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Old 04-06-2011, 10:16 PM   #1
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Adding a subpanel to a Pushmatic


Hi everyone! I have a 1965 Pushmatic main panel with 200 amp service. The existing breakers have been working fine so I'm not in a rush to swap it out.

Instead, I am hoping to add a sub-panel to serve an upcoming kitchen renovation. The label inside the panel indicates that branch circuits cannot be larger than 70 amps. Is adding a sub-panel considered a form of branch circuit?

I can purchase a double pole 100 amp reconditioned breaker to feed the sub-panel, but I'm not sure if that would violate the panel limits. Thanks in advance for your guidance.

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Old 04-06-2011, 11:01 PM   #2
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Adding a subpanel to a Pushmatic


yes, a subpanel feed would be considered to be a branch circuit from the originating panel.

a 100 amp breaker would violate the limitations of the panel.

Why would you think you need anything more than 70 amps for your kitchen panel?

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Old 04-06-2011, 11:27 PM   #3
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Adding a subpanel to a Pushmatic


Thanks for your quick response, Nap! Okay, so my subpanel will be limited to 70 amps. Good to know as I consider whether I should bite the bullet and replace the Pushmatic. I'll be remodeling the rest of the house down the road and while I won't be adding any square footage, the current code seems to require way more dedicated circuits than they did in 1965!

Back to the current project, it's an all electric kitchen and laundry (forgot to mention the latter) with a separate cooktop and wall oven. I have been working out the load calc for the whole house, but I am not sure how to do the math for a subpanel. Do you do the same analysis and just exclude the square footage component and non-kitchen appliances? If I do that I come up with a 75 amp load -- yikes!

The main panel has an existing 40A circuit for the old range, so if I can reuse that safely, I might be okay. Any suggestions?
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Old 04-06-2011, 11:41 PM   #4
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Adding a subpanel to a Pushmatic


when you do a house calc you can spread that load over as many panel boxes as you wish. So you do not need another calc for the sub panel- excluding that you need to balance the loads over the panels so as to not exceed the limit of any panel's over current device(breaker). that said the code also allows for the fact that not every load (say in your sub panel) will be on at the same time at full power. so in your new kitchen let say you have:
2 SABC 2x20a
disposal/dishwasher 1x20a
stove top ?? 30a?
oven ?? 40a?
Landry crkt 20a
lighting 20a
general plugs 1+ 15a

if all of these where put in a sub panel using you existing 40a circuit you could bet on trips.

so add up what you reasonably expect to use at the same time and you need to exceed that.
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Old 04-06-2011, 11:44 PM   #5
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Adding a subpanel to a Pushmatic


that is poorly worded hope that helps
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Old 04-07-2011, 01:10 AM   #6
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Adding a subpanel to a Pushmatic


Just get P260 breaker and you are legit on that part any breaker larger than P260 is getting dicey to find it and they are not really cheap anymore.

I will not bother to use the P2100 on that appaction due the bussbar screw spaceing and size are diffrent than the rest are.

I have see it quite few time so therefore I really think it will be wise down the road to get new load centré the new one will have alot more room and space than the old pushmatics are.

Plus what more you may have to install the AFCI breakers if your state required them the Pushmatics do not have AFCI but IIRC They do have GFCI breaker for it but pretty tough to find it.

Merci,
Marc
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Old 04-07-2011, 02:05 AM   #7
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Adding a subpanel to a Pushmatic


Saturday Cowboy (love your pic, BTW!): actually my wording was unclear. I was thinking of putting in a new 70 amp breaker to serve the sub-panel. But I would keep the 40 amp cooktop on the existing main panel breaker so as not to overload the new sub-panel. If I do that, I think I could have everything running in the kitchen and laundry (except the cooktop) and not blow the 70amp sub-panel. I think...

Marc: I found a P270 for $130 at http://www.relectric.com so that's not too bad. But merci for bringing up the AFCI issue -- I hadn't thought about that.

So...perhaps I should consider changing out the Pushmatic for a new 40/40 panel. I have read conflicting opinions on whether this is a DIY project or not. It would be great to hear from the DIYers who have done it and survived the experience. What are the tricks/tips for a successful and safe panel swap?
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Old 04-07-2011, 02:30 AM   #8
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Adding a subpanel to a Pushmatic


Lesp.,

I will speak what most electricians done with panel changeover which I have done that pretty often anyway I will give you a quick run down what it will be involded and some case it can be DIY if your state and local do permit it.

The service entrance conductor it will have to be sized to match the new main breaker so if you going with 200 amp size you will need 4/0 alum or 3/0 copper { some spots may allow 3/0 Al or 2/0 Copper but I doubt it anymore }

you will need new meter socket if the old one is not a good shape which we always do that { check with POCO to see what they require if they tell ya to keep it overhead or go with underground route }

Expect the power outage will go about half day some case little longer.
{few case it will go thru overnite if that the case then we will rig up a tempory power source to keep your fridge cold and some light and heat if need to }

You will need two ground rods and #4 bare copper to tie together.

Check with your inspector for the latest info if they do required AFCI and some may not need AFCI during service upgrading so check that out before you do anything with it.

The cost will varies a bit and other factors can get involded with the price.

I will leave few part open when you have more question and I know few DIYs did manged to change the service and upsizeing it.

And Oui. it can be DIY'er if you undestand the codes and the inspector help you with few quick pointers. { just keep in your mind there are few area that the homeowners can not change service entrance and load centre due some of the local or state regulations so check them out first before you do anything with it.}

Hope that help you a bit and if you have more question just let us know we will answer it more.

Merci,
Marc
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Old 04-07-2011, 02:48 AM   #9
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Adding a subpanel to a Pushmatic


Encore, merci Mark! Very helpful information and good questions for me to ask the local authorities.

Here's what I know so far about my current setup:
- the service entrance cable is 3/0 copper and it is already underground
- the existing 200 amp service is plenty so I won't need to do any up-sizing thankfully
- there is a visible ground wire running to the galvanized water pipe entering the basement. Is there any way to find out if there are also ground rods somewhere?
- the current panel has one neutral/ground bus above the hot buses (see pic). What do you do if the neutral/ground wires from the existing circuits won't reach the neutral/ground bus on the new service panel?


Thanks again! (J'aimerais practiquer mon francais mais ca ne serait pas poli!)
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Last edited by lesp; 04-07-2011 at 02:49 AM. Reason: French correction!
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Old 04-07-2011, 10:56 AM   #10
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Adding a subpanel to a Pushmatic


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Originally Posted by lesp View Post
Marc: I found a P270 for $130 at http://www.relectric.com so that's not too bad. But merci for bringing up the AFCI issue -- I hadn't thought about that.
with just a single breaker price of that and then having the sub panel on top of that, you might just check into an entirely new 200 amp panel with more breaker space than your current pushmatic. I'll bet you can put in a new panel for about the same price as what you are considering doing with the subpanel.

since you already have a 200 amp service, it is just a matter of changing out the panel. Since it is surface mounted like it is, it's a piece of cake.

Check your area but you can likely have the POCO pull the meter (in my area, I can pull it myself. You may be able to as well) which would kill the power to the panel. THen you can swap out the panel, make sure the grounding system is up to par, get an inspect and have the POCO plug the meter back in.

check it out, I think you will be much happier by just changing this out now.

Last edited by nap; 04-07-2011 at 10:59 AM.
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Old 04-07-2011, 04:27 PM   #11
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Adding a subpanel to a Pushmatic


Quote:
Originally Posted by lesp View Post
I found a P270 for $130 at http://www.relectric.com so that's not too bad....
New P270 on ebaY for $100

Used P270 on ebaY for $50.

Another new one for $100 -- free shipping.
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Old 04-08-2011, 02:47 AM   #12
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Adding a subpanel to a Pushmatic


Quote:
Originally Posted by nap View Post
with just a single breaker price of that and then having the sub panel on top of that, you might just check into an entirely new 200 amp panel with more breaker space than your current pushmatic. I'll bet you can put in a new panel for about the same price as what you are considering doing with the subpanel.

since you already have a 200 amp service, it is just a matter of changing out the panel. Since it is surface mounted like it is, it's a piece of cake.
Nap: I'm sold! Thanks for the encouragement. Even with the eBay prices (thank you KB!) it still seems like I would be better off going for a whole new panel. Because half the house is already gutted, I really only have 8 circuits that I will have to transition from the Pushmatic to a new load center.

I understand that if the existing conductors are too short to reach the buses in the new panel that you need to add pigtail extensions. But...what do you do if the service entrance cable is not long enough? From the picture above, I think I have some good slack on the hot conductors, but not so much on the neutral. Suggestions?

Also, do you guys have a torque screwdriver for getting the connection just right or do you do it by feel? I don't want to give the inspector any reason not to pass my job.

Thanks again for all your assistance -- this place rocks!!
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Old 04-08-2011, 09:29 AM   #13
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Adding a subpanel to a Pushmatic


if you are replacing the panel entirely, if you get a top feed panel (many/most are able to be mounted breaker up or breaker down so it doesn't make that much difference...usually) I don't see why those conductors you have now wouldn't work.

I can't tell how high your panel is but you can mount a panel with the breaker up to (and I'm not 100% positive and don't have a code book at hand at the moment. Hopefully one of the other guys will correct me if I am wrong) 6' 6" to the top of the handle with it in the up position. The breaker in your panel also sets quite a bit down from the top of the panel. Hopefully all together it will mean you don't have to alter the length of the feeders. They can be lengthened but it isn't fun to do. If you need to, we'll discuss how the best way to do it would be.


I do not use a torque screwdriver. I have never had an inspector check tension on a screw either. I have also worked in types of work where I had to use torque wrenches to accurately set torque so I can usually hit the mark pretty close.

If you don't use a torque wrench or screwdriver, one thing you have to be careful about is to not overtighten an aluminum lug (usually the larger wires will have aluminum lugs). You can pull out the threads and trash the lug.

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