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Old 07-09-2013, 02:02 AM   #16
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Proper receptacle for circuit?


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I hear that all the time. "I have an open breaker so I wanted to use it."
Having an "open" breaker is no reason to use it outside of it's intended use/range/circuit.

Breakers are CHEAP, so there is no reason for not using the proper one.
I'm glad I asked about this. It wasn't that I was trying to get away with something and using it because it was there. I had just thought 30A was typical and better suited to a garage because of the many types of things that get plugged in there.

So again, does using a 30A circuit in this way create a fire danger or other unsafe condition? If so, then what is the proper use of a 30A circuit?

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Old 07-09-2013, 06:44 AM   #17
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Proper receptacle for circuit?


The only 120V 30 amp circuit I have seen or installed was for an RV hookup.

Thirty amp 240V are used for things like dryers and water heaters.

The receptacle used on the 30 amp circuit would not match the cords on your power tools.
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Old 07-09-2013, 06:51 AM   #18
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Proper use of single pole 30A breakers is few and far between.
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Old 07-09-2013, 08:17 AM   #19
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Proper receptacle for circuit?


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Originally Posted by scottl31

I'm glad I asked about this. It wasn't that I was trying to get away with something and using it because it was there. I had just thought 30A was typical and better suited to a garage because of the many types of things that get plugged in there.

So again, does using a 30A circuit in this way create a fire danger or other unsafe condition? If so, then what is the proper use of a 30A circuit?
I used to put MWBC and two pole 15A breaker, 3 wire NM (14AWGx3) cable to duplex receptacle and cut the hot tab to feed the top and bottom outlets with each half of the breaker in my garage. Do two of these (2 double pole breakers) and you can have a power tool party in the garage.

Code now requires a GFCI outlet there so now I use double box and side by side gfci outlets with line side sharing the common neutral from the panel. If you put down stream outlets off of the gfci then you need separate load side neutrals from there forward. Takes away some of the wiring savings of a MWBC for downstream outlets but maybe the longest run is from the panel anyway.

Since you have 10-3 wire in place already (but you need 4 conductors, ground, neutral, each phase) you could put a mini panel in the garage fed from the 30A breaker. Then run a couple if 15A branch circuits to outlets in garage. If the table saw trips the breaker at least it is nearby. I am assuming attached garage, as detached has different ground needs. Be sure you understand what neutral ground bonding at the remote panel needs to be.
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Old 07-09-2013, 09:06 AM   #20
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Proper receptacle for circuit?


Quote:
Originally Posted by scottl31

I'm glad I asked about this. It wasn't that I was trying to get away with something and using it because it was there. I had just thought 30A was typical and better suited to a garage because of the many types of things that get plugged in there.

So again, does using a 30A circuit in this way create a fire danger or other unsafe condition? If so, then what is the proper use of a 30A circuit?
Yes, it could create a dangerous condition, because general purpose 15/20 amp receptacles are not designed to handle 30 amps.

I don't think there are very many single pole 30 amp devices anymore. (Someone correct me if I'm wrong). I know some direct-wire well pumps use(d) single pole 30 amp breakers. Most 30 amp devices are double pole 240 volt, and have a special 240 volt NEMA plug, like some air conditioners and clothes dryers.
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Old 07-09-2013, 12:44 PM   #21
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Proper receptacle for circuit?


Wow, I'm glad I came here before deciding to do this. I guess I made the right choice in removing the old 10/3 that was feeding 30A to those four 15A receptacles in the utility room. But now I have even more questions if you guys don't mind bearing with me.

1. The two breakers going to that wall were the 4-switch ones with the two middle ones 30A tied together with independent 20A ones on each side. My original idea (as mentioned above) was to use one of these 30A for the garage and the other for the heater, since that is one of the only remaining runs of 57 year old wire in the house. Should I keep the heater on 20A and remove these 4-switch breakers?

