Help/advice with 240V in my garage

[CatSplat]

So I'm a relative newcomer to Garage Journal, having finally gotten my first garage a couple months ago. When we bought the place, the previous owner noted that there was no 240V supplied to the garage and I took that at face value. However, while taking a look at things the other day I noticed that it seems that the garage actually does have a 240V feed but it's only been effectively used as a pair of 120V feeds.

Here's the house panel - the garage circuit is the pair of 40A breakers at top left of the panel under the main 100A breakers. The panel and breaker arrangement appears to be such that each of the two 40A breakers supplying the garage are from opposite legs of the main house feed. Outgoing wire to the garage is 8/3.

And here's the panel in the shop - as far as I can tell, each leg of the feed from the house is being used to supply one leg of the subpanel, but they are never used to create a 240V circuit.

So my question is, considering the power arrangement, is it possible to (via the existing hardware or by installing a different subpanel that allows it) to get a 240V circuit working and still retain the 120V circuits already installed? Or would I need to have another feed line and subpanel installed for a dedicated 240V circuit? It would need to support a small TIG welder, which would be the goal of the exercise.

Keep in mind that I only know enough about wiring to get myself in trouble, I'm only looking to know whether this is possible and I'd be getting a professional to do any installation.

 

[Rock knocker]

Your only issue is breaker space. With the panel you have now, you could add 120 single pole and/or 240 two pole slimline breakers and get up to four additional single pole circuits or two double pole circuits.

That is assuming the additional circuits are allowed by your panels manufacturer.

 

[sberry]

The other issue is wire size,,, what is a small tig welder? It would really need to be an inverter.

 

[CatSplat]

OK, good to know about the panel space - I think I see what you're saying, the bottom section of the panel has one available slot but I would need to put in slim breakers on the upper part to gain enough space for the 240V breaker. It might be easier to just replace the panel box itself and move the existing breakers over.

As far as a "small TIG" goes, I was thinking of something like this:
http://www.everlastwelders.ca/tigwelders/powertig-185-micro-with-foot-pedal.php

Max inrush 22A@240V, working load 14A@240V.

 

[Rock knocker]

..... I would need to put in slim breakers on the upper part to gain enough space for the 240V breaker

And that is only if it is allowed by the manufacturer.


Looks like a nice little welding machine.

 

[AlwaysFixingSomething]

That 100 amp backfeed breaker needs a hold down kit.

 

[Norcal]

That 100 amp backfeed breaker needs a hold down kit.

It may already have one, you cannot see a Siemens hold down kit installed unless your looking at the breaker opposite the lug end, but since the OP is in Canada, it may not be required.

 

[CatSplat]

And that is only if it is allowed by the manufacturer.

Understood! I think I will end up having a larger panel installed with a main breaker/shutoff, that should make wiring easier and I won't have to dole out for a bunch of replacement breakers.

That 100 amp backfeed breaker needs a hold down kit.

I have to admit, I think you've exceeded the bounds of my electrical terminology knowledge. A backfeed breaker is one that allows you to hook up a generator to power the house, I think? What does the hold down kit do that the current setup isn't doing properly? The panel (as far as I know) is exactly as it was built along with the house in 2002.

 

[jvitez]

"So my question is, considering the power arrangement, is it possible to (via the existing hardware or by installing a different subpanel that allows it) to get a 240V circuit working and still retain the 120V circuits already installed? "

Yes. The key is that it's 8/3 wire feeding the subpanel. If it was 8/2, you could only get 240V circuits.

Each leg of the bus bar is fed with one hot feeder wire, so 120V to each leg. A single pole breaker contacts only one leg, therefore 120V. A dual pole breaker contacts both legs, therefore 240V.

For a dedicated 240V circuit, you only need two hot conductors, no neutral wire. For a 120/240V circuit you need two hots and a neutral, like an electric dryer circuit. For your welder you would only need NM-D X/2 wire, 10/2 for 30 amps, 8/2 for 40 amps.

If it were me, while the wall is open and everything is accessible, I would install a new subpanel with more breaker spaces. It gives future flexibility, they're cheap, and then you don't need to stuff a bunch of wire together with tandem breakers.

