what type of main service panel is this

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aks20000

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I am enclosing an outside picture of this panel and also from inside showing the circuit breakers it has.
This main service panel, located on the outside wall of my home , has two load side circuit breakers - one 100 amp one feeds a sub-panel in the garage and another 100 amp one serves two outside AC condenser units directly.

There a 3rd 50 amp supply side breaker for solar back feed into the panel.

Based on my online search, I think it is described as meter main MLO panel , as it doesn't appear to have a breaker between utility line feed and the panel - making the panel's bus bar always hot. I am not sure if this understanding is correct and hence, requesting help.

This understanding will help me discuss my options for adding a new circuit for Tesla Wall Charger.
 

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It is a 200 amp panel. Hard to read but down lower it clearly states 200 amp max

Catalog # looks Like U8L200F

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Usually the numbers in the catalog number tell the story. For instance, this is an 8 cir (8L) 200 is for 200 amp. Not sure what the F would mean
 
aks20000 said:
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Based on my online search, I think it is described as meter main MLO panel , as it doesn't appear to have a breaker between utility line feed and the panel - making the panel's bus bar always hot. I am not sure if this understanding is correct and hence, requesting help.

This understanding will help me discuss my options for adding a new circuit for Tesla Wall Charger.
Click to expand...
So as an 8 circuit panel, you have room in there to add one more 2 pole breaker.

As to there not being a single “main”, this type of setup falls under what’s referred to as the “6 hand rule”, meaning you can have multiple disconnect means in the same place so long as a firefighter dies not have to move their hand more than 6 times to kill all power to the site.
 
Under the 2020 NEC, is it allowed to add an additional service disconnect to such an MLO service panelboard?

Cheers, Wayne
 
ptonsparky said:
How likely is he to overload the buss if Tesla, A/Cs, and Solar are all at full rate?

I know next to nothing about solar installs.
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With multiple service disconnects for loads, the sum of whose ratings may exceed the bus rating (but does not currently, as 100A + 100A (breakers) = 200A (bus rating)), only a load calculation protects the service conductors, be they of the wire type or the bus type. The presence or absence of a solar service disconnect doesn't change that, assuming no loads on the solar service disconnect.

Cheers, Wayne
 
Thanks everyone for educating me bit more to understand this panel better.
I am looking to install a Tesla war charger and my electrician explained that it shouldn't be added as a new load to this outside panel even it has space due to the code NEC 705.12 and now I understand the reasoning behind this assessment as it will exceed the busbar rating of 200 amp.
His advise is to add the wall charger circuit to my garage panel which has typical loads for a 3375 square ft home like oven, dryer etc but no water heater , cooktop etc and where his load calculation shows capacity to do this , albeit only up to 40 amp. That should be good enough for my needs but ...
Since the garage panel is 40 feet away from the charger location and the outside panel right across the wall, I preferred and still prefer to connect the charger to the outside panel. The 100 amp breaker on the outside panel dedicated for AC units ( two 5 tons 10 seer ) has no other load leaving enough capacity, that has me wondering if we can remove AC load from this 100 amp breaker and use this breaker to supply a new 100 amp sub-panel in the garage. The AC circuit will be moved to this new panel protected by its own circuit breaker and new charger circuit will be added here with its own circuit breaker too. This way, the outside panel still wouldn't exceed 200 amp limit. Moreover, my oversized two 5-ton AC are due for replacement soon with modern ac/heat pumps not exceeding 4 ton total and this will free up some more capacity on the new sub-panel.
Do you see any issue with this approach and should I even ask my electrician to evaluate this option ?
 
aks20000 said:
I am looking to install a Tesla war charger and my electrician explained that it shouldn't be added as a new load to this outside panel even it has space due to the code NEC 705.12
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That's not the reason; the busbars in your panel are service conductors, so you have a 705.11 connection, not a 705.12 connection.

