Single phase motor loads and flashing lights

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racerdave3

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Western Massachusetts
I have run into this situation several times over the years but wanted to hear some comments from others about it. In the past month I have been questioned by 2 different people about a situation in their homes, both involving washing machines, where they see the incandescent lights "flash", "surge", "pulsate" when the machine is running. I have seen this in the past with washing machines, air compressors, or other inductive motor loads. I have always viewed this as a voltage fluctuation problem caused from the load being connected to the same phase in the panel as the lighting circuit. Can anyone add their comments to this situation?
 
I am inclined to agree, but that seems to be a bit excessive. Make sure you have eliminated any posibilties of loose connections and make voltage checks at the service entrance as well. Blame it on the POCO if you can.

Do the lights actually share the branch circuit downstream of the washer?
 
I had a problem like that at my house... It was voltage drop from the Power co. House was over 350' from the transformer. It took several years of complaints, registered leter & a threat to hire an independent testing co to meter for voltage drop. BTW, It cost the power co 3 poles to install a transformer 90' from my house...
 
Another thing to consider, right now its winter, I have seen this type of thing happen during summer when the power demand load is high, consider: 1) is the service capacity able to meet the demand load. additions and remodels can affect this. 2) as been stated the overall age and detoriation of the electrical system. 3) POCO connections and electrical system. JM2CNTS. I'll think of others but I smell bacon and eggs cooking.
 
Well, I haven't been to either of these homes to do any kind of investigating as to loose connections or any other possibilities. I will tell you that in one of the cases, the lady just purchased a brand new washing machine to replace an old one that was approx. 15 years old and she said it did not happen with the old machine but does now with the new one.
 
racerdave3 said:
I have run into this situation several times over the years but wanted to hear some comments from others about it. In the past month I have been questioned by 2 different people about a situation in their homes, both involving washing machines, where they see the incandescent lights "flash", "surge", "pulsate" when the machine is running. I have seen this in the past with washing machines, air compressors, or other inductive motor loads. I have always viewed this as a voltage fluctuation problem caused from the load being connected to the same phase in the panel as the lighting circuit. Can anyone add their comments to this situation?
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Check the butt splices between the service drop and the meter. Peeling insulation is a sign of overheating.
 
I have posted this several times, you do need to rule out electrical connection issues BUT

Light flicker (dimming and restoration of light to near preflicker level) of lights from motor inrush) is a byproduct of several factors and generally is difficult to over come.

AC motor loads (in particular compressors) but all motor loads have inrush currents. These inrush currents result in voltage drop in the branch circuit, panel bus, service laterals, utility transformer and possibility the utility HV feeders.

Flicker is in addition user dependent; some people are more susceptible to flicker. For some reason flicker seems to bother women more that men (based upon personal experience).

A Voltage Drop (VD) as little as 3 volts on a nominal 120 VAC system is noticeable (by me), 2.5% VD.

We have had cases were the VD was all a byproduct of primarily single phase 120 VAC loads, in these cases we were able to put the lighting on L1 and all the motor loads on L2, the HVAC compressors were something the homeowner had to live with. This minimizes the flicker.


To test for this VD and resulting flicker to determine the source of the inrush, use a min max amp clamp and min max multimeter at the main service watch the lights(it may take two workers) and correlate to the meters.
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Current inrush could also be your problem. They could be pulsating every time the washing machine motor starts up.

What size wires are feeding into your house from the poco? What size is your house's service?

Try this: go through your house and turn on everything. Heat unit or AC - whichever has a greater load, oven on full blast, microwave, all your lights, ect ect ect... Now go out to your service and measure the load. Is it anywhere near your service size?
Just for an example let's say you have a 200A service, that doesn't mean you're putting anywhere near a 200A load on your poco service wires so even if their wires seem undersized they may be just fine.
 
I think everyone has hit this one spot on, but I would like to add that when I hear "Light Flicker" of "Lights Dimming" - I always feel the need to pay particular attention to the answer to the next question. "Are you sure the lights are not getting BRIGHTER?" A typical sign of resistive or lost neutral - but I have had customers decribe to me in words of the lay man one problem - but it turned out to be another more serious problem.

But yes as far as chasing the dimming light due to motor inrush, I agree on the checking connections on the lights from main to effected branch - but also for the current path of the motor in question. I have had a few occasions where this helped a lot. i.e. The lower voltage due to the start up current was causing most of the high current in the first place. The motor stalling slightly under its own voltage drop..... On a few occassions with large AC compressors with feeders at minimum size at max length - with the drop in the feeder to the unit sized larger I have gotten the voltage drop at the unit to be less, and as consequence the starting current is less. This isn't a guarantee - but it has helped...

Bear in mind that the circuit path to the motor is also through the main - so if that is part of the problem - you could be going way past the service drop. I've seen one mans air conditioning be the straw that broke the camels back for the transformer load. Everytime it went on it dimmed the neighborhood....:grin:
 
racerdave3 said:
Well, I haven't been to either of these homes to do any kind of investigating as to loose connections or any other possibilities. I will tell you that in one of the cases, the lady just purchased a brand new washing machine to replace an old one that was approx. 15 years old and she said it did not happen with the old machine but does now with the new one.
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with the newer high efficiency appliances, motor starting current goes up because the motors are built better, with more copper in the windings.
 
The pulsating described sounds like it is in step with the agitation of the machine in wash mode. The motor spins constantly, at low speed, but the transmission turns that rotation motion into a back-and-forth motion, so the motor load current fluctuates with the agitations.

Whether the lights dim or brighten with each current pulse tells us whether the machine and lights are on the same side of the neutral, and might help determine if the resistance is on the shared line or the shared neutral, and could well be both, but the customer doesn't care.

A simple analog (moving-coil) voltmeter can be used to help pin down the location of the resistance. I'd start at the service panel, checking for voltage swings at the branch-circuit breaker load terminals, and moving towards the main-breaker line lugs, and farther if you have to.

The meter needle will swing visibly when you have the probes on any point with a varying voltage. Check each line to neutral, line-to-line, and even checking against a remote ground (wire to waterpipe or rod) will allow you to confirm or eliminate the main neutral as a problem.
 
iwire said:
Go for the simple first, it draws to much current
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I second that. A copier typically gets a dedicated circuit in an office if you know where it's going. If you don't know where it's going, it may well get a dedicated circuit once they plop it down and try to fire it up. :)
 
LarryFine said:
The pulsating described sounds like it is in step with the agitation of the machine in wash mode. The motor spins constantly, at low speed, but the transmission turns that rotation motion into a back-and-forth motion, so the motor load current fluctuates with the agitations.
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This is it I think. The OP states that the "flashing" occurs when the machine is running. Same thing can happen with a air compressor. Variations in load in time with compressor piston travel.
 
I got this $15,000 copier from a semi truck heading to a land fill. The whole truck was loaded with furniture and stuff that a local bank was throwing away. I put the copier in my bedroom and plugged it in into a regular receptacle.

I never new that it needs to be on a dedicated circuit.
Thanks

I'll check whats the current draw on it.
 
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