5.04KW solar panel is coming up in SF Bay Area

[foo1bar]

I understand. There will be no fire . The worst case is the breaker strip and it takes 10-20 mins to cool off and you can turn it on again.
Normal household electric uses 2 AWG wire from a 100 A breaker to internal home sub-panel. If you looks up, 2 AWG wire can handle maximum 94A.
So, even you can over load 120A, you should use 94A for a long period of time or the wire itself will cause your trouble

Mine is actually aluminium - which is fairly common for these size wires.
And the right table to reference is NEC 310-16 then correct for temperature if going through a hot attic, etc.

Even if you were running 100A thorugh a #2 copper wire, it's much more likely that the breaker will trip than the wire's insulation fails

Solar will use 40A

NO
Solar supplies 40A

Pool need 30-40A (I use 2 horse power pump for my home)

If your pool pump is using 30-40A for a 2HP pump, you need to have something checked.
2HP should be using 25A or less.

Take example, if I need to do deep fry, microwave, oven (little oven) and do pressure cooker the same time (it is normal during weekend when preparing multiple things the same time), I would need minimum 15*4 = 60A. Then, Solar will take up to 40A. I already reach the max.

If I forgot to turn off the timer for the pool pump, It will draw 30A easy.
I will trip my breaker of 100A.

If your deep frier, microwave, oven and pressure cooker are all 240V appliances (doubtful) or all on one leg (unlikely) and are using a full 15A (doubtful) and your pool pump draws 30A (doubtful) you'd be at 90A.
And at that point you might trip the breaker with lights, etc.
If you add in solar that actually reduces the amount going through that 100A breaker - so now instead of it seeing 90A it sees something less. (if your solar is generating 1.2kW, you'd have 85A going through that breaker instead of 90)

For safety, I would see the following design in electrical for Solar and EV car.

Since you don't seem to understand that the solar is a supply, not a load, I would recommend you don't suggest any design.

[solar_newbie]

I understand. There will be no fire . The worst case is the breaker strip and it takes 10-20 mins to cool off and you can turn it on again.
Normal household electric uses 2 AWG wire from a 100 A breaker to internal home sub-panel. If you looks up, 2 AWG wire can handle maximum 94A. You can open the panel next to your meter to exam the wire size.

http://www.powerstream.com/Wire_Size.htm

So, even you can over load 120A, you should use 94A for a long period of time or the wire itself will cause your trouble

Solar will use 40A
1 Electric Car will use 30-40A
Household stuff is around 20-30A. If you run any AC or individual AC, you need at least 10-20A per each.
Pool need 30-40A (I use 2 horse power pump for my home)
Main AC use 40A for 3.5-4 ton AC. If you have 6 ton AC on the 2,500 square foot home, you need more.

So most new home design to separate AC to different breaker and house hold stuffs to different breaker. I would not need to count it.

So what you need to do is to arrange for time to use ...

Take example, if I need to do deep fry, microwave, oven (little oven) and do pressure cooker the same time (it is normal during weekend when preparing multiple things the same time), I would need minimum 15*4 = 60A. Then, Solar will take up to 40A. I already reach the max.
If I forgot to turn off the timer for the pool pump, It will draw 30A easy.
I will trip my breaker of 100A.

Currently without solar, I am fine ... as my AC is running on a separate 40A breaker at that time.

For safety, I would see the following design in electrical for Solar and EV car.

Meter ---- 100A/125A sub-panel 1: all household stuffs, pump, dryer (if needed) ....
---- 100A/125A sub-panel 2: Solar , EV car, AC

I took a look at few houses (old and news). Most have 3/0 AWG from meter and split into 2 breakers: 100A (for sub-panel) and 40/60A (for AC). 3/0AWG can handle 239A , so you can easy to have 2 sub-panel with 125A each (assume you can overload up to 20% or 286A).

I would agree with you that there are multiple design. Some can save money .. by overload the 100A sub-panel or upgrade it to 125A sub-panel ... but on the long run. I would have a separate 125A sub-panel ...

[foo1bar]

Same here but I would concern if putting 40a EV car into the 100a house panel along with 40a from solar panels.

I wouldn't.
Let's say it is a 125A panel with 40A of solar.
That means you can have a 100A breaker feeding that panel.
So you can have 2x40A for car chargers, and still have 20A for other misc. loads.
20A of other loads would be enough for most daily use. (probably not enough for an air conditioner to be running - but enough that you could be preparing dinner in the kitchen while the TV is on.)

