I’ve got a weird issue with my Harbor Freight v2 40amp plasma. It has the following duty cycles listed in the manual.
40amps 60%
34.6amps 80%
31amps 100%
I don’t have any issues running anything under 40amps, even 37amps is fine. But when i turn the dial to max and the display reads 40amps, the power switch which doubles as a breaker trips after about 60 seconds of cutting. This is not the duty cycle, the machine will stop the torch but remain powered on and a “hot” light will turn on if you hit the duty cycle at any other setting on the dial.
So is the power switch faulty? Is the dial faulty and attempting to go past 40amps?
Any ideas would be great. I guess i can run at 37amps instead of 40 for thicker plate, there’s probably not much difference but i would like to know what’s up with this thing.
Wall wiring is 8 gauge about 18 inches from the panel on a 50amp breaker. The manual calls for 100ft 10 gauge to a 30 amp breaker.
How would i only get 208 at the plug? House is only 10 years old, new 8g wiring, new breaker and plug, 200amp panel on the other side of the wall. Seems like all the components between the power at the street and plasma aren’t lacking…
208 is commercial power (typical of 3-phase), 220-240 is residential.
The amp ratings are optimistic (kind of like how old incandescent light bulbs are measured for brightness at 130V vs the typical 110-120v residential).
The ratings on a functional welder should be sufficient as I have a few friends who have that unit and they leave it pegged.
Most likely you lost the HF lottery where both the max setting of nominally 40A is slightly higher and your breaker is slightly lower and you’re on 220V thus causing more current for a given setting.
But I would first check the current with a clamp because it is possible that your 37A is actually 40A IRL
as most circuit breakers can handle a slight overcurrent for short periods of time and the current handling is determined by dimensional measures so its usually unlikely to be too far off.
Easiest thing to do is take it back and get it replaced if you haven’t had the thing for a while.
I might try to replace the breaker in the machine.
The mechanism that keeps the breaker on is also part of the mechanism that trips the breaker on current overload. Could just be worn out from all the times turning it on and off and the spring inside the breaker is finicky.
I think the breaker doubling as an on-off switch is a cheap design. It saves the manufacture money by not putting in an actual switch. But a majority of the welders and plasma cutters are using this design.
Could also try to measure actual amps the machine is using with an amp clamp. It will tell you if the breaker is bad or the machine is actually using more amps then it’s supposed to.
On some plasma cutters the on /off switch looks like a circuit breaker…but it is not a circuit breaker for over current. It could be a magnetic trip switch, older Hypertherm plasma used this type of switch that would trip when consumables were not properly installed in the torch to minimize the chance of damaging the torch. Before you change the input switch be sure you understand its function! Jim Colt
Thanks for the tips guys. The instruction manual says it doubles as a breaker for over current conditions. For now i guess I’ll just leave it in the high 30s instead of 40. Tightening the wires at the box won’t hurt. I may try to change the switch when i get my new Hypertherm since I’ll be keeping it for a hand torch. .