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Upgrading House Electrical Panel to 200-Amp - Considerations
- Thread starter Tanquen
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david_42
Member
The main consideration is having space on the panel for the solar input breaker. Going from 125 to 200 amps, you should have plenty of free slots.
I went from a 125 amp panel to a 225 amp panel when my solar was installed. I have older 2" conduit that runs under the driveway to connect to the transformer, so I asked the utility planner how large of a new panel I could install without trenching and putting in new conduit. That answer was a 225 amp panel, so that's what I did. They ended up maxing out the wire in my existing conduit. That got me up to 225 amps.
The solar provider asked me initially if my main breaker was feeding the center of the bus or the top of the bus (before he knew I wanted to upgrade). I guess there are some situations where they have to install a slightly smaller main breaker so that the solar input combined with high current flow from the utility doesn't combine to overload the rating of the bus in the panel...
The solar provider asked me initially if my main breaker was feeding the center of the bus or the top of the bus (before he knew I wanted to upgrade). I guess there are some situations where they have to install a slightly smaller main breaker so that the solar input combined with high current flow from the utility doesn't combine to overload the rating of the bus in the panel...
Hmm...
So looking Siemens 200-225 Amp panels they have the MC2442B1200EFV solar ready and the MC4040S1200SC with solar PV input.
As best I can tell the solar ready just has a sticker for the first two spaces noting that in CA they are for solar only but the solar PV input gives you a second 100 Amp PV input that is not on the bus before the load???
Not sure of the advantage of that but the PV input panel is about twice the price at $425.
So looking Siemens 200-225 Amp panels they have the MC2442B1200EFV solar ready and the MC4040S1200SC with solar PV input.
As best I can tell the solar ready just has a sticker for the first two spaces noting that in CA they are for solar only but the solar PV input gives you a second 100 Amp PV input that is not on the bus before the load???
Not sure of the advantage of that but the PV input panel is about twice the price at $425.
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If you want a long term strategy think abut separating a critical loads panel so you can easily integrate baatery storage to leverage your solar investment.
Also the load sharing capabilities of the HPWC might be worth considering. If you are in California you will be on TOU rates and will probably want to charge overnight to take advantage of chwater rates.
Also the load sharing capabilities of the HPWC might be worth considering. If you are in California you will be on TOU rates and will probably want to charge overnight to take advantage of chwater rates.
200A is a good call, with a 125A you could be limited depending on the size of your solar installation and your car charger current. If you didn't know, the panel limit must be large enough to handle the total current flowing through the main breaker + solar generation both of which are current sources.
How do you account for the fact that if the grid tie inverter is generating, that would reduce the net load through the main breaker?
That's surprising, they want like two grand to install the power wall in the solar roof pricing. I think they even call out service upgrades and permits so on, are on the customers. ???
nwdiver
Well-Known Member
It's about over current protection... the fact that you now have a source INSIDE the boundary of the main breaker actually INCREASES the required ampacity of the bus... this is known as the 120% rule. 120A service would only be able to accommodate a 20A breaker for solar... which would only be 16A or ~4kW.
Okay, now that you have expained it in relationship to the buss it makes sense. The current is acthually reduced through the meter and main breaker, since the solar is another source within the panel. The 120% rule applies to any load that is on continiuosly.
nwdiver
Well-Known Member
Peak.
This is a lesser known rule. I doubt many inspectors would catch it and 99% of the time you would be fine. Here's an example of where not following it could cause a problem.
You install an 8kW (32A) PV system at a 120A panel. Then one sunny day at noon you have 110A of load in the house and you start charging a car at 40A. Normally 140A would certainly trip the main breaker but 32A is being supplied by the inverter to the bus and the 120A breaker is only seeing 118A even though parts of the bus could be seeing 150A which it isn't rated for.
One way you COULD put 8kW of solar on a 120A panel would be to replace the 120A main breaker with a 100A main breaker... then the bus would be sufficiently protected from over current. That's how we complied with this rule on a 27kW project I'm helping with. It's 2 11kW inverters and NM requires a production meter so they needed a separate panel. It seemed absurd to buy a 400A panel so we installed a panel with a bus rated for 225A and a 150A main breaker. Sillier application of the rule since there are no loads in this panel but rules are rules.....
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I don't know if any AHJ still allows it, but my installers, 15 years ago, avoided the possibility of overloading the buss by installing the PV breakers at the far end, away from where the main breaker (in my case one breaker slot away from the end). It becomes physically impossible to put enough load breakers in the space left between main breaker and the PV breaker that would expose the buss to currents that exceed it's rating. I don't know if there is the technical reason that is practice seems to have fallen out favor. Is it not idiot proof enough?
arnold
arnold
My installer also put our solar breakers at the very bottom of my main panel with many empty slots in between. They could not give a satisfactory explanation why, except that it was required. This discussion about overloading the bus makes sense. However, it's a non-issue in my case because I have a 400 amp panel with only a 200 amp main breaker installed and 2x20A solar circuits.
Do you have Enphase inverters? It could be to improve the power line communication.
SoundDaTrumpet
Member
Installing a sub-panel in the garage makes solar and an EV charging convenient. (a) The sub-panel can service as a local disconnect if you decide install hardwired EV charging station (EVCS). Hardwired is cleaner, more child-resistant, and less costly. (b) Solar installers typically install a sub-panel anyway to circumvent any deficiencies with your main panel. I would recommend having the installers do that work.
Your electrical consumption habits may change after getting solar. In my case, I am contemplating replacing my tank gas water heater with heat pump hybrid electric tank water heater for the reason of: (a) new regulations and (b) as a way to consume excess solar net metering. Unfortunately, these hybrid water heaters require a 30A circuit which exceed my electrical service (based on NEC load calculations).
Your electrical consumption habits may change after getting solar. In my case, I am contemplating replacing my tank gas water heater with heat pump hybrid electric tank water heater for the reason of: (a) new regulations and (b) as a way to consume excess solar net metering. Unfortunately, these hybrid water heaters require a 30A circuit which exceed my electrical service (based on NEC load calculations).
There has to be a workaround. In hybrid mode they consume a lot less power.
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