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View Full Version : Lights pulsing dim every 30 -45 min or so


wild bill hts
Jan 6, 2008, 12:09 PM
New house just built, it seems the lights, flicker dim for a moment about 30 45 min apart, I can't seem to associate with large appliance activation, it happens when all a/c is off. Seems to happen on all circuits, the lighting is run through a sub panel feed off a main panel out side, also having bulbs burn out pretty often. Is there any thing to l ook for, check, test to narrow down the causes, How would I check if there is an issue from the feed at there pole. The ups's on the computer don't trigger when this occurs.

donf
Jan 6, 2008, 12:20 PM
UPS' can cause all manner of problems. Do you have any laser printers on a 15 Amp line? Most laser printers I know of have a low amp rating when running, however every time a printer has been idle for X amount of time it cycles the rollers and heats the fuser. In Lexmark's designs, this is an 18 amp inrush of an extremely short duration. Usually around every four or five minutes of being idle. This will cause lights to dim on a single circuit, but not the whole house.

You are seeing it across the breath of the house, how stable is the electrical supply service to your house?

wild bill hts
Jan 6, 2008, 12:31 PM
donf, thanks for the input, I just have a inkjet printer, but the problem occurs across circuits all through the house, I have no clue about stablity of the in feed, is there a way to check that or condition it if there is a problem?

tkrussell
Jan 6, 2008, 12:52 PM
Locate the circuit that is feeding the UPS, and note it.

To check if this flickering is all on one circuit, shut off the breaker that handles the lights that do flicker, does this affect all the lights that are flickering? If so, there is a problem with that one circuit.

If lights that are flickering are on more than one circuit, note which circuits these are. Are they all odds or even circuit breakers?

Reason for asking and looking for you to note these observations, there are two hot 120 volt legs in the panel. If all the lights are on one circuit, then the problem is that one circuit.

If there are lights on several breakers, and they all , for example, are on the odd number breakers, then there is a loose connection or a poor contact in that one leg, someplace, may be the main breaker, in the meter,etc.

You mention the UPS is not being affected by the flickering. A flicker that dims lights is a voltage sag, and with lights dimming the voltage is sagging down low enough for a UPS to affected.

This UPS may be on the hot leg that is not flickering, while the lights you see are on the other hot leg that has a loose connection.

Tracing this problem is difficult, unless you can stand there and keep a voltmeter connected at one location for an hour or so, and keep your eye on the meter long enough to see the volts dip during the event.

Vibration from vehicles can cause the connection to move, and light flicker, for example.

Are the affected lights on the main panel or only from the subpanel?

I hope this is enough to get you looking in the right direction.

If the problem continues to evade you, you may need an electrician to come out and check all panels, main breakers, inside the meter, or have the utility check their equipment or connections.

wild bill hts
Jan 6, 2008, 01:39 PM
Thanks for your ianswer tk, ill check into those items
All the power for the lighting is run through the sub panel, the only thing on the main is the a/c, stove, dryer, which only the a/c is currently hooked up. Ill try to isolate which breakers are issues, thanks, again

Cobraguy
Jan 7, 2008, 06:57 AM
Tk's advice holds whether it's the main panel or a sub. You just have two panels to investigate now.