Wiring a new shop

[Bob AZ]

On Jul 16,

The 60 Amp breaker feeding a subpanel is an exception according to the city permit folks. I know the inspector checked the 60 amp thing. I watched him do this.

But beware. Not all municipalities always follow all the code all the time.

A little background. Goes something like this. Years ago when 50 amp was a big panel they went to 100 amp. But the biggest branch circuit breaker that would fit in the panel was 60 amp. So they allowed 60 amp branch circuits to power a sub panel. And there was no max on the subpanel as long as it was fed by a 60 amp breaker. Thus the provision to allow a sub panel to be fed by a 60 amp breaker with no main in the sub panel. So using a bigger subpanel gives some options for lots of separate breakers/circuits in a shop like yours and mine.

Bob AZ

[B A R R Y]

If one gets sold too low of a SEER rating, are they a SEER sucker?

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[Lew Hodgett]

Be careful, the "six hand rule" applies.

IOW, all power must be disconnected with a maximum of six motions of the hand.

Install a 2P-60 as a branch c'bkr in the main panel.

Upgrade the PVC conduit size at least one size, maybe two.

Conduit is cheap, straining your back isn't.

Install a 125 MLO, 12/24 surface mount panel in shop(12-1" or 24, 1/2" branch spaces).

Add a 2p-60A main c'bkr kit along with an insulated ground bus bar since this is a sub panel.

Use 1P-20 c'bkrs for all 120V circuits of which at least 4 are dedicated to lighting.

240V circuits:

Dedicate a 2P-50 for a 5HP air compressor

2P-30 for the balance.

Run every thing you can at 240V, especially stationary tools like DC, TS, Jointer, dedicating an individual c'bkr for each load.

Use 30A locking receptacles & plugs for 240V services.

You do the above, the inspector will smile and give you your permit.

Lost count of how many of the above packages I sold over the years, but it was a bunch.

Lew

PS: Wire all your receptacles in 4" (2 gang) boxes.

Makes life a LOT easier.

[Chris Friesen]

Now I'm no pro, but it seems like some of these suggestions are overkill.

Why? I could see two for safety, but four? And why bother making the lighting circuits 20A, when they won't be drawing anywhere close to 15A?

Sounds reasonable. I didn't in my small shop, but only because I don't have room for a big compressor. I have a spare 30A circuit available for a future compressor upgrade.

This seems like overkill, since its generally only needed for 5HP motors. Given the price of copper around here, I couldn't justify it.

The individual circuits won't hurt, but it's probably overkill. In a small shop the stationary tools likely won't ever run simultaneously (and with only 60A supply, there isn't the juice for it anyways). It makes sense to have DC and compressor on individual circuits, the rest likely won't be an issue. I split mine over multiple circuits because I had the cable, but its likely not necessary.

This would require replacing the plugs on the tools. If you're using overhead drops it makes sense, but for wall or floor I don't see major benefits. I've never pulled out a cord accidentally on a stationary tool.

Chris

[Lew Hodgett]

One word: Standardization.

You buy wire in full spools instead of cut lengths.

You buy devices in quantity.

You provide for future expansion.

Overall, you save money.

Lew

[Steve]

All the units I've found on-line are 13 SEER. I found one at 14 SEER that's about $300 more than the others.

One on-line vendor claims it's illegal for someone who is not EPA-certified to mess with refrigerants - is that true?

[Lew Hodgett]

These days, yes.

Has to do with protecting the ozone layer.

Checked the price of 12 or 22, if you can even find it.

Lew

[Frank Boettcher]

Keep looking. Go to 15 SEER, and take a $300 tax credit to offset the cost. make up the rest over a couple of years with energy savings. I think a shop AC qualifies if it is at the same address as your home, but you may need to check that.

>

[Frank Boettcher]

Easily obtained? None of the low cost "packaged panels" I've seen have a 60 main. 60 main will be a different configuration than the 60 branch? Electrical supply house?

Insulated ground bar means remove the strap to the nuetral if so configured? But ground buss needs to remain bonded to the panel, correct?

Thanks,

Frank

[Lew Hodgett]

The 60A bkr is the same, but has different hardware to be used as a main bkr.

Any decent electrical distributer can help you.

NO, what you are describing is a bonding strap used to bond the neutral to the enclosure when the panel is used as a service entrance panel.

An insulated ground bus is exactly that.

