Add 50amp breaker to bus from meter line?

Users who are viewing this thread

Messages
6
Reaction score
0
Points
1
Location
Rocklin
panel pic.jpg
pic2 panel.jpg

Can I per code add a 50a breaker as in the pic to this existing bus that currently has a 100a breaker that has wire out to a sub-panel in a garage? The new breaker would be connected to this bus with 2x 6awg THHN wires going through the back wall of this panel into conduit and finally into a 6-50r that EVSE (electric vehicle supply equipment) would plug into. This is for a home in San Jose, CA. Service line from meter is 2 awg copper.

2nd question is how to do it. There's no disconnect between the bus and the meter. Do I hire an electrician to do the final hook up onto a live bus or have him decide to turn off power with PGE and pull the meter?
 

Attachments

  • pic3 panel.jpg
    pic3 panel.jpg
    64.4 KB · Views: 39

Norcal01

Member
Messages
61
Reaction score
4
Points
8
No, a vertically mounted breaker is required to have "ON" in the up position, was the dead front of the panel cut out for a second breaker? If no, would be a second reason not to, but the NEC would not allow it. Breakers mounted like that were disallowed in the 1970's.
 
Messages
6
Reaction score
0
Points
1
Location
Rocklin
No, a vertically mounted breaker is required to have "ON" in the up position, was the dead front of the panel cut out for a second breaker? If no, would be a second reason not to, but the NEC would not allow it. Breakers mounted like that were disallowed in the 1970's.
Thanks for the response. This panel was never modified. It was installed at time of house build in 1979. Sorry I'm not clear on your question on "dead front of the panel" but if you mean the cover of this panel then no, there are knock-outs for 2 breakers and only the bottom knock-out was removed for the existing 100 amp breaker/disconnect. A knock-out exists intact for the upper half where a new breaker would protrude from.

Do you have any ideas on what options exist? Can the bus be changed out or the panel itself to be compliant? Is the best path to just hire an electrician to install a new disconnect/breaker panel?
 

Norcal01

Member
Messages
61
Reaction score
4
Points
8
No way to modify the panel without voiding the UL listing, the cover is a "dead front", only proper option is replace it.
 

wwhitney

Well-Known Member
Messages
5,266
Reaction score
1,335
Points
113
Location
Berkeley, CA
Since the equipment is 43 years old, depending on its condition, now may be a good time to replace it anyway.

But if it is in in good enough condition to continue to use, you do have a couple options short of replacement:

A) You could intercept the existing 100A feeder and set a new panel that would supply 100A to the existing feeder and house the breaker for your EVSE. The feasibility of that would depend on having a reasonable location for the new panel to which the existing feeder would reach and could be rerouted.

B) It looks like there'd be room to install a couple 3 port Polaris style connectors to splice to the existing feeder. Your feeder splice would run to a 50A OCPD next to your EVSE. The spliced conductor would have to be rated for 100A, unless the layout meets one of the feeder tap rules, in which case you could just use 50A conductors. A 6-50 receptacle doesn't require a neutral, so you don't have to figure out how to connect an additional neutral to that neutral bar.

Cheers, Wayne
 
Messages
6
Reaction score
0
Points
1
Location
Rocklin
Since the equipment is 43 years old, depending on its condition, now may be a good time to replace it anyway.

But if it is in in good enough condition to continue to use, you do have a couple options short of replacement:

A) You could intercept the existing 100A feeder and set a new panel that would supply 100A to the existing feeder and house the breaker for your EVSE. The feasibility of that would depend on having a reasonable location for the new panel to which the existing feeder would reach and could be rerouted.

B) It looks like there'd be room to install a couple 3 port Polaris style connectors to splice to the existing feeder. Your feeder splice would run to a 50A OCPD next to your EVSE. The spliced conductor would have to be rated for 100A, unless the layout meets one of the feeder tap rules, in which case you could just use 50A conductors. A 6-50 receptacle doesn't require a neutral, so you don't have to figure out how to connect an additional neutral to that neutral bar.

Cheers, Wayne
Thanks Wayne. Regarding A) this seems complicated. The wires running from the existing 100a breaker are aluminum and run through hidden walls. It would be tough to intercept that I think, to me at least.

Regarding B) see attached pic below. Is this what you describe? I put a question mark at "2awg or 6awg?". It seems this part should be 2 awg. Then 6 after the new breaker.

Finally, how would this job get done with a live service wire from the meter? Do people/electricians just use PPE to work around the live wires or do they pull the meter? I can't imagine working on 2awg wire with power on.
 

Attachments

  • pic4 panel.jpg
    pic4 panel.jpg
    72.3 KB · Views: 35

wwhitney

Well-Known Member
Messages
5,266
Reaction score
1,335
Points
113
Location
Berkeley, CA
On (B), no you'd splice the load side of the breaker, not the line side. The line side conductors are factory installed and shouldn't be modified. Right now the feeder does a U, so the Polaris would actually help it with the 180.

As to #2 or #6 (at 75C that would be #3 or #8, or even #4 or #8 for a 100A residential service), that gets to the tap rules I mentioned, NEC 240.21(B). Roughly speaking, if the run is under 25', you could use the smaller size; the load end breaker provides overload protection, and the 100A breaker is sufficient for ground fault and short circuit protection. Over 25' you need the full size conductor.

