[jklingel]

I recently rented a 15 amp Husky 14" concrete cutting saw, and paid hell keeping it from tripping breakers. I tried 2 different one-item, 20A dedicated circuits and two different saws. I unplugged the one item on either circuit before I tried running the saw. After many frustrating trips inside to reset breakers, I finally figured I better change since the saw would not. If I cut 5-10 seconds, then let the saw spin freely or just stop, repeating this over and over, I could cut across 17" of concrete generally without tripping a breaker. I would then let the saw sit for a minute before resuming sawing another 17" swath. That worked better, but I still tripped a breaker now and then. It was as if the breakers were maybe getting warm from passing too much juice for a prolonged period. ???? I have no idea. I was cutting 2" deep, and never tripped a breaker on start-up or when the blade bound up a bit and the saw was straining. Very odd to me. I could run my 15A skill saw with a diamond blade or my 15A grinder with a gnarly concrete disc as long as I wanted to, but the concrete saw was torture. The house is 4 yrs old and the receptacles are all 20A. Neither of the breakers are GFCI, which concerned me since the saw has a water hose attached to it, but it also has its own GFCI breaker inline. Any ideas, just for my education? I hope to never have to do this type of job again.

 

[Nealtw]

Wonder if the saw was full of dust making it work harder.

 

[jklingel]

Good idea, but very clean. j

 

[seharper]

First time on a task you’ve never done before... any chance you are pushing the tool harder than it was intended? How fast you cut has a big impact on saw current draw; the motor is simply trying to reach balance speed of (line frequency minus a shave). The slower the motor goes (you can hear that), the more it draws.

Also, could your breakers be collectively faulty just to being a very old or obsolete panel?

 

[DanS26]

How long and what size was the extension cord?

 

[Shaneyj]

How long and what size was the extension cord?

This^^
Voltage drops. Motor maintains outout so current goes up. Your breakers were tripping on the thermal element from excessive current.
That's my shot in the dark.

Sent from my SM-G965U using Tapatalk

 

[jklingel]

Thanks for the replies; I will try to answer all. No, I am not pushing the saw, but more babying it. I am very experienced w/ running saws, etc, and know when a saw or other machine is bogging down. Good idea, though. The extension chords were 12 gauge, one 15-20', one about 25'. Breakers SHOULDN'T be weak/worn out (but you never know) as we built the house 4-5 yrs ago. Yes, somehow I think excessive current caused a thermal issue and am wondering if a 15A motor pushing a 14" diamond blade is just asking for trouble. When the renter brought the blade out, I was amazed. I figured it would be 8-10". Thanks again.

 

[DanS26]

Next time rent one of these or something similar........

https://www.amazon.com/Makita-EK7651H-14-Inch-Stroke-Cutter/dp/B00D4NTLMS

 

[jklingel]

They had two gas powered saws, but the one with depth control was huge and not easy to get into my space, and the smaller one was hand-held with no depth control. I suspect that either one would tear the guts out of the electric one I rented. BTW: There ain't gonna be a "next time"! I am burned out on this kind of work and will probably just bite the bullet and hire someone if I ever need to so such fun stink again. Wimpy, I know, but time is going by..... Thanks for the link anyway.

 

[carmusic]

saw probably has worn brushes or bearings, typical for rental stuff, already rented a gas one that died when cutting (motor was destroyed, had to get another one to finish the job...)

 

[jklingel]

I will mention that to the rental. They seem sincerely interested in resolving this.