Two years ago, I added a sub box in my garage. I ran 8/2 wire with the BLK and WHT connected to a double 30A breaker and BARE connected to ground. Most outlets and lights work fine, but the 20A breaker for the air compressor keeps popping. After a few pops, it will eventually hold. Could this be caused by not using 8/3 wire? If 8/3 wire is necessary, can I just add the neutral or ground alongside the 8/2? I'd hate to have to throw out the 8/2 that is already installed.

I'm getting ready to add a similar sub box in the attic and would like to know if I need 8/3 wire instead of 8/2? 8/2 was fine in the past, but it seems (air compressor circuit) to not function properly anymore.

Thanks,
Brax

Using the #8-2 with ground is not affecting the AC. The AC motor must be the issue, either too large for a 20 amp breaker to start the motor, or the motor is drawing too much at startup for some reason.

Unfortunately, a separate wire cannot be added as a neutral to the #8-2 with ground feeder. Using the bare as a neutral and ground is not allowed for this purpose. It is only allowed for ranges and dryers using existing cable.

3 wire with ground, for a total of 4 wires is needed for any feeder to a subpanel.

What is the voltage rating, horsepower, and LRA listed on the nameplate of the air compressor?

And before you decide to use #8 for the attic panel, be sure 40 amps will be enough.

Thank you! I've seen a lot of your reponses and they are always helpful to me.

The Air Compressor is labeled as needing only a 15A circuit.

Do I need to run 8-3 to update the garage sub box or can I leave it as is with 8-2? What problems could occur from leaving the 8-2? Is there any work around I can perform to upgrade its' safety?

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As for the attic sub box, I'm currently planning on installing a maximum of 3 ceiling fans. Rather than run individual circuits up into the attic, I thought I'd save myself some future work by placing a sub box in the attic. Since I'm currently finishing the basement (main box location), I need to run the wire before installing the Armstrong wood plank ceiling.

I was thinking of a 60A sub box. Is that 2 30A 110 lines? Why the need to keep the neutral and ground junctions separate in a sub box?

Thanks again for all of your help!
Brax

My answers to your questions are in bold:

The Air Compressor is labeled as needing only a 15A circuit.

Then the motor starting current may be too high, for some reason. Or the breaker is bad.

Do I need to run 8-3 to update the garage sub box or can I leave it as is with 8-2?

Depends on what this cable is beng used for. If your using this cable for 120 volt loads, with the bare as a neutral and an equipment ground, the only recourse is to install a 3 wire cable with ground.

What problems could occur from leaving the 8-2?

When using the bare as a neutral and ground, the neutral is current carrying under normal conditions for 120 volt circuits, and can allow current to flow out on the equipment grounding system.

Is there any work around I can perform to upgrade its' safety?

Only use it for 240 volt loads, with ground, or only use it for 120 volt loads with ground.


I was thinking of a 60A sub box. Is that 2 30A 110 lines?

A 60 amp feeder needs to be a minimum of #6 copper wire, using pulled THHN wire thru conduit, or MC cable. If you use Romex, it is only rated 55 amps, but you can use a 60 amp breaker , being the next standard size breaker.

I do have to say, the question "Is that 2 30A 110 lines?" scares me a bit. At least your asking.


Why the need to keep the neutral and ground junctions separate in a sub box?

Short answer....A neutral is considered as current carrying, a ground is only for fault currents, and for safety purposes both are kept separate.

Quote:

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Originally Posted by tkrussell

My answers to your questions are in bold:

The Air Compressor is labeled as needing only a 15A circuit.

Then the motor starting current may be too high, for some reason. Or the breaker is bad. Not the breaker - must be the motor.

Do I need to run 8-3 to update the garage sub box or can I leave it as is with 8-2?

Depends on what this cable is beng used for. If your using this cable for 120 volt loads, with the bare as a neutral and an equipment ground, the only recourse is to install a 3 wire cable with ground.BLK is hot connected to 1 bus bar in sub box. WHT is hot connected to other bus bar in sub box. BARE is neutral/ground connected to ground bar.

