Can I add some tandem breakers?


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Old 02-19-22, 02:32 PM
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Question Can I add some tandem breakers?

I've done a significant amount of wiring in my previous work shop; but just moved to a new location. I have the need to wire up two 220v plugs. When I opened the breaker box I was disappointed to see every slot used!


It appears that my box is a V-2813 with a max of 40 circuits.


I just want to verify that I can't install some tandem breakers into this existing box and that the 220v breakers on the top "count" as 2 of the 40 circuits each.

At minimum I'd need to install two tandem breakers so that I can get one 220v breaker for my appliances. (They will not need to be run at the same time)

Any suggestions are welcome! Thank you!





 

Last edited by PJmax; 02-19-22 at 03:13 PM. Reason: labeled panel pic
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Old 02-19-22, 03:21 PM
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Welcome to the forums.

That's a panel in your shop ?
That is a busy and packed panel.
I labeled the top four breakers as it looks like the breakers may be oversized based on the wire size.
Breaker 2-4 is 40A with what looks like #12 (20A) wire.
Same thing with breaker 5-7.
What are they for ?

V-2813 is the UL listing certification. Not a model number.
There should be a diagram on the door with breaker locations.
 
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Old 02-19-22, 04:37 PM
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Install a sub-panel someplace, either next to the main panel or at some convenient location. You would only need two spaces for the sub-panel. You can either relocate those two circuits to the sub-panel or just combine two lightly loaded circuits.
 
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Old 02-19-22, 05:10 PM
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I found two circuits in the main panel that are to devices that the home no longer has (freezer and jacuzzi) ...

I'm thinking I'll add a 125 amp sub panel like @tolyn suggested. Specifically this one:

https://www.lowes.com/pd/Square-D-12...-Pack/50311135

Seems like a smart thing to do with the main being so packed
 
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Old 02-19-22, 06:26 PM
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You will need to remove the breakers across from the 125 that feeds the subpanel. There are stab limits.
 
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Old 02-19-22, 07:06 PM
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@PJMax


 
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Old 02-19-22, 07:07 PM
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@pcboss, I don't understand your comment.
 
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Old 02-19-22, 11:18 PM
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@pcboss, I don't understand your comment.
Panel does not accept tandems 40 circuits max no tandems allowed.
 
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Old 02-19-22, 11:33 PM
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I believe the stab limit is 100A. A breaker connects to the panel with stabs.(contacts)
That means you could have a 125A sub panel but feed it with a 100A breaker.
 
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Old 02-20-22, 05:23 AM
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@PJmax , thanks for the clarification.


----------


I basically plan on installing a sub panel outside the wall like this - https://www.youtube.com/watch?v=em1QpsZIUvE

Sub Panel - https://www.lowes.com/pd/Square-D-12...-Pack/50311135

#2 4 Wire from main to the sub panel - https://www.lowes.com/pd/Southwire-2...ble/5002300757

100amp breaker - https://www.lowes.com/pd/GE-Q-Line-T...reaker/3128201

AntiScaling - https://www.lowes.com/pd/Gardner-Ben...mpound/4514334


-------------

* Floating neutral with dedicated ground in the sub panel

--------------

I'm thinking I'll put a junction box directly below my current main to bring the wires out of the wall, then run some flex PVC from that box to the sub panel.




 
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Old 02-20-22, 09:18 AM
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Do not follow what is shown in that YouTube video! Conduit is required to be a continuous assembly in order to use individual conductors. He just runs them in a wall cavity which is not allowed with individual wires. Also, you may only splice in an LB if it is marked with the cubic inch volume on the conduit body. (I added a comment on YouTube.) The best option might be to run Flexible Metal Conduit the entire way from the panel to the sub-panel.

You posted URD/MHF which is not allowed inside a building. If you were going to use conduit you will want to use XHHW or THHN wires. If you want to use a cable then SER would be the cable of choice. Of course, if the cable is run on the surface you need to protect it.

#2 aluminum XHHW is only rated for 90 amps and #2 SER is rated for 80 amps. If you want 100 amps you need to use #1 aluminum or #3 copper.
 

Last edited by Tolyn Ironhand; 02-20-22 at 10:38 AM.
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Old 02-20-22, 01:38 PM
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URD and MHF are two different wire types. URD is strictly outside use only because it only carries a USE-2 rating, whereas MHF has RHH/RHW-2/USE-2 and can enter the structure but does need to be in conduit when above ground.
Also #2 Al SER is 90A, not 80A. It's sized at 75C deg.
 
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Old 02-20-22, 04:22 PM
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Also #2 Al SER is 90A, not 80A. It's sized at 75C deg.
If your location is under 2014 NEC, and the cable is installed in insulation, SER is limited to the 60-degree column similar to NM cables. That is 75 amps. Using the round-up to the next standard breaker rule that puts it to 80 amps max.
 
