Adding additional circuits?

[dwall174]

I have a 100-amp Square-D QO series sub panel in my garage with only 2-spaces left.
It's currently only set-up as a 60-amp panel with 6ga. wire & a 60-amp main breaker due to a limited main house service entrance line.



I just picked up a Heat Storm 6000-watt heater for the garage.


The heater is 240-Volts & it draws 25-amps at full power & the owner's manual states to wire it to a 30-amp breaker.
The heater is a 3-wire connection no neutral so, it would be a pretty straight forward normal install. 2 - 10ga. wires, black/red & a 10ga. ground wire in 1/2" EMT conduit.

Being I only have two spaces left; I was wondering if I could run a 40-amp breaker with two 8ga. wires black & red with a 10ga. ground wire & a 10ga. white neutral wire through 1/2" EMT to another 70-amp sub panel like this one.

It would have one tandem 30-amp breaker for the heater, and two 15-amp 120-Volt breakers for a couple of extra 120v outlets.

 

[mm08822]

Replace what you have with a SQ D QO panel that has more spaces.
Re-use the existing cbs. If attached garage, then a main cb in garage panel isn't required.

Check height of new proposed box first and determine which conduits could be trimmed to make it fit.

 

[dwall174]

Replace what you have with a SQ D QO panel that has more spaces.

I just went through swapping the guts of this Panel from 12-spaces to 16-spaces back in April.
It's surprising how fast they fill up, especially when mostly 240-volt breakers are used.

 

[75gmck25]

Simple solution, but not elegant - Use the remaining two space breaker to add a sub-panel that has 16 more breakers. Install it in the most convenient location for future needs. Subpanels are relatively cheap, and it's an easy solution if you have wall space for it.

 

[wyliesdiesels]

#8 THWN is good for 50a not 40a.

 

[Lorydr]

2 8ga + a 10ga would be hard to pass through 1/2" anything, or would probably overfill per code. I believe anyway. A 70A panel will require 4ga for current-carrying conductors.

 

[mm08822]

I just went through swapping the guts of this Panel from 12-spaces to 16-spaces back in April.
It's surprising how fast they fill up, especially when mostly 240-volt breakers are used.

I'm talking about a bigger box. I would have gone to 20 or 24 spaces. Anything less isn't worth the effort. Now I would do 24.

 

[mm08822]

Simple solution, but not elegant - Use the remaining two space breaker to add a sub-panel that has 16 more breakers. Install it in the most convenient location for future needs. Subpanels are relatively cheap, and it's an easy solution if you have wall space for it.

That is the OP's initial thought. It's just more clutter on the wall IMHO.

 

[mm08822]

2 8ga + a 10ga would be hard to pass through 1/2" anything, or would probably overfill per code. I believe anyway. A 70A panel will require 4ga for current-carrying conductors.

The 60a feed is fine regardless of the panel rating. Ocp in main panel will protect feeder and panel. Subpanel can be higher ampacity than feeder.

 

[dwall174]

2 8ga + a 10ga would be hard to pass through 1/2" anything, or would probably overfill per code.

According to a conduit fill calculator I used it's just within the 40% code for more than two wires.

The conduit run is only about 30 feet with (2) 90-degree bends, so it shouldn't be too hard.

I believe anyway. A 70A panel will require 4ga for current-carrying conductors.

The panel is rated at 70A max! It can be supplied with anything lower than that.

 

[dwall174]

#8 THWN is good for 50a not 40a.

Thanks for pointing that out!
I knew that the THHN/THWN had a little bit higher rating than the normal Romex NM-B, but I never really took a closer look at the differences.

 

[alfredeneuman]

2 8ga + a 10ga would be hard to pass through 1/2" anything, or would probably overfill per code.

You're allowed to have 3-#8 in a 1/2" conduit.

 

[theoldwizard1]

They make tandem 240V breakers. Replace 2 and you now have a double slot open.

 

[theoldwizard1]

Replace what you have with a SQ D QO panel that has more spaces.
Re-use the existing cbs. If attached garage, then a main cb in garage panel isn't required.

Check height of new proposed box first and determine which conduits could be trimmed to make it fit.

