Electric question

[cincinnati]

I am going to wire this electrical heater from Northern tool.

http://www.northerntool.com/webapp/w...t_6970_595_595

They recommend 10/2 wire and 30 amp breaker for the install.

I have a 240 volt circuit that ran to and old air compressor that has been removed. Nothing is now on this circuit. This circuit has a 40 amp breaker and 8 ga wire. I am going to run off this box for the heater. I need to extend the wiring about another 30 or 40 feet.

My question......

-Is it ok to run the recommended 10/2 wire off the box that has 8 ga wire?
( I have 10ga on hand)

-I am going to replace the breaker in the box from the old 40 amp to the recommended 30 amp. This OK?

- There is no ground wire in the box. The box is all connected with metal conduit. I am assuming the metal box is grounded. How do I test for sure?
The breaker box has a ground running from it to the ground (dirt) outside. All the electrical outlets are 3 prong. This is in a block garage so everything is in conduit.
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[JPG40504]

1) LINK DOESN'T WORK NORTHERN....
2) Since you ARE downsizing(40A to 30A) at start of branch, it IS ok to run #10 as part of this branch. The breaker is sized to protect the wires. Original breaker is sized to protect #8 (40A). Proper size for #10 is 30A.

3) Since you ARE dealing with 'conduit' I recommend adding a ground wire. It should be sized at least as large as the conductors on its branch circuit.(#8 to current 'box' and #10 to added wiring.

4) Conduit can serve as the ground, but it sometimes is unreliable. I am assuming the conduit referred to IS METAL not pvc. The choice to add ground wire or not is up to you. Depending on how many bends there are it can be difficult(PITA).

[a1gutterman]

I am going to wire this electrical heater from Northern tool.

http://www.northerntool.com/webapp/w...t_6970_595_595

They recommend 10/2 wire and 30 amp breaker for the install.

I have a 240 volt circuit that ran to and old air compressor that has been removed. Nothing is now on this circuit. This circuit has a 40 amp breaker and 8 ga wire. I am going to run off this box for the heater. I need to extend the wiring about another 30 or 40 feet.

My question......

-Is it ok to run the recommended 10/2 wire off the box that has 8 ga wire?
( I have 10ga on hand)

No. You should never use different gauge wire in the same circuit (see note below).

-I am going to replace the breaker in the box from the old 40 amp to the recommended 30 amp. This OK?

Yes. Over sized wire is okay in a circuit, so a smaller breaker with "oversized" wire is oakay! BUT, the 40amp breaker is really a double breaker and it is attached to both hot bars; one for each of the breaker halves. The 30amp breaker is only attached to one hot bar. That will knot hurt anything, but you will only have one hot wire going to your box; the other one will be dead. You will also have a "loose" wire in your panel too, if you do that.

- There is no ground wire in the box. The box is all connected with metal conduit. I am assuming the metal box is grounded. How do I test for sure?

As long as there is a continuous metal to metal connection from the metal box to the breaker panel, and as long as there is a ground wire that goes from the ground bar inside the panel to the breaker box itself (all required by code), your metal box is grounded. To test, just take a test light, put one end on the hot wire and the other on the box. Make sure that you do knot touch any metal parts while doing this. If the light comes on, all is well. If it does knot, either the box is knot grounded or you have a bad test light.

The breaker box has a ground running from it to the ground (dirt) outside. All the electrical outlets are 3 prong. This is in a block garage so everything is in conduit.

Old code required 2 hots and a neutral in a 240 circuit. New code requires 2 hots a neutral AND a ground in a 240 circuit (that is why old dryers and ranges had a three prong plug, but the new ones have a four prong plug). If you have all your wire in conduit, you may be able to "fish" a ground wire through. All ground wires and neutral wires are connected to the same bar in the breaker panel, which then goes to the ground rod that you see outside.
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Cin, If you leave the breaker alone, you can install a smaller breaker box (one that holds 4 breakers for instance), at the end of the run, where the compressor used to be hard wired in. From that point, you can run smaller gauge wire (10ga) to the heater, from one leg of the small panel, and still have room for another 30amp, or a couple of 20amp (12ga wire) or 15amp (14 guage) circuits. MORE POWER!! :D

Make sure that you are using the proper wire in the conduit. Wire marked "THHN" is the right stuff. DO KNOT put Romex type wire in conduit; it will over heat and can cause a fire.

PS: When you use two different gauges of wire in the same circuit, you are asking for trouble. In your case, the example is that YOU may know what you did, but down the road, the next guy may knot realize it, and since he sees 8ga wire, he may put back a 40amp breaker, and then he will have problems. Code does knot allow it.

[cincinnati]

Thanks!

Sorry about the link. http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_595_595

[cincinnati]

Make sure that you are using the proper wire in the conduit. Wire marked "THHN" is the right stuff. DO KNOT put Romex type wire in conduit; it will over heat and can cause a fire.[/QUOTE]

The new 10ga wire I was going to run without conduit. using 10/2 with ground wire. The outer jacket of the wire is colored orange. Never noticed that before. Only used the white stuff before.

[JPG40504]

Cin, If you leave the breaker alone, you can install a smaller breaker box (one that holds 4 breakers for instance), at the end of the run, where the compressor used to be hard wired in. From that point, you can run smaller gauge wire (10/2 with ground) to the heater, from one leg of the small panel, and still have room for another 30amp, or a couple of 20amp (12ga wire) or 15amp (14 guage) circuits. MORE POWER!! :D

Make sure that you are using the proper wire in the conduit. Wire marked "THHN" is the right stuff. DO KNOT put Romex type wire in conduit; it will over heat and can cause a fire.
GOOD SUGGESTION TIM!:) HOWEVER, THE ORIGINAL RUN DOES not INCLUDE A NEUTRAL, SO ONLY 230V CIRCUITS COULD BE ADDED. ADDING A NEUTRAL(#8) TO ORIGINAL RUN WOULD ALLOW 120V CIRCUITS.:D

[cincinnati]

Cin, If you leave the breaker alone, you can install a smaller breaker box (one that holds 4 breakers for instance), at the end of the run, where the compressor used to be hard wired in. From that point, you can run smaller gauge wire (10ga) to the heater, from one leg of the small panel, and still have room for another 30amp, or a couple of 20amp (12ga wire) or 15amp (14 guage) circuits. MORE POWER!! :D

Make sure that you are using the proper wire in the conduit. Wire marked "THHN" is the right stuff. DO KNOT put Romex type wire in conduit; it will over heat and can cause a fire.

PS: When you use two different gauges of wire in the same circuit, you are asking for trouble. In your case, the example is that YOU may know what you did, but down the road, the next guy may knot realize it, and since he sees 8ga wire, he may put back a 40amp breaker, and then he will have problems. Code does knot allow it.

All I have in the box the old compressor was wired to is two black wires.

[JPG40504]

[COLOR=#0000ff]

The new 10ga wire I was going to run without conduit. using 10/2 with ground wire. The outer jacket of the wire is colored orange. Never noticed that before. Only used the white stuff before.

I DO NOT KNOW YOUR LOCAL CODE, BUT SINCE IT IS IN A GARAGE YOU MIGHT WANT TO CONSIDER CONDUIT. PVC IS INEXPENSIVE AND EASY TO WORK WITH. THE WIRE TIM RECOMMENDED HAS A HIGHER TEMPERATURE INSULATION.