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Old 02-20-22, 06:27 PM
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SER at 60C deg is only required if buried within insulation for more than 10% of its length for a max of 10ft. Example if 30ft of SER has 3ft or less buried in insulation it's 75C. If more than 3ft then it's 60C. Just to note, the 60C limit was removed in 2017 on SER larger than #10.
 
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Old 02-20-22, 07:16 PM
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Whops, already did it. Doesn't seem unsafe, I do wish I read this before about the metal conduit coming from the box and out the wall, that could have worked.

 
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Old 02-20-22, 09:08 PM
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Often more circuits are needed on full main panel. One solution is finding place where several cables to that panel come together 10 or 20 feet then bundle to main panel.

At “together” area install a sub-panel and connect those cables to breakers in it.

On main panel remove old unused breakers and use #60 or #80 cable from new sub panel a double pole breaker on main to feed it. For remote high current loads like electric heaters, 20 amp circuits this can be helpful.

On main panel unused breakers are available for new circuits. And with less "home runs" to main reduces clutter and wiring costs.

When DH 30 breaker panel was full, put 12 breaker panel 30 feet away and another 10 breaker 20 feet away. Main now has spare slots.
 
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Old 02-20-22, 09:54 PM
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In your sub panel you put a nice PVC bushing on a PVC plastic connector.
What happened in the main panel ?
That upside down connector can be pretty sharp.
 
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Old 02-21-22, 05:11 AM
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Yeah another PVC bushing would have been smart...
 
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Old 02-21-22, 07:34 AM
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I think the real question is, "What type of 'raceway' did you run between the main panel and the plastic junction box?"

To me, the reversed romex connection says none.
 
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Old 02-21-22, 08:49 AM
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Not to pile on but the NM cable clamp is not correct for use on the individual MHF conductors. That style clamp is for jacketed cable. And the MHF needs to be completely within conduit all the way to the panel.
 
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Old 02-21-22, 11:50 AM
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@PJmax & @pattenp - I took it all apart this morning, removed the cable clamp, installed an PVC bushing with PVC plastic connector on top. Currently there is non-jacketed MHF in the 4'' span between the plastic junction box and the main breaker box.
 
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Old 02-21-22, 01:20 PM
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NEC wise that 4" gap is a violation.
 
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Old 02-21-22, 05:32 PM
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1.) Why is that rule in place? Just curious...
2.) How do you know how "big" of a sub panel you can have? Seems shady to daisy chain from the main. How do I know if I'll overrange my service or not?
3.) I'm trying to think of a way to bridge the wall cavity easily... Could I use this 1-1/2 flex PVC that they use for spa hose? They sell it by the foot in the size I need.... I know it's not gray.


https://www.lowes.com/pd/EZ-FLO-1-1-...ose/1000180599

-----------

As an update... I got my 20 amp and 50 amp 240v outlets wired in. They're working as intended.
 
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Old 02-22-22, 06:24 AM
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The white flex PVC is not rated for use as a conduit. There is a gray flexible conduit that can be used.
 
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Old 02-22-22, 07:55 AM
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Anyone know of a place that sells that stuff by the foot? In 1-1/2''
 
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Old 02-22-22, 07:57 AM
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Try your local electrical supply.
 
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Old 02-22-22, 07:18 PM
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Does anyone know the answers to 1 and 2 in post #23?
 
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Old 02-24-22, 07:26 PM
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"CircuitBreaker: How do you know how "big" of a sub panel you can have? Seems shady to daisy chain from the main. How do I know if I'll overrange my service or not?"

Codes are about capacity of wire, not panel. A main panel with 200 amp main breaker may have many breakers whose total rating exceeds 200 amps.

Fuses and circuit breakers are commonly sized and limited to rating of wire used for circuit.

High current items i.e. air conditioners, electric ovens, etc. should be direct to main panel.

Calculating sub-panel feed amps should consider with long high current loads like electric heaters and window ACs.

Sub-panels are good where there are a number of 15 and 20 amp lighting and receptacle circuits distant from main panel. In existing homes it may easier wiring to nearby sub panel than xx additional feet to main.

New reality check: While modern homes have more electric powered items, power draw has gone down. Old TVs were 300 watts, new large screen flat panel less than 100 watts. 100 watt light bulb now 10 watt LED. DH original 1967 central AC 26 amp compressor was replaced with 13 amp.
 
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Old 02-26-22, 06:42 AM
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1.) Why is that rule in place? Just curious...
It is because the wire is not rated to be in a wall cavity without conduit and could be a safety issue. I would guess it releases toxic smoke when burned. This is why I posted to use FMC in post #11
 
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Old 02-28-22, 10:22 AM
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So, if the wire was undersized or a breaker failed; it could burn and release toxic smoke into the wall cavity?
 
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Old 03-03-22, 07:49 PM
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It can also start other things on fire inside the wall as well.
 
 

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