Elec Svc Needed?

[ToddRD]

Hi all - I have a 40A breaker for a 160 amp welder and a plasma cutter. I am looking at the Miller Thunderbolt XL AC/DC 225/150 and it shows an input requirement of 230V 47.5A. Can I use the 40 amp service safely with the miller or should I break out another outlet/breaker for it? I don't want to lose the protection for the smaller machines. My thoughts were that if I use the 40A breaker for the Miller it will just trip sooner and protect it more by not letting me go to the upper limit of the machine. The area I am working in has a 100A service in a GE panel. Thanks in advance.

[MAC702]

First, the breakers do not protect the machines. They protect premesis wiring. What wires are connected between your existing 40A breaker and welder receptacle? I'm betting it's either #10 or #8.

Even if it's #10, the duty cycle of the Miller Thunderbolt is so low that you can legally and safely change to the 50A breaker for a receptacle that IS DEDICATED to it or other low duty cycle welding machines.

You are also correct that you can plug the machine in as is and just not be able to use its upper limits without the breaker tripping.

Do you have room for more circuits in that small 100A panel? Do you have TQL, THQL, or some other type breakers in it?

[ToddRD]

MAC - The wires are 8/3. The panel is a full panel so room is not an issue. I have broken out a 15A for lights, a 20A for 120v outlets and a separate breaker for a well pump that is only used to water the yard. The well and welders are not used at the same time. My air compressor is small enough to not demand much. I believe there are TQL breakers in the box now.

Thanks for your reply on the comparison yesterday. I am looking to Miller now because of availability and service. The Firepower 235 looks nice but if you can't readily get parts your out of luck. Just my take on it.

Thanks for all the advice.

[MAC702]

The last 100A GE TQL panel I was in had provisions for tandem breakers in the bottom two slots of each side, allowing me to use GE Type TR tandem breakers for four more circuits. But you say space is NOT an issue?

Anyway, with #8 wires, you can swap to a 50A breaker and go to town with no worries, even for machines with 100% duty cycles. We are talking about COPPER wires, right? If aluminum, than the small duty cycle rules apply again.

[ToddRD]

Since last writing I dug out the paperwork on the panel. It's a 125A GE Powermark Gold Load Center with 12 1" or 24 1/2" spaces. It is identified as TLM1212CCU. I only use copper. The breaker that provides for this box at the house is a 100A. Thanks again.

[MAC702]

Since last writing I dug out the paperwork on the panel. It's a 125A GE Powermark Gold Load Center with 12 1" or 24 1/2" spaces. It is identified as TLM1212CCU.
Interesting. What do you have that shows you can use 1/2" breakers? Usually, the 1212 in the model of the panel means it has 12 fullsize spaces and is also only designed for a maximum of 12 circuits, meaning you can't use tandem or 1/2-size breakers. Do they fit in your panel?

For example, the last TQL panel I was in had a 1216 in the model number, meaning 12 spaces, but with up to four tandems allowed for up to 16 total circuits. Many modern 100A panels are 1224, meaning 12 spaces, but tandems are allowed in all of them for up to 24 circuits.

I realize this is just side information, though. You already have the ability to run the new machine at maximum output by just swapping the breaker.

[ToddRD]

Just reading the label that came with it as a reference along with the limited paperwork.