Remember, the size of the main breaker in the garage panel DOES NOT HAVE TO. MATCH THE SIZE OF THE BREAKER FEEDING IT ! So you can install a box with a 100A main in the garage. If you exceed the current of the breaker feeding it, you will have to reset it in the house.

 

[mike93lx]

If the panel allows, I'd throw in a couple tandems before adding another sub. It's o much easier.

I'd also swap the panel before adding a sub next to it. Multiple subs in one place is messy

 

[Mr onetwo]

not all panels allow tandem breakers

 

[AffableCurmudgeon]

The heater is 240-Volts & it draws 25-amps at full power & the owner's manual states to wire it to a 30-amp breaker.
The heater is a 3-wire connection no neutral so, it would be a pretty straight forward normal install. 2 - 10ga. wires, black/red & a 10ga. ground wire in 1/2" EMT conduit.

For the heater wiring, do you need a separate ground conductor when using EMT? Some electricians may correct me but with a properly bonded EMT conduit, I don't think you need a separate ground conductor.

 

[Norcal]

Thanks for pointing that out!
I knew that the THHN/THWN had a little bit higher rating than the normal Romex NM-B, but I never really took a closer look at the difference

They make tandem 240V breakers. Replace 2 and you now have a double slot open.

Only GE, & obsolete Zinsco, Challenger, Crouse-Hinds, & FPE, has that capability.

 

[alfredeneuman]

or the heater wiring, do you need a separate ground conductor when using EMT?

No. In fact the EMT (when properly installed) carries the bulk of the fault current.

 

[theoldwizard1]

Only GE, & obsolete Zinsco, Challenger, Crouse-Hinds, & FPE, has that capability (tandem 240V breaker).

Square D (QO) DOES sell an add on the locks 2 inner breakers of 2 tandem breakers. The outer breakers are NOT locked. BUMMER !

OP does have a pair of single volt breakers that could be replaced by a tandem.

 

[Norcal]

Square D (QO) DOES sell an add on the locks 2 inner breakers of 2 tandem breakers. The outer breakers are NOT locked. BUMMER !

OP does have a pair of single volt breakers that could be replaced by a tandem.

My point was that A twin "tandem" breaker cannot supply 240V except in other manufacturers, most who a defunct, and your post only mentioned a twin, most require a quad & SQ D is limited for those.

 

[theoldwizard1]

My point was that A twin "tandem" breaker cannot supply 240V except in other manufacturers, most who a defunct, and your post only mentioned a twin, most require a quad & Square D QO is limited for those.

Bad terminology on my part !

 

[dwall174]

I decided to go the easy route & just use the one empty space I had & run a regular 30-amp line with 10ga. THHN wire for now.

Replace what you have with a SQ D QO panel that has more spaces.

I think that's what I'll do latter this year if something else comes up.

Check height of new proposed box first and determine which conduits could be trimmed to make it fit.

Being that most of the lines are ran from the top of the panel, it wouldn't be a really big swap.

 

[Norcal]

Strapping the cord to the wall is a big no-no, should have hard wired it.

 

[dwall174]

Strapping the cord to the wall is a big no-no, should have hard wired it.

I didn't know that!
Would it be better to just let it hang/drupe freely?

This is basically a temporary set-up until I can get a ceiling installed.
Once I get a ceiling installed & insulated, I'll hard wire it using flexible conduit.

 

[mike93lx]

I didn't know that!
Would it be better to just let it hang/drupe freely?

This is basically a temporary set-up until I can get a ceiling installed.
Once I get a ceiling installed & insulated, I'll hard wire it using flexible conduit.

I'd leave it alone and change it when you do the ceiling

 

[dwall174]

Strapping the cord to the wall is a big no-no.

Would strapping flexible conduit to the wall also be a violation?

I knew that a power cord should not be ran inside a wall or behind drywall & ceiling panels, but I've seen a lot of wall mounted TV's where the cord is attached to the wall inside of surface mounted conduit like this.

 

[dwall174]

Strapping the cord to the wall is a big no-no.

Just curious, what article of the code covers the no attaching the cord to the wall?

I see something like what you're referring to in section 400.8
But it also states unless permitted in section 400.7

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