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Message
Dimming lights when I run power tools
Posted on 4/20/16 at 11:56 am
Posted on 4/20/16 at 11:56 am
Okay, so I finally decided to try and solve the mystery of my dimming lights, and think I need the OB's help with this one. I have a 200A main panel and a 100A panel for my shop. All breakers, outlets, and wiring are rigged for 20A (except appliances).
When I use any type of load power tool in any outlet, my lights dim and flicker in the house, and I can sometimes get my DirectTV box to shut off. Welding machine and cutoff saw do it the most. The cutoff saw is 15A, and idk about the welding machine, but I don't go too heavy on it. I have only tripped the breaker twice using the welding machine. Both of those get used from a dedicated 20A in the shop. When I get on the cutoff saw hard, they for sure dim.
The problem is that the lights even dim for a second when I use my 7.5A angle grinder from an outlet in the front of my house. I can also make it happen when I use a 10A heat gun or hair dryer from an interior outlet. Just barely dims when my AC kicks on.
Is the power line coming to my house too small or something? It looks to be the same aluminum gauge running to every house, but mine runs like 150-175ft from the pole
When I use any type of load power tool in any outlet, my lights dim and flicker in the house, and I can sometimes get my DirectTV box to shut off. Welding machine and cutoff saw do it the most. The cutoff saw is 15A, and idk about the welding machine, but I don't go too heavy on it. I have only tripped the breaker twice using the welding machine. Both of those get used from a dedicated 20A in the shop. When I get on the cutoff saw hard, they for sure dim.
The problem is that the lights even dim for a second when I use my 7.5A angle grinder from an outlet in the front of my house. I can also make it happen when I use a 10A heat gun or hair dryer from an interior outlet. Just barely dims when my AC kicks on.
Is the power line coming to my house too small or something? It looks to be the same aluminum gauge running to every house, but mine runs like 150-175ft from the pole
This post was edited on 4/20/16 at 12:05 pm
9
Posted on 4/20/16 at 11:57 am to Hammertime
your tool could be too big.
twss
twss
Posted on 4/20/16 at 12:07 pm to Hammertime
You could have one leg loaded more than the other.
Is the welding machine 110 or 220?
What size wires are feeding everything?
Do the lights dim when you fire a saw up but come back bright if the load isn't heavy?
Is the welding machine 110 or 220?
What size wires are feeding everything?
Do the lights dim when you fire a saw up but come back bright if the load isn't heavy?
Posted on 4/20/16 at 12:21 pm to Hammertime
Measure your incoming line voltage. Right now mine is 250/125VAC. If you're below 220/110 that could be the problem. If so, contact power company about raising their line voltage or changing taps on your transformer.
Posted on 4/20/16 at 12:21 pm to Hammertime
Current in-rush is a bitch ain't it? There isn't much you can do about it, power tools consume far more power than household lights and the current draw is going to pull down the voltage a bit and dim the lights a little. You can see if the utility will run a heavier line to your house (for some reason my house has much thicker cables than any of my neighbors) or you can run a UPS for things like your cable box.
This post was edited on 4/20/16 at 12:22 pm
Posted on 4/20/16 at 1:06 pm to Hammertime
Voltage sag at the lights is the direct cause for the dimming (obviously).
The voltage sag itself is caused/exacerbated by a couple of issues, most likely either an undersized transformer or voltage drop (which is a result of the additional current you draw when you run relatively large loads like a welding machine or power tools).
Voltage drop is caused by the resistance in the wire from the transformer all the way to the point of the system where you're seeing voltage sag, as well as by the total amps you are drawing at any given point. This includes the service conductors to the house and any conductors from there to additional panels and then on to the lights themselves. The resistance in the wire is increased when the wires are either small or they run a long way.
So, you have a couple of options:
Increase the wire size from the pole to your panel
Increase wire size from the panel to the lights
Increase XFMR size
Also, if your 100A shop panel is sub-fed through your 200A main panel, you could up the wire size from the main to the sub panel (or find a shorter route, which is unlikely). I would check the available voltages at the panels and at the lights with a meter to see what voltage your system is actually maintaining when the power tools are not in use. If they're low to begin with, I would think you probably are looking at voltage drop issues in the cables.