2. The old wire in the wall in question was coming from a large junction box that I think actually used to be a fuse box. The wire from the main panel to that box is 2 runs of new 10/3 that was feeding the old wire I removed. My question here is, can I use that existing 10/3 on a 20A breaker in the main panel and run 12/2 (or 12/3) from the junction box to the garage wall? Or do I have to rip out all that 10/3 and run 12/2 all the way?

3. I know GFCI is required in kitchens and bath, but why is it required in the garage and not the rest of the house?

Thanks,
Scott
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Old 07-09-2013, 01:07 PM   #22
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If you have 10-3 with ground you could install a subpanel in the garage fed from the 30 amp circuit. At the sub you would switch to #12 or #14 and add breakers for the receptacles.

The breaker you are describing a two tandem breakers. The inner pair is one breaker and the outer pair is the other.
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Old 07-09-2013, 01:23 PM   #23
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Proper receptacle for circuit?


Jim Port has a good idea with the sub panel.

What kind of wire do you have feeding the heater, and what kind of heater is it?

It doesn't really matter if you use 10/3 to feed receptacles, the breaker just has to be 20 amps

GFCIs are required in garages I believe because they are considered a damp location.
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Old 07-09-2013, 01:38 PM   #24
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Proper receptacle for circuit?


Most garages are concrete slab on grade, which is much more conductive than your house floor.
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Old 07-09-2013, 04:21 PM   #25
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OK, the heater is a Heil and there is the a/c evaporator coil in there. None of the labels have amperage ratings on them. I've been wanting to replace the whole system. Anyway, the old wire running to it from the main panel is 10/3 or 12/3 but only the black is connected to one of the outside 20A switches mentioned above. At the heater closet, the wire first comes in to a metal switch box that has a single switch (like a light switch) on bottom and a screw in fuse covered by a metal box. If I get a new HVAC system, is there any chance it would require 30A?

So if I understand all your answers to my other question correctly, I can use the existing 10/3 from the main panel to the junction box as long as it's connected to a 20A breaker. Then I can run 12/2 (or whatever) from there to the garage wall.--

OR, I could turn that large junction box into a mini sub-panel with the 30A coming in and sending 20A to the garage wall. If I do this, are there any special things I need to do like build in ground and neutral bars? Any ideas on how to safely make this sub-panel appreciated.

Thanks a lot!
Scott
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Old 07-09-2013, 05:20 PM   #26
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If this is just a regular gas furnace, it's probably just on a 15 or 20 amp 120 volt circuit. The only high draw item would be your outside condenser unit, which is on its own 240volt circuit.

As far as the sub panel goes, you are correct. It will come with a ground and neutral bar that will be bonded together. Since this is a sub panel, the ground and neutral must remain separate, so you remove this bonding jumper.
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Old 07-09-2013, 08:25 PM   #27
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If this is just a regular gas furnace, it's probably just on a 15 or 20 amp 120 volt circuit. The only high draw item would be your outside condenser unit, which is on its own 240volt circuit.

As far as the sub panel goes, you are correct. It will come with a ground and neutral bar that will be bonded together. Since this is a sub panel, the ground and neutral must remain separate, so you remove this bonding jumper.
I guess what I was getting at was, do I need to buy a whole sub-panel box just to convert one 30A circuit to 20A? If so, I imagine it would be cheaper just to change the 30A breaker to a 20 in the main panel.
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Old 07-09-2013, 09:01 PM   #28
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It would be cheaper, yes, just to change the breaker. You can only have a 20 amp breaker on this circuit.
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Old 07-10-2013, 11:06 AM   #29
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OK, now you are giving me more ideas.

If I did this sub-panel, how many 20A breakers could I safely run on one 10/3 30A feed (both red and black connected)?
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Old 07-10-2013, 11:26 AM   #30
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Proper receptacle for circuit?


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OK, now you are giving me more ideas.

If I did this sub-panel, how many 20A breakers could I safely run on one 10/3 30A feed (both red and black connected)?
As many as you want to, until the 30 amp breaker trips!


You need to do a load calculation to determine that.
Just because you install 20 amp breaker does not mean that you will be pulling 20 amp through each circuit.

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