# Fused disconnect on welder circuit



## leeko (Aug 17, 2014)

Hi all, 

My garage has a 20amp 220v circuit on awg12 wire,  which I can't upgrade (yet). I have a couple of 220v welders (175amp mig and 180amp stick), which have been running fine on the circuit. I don't hit the top end often,  and then only for short runs. I've yet to trip the breaker (yet). 

I'd like to add a disconnect for the entire 220v service in the garage,  so I can switch everything off when I'm not working. I have a 30amp fused safety switch which I was planning to use.  

My question is related to the fuses.  They're time-delay fuses,  which I think is better for the welder circuit to avoid nuisance trips.  But,  what rating should the fuses be? The 20amp breaker and 12awg wire "tolerate" the higher current load of welding for short times,  but is that the same for the fuses? I.e. they should be rated at 20amp? Or will they trip constantly while welding? 

Thanks, 

Lee



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## xalky (Aug 17, 2014)

The fuses should be rated at 20 amps. A higher rated fuse would offer no circuit protection.


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## JimDawson (Aug 17, 2014)

This is an excerpt from the National Electric Code.  This pretty much applies to all home type wiring.

* Unless specifically permitted in Section 
240.4(E) through (G), *the overcurrent *
*protection shall not exceed* 15 amperes 
for 14 AWG, *20 amperes for 12 AWG*, and 
30 amperes for 10 AWG *copper*; or 15 
amperes for 12 AWG and 25 amperes for
 10 AWG aluminum after any correction
factors Tor ambient temperature and 
number of conductors have been applied. 

20 Amp time delay fuses should be OK.  I think that with a 20 amp breaker ahead of the fuses, you can use higher amperage fuses (or copper bars) in the disconnect and use it as a service disconnect rather than circuit protection. Check your local electrical code or with a local electrician.


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## hardware1170 (Aug 18, 2014)

If you find that you are blowing the 20A fuse and not tripping the breaker you would be safe to go to a 25A fuse.


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## Hawkeye (Aug 18, 2014)

If you have proper overcurrent protection on the supply, virtually any size fuse will work. If too much current is drawn, the supply breaker will blow. If all you want is a disconnect, why not install a 30 amp, 2-pole switch instead?

The only advantage of a fused disconnect is if your supply is at a higher current than the device in question requires.


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## leeko (Aug 19, 2014)

That makes sense.  All I want is a disconnect,  so I'll plan to install copper bars in place of the fuses and treat it as a switch. 

Thanks! 

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## jim18655 (Aug 19, 2014)

Either put 20 amp time delay fuses in or 2nd choice would be 25 or 30 amp fuses since you have the breaker at the feed end. Copper bars will be a big code violation since they aren't "listed or labeled" parts. Last thing you need is a fire and have an insurance agent deny the claim because you used copper bars, even though they didn't cause the fire.


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## Vladymere (Aug 19, 2014)

Why do you want a disconnect?  What advantage willit provide you?

Vlad


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## Cholmes (Aug 19, 2014)

Vladymere said:


> Why do you want a disconnect?  What advantage willit provide you?
> 
> Vlad



Easier to grab a big handle on a disconnect in an emergency that fumbling for a breaker tab.


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## countryguy (Aug 19, 2014)

All great stuff here!  And if you really wish to know the draw ... Hook up a Clamp on Ammeter. There are really cheap these days!  Just a note to say why wonder what you are pulling and pop up the DigiMeter to see it live.    I love mine!  Fun to experiment w/.   
Overall, sounds like you are fine overall and are keeping it SAFE!    
 When you say "upgrade the wiring yet" are you looking to put in a #6 / 50amp or something later on?   

anyway.... enjoy the toys! 
CG


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## John Hasler (Aug 19, 2014)

Cholmes said:


> Easier to grab a big handle on a disconnect in an emergency that fumbling for a breaker tab.



In that case you really want a contactor so that you can kill power by hitting a button.


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## leeko (Aug 19, 2014)

Main reasons for the disconnect are: 
1) the breaker box is in the basement, the disconnect will be close to the machines in the garage
2) I'd like to be able to easily kill all of the 220v to the garage when I'm not going to be working in there. 
Thanks for all the advice 

Lee

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## leeko (Aug 19, 2014)

Countryguy: yes,  assuming my job situation works out and we get to stay in our current place permanently,  I'll be running a 100a sub panel out to the garage, and hiring an electrician to do it all right 

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## James41 (Aug 20, 2014)

Yes we should use at least at most  120 amp. It will never be harmful for your welder circut. It will make your machine circuit never stop.


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## theoldwizard1 (Aug 20, 2014)

The purpose of any fuse/breaker is to protect the WIRE between the load center and the load.  Assuming that your 240V receptacle is the only load on that circuit, a fuse/breaker on that circuit in the garage is redundant because the fuse/breaker at the main load center is protecting the wire.



leeko said:


> I'd like to add a disconnect for the entire 220v service in the garage, so I can switch everything off when I'm not working. I have a 30amp fused safety switch which I was planning to use.



First, if the switch is fused, you should be able to swap in smaller rated fuses.  I would use a slow blow 20A fuse.

Second, while the "code lawyers" will probably say otherwise, I would go ahead and use it, even with the 30A fuse.  It will work fine as a disconnect.  If you do overload the circuit the fuse/breaker in the main load center will trip and you will have to walk to that location to reset it.


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## John Hasler (Aug 20, 2014)

theoldwizard1 said:


> The purpose of any fuse/breaker is to protect the WIRE between the load center and the load.  Assuming that your 240V receptacle is the only load on that circuit, a fuse/breaker on that circuit in the garage is redundant because the fuse/breaker at the main load center is protecting the wire.
> 
> 
> First, if the switch is fused, you should be able to swap in smaller rated fuses.  I would use a slow blow 20A fuse.
> ...



You're right.  Just use it as-is.


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## James41 (Aug 23, 2014)

James41 said:


> Yes we should use at least at most  120 amp. It will never be harmful for your welder circut. It will make your machine circuit never stop.


Hmm 120 amp is essential.


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## dogman1313 (Sep 21, 2014)

It's funny that people quote you the electrical code & tell you not to fuse over 20 amps, then you have the others say go ahead. Just remember the NEC is written for safety for electrical and fire hazards. But it's not their house or garage that may burn down. Please do it right. Consult a qualified electrician. It may cost you a little bit, but your tools are valuable to you.


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## Falcon67 (Sep 21, 2014)

The deal is, that if the shop feed is protected by a 20A breaker at the source (the house panel) then anything in the shop is just a disconnect.  My shop is fed with 2-2-2-4 MHF and I used a 20 slot 100A panel in the shop with a 100A main breaker.  The feed is breakered at 70A at the source, which is a panel installed by the utility right off the house meter.  I can shut down the entire shop at the shop panel, or at the breaker panel on the far side of the house.  The 2-2-2-4 is good to a max of 90A, I used 70A because that's what HD had on the shelf and it's plenty, even with 960 sq/ft full of stuff.


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