It will look like the neutral bus but be insulated from the panel.

An electrical distributer will have them as a kit.

NO, not at the sub panel, but yes at the main service entrance panel.

You need to have a heart to heart with the local building department.

Local codes vary.

Some places will want a ground rod at the sub panel, some may not and want the earth ground carried all the way back to the service entrance panel.

If you try to out guess the inspector, you lose, every time out of the box.

Lew

[Chris Friesen]

At least in my circumstance the subpanel did not use an insulated ground. The bonding screw was removed from the neutral bus (so that neutral was separate from ground), but the ground bus is bonded to the panel (and is tied to the main panel ground via a bare conductor).

The inspector signed off on it no problem.

What's the point of an insulated ground?

Chris

[Doug Miller]

He's confused. The subpanel needs an insulated *neutral* bus. The ground bus

*must* be bonded to the panel chassis. And the bonding strap between the neutral and ground buses must be removed.

[Doug Miller]

Yes, at the subpanel, as well as at the main panel. He's asking about the ground bus. Not the neutral bus.

Correct is: Ground bus *must* be bonded to panel chassis in main *and* subpanels. Neutral bus *must* be bonded to ground in main panel. Neutral bus *must*not* be bonded to ground in a subpanel.

[Lew Hodgett]

It allows the entire distribution system to be grounded at the service entrance point.

Single point grounding eliminates "Ground Loops" which can be quite nasty.

The cathodic electrode industry exists to minimize the effects of "Ground loops" or stray electrical currents in the soil.

Lew

[Doug Miller]

We've had that discussion here before. :-)

There's *no* reason to use 3-conductor cable for 240V power tools. It's just unnecessary expense. Three-conductor cable is needed for combined 240/120 loads such as a range or a dryer, that have 240V heating elements and 120V motors and/or control circuits. A power tool with a 240V motor needs only two-conductor cable; there isn't even anything to attach the third conductor to, if it's present.

If you want to plan for "in case you need it some day" it's better to not run cables at all, but instead pull individual conductors through conduit: pull what you need now, now; pull what you need later, later.

[Chris Friesen]

I'm aware of ground loops. What does this have to do with an insulated ground bus in a subpanel?

In my panel for instance, the ground bus is bonded to the panel, which is in turn grounded via a conductor going back to the main panel. As you mentioned, the entire system is grounded at the service entrance.

Chris

[Frank Boettcher]

No, I'm describing a tie bar that ties the nuetral and ground buses together which is normal in a service entrance panel but not for a subpanel.

Goes against everything I've read. In many main panels the nuetral and ground buss are tied together with a strap or tie bar, which insures that both buses are grounded. Removing that strap in a panel makes it suitable to use as a subpanel. Both the insulated ground and the nuetral in the sub continue to be grounded through their paths back to the main.

Again, goes against everything I've read and instinctively know to be true. Without the bond, the subpanel panel itself is not grounded and it has to be.

Frank

[Doug Miller]

Absolutely nothing. He may be confusing "insulated ground" with "isolated ground" or perhaps with "insulated neutral."

In any event, it is a Code violation to insulate the grounding bus from the panel chassis in either a main panel or a subpanel: metal enclosures are

*required* to be grounded.

And that is as it should be. This talk of insulating the grounding bus from the panel is nonsense.

[dpb]

I have seen (but _very_ few (well, actually, precisely two :) ) --don't know of any current-day that do) a couple of planers that used that as well -- the main feed/cutterhead motor was 220V while the table lift and an auxiliary sharpening attachment were 110V. Fella' in a shop in VA had them. But certainly I'm unaware of anything currently on the market set up that way.

That's not bad advice, either... :)

[Doug Miller]

Gentlemen, you're *both* right here. In main panels, as you're both aware, the neutral bus is bonded to ground. The method of doing so varies depending on manufacturer. I've seen four different types of jumpers:

- bonding strap connecting the neutral bus to the panel chassis

- bonding strap connecting the neutral and ground buses

- bonding *screw* through the neutral bus into the panel chassis

- solid copper wire connecting the two buses Regardless of the method, the jumper must be removed if the panel is used as a subpanel.

You've got that backwards -- it's the *neutral* bus that's insulated from the panel, *not* the ground bus.

Ground bars *must* be bonded to the panel.

Exactly right.

Wrong. Ground bus *must* be bonded to the panel, without regard to whether it's a main or sub.

Exactly right.