[Delasangre]

Hey I have a Miller XMT 350 and a Series 70 feeder unit with the factory Bernard gun which according to Miller a 400A gun is included. I am running .045 dual shield steel wire and 23-24.5 volts at 250-350 wire. When welding for a while continuously I have recently started having a problem where I am mid-weld and suddenly the power cuts but itll keep feeding and the machine says HELP-3 on it. If I wait 60 seconds and turn off then on the machine it continues welding. But I usually let it sit and rest for a while. Googling shows this is a code related to the trigger being pressed while booting the machine, but this is not my problem since I am mid weld. Is this overheating the gun? Overheating the machine or what is the problem?

[Delasangre]

Nevermind, I was looking at the wrong manual. This machine has a pretty low duty cycle. At my power levels it says I can only weld for 6 minutes and let it cool down. I have been going for about 20 so it overheated. Help-3 means the machine overheated and it cut power to let the fan get it back to a safe temp.

[sbaker56]

I'm kind of surprised honestly, at those settings you should be roughly around 200-230 amps and even at on single phase that should be around 100% duty cycle. What is the output of your machine saying?

[Delasangre]

I put one of those clamp on Amp meters on the cable and at 24v its running 220a and at 23v I get 200a. Then I finally remembered the arc control. When I turn that from 100% to 60% at 23v I now get 180a.

[sbaker56]

That sound about right, didn't know arc force worked on CV though, learned something new I suppose. Still surprised your hitting thermal overload, when I pulled up the manual for the XMT 350 on single phase, it shows a 100% duty cycle at around 230 amps with a 6 gauge cord and a 70% duty cycle with an 8 gauge one, I have NO idea how the machine could possibly tell a difference unless you can program it accordingly. I'd think that if you weren't within the range of 100% duty cycle, you'd be close enough that unless you were welding continuously with a robot any short breaks you took would be enough to avoid overheating the machine.

Clearly you are overheating through, I'm just very surprised.

[Delasangre]

Me too, maybe I need open up the case and blow the dust out? I am also running 3-phase I think so the duty cycle should be even higher. If it continues I will have to call Miller because the machine isn't more than 2 years old.

[sbaker56]

If you have 3-phase, then something definitely isn't right. You should have 100% duty cycle at up to around 275 amps give or take 10. Also I would assume that for every 10 minute period you'd at least have a minute or two not welding, I don't know what you're doing, but it seems like you'd need to stop to chip slag, reposition, get a drink of water or something at least. So in reality you should probably be good up to around 300 amps or so.

Here is the manual, though I think you've said you found it, the duty cycle chart is a lot higher than you're running.

https://www.millerwelds.com/files/owner ... 5q_mln.pdf

[Arno]

Me too, maybe I need open up the case and blow the dust out?

Definitely do that.

If there's dust and debris caked on the components then it can't shed the heat and will thermally overload much sooner than expected.

Also check that the intake and exhaust vents are not obstructed (eg. dirty filter if present or anything close to the unit) and that (all) the fan(s) is/are spinning freely.

Periodically opening up, examining and cleaning/blowing out the machine can really extend their lifespan.

Take a good look at where the welder is located and what air it's drawing in. It it's ingesting hot air from somewhere else then the duty cycle drops quite a bit as well.

If that's all OK and it still cuts out much too soon then it may need some warranty work. Eg. cooling fins/blocks on the electronics not seated well or thermal conducting compound not applied correctly so it's not distributing the heat.

Bye, Arno.