The reason for the 2020 NEC would be 230.71(B), which no longer allows MLO service panelboards--each service disconnect needs to be in its own compartment. So I would think your existing MLO service panelboard is legal non-conforming, so to speak, but that you couldn't expand it by adding another breaker.

aks20000 said:
The 100 amp breaker on the outside panel dedicated for AC units ( two 5 tons 10 seer ) has no other load leaving enough capacity, that has me wondering if we can remove AC load from this 100 amp breaker and use this breaker to supply a new 100 amp sub-panel in the garage.
Click to expand...
That's a possibility. How is the 100A supply currently divided between the two AC units? And what are the nameplate data on those two units, in particular MCA and MOCPD? And if each one just lists one RLA number and one FLA number, what are those numbers?

Cheers, Wayne
 
wwhitney said:
That's not the reason; the busbars in your panel are service conductors, so you have a 705.11 connection, not a 705.12 connection.

The reason for the 2020 NEC would be 230.71(B), which no longer allows MLO service panelboards--each service disconnect needs to be in its own compartment. So I would think your existing MLO service panelboard is legal non-conforming, so to speak, but that you couldn't expand it by adding another breaker.


That's a possibility. How is the 100A supply currently divided between the two AC units? And what are the nameplate data on those two units, in particular MCA and MOCPD? And if each one just lists one RLA number and one FLA number, what are those numbers?

Cheers, Wayne
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The RLA on both the units is 28.1 amp. I didn't see any MCA or MOCPD , but did see FLA of 1.2 under the FAN section. Enclosing a picture of the nameplate of these ACs.
I couldn't find how the 100 amp ac is divided between two ACs. These are located within 10 feet of each other , each having its own service cutout box. The cutout boxes are supplied from a small common junction box 10"x8" , which I couldn't open to see inside.
 

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aks20000 said:
The RLA on both the units is 28.1 amp. I didn't see any MCA or MOCPD , but did see FLA of 1.2 under the FAN section. Enclosing a picture of the nameplate of these ACs.
Click to expand...
MCA/MOCPD are at the bottom, spelled out as "Minimum Circuit Ampacity" and "Maximum Overcurrent Protective Device." So for one unit MCA = 36.5A, and MOCPD = 60A.

In the simple case of your type of equipment, for one unit MCA = 1.25*RLA + FLA, which works for the numbers on your nameplate. When you put two of those together on one supply (the 100A breaker), then you only need the extra 25% on one instance of the largest number. So the portion of the 100A feeder that is being used is 1.25 * 28.1 + 28.1 + 1.2 + 1.2 = 65.6A.

Thus if you want to add an EVSE to that 100A supply, you'd be limited to a circuit of size 34A, which would mean an EVSE that is set to a maximum of 34/1.25 = 27A continuous. A typical EVSE would only have standard settings of 24A and then 30A or 32A, so you'd be limited to 24A.

Cheers, Wayne
 
Thanks Wayne for your help. Your assessment of my situation was very valuable and I sincerely appreciate it.
I think the best option for me is to put the Tesla charger on my garage panel only, as moving the ac circuit to new panel doesn't buy me any extra capacity for wall charger.
One question I still have for the load calculation on the garage panel. When I followed the guidelines from my city website here to calculate this load, I came up with a load of 78 amp. So, I thought that my panel doesn't have enough extra capacity . But my electrician says that capacity of the charger will be calculated with reference to entire service rating of 200 amp, despite the OPCD for this charger going on the sub-panel. He came up with a number of 50 amp max for this.

My sub panel is rated for 200 amp, but is supplied by 100 amp from the main outside service panel. It has typical loads for a 3375 square feet home having a electric dryer, electric oven, microwave, two indoor hvac air handlers, sink disposal etc but no water heater, electric cooktop, spa or compactor etc.

I hope he is correct in his advice and the install gets through inspection in the first go.
 
aks20000 said:
One question I still have for the load calculation on the garage panel. When I followed the guidelines from my city website
Click to expand...
So, that form is a calculation for the whole service. But once the service is split into the two 100A feeders, that calculation method would not apply to either 100A feeder.

How about a close up picture of the service panel label to the right of the breakers, one that allows reading all the fine print?

Cheers, Wayne
 
I think the best thing to do at this point is for the OP to trust his EC or maybe consult with a second if he has doubts about the first. He has been given food for thought that he can use to have an intelligent conversation with the EC.

So we will close the thread at this time
 
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