Transition Romex to THHN

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  #1  
Old 08-09-14, 11:53 AM
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Transition Romex to THHN

Looking for some advice.

I am going to be running two new 20A circuits using two 12/2 romex runs in my basement across the ceiling joists. Then I am going to run them down a masonry wall with both in a single piece of 1" EMT and then terminate them into a single 2-gang box with two 20A GFI receptacles.

My understanding is that I need to (or should) convert the romex to THHN before it enters the EMT. My question is, how do I convert it? I was planning on installing a handy box, but I don't know what to use to join the romex wires to the THHN wires. Can you even use wirenuts for a 20A load?

Also, is there anything I should take into account because the masonry is a cinder block wall with earth on the other side? Any corrosion issues I should be aware of? I was planning on mounting the hole straps with standard Tapcon screws.

btw, the use of EMT is only for protection against physical damage. Thanks.
 
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  #2  
Old 08-09-14, 12:31 PM
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You make the transition in a permanently accessible junction box and secure the splices with the appropriate wire nut twist-on connector. I believe the red ones from most manufacturers would work fine. OR....since the EMT is just for physical protection and just a protective sleeve, just route the 2 NM-B cable (aka romex) down the conduit into the box and don't have the hassle of a junction box.

terminate them into a single 2-gang box with two 20A GFI receptacles.
Why are you going to the extra expense of 20 amp GFCI receptacles when all you need is 15 amp rated devices? By the way, current code requires the 2 new circuits to be AFCI protected and the GFCI receptacles to be tamper resistant.
 
  #3  
Old 08-09-14, 12:57 PM
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It's for running a chest freezer and a refrigerator, each requiring a 20A circuit.

Will I need to increase the diameter of the EMT conduit to take into account for conduit fill %?

Our home was built in 2003 and there are AFCI breakers for the bedrooms, are AFCI breakers a requirement for most new circuits?

Also, is this what you're talking about (for a CH style box)? - Eaton Type Ch 20 Amp Combination Arc Fault Circuit Breaker
 
  #4  
Old 08-09-14, 01:04 PM
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A chest freezer is fine on a 15A circuit.
 
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Old 08-09-14, 01:15 PM
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By the way, current code requires the 2 new circuits to be AFCI protected and the GFCI receptacles to be tamper resistant.
I thought all receptacles had to be TR and AFCI was required for all living spaces. Is the basement finished?
 
  #6  
Old 08-09-14, 01:27 PM
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I thought all receptacles had to be TR and AFCI was required for all living spaces. Is the basement finished?
The basement is 3/4 finished, but the receptacles will be on a masonry wall on the unfinished side.

So the chest freezer can be a 15A circuit, but does the fridge still need a 20A circuit?
 
  #7  
Old 08-09-14, 03:05 PM
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The price is the same for a 15 and 20 amp breaker. You already ran the wire to support the 20 amp circuit.

Since this mix unfinished you do need GFI protection.
 
  #8  
Old 08-09-14, 05:20 PM
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The price is the same for a 15 and 20 amp breaker. You already ran the wire to support the 20 amp circuit.
Well I haven't actually run anything yet, but I think I'll just go with two runs of 14/2 romex on 20A circuits from the breaker box to a 2-gang handy box, use wire nuts to transition it to THHN and run it down a single piece of EMT.

Can I get away with 6 conductors in 1" EMT?
 
  #9  
Old 08-09-14, 05:38 PM
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You cannot use #14 on 20 amp circuits.

You can just sleeve the NM down the conduit without a junction box. Use a bushing at the top of the sleeve.
 
  #10  
Old 08-09-14, 05:57 PM
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if you go to all the work to pull 2 cables.....pull 12-2 wg on 20 amp breakers ............with 2 pvc conduits for protection against physical damage going to 2 boxes.use the gray pve outdoor boxes for a clean look.

You can just sleeve the NM down the conduit without a junction box.
 
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Old 08-09-14, 05:59 PM
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You cannot use #14 on 20 amp circuits.

You can just sleeve the NM down the conduit without a junction box. Use a bushing at the top of the sleeve.
Sorry, that was a brain fart on my behalf - I meant 12/2 like I stated in my original post.

So I can run 2 lengths of 12/2 romex down a single piece of 1" EMT and not need to worry about heat buildup or whatever? I just want to be sure. Thanks.

if you go to all the work to pull 2 cables.....pull 12-2 wg on 20 amp breakers ............with 2 pvc conduits for protection against physical damage going to 2 boxes.use the gray pve outdoor boxes for a clean look.
(Sorry, I just saw your post) That's a definite possibility. I think I am just trying to go between too many possible solutions.

Regardless of the conduit material, I will end up running 12/2 romex to the box(es) with no THHN involved.
 
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Old 08-09-14, 06:10 PM
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So I can run 2 lengths of 12/2 romex down a single piece of 1" EMT and not need to worry about heat buildup or whatever? I just want to be sure. Thanks.
yes



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  #13  
Old 08-09-14, 07:40 PM
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It's for running a chest freezer and a refrigerator, each requiring a 20A circuit.
I agree with installing 20 amp circuits for both appliances, but you still do not need more than 15 amp GFCI receptacles.

Also, is this what you're talking about (for a CH style box)? - Eaton Type Ch 20 Amp Combination Arc Fault Circuit Breaker
That would be correct if you have the tan colored CH series Cutler-Hammer panel. If you have the gray colored BR series Cutler-Hammer box you'll need a different breaker. Check with your local AHJ to see if they'll require you to use the AFCI breaker and also ask if the GFCI receptacles need to be tamper resistant.
 
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Old 08-09-14, 09:29 PM
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I agree with installing 20 amp circuits for both appliances, but you still do not need more than 15 amp GFCI receptacles.
Okay. Can you expand on that at all? Is that simply because an appliance that actually required 20A would have a plug with one of the slots sideways, so these appliances (which do not have a 20A plug configuration) wouldn't require a 20A receptacle but a 20A circuit breaker would be warranted in case of spikes when the compressor kicks on?

That would be correct if you have the tan colored CH series Cutler-Hammer panel. If you have the gray colored BR series Cutler-Hammer box you'll need a different breaker. Check with your local AHJ to see if they'll require you to use the AFCI breaker and also ask if the GFCI receptacles need to be tamper resistant.
It's definitely the CH style. It's a tan colored panel and explicitly states that CH type breakers are to be used. I'll check to see what is required for code.
 
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Old 08-09-14, 11:29 PM
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The code allows for 15 amp slot devices to be used if there is more than one place to plug into the circuit. A standard duplex is two.
 

Last edited by pcboss; 08-10-14 at 07:42 AM.
  #16  
Old 08-10-14, 07:38 AM
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Okay. Can you expand on that at all? Is that simply because an appliance that actually required 20A would have a plug with one of the slots sideways, so these appliances (which do not have a 20A plug configuration) wouldn't require a 20A receptacle but a 20A circuit breaker would be warranted in case of spikes when the compressor kicks on?
yes

AND you may install a 20 amp GFCI receptacle outlet on a 12 gauge,20 amp protected circuit if you wish to.
 
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Old 08-10-14, 08:10 AM
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AND you may install a 20 amp GFCI receptacle outlet on a 12 gauge,20 amp protected circuit if you wish to.
Yes, you may use 20 amp devices, but it's rare that 20 amp devices are ever really needed in a residential installation. Commercial installations is another story.
 
  #18  
Old 08-10-14, 08:26 AM
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some hot tubs need a 20 amp outlet

some window a/c 's use a 20 amp outlet.
 
  #19  
Old 08-10-14, 12:46 PM
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The wall that I plan on running the wire down is a cinder block wall with ground (dirt in this case) on the other side. Does that constitute a "wet location" and would I need to adjust my setup accordingly? What would that entail?

Please advise. Thanks.
 

Last edited by brshoemak; 08-10-14 at 01:02 PM.
  #20  
Old 08-10-14, 01:25 PM
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Inside a basement would not meet the definition of a wet location in the NEC.
 
  #21  
Old 08-10-14, 08:54 PM
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some hot tubs need a 20 amp outlet

some window a/c 's use a 20 amp outlet.
In the big picture, those would be rare.
 
  #22  
Old 08-12-14, 10:16 AM
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Ok, I'm back. Went to Lowes picked up a shload of supplies. I'm going to do AFCI --> romex --> junction box --> THHN (with wire nuts) --> 2-gang box with 2 GCI (everything 12AWG and 20A gear). There will be two pieces of romex entering the junction box and 6 strands of THHN leaving the box.

First off, holy crap are AFCI breakers expensive! Now, on to my question:

In the junction box where I'm going to convert the romex to THHN, the rear of the box has a location for a ground screw.

How should I handle grounding? Am I correct in assuming I can just wrap a separate piece of 12AWG THHN wire around that screw, then twist and wirenut that piece along with the grounds the romex and THHN - for one circuit? Then would I do the same for the other circuit - so only two pieces of 12AWG wire would be wrapped around the ground screw, one for each circuit?

