source of subpanel power

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Old 04-10-20, 08:02 PM
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source of subpanel power

I want to add a subpanel to hold breakers for three under sink hot water heaters at 40 amps each, 240 volts, and an outlet for an electric car charger. That will be a bit much for the main breaker for the house. Can the sub panel be connected to the high side of the main breaker? The would be right on the output from the utility meter.
Forgot to say we are in California, residential.
 

Last edited by bkelly13; 04-10-20 at 08:07 PM. Reason: add location
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Old 04-10-20, 09:35 PM
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The service would need to be upgraded. The wiring from the meter to the current panel would sized for the current panel not the extra load you are planning to add.
 
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Old 04-11-20, 05:53 AM
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You may want to do some additional research to see how much electricity those heaters use and whether the flow rate is high enough with the desired temperature.
 
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Old 04-11-20, 06:26 AM
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Can the sub panel be connected to the high side of the main breaker? The would be right on the output from the utility meter.
Please clarify this statement. Are you asking if you can tap into the lugs (to feed the sub panel) of the main panel where the power comes in off the street by passing the main breaker? If this is what you plan to do the answer is NO.
 
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Old 04-11-20, 10:51 AM
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What size service do you have now? Likely the best option is to put the larger loads in the main panel and relocate the smaller loads to the sub-panel.
 
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Old 04-11-20, 11:52 AM
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Per OP in original thread......... 200A service.
https://www.doityourself.com/forum/e...ire-attic.html
 
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Old 04-11-20, 11:54 AM
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Per OP in original thread......... 200A service.
Then for sure install the EV charger and water heater loads in the main panel and move smaller general-purpose circuits to the sub-panel.
 
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Old 04-11-20, 01:30 PM
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Forum questions for electrical



https://www.askmediy.com/question/wi...el-from-meter/

To AFJES,

To ensure no miss communications create some identifiers:
UI = Utility In, wires from the utility provider. These go underground

UM = Utility side of the power meter.

RM = Residence side of the power meter

BU = Breaker utility or hot side. This side is remains energized when the main breaker is in the off position. It connects to RM.
BH = Breaker house, this provides power to the house, not energized when the main breaker is off.

(Are there some standard names for those things I just created names for?)

I am aware and understand that UI and UM are off limits to the home owner. I presume that RM side of the meter is off limits for essentially the same reason.

BU, I am unsure of this but since it is “down stream” of the power meter I presume it with within the home owner’s domain. My tentative position is that these wires can be extended to a sub panel. As it is “down stream” of the power meter, I suspect that So Cal Edison, the power company here, is not concerned about it.

So yes, my first thought is to connect the subpanel there.

Addressing all the remaining posts:

However, the suggestion that all the low power circuits be moved to the sub panel seems like a great idea. It will require considerable work to complete, but makes the best sense.

We had a licensed electrician install a new panel with a larger breaker. BUT, he selected a panel with too few slots and has decided to not return and finish the job. But that is another story and don’t want to go there.

A new panel, in the garage, would be closer to the living area meaning the existing cables should all reach that panel with no problem at all. As noted, that will be more work to accomplish, but makes good sense.

I cannot see everything and do not know what size the service cables are that enter the garage, underground, from the transformer out in the front yard. Their limit might be 200 amps.

The best suggested solution so far:

Put all the 120 service stuff in the new panel and wire it to the main panel via a, estimated, 100 amp breaker. This would be a 240 breaker and the 120 stuff would alternate between the two 240 hots to balance the load. (Yes, I have read and understood several articles about installing a subpanel with a 4 wire cable, keeping ground and neutral separate)

Put all the 240 stuff in the main original panel.

Does that appear to be a good idea?

And to two obvious considerations:

1. The work must be planned and detailed and have an county inspector visit before starting work.

2. This may be more than I want to do myself and may find a new electrician to do the panel work.
 
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Old 04-11-20, 02:02 PM
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1. The work must be planned and detailed and have an county inspector visit before starting work.
Typically you pull the electrical permit and do not have the inspector out until:
1) Anything installed that will be covered by finish materials (Drywall, etc) That would be a rough-in inspection.
Or
2) When job is completed. Final.

You can add an additional service on the load side of the meter (BU) but the wires are required to be sized according to the tap rules. The panel would not be a sub-panel but would be a 2nd service and would need to be installed as a service (Grouping, bonding to the existing grounding system, located next to the existing service, etc) You would also need to install double lugs in the meter which would require shutting down power to your house to do it safely. An electrician may be OK doing it hot.
 
 

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