What problems could occur from leaving the 8-2?

When using the bare as a neutral and ground, the neutral is current carrying under normal conditions for 120 volt circuits, and can allow current to flow out on the equipment grounding system.Is this something that was recently discovered? Why make 8-2 wire then?

Is there any work around I can perform to upgrade its' safety?

Only use it for 240 volt loads, with ground, or only use it for 120 volt loads with ground. 240 loads with ground or 120 loads with ground? What else is there? Please explain.


I was thinking of a 60A sub box. Is that 2 30A 110 lines?

A 60 amp feeder needs to be a minimum of #6 copper wire, using pulled THHN wire thru conduit, or MC cable. If you use Romex, it is only rated 55 amps, but you can use a 60 amp breaker , being the next standard size breaker. In main box, using a double pole 30A breaker - BLK to one hot and RED to other hot. WHT and BARE to ground. In sub box, BLK to one hot bar and RED to other hot bar. WHT to neutral bar and BARE to ground bar that must be added. Using 8-3 wire for this connection. What amp sub box should I purchase?

I do have to say, the question "Is that 2 30A 110 lines?" scares me a bit. At least your asking.Trying to learn which is sometimes scary.


Why the need to keep the neutral and ground junctions separate in a sub box?

Short answer....A neutral is considered as current carrying, a ground is only for fault currents, and for safety purposes both are kept separate.

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Why are they connected in the main box then?

Thanks again!

Do I need to run 8-3 to update the garage sub box or can I leave it as is with 8-2?

Depends on what this cable is being used for. If your using this cable for 120 volt loads, with the bare as a neutral and an equipment ground, the only recourse is to install a 3 wire cable with ground.BLK is hot connected to 1 bus bar in sub box. WHT is hot connected to other bus bar in sub box. BARE is neutral/ground connected to ground bar.
You have it hooked up for 120/240 volts. If you have any single pole breakers (120 volt circuits) or any 240 volt circuits that have neutral wires connected to the grounding bus, it is unsafe. 240 volt devices that don't require a neutral (like a heater or some tools) are safe to use in your current configuration. If you intend to use any 120/240 volt devices (240 volt devices that have a neutral) or any pure 120 devices, you will need to convert it to 8/3. If you only need 120 volt devices, you can stick with 8/2, but it will need to be reconfigured.

What problems could occur from leaving the 8-2?

When using the bare as a neutral and ground, the neutral is current carrying under normal conditions for 120 volt circuits, and can allow current to flow out on the equipment grounding system.Is this something that was recently discovered? Why make 8-2 wire then?
Electric heaters don't need a neutral to comply with the NEC. Other devices that only use 240 volts are in the same boat. Devices that have smaller components that run on 120 volts will need a neutral.


Is there any work around I can perform to upgrade its' safety?

Only use it for 240 volt loads, with ground, or only use it for 120 volt loads with ground. 240 loads with ground or 120 loads with ground? What else is there? Please explain.
Answered above.


I was thinking of a 60A sub box. Is that 2 30A 110 lines?

A 60 amp feeder needs to be a minimum of #6 copper wire, using pulled THHN wire through conduit, or MC cable. If you use Romex, it is only rated 55 amps, but you can use a 60 amp breaker , being the next standard size breaker. In main box, using a double pole 30A breaker - BLK to one hot and RED to other hot. WHT and BARE to ground. In sub box, BLK to one hot bar and RED to other hot bar. WHT to neutral bar and BARE to ground bar that must be added. Using 8-3 wire for this connection. What amp sub box should I purchase?
If you have a double pole 30 amp breaker feeding the box, you can use any box rated for at least 30 amps. The 30 amp double pole breaker will give you 60 amps of power at 120 volts before tripping (both hot legs maxed out at their 30 amp capacity).

I do have to say, the question "Is that 2 30A 110 lines?" scares me a bit. At least your asking.Trying to learn which is sometimes scary.


