Help with Welder wiring.

I have a question on wiring up a welder that I bought at an auction. I’ll give you the facts and then the first two paragraphs of the National Electrical Code. This welder is an Hobart TR-250-HF.

The machine equipment tag reads.

Voltage - 208/240/480 Single Phase
Amps - 118/96/48

The front of the welder has the following:

Stick 310 Amps @ 25% duty cycle
Tig 310 Amps @ 20 duty cycle.

Now from the National Electrical Code:

A. General

630-1. Scope. This article covers electric arc welding, resistance welding apparatus, and other similar welding equipment that is connected to an electric supply system.

B. AC Transformer and DC Rectifier Arc Welders

630-11. Ampancity of Supply Conductors. The ampacity of conductors for ac transformer and dc rectifier arc welders shall be as follows:

(a) Individual Welders. The rated ampacity of the supply conductors shall not be less than the current values determined by multiplying the rated primary current in amperes given on the welder nameplate and the following factor based upon the duty cycle or time rating of the welder.

Duty Cycle 1.00 .90 .80 .70 .60 .50 .40 .30 .20or less
(percent)
Multipilier 1.00 .95 .89 .84 .78 .71 .63 .55 .45

Now for the questions – What breaker amp size to the machine and what size wire to the welder based on the fact that I would like about 20’ of cord so I can roll it outside to weld. Can I use a breaker or should I use fuses?

Thanks,

Jeff

 

You most definately need to know what voltage this machine was running on. There is an input voltage jumper in the machine. There may even be a diagram on the cover somewhere. Most places (normal residential or commercial single pahse service) are going to be 240 so you need to check that the jumpers are connected for that. You could use fuses or breaker. Is there a panel near there,, just put a 60 in and some number 6 to a recept. If you can find a number 6 mobile home cord they work great for these machines. I have a Miller square wave that is similar to that and I really use it only for heli-arc but have it on a 60. These machines actually call for way bigger input stuff but its assuming that you are using it way up in the ranges. You can run a 5/32 lo-hi there with no problem. For full power it needs a number one cable and a 225 breaker,, like if you were trying to air carbon-arc or something.

 

it do'sn't mater much weather use bracker or fuses what is your main panal breakers or fuses if its breakers it should be a 100 amp double pull branch braker. for the wire if you are running the wire inside the wall you can use nylon nmd90 or if you are running the wire on the face you can use BX in ether case it should be #2 copper 2 or 3 conductor depending weather or not your welder uses a nuetrul wire or not most welders do not use a nuetrul wire then run this wire from your main panal to your door and put a welder plug by the door then wire the welder with 20' of #2 2 or 3 conductor cab tire. make sure you wire the cab tire to the 240 volt pins in the welder

 

you do not need a breaker biger then 100 amps as the top amp input is only 96 amps on 240 volt

 

Yes. you probably wouldnt need more than a hundred amps breaker on that,, but it is allowable to 225 on that machine to allow for current in-rush. That thing has a big heavy transformer on it and if you were air arcing or similar operations that tended to short the secondary out where you may have high current spikes on the primary side it may nussiance trip a breaker. Nec allows overbreaker with welders just like motors. However it is recommended to use a smaller one and if there is a problem then increase as necessary to the max limit. I have seen machines trip brkrs using nickel welding rods for some reason,, I think it is the nature of the globular transfer of the metals that tends to increase current draw. Miller suggests 1/0 input for the machine similar to that one without power correction factor and number one with it I believe. You are right about the 96 a requiring only 2 or so,, they might be covering their warranty rear with the larger cables or factoring in-rush current. We run them on lot lighter,, but really less than half way up on the dials tho and obviously its been using under 60 a of current. Never had a trip with it. I usually put a probe on and check when I get a machine but havnt had occasion to do so with that one under load yet.

 

When I purchased it, it was wired for 480 and I have changed the jumpers on the inside for 240 volts. In reading the code book it seems that if I use 96 amps @ the multiplier of .55 for 30% duty cycle it works out to 52.8amps. My plan if it makes sense is to wire in a 60amp breaker and use about 20' of 6-2/with ground for the hookup from the breaker to the welder.

Again this is not going to be used for production just the normal fix this / weld this projects.

Thanks,

Jeff

 

Yup,,, that will work