the line voltage would affect it that much.  If its off one of the other voltages then maybe a line drop would affect it, but that goes back to the paragraph above.
>
> On the ups side.  Some ups's run full time and protect against voltage dips, others take some time to switch on and support voltage dips like that.  There may also be an adjustment in hardware or software for the switch over to battery point.  Some ups's also have a delay before they switch to battery so they may not pick up in time.
>
> If you have an appropriate meter you might want to measure the dip to quantify it.  It could also be the pump is going bad and drawing way too much starting current.  Or another possibility is a faulty neutral between the house and pole, that can cause all sorts of nasty voltage swings and has been know to blow out equipment and cause fires.
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: telnet://k1ttt.net:7373
>
>
> -----Original Message-----
> From: RFI <rfi-bounces+k1ttt=arrl.net at contesting.com> On Behalf Of Ron Hunsicker via RFI
> Sent: Saturday, November 21, 2020 12:32
> To: rfi at contesting.com
> Subject: [RFI] Motor starting and UPS
>
> Hello,
>
> The power to my computer is via a UPS.  My SDR is powered from the computer.
>
> When one of the water circulation pumps for my heating systems starts (an old B&G), the voltage dips so much that it is apparent in the waterfall and a drop/loss of audio.
>
> I've tried switching legs (red v black) but that didn't help. Let's ignore the idea that the service is too small.
>
> I thought that UPS might "protect" against such dips in the voltage and am (obviously) surprised that it does not.
>
> Whadaya think?
>
>
> Ron
>
> --
> Ron Hunsicker
> 1238 Cleveland Avenue
> Wyomissing, PA 19610-2102
> 610-478-0371
> ronhunsi at ptd dot net
>
>
> *"Democracy dies in darkness"***
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