Why the need to keep the neutral and ground junctions separate in a sub box?

Short answer... A neutral is considered as current carrying, a ground is only for fault currents, and for safety purposes both are kept separate.

Why are they connected in the main box then?
Neutral is made at the main breaker. The utility provides two hots and a grounded line. In the house, you separate the ground and the current's return path (neutral) for safety. However, because of the way the house and utility connect, there must be exactly one connection between your neutral and the grounding system. This connection must be made at the main breaker. If your main breaker is at your main electrical panel, these will be at the same place. If you have a remote main breaker, you must have isolated ground and neutral in your main panel. All devices elsewhere in the home must isolate ground and neutral. In panels, this usually means purchasing a separate bus bar to be the ground and removing the grounding screw from the included bus bar to make it neutral.

Sorry, but I have to ask. What are you going to do with 60 amps in you attic. I am believer in planning ahead but this sounds like excess. Why not pull a 12/3 cable to the attic and terminate it in a box. This would provide 2 20 amp circuits with a common neutral for fan installation. More than adaquate for 3 ceiling fans. If you want a couple of spare circuits pull a second 12/3 cable.

Quote:

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Originally Posted by bolt in blue

Do I need to run 8-3 to update the garage sub box or can I leave it as is with 8-2?

Depends on what this cable is beng used for. If your using this cable for 120 volt loads, with the bare as a neutral and an equipment ground, the only recourse is to install a 3 wire cable with ground.BLK is hot connected to 1 bus bar in sub box. WHT is hot connected to other bus bar in sub box. BARE is neutral/ground connected to ground bar.
You have it hooked up for 120/240 volts. If you have any single pole breakers (120 volt circuits) or any 240 volt circuits that have neutral wires connected to the grounding bus, it is unsafe. 240 volt devices that don't require a neutral (like a heater or some tools) are safe to use in your current configuration. If you intend to use any 120/240 volt devices (240 volt devices that have a neutral) or any pure 120 devices, you will need to convert it to 8/3. If you only need 120 volt devices, you can stick with 8/2, but it will need to be reconfigured.

How can the 8/2 be reconfigured for use with only 120V devices?

Why is it unsafe to have neutral wires grounded to the grounding bus?

What problems could occur from leaving the 8-2?

I was thinking of a 60A sub box. Is that 2 30A 110 lines?

A 60 amp feeder needs to be a minimum of #6 copper wire, using pulled THHN wire thru conduit, or MC cable. If you use Romex, it is only rated 55 amps, but you can use a 60 amp breaker , being the next standard size breaker. In main box, using a double pole 30A breaker - BLK to one hot and RED to other hot. WHT and BARE to ground. In sub box, BLK to one hot bar and RED to other hot bar. WHT to neutral bar and BARE to ground bar that must be added. Using 8-3 wire for this connection. What amp sub box should I purchase?
If you have a double pole 30 amp breaker feeding the box, you can use any box rated for at least 30 amps. The 30 amp double pole breaker will give you 60 amps of power at 120 volts before tripping (both hot legs maxed out at their 30 amp capacity).


Why the need to keep the neutral and ground junctions separate in a sub box?

Short answer....A neutral is considered as current carrying, a ground is only for fault currents, and for safety purposes both are kept separate.

Why are they connected in the main box then?
Neutral is made at the main breaker. The utility provides two hots and a grounded line. In the house, you separate the ground and the current's return path (neutral) for safety. However, because of the way the house and utility connect, there must be exactly one connection between your neutral and the grounding system. This connection must be made at the main breaker. If your main breaker is at your main electrical panel, these will be at the same place. If you have a remote main breaker, you must have isolated ground and neutral in your main panel. All devices elsewhere in the home must isolate ground and neutral. In panels, this usually means purchasing a separate bus bar to be the ground and removing the grounding screw from the included bus bar to make it neutral.

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Thanks!

