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Old 02-07-2009, 04:34 PM   #1
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Converting Main Panel to Sub: How to jumper?


My current house has a 200 AMP Main Panel. I added a new guesthouse and will be moving the overhead incoming electrical line underground going to a new 400 AMP main panel in the guest house (because it's closer to the utility pole) and then run a new 200 AMP underground to my current house and will need to convert the existing 200 AMP main panel to a subpanel without a meter. I don't want to rewire everything there, so my thoughts are they will pull the meter and provide a cover, but then it's up to me to make the main connections from the new main.

Can I just wire the 2/0 wires into the old lugs and get some type of jumper bars to close the gap where the meter used to be, or can I buy such jumper bars, or what is best? Thanks for the advice.

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Old 02-07-2009, 04:39 PM   #2
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Converting Main Panel to Sub: How to jumper?


Rip the old meter out completely and refeed the existing panel with 4 new wires from the guest house, and your going to have to separate the grounds and neutrals as well.


Last edited by chris75; 02-07-2009 at 04:42 PM.
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Old 02-07-2009, 04:44 PM   #3
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Converting Main Panel to Sub: How to jumper?


Remove the meter can and replace with a main disconnect. Many areas (like in CT) will require this anyway. Fireman prefer to have an external disconnecting means also.
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Old 02-07-2009, 05:20 PM   #4
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Converting Main Panel to Sub: How to jumper?


Quote:
I don't want to rewire everything there, so my thoughts are they will pull the meter and provide a cover, but then it's up to me to make the main connections from the new main.
I don't want to get up and drag my ass to work every day but....whatcha gonna do?

You will need to do some rewiring anyway to separate the grounds/neutrals so you might as well do it right and install the appropriate panel.

I have seen it done before but it's just not right. You are building a guest house and upgrading your service so do it right. Your electrical system is not the place to try and scrimp.

I would make an exception if :

1. The inspector allowed it.

2. The existing panel was under a decade old and in otherwise good shape.

3. The method of getting the new feeders into the panel didn't look like crap.

pics?
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Old 02-07-2009, 10:03 PM   #5
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Converting Main Panel to Sub: How to jumper?


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Originally Posted by 220/221 View Post
I don't want to get up and drag my ass to work every day but....whatcha gonna do?

You will need to do some rewiring anyway to separate the grounds/neutrals so you might as well do it right and install the appropriate panel.

I have seen it done before but it's just not right. You are building a guest house and upgrading your service so do it right. Your electrical system is not the place to try and scrimp.

I would make an exception if :

1. The inspector allowed it.

2. The existing panel was under a decade old and in otherwise good shape.

3. The method of getting the new feeders into the panel didn't look like crap.

pics?
Thanks for the replies.

1. Still not sure if this will be inspected or not. (Yeah, yeah...I know...but I'm not into all this red tape.)

2. The existing panel is about 8 years old or so...I personally put it in when I rebuilt the house. It's a pretty big 200 AMP Murray panel with about 20 breakers at least.

3. The new feeders are already in and have been inspected. (I had to go about 76' distance underground in a 2" conduit.) So currently the existing 200 amp feed is coming in from above and I have the new feeds coiled and ready in the lower part of the panel - ready to be connected.

Pics? Of the open panel? I can take some tomorrow in daylight.
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Old 02-07-2009, 10:13 PM   #6
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Converting Main Panel to Sub: How to jumper?


Quote:
Originally Posted by HomeOwner42 View Post
Thanks for the replies.

1. Still not sure if this will be inspected or not. (Yeah, yeah...I know...but I'm not into all this red tape.)

2. The existing panel is about 8 years old or so...I personally put it in when I rebuilt the house. It's a pretty big 200 AMP Murray panel with about 20 breakers at least.

3. The new feeders are already in and have been inspected. (I had to go about 76' distance underground in a 2" conduit.) So currently the existing 200 amp feed is coming in from above and I have the new feeds coiled and ready in the lower part of the panel - ready to be connected.

Pics? Of the open panel? I can take some tomorrow in daylight.
Do you have the grounds and neutrals separated? Are the neutrals on an isolated bar? Do you have ground rods installed? How many wires did you pull in the conduit?

This isn't really the kind of project you want to be skipping the inspection on. What would the red tape be, them forcing you to make this a legal and safe install?

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Old 02-07-2009, 10:18 PM   #7
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Converting Main Panel to Sub: How to jumper?


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Originally Posted by jamiedolan View Post
Do you have the grounds and neutrals separated? Are the neutrals on an isolated bar? Do you have ground rods installed? How many wires did you pull in the conduit?

This isn't really the kind of project you want to be skipping the inspection on. What would the red tape be, them forcing you to make this a legal and safe install?

Jamie
The main red tape is the delay in inspection...since I live here now and can't afford to have the power off for more than a few hours. On the other hand, of course I want it safe.

I'll have to check in the morning about the neutrals and grounds. Ground rods? I believe so. How many wires? 3x 2/0 and 1x 6 gauge ground.
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Old 02-08-2009, 01:35 AM   #8
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Converting Main Panel to Sub: How to jumper?


You have a 400 amp main panel in the guest house? or do you mean you have a 400 amp meter base at the guest house commonly called a 320.
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Old 02-08-2009, 01:58 AM   #9
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Converting Main Panel to Sub: How to jumper?


Meter main combos are typical in the west. 400 amp meter/main with an additional 200 amp breaker to refeed the main house.


If your existing panel has a wire fed main breaker you could probably just take the wires out and feed into the breaker. Pics will help a lot.

