Lights dimming when dishwasher cycles

[jim dungar]

210114-1044 EST

jim dungar:

Whether you have a 1 W or 1 MW 60 Hz power transformer the "T" equivalent circuit is a fairly good approximation to a real power transformer.

I was not talking about equivalent circuits. My comment was about the values you presented from your bench test. The points l mentioned are some of the reasons that test values differ from theoretical ones and may not be repeatable when someone replicates the test using transformers with different construction.

 

[gar]

210114-1202 EST

jim dungar:

My bench tests of a particular transformer were to illustrate what one can generally expect from a power transformer.

These specific values were not meant to imply that exactly the same percent variations could be expected from some different transformer.

However, what my experiment showed was that with a center tapped secondary, or with two separate secondaries, that loading 1/2 of the secondary would cause some voltage drop on the other secondary half, but not nearly as much drop as occurs on the loaded half. This results from some voltage drop occurring on the unloaded secondary that is related to primary series impedance having a voltage drop caused by the current in the loaded secondary half that reflects back thru the primary series impedance.

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[ptonsparky]

210113-2208 EST

ptonsparky:

There is no need to bother the power company if there is little voltage change at the main panel on the phase the washer is on when the motor cycles. I have already provided information on the amount of voltage change to an incandescent that is needed to get some degree of flicker. From experiments I have performed before it is about the same for both incandescents, and LEDs.

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For all we know the POCO has a #4 ACSR stretched to the other end of the block.

Finally got back to that job
Measured voltage at both panels
New 320 continuous service I installed
125/126 volts on both phases in both panels OP: While the DW is cycling?
All connections tight
Swapped phase of dishwasher and kitchen lights stopped flickering
Didn’t have much time so I left
Now I’m told a different lighting circuit is flickering that was not before
Must be due to phase swap
Just a pain in the neck as homeowner thinks because I did a service upgrade all pre existing branch circuit problems should go away
Going back soon to investigate further

 

[gar]

210114-1625 EST

ptonsparky::

It does not matter what the power company has for the supply lines, if the voltage change at the main panel is small (for example 2 V, hard to see any flicker) for some load change, and there is substantial flicker on some branch circuit, then the problem is not a power company problem, and can not be corrected by the power company.

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[gar]

210117-2352 EST

angus1:

Are you going to provide some feedback on how you have handled this problem with the customer?

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