Quote:

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Originally Posted by hkstroud

Sorry, but I have to ask. What are you going to do with 60 amps in you attic. I am believer in planning ahead but this sounds like excess. Why not pull a 12/3 cable to the attic and terminate it in a box. This would provide 2 20 amp circuits with a common neutral for fan installation. More than adaquate for 3 ceiling fans. If you want a couple of spare circuits pull a second 12/3 cable.

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Good question; I'm also a big believer in planning ahead. But, maybe the 12/3 will suffice in this case.

Tak sa mychet!

Just bought the 12/3 wire instead; thanks for everyone's help!

Any ideas on how to redo the 8/2 line to upgrade the safety level of my garage sub box?

Make sure you know what you're doing with the shared neutral circuits. Remember to use a double pole 20 amp breaker to control the two circuits that share a neutral, so that it is impossible to have current flowing in a circuit while you're working on it. Otherwise, if you only turn off one of the shared circuits, you will still have current flowing in its neutral lines.

Using a double pole breaker also prevents someone from later moving one of the breakers and unsafely putting both halves of the circuit on the same hot leg of the electric service. A shared neutral is only allowed when both circuits are on different hot legs, otherwise, the neutral could carry too much current and is an immediate fire hazard.

About the garage: you can do one of three things
1) Pull new 8/3 cable and add a ground bar to the panel (allows for 120/240 loads)
2) Only use the box for pure 240 volt loads (this may work if you have the panel there to support large power tools and can lose or reroute to the main panel any 120 volt circuits in it)
3) Use the existing wiring and reconfigure the panel and wiring for 120 volt only operation - this may be your best choice if you don't need that much electrical capacity at the panel and can live without 240 volts. This requires a lot of description, so I'll hold off for now.

We can better advise you which option makes the most sense if you let us know all of the connected loads (amps and poles) in the subpanel. A picture can be an easy way to capture this information.

Quote:

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Originally Posted by bolt in blue

3) Use the existing wiring and reconfigure the panel and wiring for 120 volt only operation - this may be your best choice if you don't need that much electrical capacity at the panel and can live without 240 volts. This requires a lot of description, so I'll hold off for now.

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Running new wire is not an option at this time, so I'd like to reconfigure if it is indeed a safety hazard.

Loads -

20A - Dedicated line for refrigerator

20A - Dedicated line for 1 outlet (used for 120 power tools)

20A - Dedicated line for 4 outlets at workbench

15A - Dedicated line for lights

It sounds like making this a 120 volt panel is definitely the correct solution for you.

Starting at the main panel, you will need to change how the subpanel is fed. You will want the subpanel to be fed off a 40 amp single pole breaker (that is the largest breaker you can use with the #8 cable). Make sure that it's properly labeled as the garage subpanel in the main panel. Connect the white wire to the neutral bar and the ground to the ground bar (these may be mixed since ground and neutral are bonded here).

In the subpanel, connect the white wire to the insulated bus bar (this is now the neutral bus). Connect the bare ground to a bus bar that is bonded to the box (this is now the ground bus). Note that you may need to purchase a second bus bar for your panel - they usually only come with one. You can usually buy these at a "big box" store if they carry your brand of panel.

Now about the hot line in the sub panel: what you want to do is connect the black wire coming from your main panel to BOTH hot terminals. That way, you can still use all the spaces in the panel with your one hot line. It's hard for me to say how to best do this without seeing your subpanel or at least knowing what brand it is. If you have access to a digital camera, we can tell you how to upload a picture here and get a better look.

One last reminder: now that you have separate neutral and ground buses in your subpanel, make sure that you move all the neutrals from the branch circuits to the neutral bar and move all the grounds from the branch circuits to the ground bar. Mixing these here would just undo all the work you would have done.

Hope this all goes well - I really think that the 120 volt subpanel is your best way to fix your problem here.

Quote:

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Originally Posted by bolt in blue

It sounds like making this a 120 volt panel is definitely the correct solution for you.

