Sub Panel or Not

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  #1  
Old 07-04-04, 07:25 PM
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Sub Panel or Not

I have an old house with the old BX wiring...I want to replace it all...I have 150 amp service and it seems like they have about 3 breakers running the whole house.

Instead of running multiple feeds to the second floor, is it wiser to run a sub panel and just run the 2nd floor off of that.. If so what size wire would I run and how big would I have to make the subpanel.

Thanks

Tearflop
 
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  #2  
Old 07-04-04, 09:41 PM
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There are a number of potential issues.

What is your service size? 60-amps? 100-amps? 150-amps? 200-amps? The answer can be determined by the size of your main breaker. Then you have to ask yourself if that is adequate or not.

If your service size is inadequate, you will start by increasing the service and installing a larger panel. Once you install a 40-space panel, a subpanel will be unnecessary. In most cases, a subpanel within one structure is not helpful unless you are doing it because your otherwise-adequate service panel is full.
 
  #3  
Old 07-05-04, 07:26 AM
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My main service is 150 Amps..and no it is not full.....the reason I was thinking of running the sub panel to the second floor is because I want to rewire. I think it would be a real hassle to rewire the entire 2nd floor without ripping all the walls out. I figured it would be easier to run 1 wire to the second floor then to try and run many. What do you think.

Thanks

Tearflop
 
  #4  
Old 07-05-04, 08:13 AM
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Originally Posted by Tearflop
My main service is 150 Amps..and no it is not full.....the reason I was thinking of running the sub panel to the second floor is because I want to rewire. I think it would be a real hassle to rewire the entire 2nd floor without ripping all the walls out. I figured it would be easier to run 1 wire to the second floor then to try and run many. What do you think.
I'm presently designing a house I hope to be building in a few years. But despite it being a new construction, I plan to be doing subpanels in it. One reason is that I want to be prepared to add circuits with a minimum of running new wire. And the other is that I plan to divide circuits in greater numbers (more than the limit of 42 for one box), and I don't want a zillion cables all converging in one place. Some of my current plans include as many as 3 subpanels (basement, kitchen, bedrooms).

If you are really going to be tearing the 2nd floor apart to rewire, then I'd agree with you that a subpanel up there would be a good idea. And considering that AFCI breakers are now required in bedrooms, and they could be subject to some false tripping, it would be a big convenience to have them up there. It's how I would do it. Be sure you check to make sure the panel box you intend to use will fit the larger AFCI breakers with plenty of wiring room left over. Some of the smaller panel boxes I've seen don't look like they have enough room.

You should also price out the AFCI breakers. Be prepared for "sticker shock". You might want to have fewer circuits than you otherwise planned, depending on the price you can get.
 
  #5  
Old 07-05-04, 08:25 AM
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It sounds like you have a good application for a subpanel. So go for it.

Subpanels usually increase the cost somewhat, but if that's not an issue, then okay. Another thing to watch out for with subpanels is that they partition your available power. Don't box yourself in such that you have sufficient service capacity, but insufficient capacity in one of your subpanels. The best way to avoid this problem is to keep your largest loads in the main panel.
 
  #6  
Old 07-07-04, 08:20 PM
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So can you reccommend a subpanel size...type . My service is 150 amps...I will probably use the sub to wire 4 bedrooms and 2 baths. The main panel will take care of the basement, LR, DR, Kitchen, garage and study.

Thanks Tearflop
 
  #7  
Old 07-08-04, 12:45 AM
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Probably the cheapest route would be to go with a 100A panel for the sub, simply because they're the most common, and hence the pricing is better. Buy them as a "value Pack" with a handful of breakers included and they're probably a much better deal than going with a smaller 60A panel and buying breakers separately.

You don't have to use the full rated capacity of the subpanel, however. So wiring it up to a 60A double-pole breaker in your main panel will likely be more than sufficient.

You should be able to wire it with 6-3 NM then, rather than running conduit with 2 ga. conductors, which would be a lot tougher.
 
  #8  
Old 07-09-04, 09:55 PM
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This raises a question I posted about the amperage for a sub panel: I have a 100 amp main panel, may I run a 100 amp sub panel from that main? I will be powering a master bedroom, bathroom, stairwell, garage, exterior garage light and a future circuit for a jacuzzi which will be 220v. ????? If I understand correctly, I don't need to wire the entire panel so it will not be using the entire amps for which it is rated...right? Or would I be better to get a smaller amp sub panel, say 65amps???
 
  #9  
Old 07-09-04, 10:24 PM
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Yes, you can certainly run a 100-amp subpanel from a 100-amp main panel. That certainly simplifies the calculations because there is no calculation to make. If the distance between the panels is small, the extra cost is trivial.
 
  #10  
Old 07-10-04, 06:04 AM
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John, thanks, it does simplify things. See my comments on the 'sub panel amperage' post. Mike
 
  #11  
Old 07-12-04, 08:09 AM
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What does it entail to change your existing service 100 amp to a 150 or 200.

Thanks Tearflop
 
  #12  
Old 07-12-04, 08:20 AM
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Depends on a few factors. First step is to contact your utility and find out what thier procedures are.

Thy may have to install a new meter. You may have to install (or have installed) a new meter socket.

If your service is overhead (aerial), you'll probably need to replace the wire running from the meter socket to the drip-loop past the mashhead, which will almost certainly require new conduit and a new masthead.

You'd probably need to replace the wire running from your meter socket to the main panel also, and of course you'd have to peplace the main panel.

The sequence of events usually looks like this:

Contact utility and find out specifics of what they require.

Get permit.

Have utility disconnect service.

Change out all necessary components.

Get the project inspected and signed off on. Often will require that certain other portions of the house be brough up to current code too.

Utility reconnects service after inspection.

This process can take up to days or weeks, depending on the availability of the inspection and utility crews in your area. This is why even most die-hard diy-ers contract this one out to an electrician that can get it all wrapped up within a day.
 
  #13  
Old 07-12-04, 09:46 AM
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Thanks for the input.....I have a 100 amp now , I wonder If I really need to upgrade.

Tearflop
 
  #14  
Old 07-13-04, 07:56 PM
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ok , I ready to wire up the sub, got the panel and some 6-3 wire......( red & black are hot), white is neutral and copper grnd. I was told that in the sub panel the neutral and copper should go to separate bars, Does that go for the main also (red and black to breaker).....my main presently has copper and white on the same bar.

Any input appreciated

Thanks tearflop
 
  #15  
Old 07-13-04, 08:13 PM
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For once, someone at a store seems to have given useful advice

On the mains the neutral and ground are generally connected (unless there is a seperate disconnect switch between the meter and the main panel). One note though. You can have (if the panel is rated for it), more than one ground wire under a single screw, but you can never have more than a single neutral wire under a screw. This is true for mains and subs.

But with the sub you will need to keep the neutral and grounds on separate bars. To do this you need to either remove (if pre-installed), or not install the neutral bus bonding screw or strap. This is *usually* a green screw that goes through the neutral bar into the chassis of the panel.

You will need a separate grounding bar, which is usually sold as a separate kit for your panel. The documentation should tell you the part number you'll need, and how/where it should be mounted in the panel.

The reason is that there should be one, and only one point in a structure where the neutral and ground are connected together, and it should be as near to the incoming source as possible. If you want to understand why, search back through this forum. The topic has been beaten to death several times in the last couple of months alone
 
  #16  
Old 07-14-04, 07:44 PM
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Vector, Thanks for the response.

I did get the extra bar for the panel and will be setting it up. Glad to hear that HD employee gave good info..

Thanks

Tearflop
 
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