Need to upgrade main panel?

[sjaffa]

I have been meeting with solar system installers to install a grid-tied system at my house. Before I commit I want to verify whether I need to upgrade my main service panel.
I have been reading about the 120% rule and am not sure if my current main service panel is sufficient. Any assistance would be greatly appreciated.

I will be getting a 9.28 kW system with a SolarEdge SE7600H-US Inverter (the model with an EV charger). I built my home 6 years ago and looking at my city permit paid for a 200 Amp service from the utility company. I believe my main service panel has a 150 A main service breaker that feeds my subpanel in my basement along with the majority of my breakers installed there. There are a few extra breakers installed in my main service panel. The labeling on my main service panel states "Mains 250 A max". Attached are pictures of my main service panel with the cover off and the label information.

My understanding is that the formula goes Busbar Rating * 120% - Main Service Breaker = Max Size of Inverter Breaker. So in my case does the label "Mains 250 A max" equal the Busbar rating so would my equation be 250 A * 120% - 150 A = 150 A? Which would be plenty big for a 40 A breaker for my system?

 

[telectrix]

most of us are UK based so ain't got a scooby. however there are a few US members who may be able to help when they come online.

 

[Megawatt]

I have been meeting with solar system installers to install a grid-tied system at my house. Before I commit I want to verify whether I need to upgrade my main service panel.
I have been reading about the 120% rule and am not sure if my current main service panel is sufficient. Any assistance would be greatly appreciated.

I will be getting a 9.28 kW system with a SolarEdge SE7600H-US Inverter (the model with an EV charger). I built my home 6 years ago and looking at my city permit paid for a 200 Amp service from the utility company. I believe my main service panel has a 150 A main service breaker that feeds my subpanel in my basement along with the majority of my breakers installed there. There are a few extra breakers installed in my main service panel. The labeling on my main service panel states "Mains 250 A max". Attached are pictures of my main service panel with the cover off and the label information.

My understanding is that the formula goes Busbar Rating * 120% - Main Service Breaker = Max Size of Inverter Breaker. So in my case does the label "Mains 250 A max" equal the Busbar rating so would my equation be 250 A * 120% - 150 A = 150 A? Which would be plenty big for a 40 A breaker for my system?

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Sjaffa the 200 amp panel you have is right where it needs to be so no upgrade is needed and the 150 amp breaker that is fed from your service panel to you sub panel should be fine also. My only concern is the rating of the panel which is being sub fed, normally the breaker should be 100 amps. The reason I say that is according to the NEC you cannot exceed the panel rating but I would think you are going to be fine, let us know how it works out

 

[sjaffa]

@Megawatt how do you know this is a 200 amp panel? I was confused looking at the label with the 250 amp max language, and the 150 amp main service breaker so wasn't sure exactly what it was.

Also, do you know if the inverter 40 amp breaker would be installed in the top two slots or the two slots below those that look like they are connected to the busbar? The installers I have talked to haven't been able to answer these questions so it hasn't given me much confidence that they will install it correctly.

 

[Megawatt]

@Megawatt how do you know this is a 200 amp panel? I was confused looking at the label with the 250 amp max language, and the 150 amp main service breaker so wasn't sure exactly what it was.

Also, do you know if the inverter 40 amp breaker would be installed in the top two slots or the two slots below those that look like they are connected to the busbar? The installers I have talked to haven't been able to answer these questions so it hasn't given me much confidence that they will install it correctly.

Yes they will put the 40 amp breaker in the top spaces and don’t pay that 250 max no attention. That is information for the electrician which simply put is that panel can with stand 250 amps. Go outside and look at the writing on the meter and it should have 200 amps, probably on the left side. Trust me you have nothing to worry about.

 

[sjaffa]

Thank you @Megawatt, you have been very helpful!

 

[Megawatt]

Yes they will put the 40 amp breaker in the top spaces and don’t pay that 250 max no attention. That is information for the electrician which simply put is that panel can with stand 250 amps. Go outside and look at the writing on the meter and it should have 200 amps, probably on the left side. Trust me you have nothing to worry about.

The company doing the install on the solar panels couldn’t answer your questions because they are not electricians, all they do is install panels and they will probably have a an electrician to put the 40 amp breaker in and wire it up

 

[davesparks]

I might be missing something obvious here, but why does the 150A breaker appear to be four pole with 4 wires?

 

[Megawatt]

I might be missing something obvious here, but why does the 150A breaker appear to be four pole with 4 wires?

Dave I just looked at that breaker and you are right and I’ve never seen this before but look at the schematic for the meter and it appears to be a parallel feeder to the house panel

 

[sjaffa]

@Megawatt so am I still okay using this panel with this solar system?

 

[Megawatt]

@Megawatt so am I still okay using this panel with this solar system?

Yes I looked at the schematics you took pitchers off which helped a lot I would bet my license on it. No worry’s, please keep in touch and I will help you all I can

 

[davesparks]

Dave I just looked at that breaker and you are right and I’ve never seen this before but look at the schematic for the meter and it appears to be a parallel feeder to the house panel

Looking at the diagram it appears this panel is quite different to how a UK DB would be set up, I hadn't realised that the 150A breaker is the incoming way rather than an outgoing circuit.

 

[Megawatt]

Looking at the diagram it appears this panel is quite different to how a UK DB would be set up, I hadn't realised that the 150A breaker is the incoming way rather than an outgoing circuit.

Dan I’ve never been a big fan of square-d panels, I had to really look hard to figure it out but the home owner is good to go. With this forum we are here to help and now a days nothing’s seems to shock me, just trying to learn the UK ways of doing things. We make it work

 

[davesparks]

Dan I’ve never been a big fan of square-d panels, I had to really look hard to figure it out but the home owner is good to go. With this forum we are here to help and now a days nothing’s seems to shock me, just trying to learn the UK ways of doing things. We make it work

Well we have something in common then, I've also never been a fan of square D distribution boards.
Though I do trust them a lot more now that schneider have taken over.

 

[norcal]

I might be missing something obvious here, but why does the 150A breaker appear to be four pole with 4 wires?

The 4 pole wide breaker is actually 2 pole with parallel conductors, manufacturers have been doing that since the 1970's starting with the ITE Imperial Corp., (now Siemens), General Electric (now owned by ABB), Cutler-Hammer, (now Eaton), and the Square D Homeline panel above, The C-H panel on my house, and the 1980 vintage Gould/ITE (successor to ITE Imperial), on my rental uses the same type of main, residential panels are super competitive so any way to shave a few pennies off their cost will be undertaken.