Also, IF the XFMR has adjustable taps on it (i don't know what kind the utility uses, but it's worth asking because it makes for an easy fix if so) you could ask them to adjust the tap setting on the XFMR to account for your long runs. This would change the nominal voltage on the XFMR secondary side, usually in 2.5% increments. For example, if the XFMR is single phase, 7200V:220V, moving the XFMR tap up would change the voltage to 7200V:225.5V.
The voltage sag itself is caused/exacerbated by a couple of issues, most likely either an undersized transformer or voltage drop (which is a result of the additional current you draw when you run relatively large loads like a welding machine or power tools).
Voltage drop is caused by the resistance in the wire from the transformer all the way to the point of the system where you're seeing voltage sag, as well as by the total amps you are drawing at any given point. This includes the service conductors to the house and any conductors from there to additional panels and then on to the lights themselves. The resistance in the wire is increased when the wires are either small or they run a long way.
So, you have a couple of options:
Increase the wire size from the pole to your panel
Increase wire size from the panel to the lights
Increase XFMR size
Also, if your 100A shop panel is sub-fed through your 200A main panel, you could up the wire size from the main to the sub panel (or find a shorter route, which is unlikely). I would check the available voltages at the panels and at the lights with a meter to see what voltage your system is actually maintaining when the power tools are not in use. If they're low to begin with, I would think you probably are looking at voltage drop issues in the cables.
Also, IF the XFMR has adjustable taps on it (i don't know what kind the utility uses, but it's worth asking because it makes for an easy fix if so) you could ask them to adjust the tap setting on the XFMR to account for your long runs. This would change the nominal voltage on the XFMR secondary side, usually in 2.5% increments. For example, if the XFMR is single phase, 7200V:220V, moving the XFMR tap up would change the voltage to 7200V:225.5V.
Posted on 4/20/16 at 1:06 pm to Hammertime
Have you tried running an extension cord from your neighbors house?
Posted on 4/20/16 at 1:12 pm to Hammertime
quote:
The problem is that the lights even dim for a second when I use my 7.5A angle grinder from an outlet in the front of my house. I can also make it happen when I use a 10A heat gun or hair dryer from an interior outlet. Just barely dims when my AC kicks on.
Then you're having voltage sag issues at both panels. Probably correct in your assessment that the power line coming to the house is too small. The XFMR tap thing would still work though if the XFMR has movable taps. Otherwise it's probably a wire size thing, but the XFMR could be undersized. Need to get the XFMR size and a load check on your incomer to be sure though.
Posted on 4/20/16 at 2:04 pm to Hammertime
Start with your extension cords for your tools, they may be too long or too weak. 18 g cords are just too small for most heavy tools but people buy on price and then buy them too long.
Next I would look at the circuits you are plugging in to. You may have too many in series sharing the breaker. I prefer to have a dedicated 20 amp breaker circuit on my bench just for tools.
Not sure of all the effects it may have but perhaps your ground is bad, check it at the breaker box, it will be a solid wire going down to the ground and attached to a rod that should be inserted 4-8' into the soil.
Next I would look at the circuits you are plugging in to. You may have too many in series sharing the breaker. I prefer to have a dedicated 20 amp breaker circuit on my bench just for tools.
Not sure of all the effects it may have but perhaps your ground is bad, check it at the breaker box, it will be a solid wire going down to the ground and attached to a rod that should be inserted 4-8' into the soil.
Posted on 4/20/16 at 3:18 pm to Hammertime
Do you have any problems with your 240 volt appliances? If not it sounds like it could be a problem with your neutral.Corrosion can drop the effective size of your neutral so that even small loads will overload its capacity. Check from your weatherhead to your meterbase and from your meterbase to your breaker panel. Have the utility check the neutral on your triplex service drop.
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