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Lights dim when AC comes on

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Posted by ttown (My Page) on
Sun, Jun 19, 11 at 9:32

We have a house that was built in 1960, and had it rewired in 2005 because of the old wiring. Lately the lights have started dimming a little when the AC unit kicks on. What could cause this and should it be a concern

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RE: Lights dim when AC comes on

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It is actually not that abnormal, but if it is NEW it may indicate the AC is taking longer to start up.

When induction motors like the one in the AC compressor outside start up they pull a VERY large starting current.
Often 2-3 times there running current.

If you want to see how much difference there is between starting and running, there should be a running current (often marker FLA, for Full Load Amps) and a Locker Rotor Amps (LRA) that indicate show high the starting surge can go.

If it is new it may indicate you need to start saving to replace the condenser (and possibly the evaporator inside so they match up correctly).

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RE: Lights dim when AC comes on

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Call your POCO and tell them you have flickering lights.
They will, (should), put a recorder on at the meter box.
If the voltage dips show up there, then the problem is
with their equipment and they should fix it. There
will be no charge for this from them. If the voltage dips
don't show up where the power comes to the house, (meter box), then the problem is in your equipment.

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