In your existing panel the grounds (bare) and neutrals (white) will all be on the same bus. When this necomes a "sub" panel the neutrals will have to be isolated from the enclosure on their own bus. The grounds will remain on the bus that is bonded to the enclosure.

And......I think you need 3/0 copper feeders for your 200 amp feeders.
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Old 02-08-2009, 02:06 PM   #10
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Converting Main Panel to Sub: How to jumper?


Yes, the new guest house panel is a Siemens 400amp main with two 200amp breakers in it - one for the guest house and one for the main house. Attached are photos of the older Murray 200amp main panel that I need to convert into a subpanel. It only has a single ground/neutral bar.

In the first photo you can see the whole panel with the new feeds and greeen ground wire coming in from the bottom...unattached thus far. You can also see the existign feeds coming in from the top, then looping to the connection as shown in the second photo.

For a new neutral bus to separate grounds and neutral, how do I attach it and where do you suggest?
Attached Thumbnails
Converting Main Panel to Sub: How to jumper?-image_085.jpg   Converting Main Panel to Sub: How to jumper?-image_087.jpg  

Last edited by HomeOwner42; 02-08-2009 at 02:09 PM.
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Old 02-08-2009, 03:26 PM   #11
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Converting Main Panel to Sub: How to jumper?


GAH!!

Did you stucco around that service?

I am an electrician so it would be easier for me to install a new panel than to cobble this one together.

First, this type of panel gives you very little room to work with. The circuit breaker side of newer panels are twice that wide leaving plenty of room for two bus bars.




If this^ were the type of service you had, I'd say keep it.


Second, the main breaker you have is fed from busing, not wires. In some cases you would simply disconnect the wires feeding the breaker and replace them with your new ones.

Third, you would have to install some kind of jumpers in the existing meter socket or somehow rebuild the bus behind the meter. Is this possible? Can't tell without looking behind the meter.

I think the only room you have to work with is in the bottom left side of the service which is designed for power company wiring.

I doubt that it would pass any type of inspection but in theory you could install neutral bus, isolated from the enclosure in the utility compay section. You would have to provide an adequate opening between the sections to get the neutrals over there. You would hook the ground to the lug where the existing neutral is.

It's too much effort to end up with a cobbled up mess. The time spent will be more than the time spent installing a new panel. Spend a couple hundred and do it right. Looks like you have plenty of cable to work with and you can get rid of those twin breakers. Find a panel with a main that can be installed at the bottom because you don't have a lot of extra feeder wire
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Old 02-08-2009, 06:50 PM   #12
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Converting Main Panel to Sub: How to jumper?


Well, sure that new panel looks like it has more room and would be easier to install....that is until you consider having to deal with ripping out the old panel, buying a new panel, installing a new panel, getting the feed wires into the top of the new panel, and then having to repair all the stucco damage you just did. Of course, if you just an electrician and that is all you deal with you can ignore the rest of the problems, but it's my house and I have to get it all back together, not just a new panel or I'll have to deal with a mad wife. Since the left side of the panel will no longer have a meter, I'm thinking I should be able to modify the the lug connection points so I don't have to jumper across where the meter used to be. Then, separate the neutral and grounds, install a new neutral that is not bonded to the panel and I should be good to go.
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Old 02-08-2009, 09:18 PM   #13
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Converting Main Panel to Sub: How to jumper?


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Since the left side of the panel will no longer have a meter, I'm thinking I should be able to modify the the lug connection points so I don't have to jumper across where the meter used to be. Then, separate the neutral and grounds, install a new neutral that is not bonded to the panel and I should be good to go.
Like I said, if you are a good mechanic, it could happen. If you feel you can safely modify the lugs, give it a shot. Just remember you assume all liability from here on for the installation.

I'm an excellent machanic and I know it would take me more time to cobble together the old panel than it would to install a new one. I also strive for quality work and I have a feeling that this one's not gonna be pretty.

Take some pics when you are done and impress me
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Old 02-08-2009, 10:09 PM   #14
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Converting Main Panel to Sub: How to jumper?


As said you have a few issues. This old panel is a meter main with permanently bonded neutral. It is meant for service equipment only.. not a sub-panel with 4 wire feeder neutral and ground separated. I really don't see how you can use it and be code compliant.
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Old 02-08-2009, 11:17 PM   #15
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Converting Main Panel to Sub: How to jumper?


Thanks for the info. Yeah, it won't be the prettiest panel in the world.....mainly due to some cramped space, but on the other hand...I have a lot of extra wire bundled up on the left of the breakers, so it looks uglier now than it is.

I think this is my plan:
1. Either jumper across where the meter was, or (preferred) move the lugs from the lower part to the upper part of the meter connector, thus eliminating the need to jumper across a gap and at the same time making more room in the left side of the enclosure.
2. Possibly punch a hole in the separation panel to fed the neutral wires though and attach the neutral bus bar on the left side where I'll have plenty of room. The separation between the left and the right is only needed when it was a main panel. As a "sub" panel it really isn't required for code requirements (just a guess ).
3. Attach a new neutral bus, not bonded to the panel.
4. Separate the neutral lug from the connecting bar and attach it using a plastic separator plate to the panel. Connect it to the neutral bus bar using some insulated wire (#6 gauge?)
5. Remove all the neutrals off the existing shared bus bar and attach the neutrals to the new neutral.

Given that, it may not be that bad. It will take a little bit of metal work and grinding, but it would be a lot less work (and less money) than having to install a new panel and doing stucco work (you keep forgetting the stucco part!). Plus I'd never be able to match up the stucco color, so next on the list would be a whole house (or wall) paint or re-stucco to make it look right.

Sound ok? (Yeah, I know....I take full responsibility. Duh..)

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