Cheers, Wayne
 

Norcal01

Member
Messages
61
Reaction score
4
Points
8
One thing that one has to realize that the conductors on the line side of that breaker has absolutely no overcurrent or short circuit protection, it's best not to mess with them. With your location of Rocklin, I assume it's CA? Are you in PG&E, or SMUD, territory?
 
Messages
6
Reaction score
0
Points
1
Location
Rocklin
One thing that one has to realize that the conductors on the line side of that breaker has absolutely no overcurrent or short circuit protection, it's best not to mess with them. With your location of Rocklin, I assume it's CA? Are you in PG&E, or SMUD, territory?
I'm in Rocklin, CA but the house is in San Jose, CA and it's PGE.
 
Messages
6
Reaction score
0
Points
1
Location
Rocklin
On (B), no you'd splice the load side of the breaker, not the line side. The line side conductors are factory installed and shouldn't be modified. Right now the feeder does a U, so the Polaris would actually help it with the 180.

As to #2 or #6 (at 75C that would be #3 or #8, or even #4 or #8 for a 100A residential service), that gets to the tap rules I mentioned, NEC 240.21(B). Roughly speaking, if the run is under 25', you could use the smaller size; the load end breaker provides overload protection, and the 100A breaker is sufficient for ground fault and short circuit protection. Over 25' you need the full size conductor.

Cheers, Wayne
Wayne, thanks again for the advice. That makes sense not to mess with the line side.

I've attached another pic to graphically display what I think you're describing. I put a question mark "awg?" in the pic for the wires I'm guessing should be at least #2. I'll look at the existing load, aluminum wire gauge and match an equivalent copper gauge to it. I feel like that would keep all things equal. Is that correct?

With this schematic, however, I feel like it's possible the 100 amp breaker in the pic could trip if I'm sharing load with the house and charging the car at steady 40 amps at the same time. Or is overloading like that not a common occurrence?
 

Attachments

  • pic5 panel.jpg
    pic5 panel.jpg
    83.3 KB · Views: 33

Norcal01

Member
Messages
61
Reaction score
4
Points
8
I assume your charging at night, if that is the case it really should not be a problem, in reality residential loads really are not that big, since with a 100A service doubt your all electric.
 

wwhitney

Well-Known Member
Messages
5,266
Reaction score
1,335
Points
113
Location
Berkeley, CA
Service line from meter is 2 awg copper.
That suggests your meter main is rated 125A, and you could confirm that by checking the label. Then if that is the case, and if the service conductors on the line side of the meter are sufficiently large (overhead or underground service?), then it would be possible to upgrade your service from 100A to 125A. I think that requires notifying PG&E, which could lead to them deciding their service conductors need to be upsized, which could be expensive for you if it's an underground service. On the other hand, they may have treated it as a 125A service already, if that's the equipment rating.

To take advantage of the 125A service, you could upsize the breaker from 100A to 125A, if your existing Al feeder conductors are at least #1/0, or if you set a new panel next to your panel to house a smaller breaker for them. Or if the manufacturer of that panel makes plug-on sub feed lugs without OCPD, then you could use the upper bus stab to extend your service conductors to a 2nd service disconnect right next to your meter main.

Having said all that, in practice the 100A breaker is unlikely to trip due to the new load of the EVSE, particularly if you are charging at night. You are, however, supposed to do a load calculation for the entire house to determine if 100A is sufficient or not.

As to the last photo with the (?) AWG markings, if you stick with the single 100A breaker, then the minimum ampacity for the short segment on the left is 83A. For the new conductors to the 50A disconnect, the minimum ampacity is 50A if you use a raceway method (a requirement of the tap rules) or 83A if you use a cable method. For copper conductors, 75C insulation, 83A means #4 Cu, and 50A means #8 Cu. You can, of course, use large conductors.

Cheers, Wayne
 
Last edited:
Messages
6
Reaction score
0
Points
1
Location
Rocklin
That suggests your meter main is rated 125A, and you could confirm that by checking the label. Then if that is the case, and if the service conductors on the line side of the meter are sufficiently large (overhead or underground service?), then it would be possible to upgrade your service from 100A to 125A. I think that requires notifying PG&E, which could lead to them deciding their service conductors need to be upsized, which could be expensive for you if it's an underground service. On the other hand, they may have treated it as a 125A service already, if that's the equipment rating.

To take advantage of the 125A service, you could upsize the breaker from 100A to 125A, if your existing Al feeder conductors are at least #1/0, or if you set a new panel next to your panel to house a smaller breaker for them. Or if the manufacturer of that panel makes plug-on sub feed lugs without OCPD, then you could use the upper bus stab to extend your service conductors to a 2nd service disconnect right next to your meter main.

Having said all that, in practice the 100A breaker is unlikely to trip due to the new load of the EVSE, particularly if you are charging at night. You are, however, supposed to do a load calculation for the entire house to determine if 100A is sufficient or not.

As to the last photo with the (?) AWG markings, if you stick with the single 100A breaker, then the minimum ampacity for the short segment on the left is 83A. For the new conductors to the 50A disconnect, the minimum ampacity is 50A if you use a raceway method (a requirement of the tap rules) or 83A if you use a cable method. For copper conductors, 75C insulation, 83A means #4 Cu, and 50A means #8 Cu. You can, of course, use large conductors.

Cheers, Wayne
Great! Understood. Thanks for the explanation. I'm glad to read I have at least a couple options. I'll update in a few weeks when I complete the work.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks