adding subpanel to 1950s exsting panel

[Riograndeelectric]

I have been asked to give an estimate to a private school installing 4 -20 amp circuits for laser printers, and computers the Students learn on.
the building was built in the 1950s.

The electrical panel feeding the computer lab and existing fluorescent lights etc is a QOC30 (30) space MLO single pahse panel.
the neutral buss is totally filled with no room to add any more Nutral conductors. the feeders to this panel are cloth coverd Copper tinned ? conductors 2/0 or 4/0 can not find marking for wire size. panel is protected by a 200amp Fuse-able disconnect with 200A fuse's.
the Nutreal. and ground are tied together in the existing panel.

I would like to install a 60 Amp subb panel next to the existing panel and relocate 2- 20 amp existing circuits to sub panel to make room for the 60A sub main.

if I separate the ground and neutral and the Sub I should be OK.

what if any could be issues with this.

the job will be inspected by the AHJ since this is for a School.

I do not know what the fault current rating is on this panel or main service. main service comes in to a gutter and then tapps off to feed several 200A disconects to other panels the Building

 

[kwired]

Outside of existing problems you have not mentioned anything yet that appears to be wrong with your proposed work.

 

[Buck Parrish]

Hmmmm, to bad they didn't call you in the fall. The summer would have been a good time for an upgrade.


I have saw similar installs and it did seem that type of equipment was very well built back then.

What you have described sounds okay. Not knowing the loads though I'm not sure.

I would make it clear to them that they should have a very modern fire alarm system.

You may also want to talk to the AHJ, They may have some local ordinances for school equipment.

 

[LEO2854]

I have been asked to give an estimate to a private school installing 4 -20 amp circuits for laser printers, and computers the Students learn on.
the building was built in the 1950s.

The electrical panel feeding the computer lab and existing fluorescent lights etc is a QOC30 (30) space MLO single pahse panel.
the neutral buss is totally filled with no room to add any more Nutral conductors. the feeders to this panel are cloth coverd Copper tinned ? conductors 2/0 or 4/0 can not find marking for wire size. panel is protected by a 200amp Fuse-able disconnect with 200A fuse's.
the Nutreal. and ground are tied together in the existing panel.

I would like to install a 60 Amp subb panel next to the existing panel and relocate 2- 20 amp existing circuits to sub panel to make room for the 60A sub main.

if I separate the ground and neutral and the Sub I should be OK.

what if any could be issues with this.

the job will be inspected by the AHJ since this is for a School.

I do not know what the fault current rating is on this panel or main service. main service comes in to a gutter and then tapps off to feed several 200A disconects to other panels the Building

Turn on all the loads conected to the old panel and take an amp reading
if the load is low enugh then you can add the new panel
The only ?? i have is on the ground and grounding conductors being together
if the old panel is a sub panel then they need to be seperated
You can by a neutral bar and a ground bar just drill and tap for the screws supplyed.

 

[LEO2854]

ask the inspector about the fault current i don't beleve that it is marked on the old panels:-?

 

[masterinbama]

In a lot of older schools around here the panels have GRS feeder conduits. We will install a ground wedge and separate the neutrals and grounds. And go on our way.

http://www.drillspot.com/products/684212/thomas_and_betts_3655_conduit_connector_grounding_wedge?s=1

 

[kwired]

ask the inspector about the fault current i don't beleve that it is marked on the old panels:-?

unless the POCO transformer is literally right next to the equipment in question available fault current drops rapidly the farther away you are from the source. The OP is not even dealing with the service equipment but instead a panel fed from a feeder within the building. If there is at least 25 or 30 feet of feeder conductor his available fault current at the panel in question is likely reduced to a level acceptable for 10K rated equipment and in many cases even 5K rated equipment. I believe non marked equipment must be assumed to be 5K.

 

[fridaymean]

Why not change the panel to a 42 ckt panel....Is the disconnect near the panel? You could change the feeder to 3/0 and the panel. Might result in a better install.....

 

[Riograndeelectric]

Why not change the panel to a 42 ckt panel....Is the disconnect near the panel? You could change the feeder to 3/0 and the panel. Might result in a better install.....

changing out the existing panel would be a nightmare. ,most conduits 1/2 & 3/4 come out of the top. others come out the side. the feeder conductors would be to short to reach the lugs of a new panel board given the clearance required by todays standard vs the standards form the 1950s

 

[Riograndeelectric]

Turn on all the loads conected to the old panel and take an amp reading
if the load is low enugh then you can add the new panel
The only ?? i have is on the ground and grounding conductors being together
if the old panel is a sub panel then they need to be seperated
You can by a neutral bar and a ground bar just drill and tap for the screws supplyed.

I suppose you are right in that my second floor panel is a sub panel since it is feed form a 200A disconnect which is tapped of the main service conductors. there is very minimal room at the bottom of the panel were the feeder Neutral and hots terminate. there are no Grounding conductors for any of the branch circuits as they are in EMT wired in the 1950s . conduit is used for Equipment grounding.

the other issue is I do not believe this Panel is listed for more than 30 Circuits. you could use some Square D twins that are listed for older panels and do not have the rejection foot on the Back of the Breaker.