Also, since the metal junction box will be the ground point for all the connected metal conduit/boxes, I don't need to worry about adding a ground point to the box where the receptacles will be correct? Obviously the receptacles themselves would be grounded.

btw, if seemingly everything residential requires a AFCI nowadays (with the latest NEC), why are there so few AFCI breakers on the shelves, but boxes upon boxes of 'normal' circuit breakers remain? Am I safe to assume that commercial work does not require AFCI in most cases?
 
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Old 08-12-14, 10:31 AM
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Am I correct in assuming I can just wrap a separate piece of 12AWG THHN wire around that screw, then twist and wirenut that piece along with the grounds the romex and THHN - for one circuit? Then would I do the same for the other circuit - so only two pieces of 12AWG wire would be wrapped around the ground screw, one for each circuit?
No. All the grounds get connected together and with a wire nut they should be connected to one pigtail that is connected to the ground screw. Just that one ground pigtail is attached to the ground screw.

if seemingly everything residential requires a AFCI nowadays (with the latest NEC), why are there so few AFCI breakers on the shelves, but boxes upon boxes of 'normal' circuit breakers remain? Am I safe to assume that commercial work does not require AFCI in most cases?
I am not aware of any commercial requirements for AFCI protection. You see relatively few AFCI breakers in the big box store because of the cost. The regular breakers are relatively inexpensive in comparison and that is what most DIYers will use regardless of code requirements because most DIYers are not getting permits and/or inspections. In addition, many areas have not adopted the latest codes requiring high use of AFCIs or may have amended those requirements out of their adopted code. What you saw in Lowes (or any other box store) was probably a display of the AFCI and GFCI breakers on a cumbersome rack designed to take some time to remove just one blister packed breaker. These are designed to take some effort to remove the breaker because of the high theft rate experienced by the big box stores of these expensive items. I can assure you they have more AFCI breakers in their stock than you see, most likely in top stock not available for theft by the common shoplifter. When sales of these expensive items increases, so will the stock each store maintains.
 
  #24  
Old 08-13-14, 07:53 AM
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Thanks for the information - makes sense. Now I just need to be able to figure out how to successfully pretwist the 5 grounds so they'll be secure in the wire.

Now, in terms of running romex, am I correct that you can't bundle two cables under a single staple and instead need to run them side-by-side?

Also, usually I see romex ran along joists, but is there any limitation in running it along the perpendicular wood beam that supports the joists? Will hammering romex staples into it cause any problem to the joists?
 
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Old 08-13-14, 08:05 AM
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makes sense. Now I just need to be able to figure out how to successfully pretwist the 5 grounds so they'll be secure in the wire.
Read the instructions on the wire not box, pre-twisting is not necessarily a requirement.

is there any limitation in running it along the perpendicular wood beam that supports the joists? Will hammering romex staples into it cause any problem to the joists?
You may run along the wood beam and you may staple two cables with one long staple, but I would drill the floor joists and run through the series of bored holes, no staples needed till you reach the junction box.
 
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Old 08-13-14, 08:09 AM
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makes sense. Now I just need to be able to figure out how to successfully pretwist the 5 grounds so they'll be secure in the wire.
Read the instructions on the wire not box, pre-twisting is not necessarily a requirement.

is there any limitation in running it along the perpendicular wood beam that supports the joists? Will hammering romex staples into it cause any problem to the joists?
You may run along the wood beam and you may staple two cables with one long staple, but I would drill the floor joists and run through the series of bored holes, no staples needed till you reach the junction box.
 
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Old 08-13-14, 08:20 AM
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Old 08-13-14, 09:22 AM
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Basic Electrical Skills :: How to Install a Wire Nut
Yeah, thanks. I know how to use wire nuts. I'm saying that it's just a tad bit more difficult to twist together 5 #12 wires vs 2.

Read the instructions on the wire not box, pre-twisting is not necessarily a requirement.
I'll check the instructions, but even if it were not required I'd be wary of trying to do that with 5 #12 wires and being sure they were all making contact inside the wire nut instead of having some being pushed out. Regardless, thanks for the information.
 
  #29  
Old 08-13-14, 02:22 PM
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I'd be wary of trying to do that with 5 #12 wires and being sure they were all making contact inside the wire nut instead of having some being pushed out.
I think if you follow the instructions and tighten the wire nut enough, you will also twist the wires into a tight connection. A wing nut might be a better choice to get additional leverage.
 
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Old 08-13-14, 08:21 PM
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I'm saying that it's just a tad bit more difficult to twist together 5 #12 wires vs 2.

where are you twisting 5 grounds

run the 2 cables all the way to the outlets.............if you use EMT place a connector with a bushing at the top.

My understanding is that I need to (or should) convert the romex to THHN before it enters the EMT.
no
 
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