Power tools extension cord voltage drop - more than ...

Another thing I thought about, is the wiring in the added garage circuit. I put it in myself - w/ GFCI - yrs ago when 20A resid. circuits still used 12ga.
It's a home run from the load center to the 1st outlet on that circuit + 2 outlets off of it. Don't know the exact distance, but I'd guess 45 ft to 1st outlet ( I tested from last nite). The other outlets on the circuit are ~ 15' & 20' farther. Nothing else runs on that circuit - unless I plug it in.

But that means there's already a 45' to 60' - 65' "cord" in the equation (for V drop), before plugging in cords. IF... I run it off the farthest outlet, then another 75' (min.) of ext. cord, to reach most of the yard. (may have to set a sub-panel by the mail box - LOL).
I can easily measure V drop using 1- 50', 12ga cord, then on 100' of 12 ga. I'm guessing on 100', 12ga cord, I'll see about 112 V (if no load V=120). Even less if it's really hot outside.
Whether I need to (get a loan) for a 25' - 50', 10ga cord, not sure.

I read one reviewer of this trimmer say "it runs fine on 100' 12ga cord." Maybe, but it may be slowly shortening the tool's life.


"series-wound brush-type motor... will not be harmed by low voltage or high source impedance. ...and draw less current, and generate less heat"
If that's true, why do all quality mfg's make a very big deal about not running tools (outdoors, attended to) on lighter extension cords or circuits than they or some authority recommends?
Why do more expensive (some inexpensive) motors have thermal protection (or circuit breakers) built in, if all that running them at lower voltage will do, is (mostly?) cause a performance decrease? I don't mean to be sarcastic - just whether I understand you correctly?

a range of acceptable under/over rated voltages of +/- 10% over motor rating.
I could ask to speak to their engineering dept - see what they say. -10% would be 108V on low side, which is fairly low. IFF... motors are specifically designed for that, it might be OK. I don't know I've ever seen (anywhere) a power tool mfg state an acceptable voltage range. It may be in design specs, but I've never seen those specs hinted at,

Winnie, I appreciate your comment - it's not a DIY site. I'm a bit past diy'er when it comes to electricity. As you hinted, I'm trying to compare theoretical vs. real world effects of "too much V drop." Based on research, I was surprised at the measured V drop vs. tables & calculators show.

I'm not (totally) sure about part of your statement. The motor on this trimmer or on my 240V table saw can't violate laws of physics or of electricity.

Thanks for the replies.Another thing I thought about, is the wiring in the added garage circuit. I put it in myself - w/ GFCI - yrs ago when 20A resid. circuits still used 12ga.It's a home run from the load center to the 1st outlet on that circuit + 2 outlets off of it. Don't know the exact distance, but I'd guess 45 ft to 1st outlet ( I tested from last nite). The other outlets on the circuit are ~ 15' & 20' farther. Nothing else runs on that circuit - unless I plug it in.But that means there's already a 45' to 60' - 65' "cord" in the equation (for V drop), before plugging in cords. IF... I run it off the farthest outlet, then another 75' (min.) of ext. cord, to reach most of the yard. (may have to set a sub-panel by the mail box - LOL).I can easily measure V drop using 1- 50', 12ga cord, then on 100' of 12 ga. I'm guessing on 100', 12ga cord, I'll see about 112 V (if no load V=120). Even less if it's really hot outside.Whether I need to (get a loan) for a 25' - 50', 10ga cord, not sure.I read one reviewer of this trimmer say "." Maybe, but it may be slowly shortening the tool's life. @drcampbell (not the same Campbell that taught ground water remediation?) -If that's true, why do all quality mfg's make abig deal about not running tools (outdoors, attended to) on lighter extension cords or circuits than they or some authority recommends?Why do more expensive (some inexpensive) motors have thermal protection (or circuit breakers) built in, if all that running them at lower voltage will do, is (mostly?) cause a performance decrease? I don't mean to be sarcastic - just whether I understand you correctly? @hbiss - "...I could ask to speak to their engineering dept - see what they say.on low side, which is fairly low. IFF... motors are specifically designed for that, it might be OK. I don't know I've ever seen (anywhere) a power tool mfg state an acceptable voltage range. It may be in design specs, but I've never seen those specs hinted at,Winnie, I appreciate your comment - it's not a DIY site. I'm a bit past diy'er when it comes to electricity. As you hinted, I'm trying to compare theoretical vs. real world effects of "too much V drop." Based on research, I was surprised at the measured V drop vs. tables & calculators show.I'm not (totally) sure about part of your statement. The motor on this trimmer or on my 240V table saw can't violate laws of physics or of electricity.

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