Eg. : http://www.homedepot.ca/product/12-24-circuit-100a-120-240v-siemens-loadcentre/941191

You keep to Siemens panels which are good quality, it's the same as your main panel so only brand of breakers needed, it has 12 full breaker spaces, but if you need more in the future you can start substituting tandem breakers up to a max of 24 circuits total.

 

[jvitez]

Our posts crossed. I see you want a main breaker subpanel panel. Good idea.

 

[Rock knocker]

I have to admit, I think you've exceeded the bounds of my electrical terminology knowledge. A backfeed breaker is one that allows you to hook up a generator to power the house, I think? What does the hold down kit do that the current setup isn't doing properly? The panel (as far as I know) is exactly as it was built along with the house in 2002.

The house main panel was not supplied with a built-in main breaker, so they back-fed into the 100A two-pole breaker in the upper left of the house panel to act as a main. In the US, current code would require this back feed to be secured to the panel with a strap is it could not be mistakenly removed, and to act as a reminder to those working on the panel that the lugs on that breaker are always hot.

Whether this is required in Canada, or was required when the house was built, I do not know.

 

[C96]

Just remember, even though you upgrade the panel to a larger one you still are limited to 40 amps unless of course you upgrade the feeder as well.

 

[CatSplat]

"So my question is, considering the power arrangement, is it possible to (via the existing hardware or by installing a different subpanel that allows it) to get a 240V circuit working and still retain the 120V circuits already installed? "

Yes. The key is that it's 8/3 wire feeding the subpanel. If it was 8/2, you could only get 240V circuits.

Each leg of the bus bar is fed with one hot feeder wire, so 120V to each leg. A single pole breaker contacts only one leg, therefore 120V. A dual pole breaker contacts both legs, therefore 240V.

For a dedicated 240V circuit, you only need two hot conductors, no neutral wire. For a 120/240V circuit you need two hots and a neutral, like an electric dryer circuit. For your welder you would only need NM-D X/2 wire, 10/2 for 30 amps, 8/2 for 40 amps.

If it were me, while the wall is open and everything is accessible, I would install a new subpanel with more breaker spaces. It gives future flexibility, they're cheap, and then you don't need to stuff a bunch of wire together with tandem breakers.

Eg. : http://www.homedepot.ca/product/12-24-circuit-100a-120-240v-siemens-loadcentre/941191

You keep to Siemens panels which are good quality, it's the same as your main panel so only brand of breakers needed, it has 12 full breaker spaces, but if you need more in the future you can start substituting tandem breakers up to a max of 24 circuits total.

Thanks for the excellent and detailed post, that confirms what I'd gathered so far and the extra information about wiring for the welder is very much appreciated. I agree that a new panel is the best solution and will probably save me some potential future headaches. I wish the previous owner had installed that larger panel to begin with, haha! Seems like a silly way to save $20.

The house main panel was not supplied with a built-in main breaker, so they back-fed into the 100A two-pole breaker in the upper left of the house panel to act as a main. In the US, current code would require this back feed to be secured to the panel with a strap is it could not be mistakenly removed, and to act as a reminder to those working on the panel that the lugs on that breaker are always hot.

Whether this is required in Canada, or was required when the house was built, I do not know.

Aha, I see what you mean with how the main breaker is tied into the main feed. The next time I talk to an electrician I'll be sure to ask them if the hold-down should have been installed in the first place. Thanks for the tip!

Just remember, even though you upgrade the panel to a larger one you still are limited to 40 amps unless of course you upgrade the feeder as well.

Yessir, some initial research tells me that Canadian code is a bit different than the NEC and may allow 50A over 8/3 NMD90 (obv. a 50A 75-deg double pole would need to be installed at the main panel if this is indeed allowed) but for now I'll just play it safe and manage the 40A I have.

 

[Rock knocker]

Aha, I see what you mean with how the main breaker is tied into the main feed. The next time I talk to an electrician I'll be sure to ask them if the hold-down should have been installed in the first place. Thanks for the tip!

It may not have been a requirement back then. It certainly is a cheap addition.

 

[Norcal]

It may not have been a requirement back then. It certainly is a cheap addition.

The hold down will only fit certain locations, but NEC/CEC requirements can vary.