Starting at the main panel, you will need to change how the subpanel is fed. You will want the subpanel to be fed off a 40 amp single pole breaker (that is the largest breaker you can use with the #8 cable). Make sure that it's properly labeled as the garage subpanel in the main panel. Connect the white wire to the neutral bar and the ground to the ground bar (these may be mixed since ground and neutral are bonded here).

In the subpanel, connect the white wire to the insulated bus bar (this is now the neutral bus). Connect the bare ground to a bus bar that is bonded to the box (this is now the ground bus). Note that you may need to purchase a second bus bar for your panel - they usually only come with one. You can usually buy these at a "big box" store if they carry your brand of panel.

Now about the hot line in the sub panel: what you want to do is connect the black wire coming from your main panel to BOTH hot terminals. That way, you can still use all the spaces in the panel with your one hot line. It's hard for me to say how to best do this without seeing your subpanel or at least knowing what brand it is. If you have access to a digital camera, we can tell you how to upload a picture here and get a better look.

One last reminder: now that you have separate neutral and ground buses in your subpanel, make sure that you move all the neutrals from the branch circuits to the neutral bar and move all the grounds from the branch circuits to the ground bar. Mixing these here would just undo all the work you would have done.

Hope this all goes well - I really think that the 120 volt subpanel is your best way to fix your problem here.

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Perfect, thanks for the thorough answer!

I'll probably just daisy chain the BLK from one hot bar to the other. Is that a safe situation?

When you say "bonded to the box", what do you mean? Uninsulated?

Daisy chaining from one hot bar to the other is a safe solution if there are two sets of terminals on the hot bar (so you're not putting two cables under one connector). Remember that this jumper between bars must be at a minimum #8 to match your incoming line.

If you don't have two sets of terminals on each hot bar, maybe TK or one of the other guys will jump in. TK is god here and there are some other electricians on here. I have a degree in electrical and computer engineering, so my experience is limited to designing things on paper, doing work on my own home, this forum, and looking at the National Electric Code.

By bonded to the box, I mean connected to the box (uninsulated). The metal box needs to be grounded through the electrical ground. This is usually accomplished by a screw that connects the box to the bar.

Hope your work goes well!

While converting a 120/240 volt panelboard to 120 volt only is not the worse thing in the world you could do, I do not subscribe to this practice.

The panel is UL listed as a 120/240 volt panel, not straight 120 volt, so the UL listing is violated, and so is Code.

The lugs are only rated for one conductor. So the wiring needs to be spliced, or a double port lug is needed, if the lug can be changed.

The panel can still accept two pole 240 volt breakers, so a new subsequent owner will be in trouble trying to connect a 240 volt circuit, so clear labeling will be needed.

The total 120 volt load from all circuits will still be limited to 40 amps.

This plan has Disney all over it.

You already have my answer, pull a new 4 wire feeder.

So now you have two answers. Perhaps you should check with your local inspector to see what resolution you can arrive at.

"Bonding" in a panel is the action of connecting the neutral to the equipment ground and the grounding electrode conductor. The back box is to be grounded, and the equipment ground bar is to be bolted directly to the metal can to insure the can is grounded.

BraxaRI, what makes you think that you can't pull a new 4 wire feeder?

TK, would you think that changing out the panel to a 120 only panel would be the correct answer if the wiring can't be upgraded?

I don't think that a straight 120 volt panelboard that can handle several circuit exists. I have never seen one, in over 30 years, but that does not mean it does not exist.

If one does then that would be a solution.

Quote:

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Originally Posted by bolt in blue

BraxaRI, what makes you think that you can't pull a new 4 wire feeder?

TK, would you think that changing out the panel to a 120 only panel would be the correct answer if the wiring can't be upgraded?

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It is not that I don't think I can run the line; it all comes down to wasting 80' of 8/2 and having to buy 80' of 8/3.

Copper is at about $3.00 a pound as scrap, so all is not lost.

Or keep it to be used as a feeder for a 240 volt air conditioner, or air compressor.