rlane00
Member
- Location
- Clackamas, OR
- Occupation
- Electrical Contractor, Supervising Electrician, Electrical Engineer
A house we wired has some of the lights dim when the homeowner runs the vacuum cleaner (or a hole hawg), but not when a slighter greater resistive load from a heat blanket is applied. We are trying to figure out why that is happening so that we can remedy the situation and would appreciate any advice.
Here is some additional information about the situation:
- The house has a 320-a continuous meter-base feeding two main-breaker panels. One panel feeds a sub-panel dedicated to high-end audio equipment.
- There is a whole house generator backing up both main panels with two transfer switches.
- There is a variety of lighting in the house, including integrated LED ceiling cans, wall-mounted library sconce lights, vanity lights, LED pucks, etc.
- The house has a lot of Lutron Caseta dimmers w/o neutral (PD-6WCL), but we removed those as part of troubleshooting and the issue persists - so they don't appear to be a factor.
- All lights and dimmers work fine all of the time... as long as the vacuum cleaner (or similar device such as whole hawg) is not running. When the vacuum is plugged into a receptacle that also has lights on the same circuit, then some of the lights dim considerably, and stay dim the whole time the vacuum is running (not just due to inrush). The lights that dim are generally wall-mounted sconces with screw-in LED bulbs), while other lights on the same circuits (such as the LED can lights) operate normally.
- We measured voltage at both main panel(s) at 122 volts.
- We measured voltage at the switch location at 121 volts (without any load)
- After turning on the lights (with regular switch, not dimmer) and plugging in the vacuum, voltage initially dipped to 104V (current of 17.8 amps), then recovered to 110 v (current of 8.8 amps) -- and only the wall sconce lights dimmed and stay dimmed while vacuum ran.
- After turning on the lights (with regular switch, not dimmer) and plugging in the heat blanket, voltage dipped to 102.4V -- and all the lights operated normally while vacuum ran.
- Since the problem appeared to be related to just fixtures with screw-in LED bulbs (but not every fixture with screw-in bulbs), we tried a few other bulb types (CFL, incandescent, a couple of different LEDs). They all had the same problem.
- We then used a table lamp with screw-in bulb to try in different parts of the house to see if that fixture dimmed with the vacuum running or not. The results were:
- The table lamp dimmed (when vac was running) when plugged into a variety circuits from both main panels, both A and B phases, including the circuits that experienced the dimming fixtures.
- The table lamp did NOT dim (when vac was running) when plugged into other circuits from both main panels, both A and B phases.
- The utility has apparently investigated their side of things and said everything is fine on their end - no loose neutrals or anything like that.
We are planning to go back and do the following additional steps:
- Bypass all the in-house wiring and temporarily provide power (via extension cord) to one of the fixtures that dims and see what happens when we run only the vac and that one fixture. If the fixture dims, then we should be able to rule out issues with any house wiring. If fixture doesn't dim, use that temp cord to feed power to devices earlier in the circuit to see if we can isolate the section causing the problem.
- Also bring a keyless with us and replace one of the fixtures that dims with the keyless to see if they all dim, or if the keyless doesn't.
Any other ideas or suggestions? Thanks!
Here is some additional information about the situation:
- The house has a 320-a continuous meter-base feeding two main-breaker panels. One panel feeds a sub-panel dedicated to high-end audio equipment.
- There is a whole house generator backing up both main panels with two transfer switches.
- There is a variety of lighting in the house, including integrated LED ceiling cans, wall-mounted library sconce lights, vanity lights, LED pucks, etc.
- The house has a lot of Lutron Caseta dimmers w/o neutral (PD-6WCL), but we removed those as part of troubleshooting and the issue persists - so they don't appear to be a factor.
- All lights and dimmers work fine all of the time... as long as the vacuum cleaner (or similar device such as whole hawg) is not running. When the vacuum is plugged into a receptacle that also has lights on the same circuit, then some of the lights dim considerably, and stay dim the whole time the vacuum is running (not just due to inrush). The lights that dim are generally wall-mounted sconces with screw-in LED bulbs), while other lights on the same circuits (such as the LED can lights) operate normally.
- We measured voltage at both main panel(s) at 122 volts.
- We measured voltage at the switch location at 121 volts (without any load)
- After turning on the lights (with regular switch, not dimmer) and plugging in the vacuum, voltage initially dipped to 104V (current of 17.8 amps), then recovered to 110 v (current of 8.8 amps) -- and only the wall sconce lights dimmed and stay dimmed while vacuum ran.
- After turning on the lights (with regular switch, not dimmer) and plugging in the heat blanket, voltage dipped to 102.4V -- and all the lights operated normally while vacuum ran.
- Since the problem appeared to be related to just fixtures with screw-in LED bulbs (but not every fixture with screw-in bulbs), we tried a few other bulb types (CFL, incandescent, a couple of different LEDs). They all had the same problem.
- We then used a table lamp with screw-in bulb to try in different parts of the house to see if that fixture dimmed with the vacuum running or not. The results were:
- The table lamp dimmed (when vac was running) when plugged into a variety circuits from both main panels, both A and B phases, including the circuits that experienced the dimming fixtures.
- The table lamp did NOT dim (when vac was running) when plugged into other circuits from both main panels, both A and B phases.
- The utility has apparently investigated their side of things and said everything is fine on their end - no loose neutrals or anything like that.
We are planning to go back and do the following additional steps:
- Bypass all the in-house wiring and temporarily provide power (via extension cord) to one of the fixtures that dims and see what happens when we run only the vac and that one fixture. If the fixture dims, then we should be able to rule out issues with any house wiring. If fixture doesn't dim, use that temp cord to feed power to devices earlier in the circuit to see if we can isolate the section causing the problem.
- Also bring a keyless with us and replace one of the fixtures that dims with the keyless to see if they all dim, or if the keyless doesn't.
Any other ideas or suggestions? Thanks!