But you seem concerned about solar as part of the equation.
If you actually were charging during the day (bad idea economically if you're on TOU plan and net metering - but lets say you do)
If you were doing that, then you would actually have even more available power for other daily use before you'd trip the 100A breaker.

In reality, you would probably want to stagger the 40A car charging - and you'd probably do it late at night when power is cheap.
You might do one from 10PM until 1AM and the other from 1AM until 4AM, or something similar.
AFAIK all the cars handle that kind of scheduling. It's an expected feature.

And it really isn't going to cause any fires - even in a poorly designed install you would only trip the 100A breaker if you were doing two 40A draws along with other things (AC, hairdryers, clothes driers, etc) that added up to more than the 100A that the breaker should trip at. It wouldn't cause a fire.
And in a well designed install, the installer would upgrade the panel to 200A and 200A wires feeding it - or recommend you use a smaller amperage car charger so that you dont' have "nuisance" breaker trips.

My house is right now using ~1100W (~5A) - that's lights on, TV and computers going, dinner cooking.
When the AC kicks in and the pool pumps are running, usage can get up to 9000W (~38A)
So just because your house panel is 100A, don't think that you're using anywhere near that amount during a normal day.

[solar_newbie]

Same here but I would concern if putting 40a EV car into the 100a house panel along with 40a from solar panels.

[jflorey2]

Do not forget electric car draw 30amp during the night... It will interfere with other usage as you usually has 90-100amp bus on the house sub-panel. What if 2 cars, the house will burn

Wouldn't worry too much about that. Not only will a typical 200 amp service support that, you are drawing power during the time when utilities have too much generation from their baseload plants.

[solar_newbie]

First I started with replace electric usage for my home. All estimate come with 3.5kw to replace for 5,500kwh/year.
Then, I got a lease of electric car. It make sense to upgrade to 5kw since I would expect to use 3,300 kWh more.
I got quote and join this forum. Learn that I should super size mine plus learning from all site visit guys that it is best to have separate sub-panel from the house and has level 2 charger connect to it or a separate plug from the main panel.
Do not forget electric car draw 30amp during the night... It will interfere with other usage as you usually has 90-100amp bus on the house sub-panel. What if 2 cars, the house will burn

[ZybdZY]

Very low price compare to this show room. If take out the cost for those extra, it can go close to the $3 target.

I guess you went with this vendor you referred earlier in another thread :-

SW panel and enphase inverter : $3.17/w

Btw -- how many threads have you started now

Question -- In your earlier thread, you mentioned going for around 3.5 and now it is 5+ --> what caused the change - expected increase of usage ? or ?

[SolarQuadrant]

Very low price compare to this show room. If take out the cost for those extra, it can go close to the $3 target.

Is it a well established solar company or a local electrician doing the work; if you could pm the installer, much appreciated. Thank you

[J.P.M.]

Very low price compare to this show room. If take out the cost for those extra, it can go close to the $3 target.

Care to share a specific $ number ?

[solar_newbie]

Very low price compare to this show room. If take out the cost for those extra, it can go close to the $3 target. Total cost is around 3.5/w

[J.P.M.]

Hi All,

Thank you for all references and posted. I have learn a lot from this forums to make final decision.
18 SW280 mono panel (Best on 0-5% plus and 0.7% annual degrade ... And MADE IN USA. I really do not want to use other panel except SunPower ... but it is too expensive)
18 Enphase m250
Enphase Monitor system
1 2nd 125A sub-panel (plenty room for other application in the future)
1 40A electric car plug (on this new panel) --> I am going to get an EV car soon

Installation is planned.... This is the best offer since I will get it installed in few weeks.

I will update the picture once it is installed and reported progress.

How much, before tax credits/rebates ?

[solar_newbie]

I interviewed 12 installers and decided to choose my current installer based on the balance of waiting time, price, and knowledge of installers. I really do not trust sale guys who just know to sale and do not have any knowledge about solar and electrical. I do not want to consider any quote if the site survey person do not jump on the roof and show me the electrical path.

My based usage needs a system of 3.5KW. I decided to super size to cover for panel degrade over time and EV car usage. My new system is 5.04KW. It will cover up to 10 years of current project usage with EV car.

18 SW280 Mono Black panels (Best on 0-5Wp and 0.7% annual degrade ... and MADE IN AMERICA. I really do not want to use other panels except SunPower ... but it is too expensive)
18 Enphase M250
1 Envoy computer with WIFI
1 2nd 125A sub-panel
1 240V 40A breaker for EV charger and Charger installation (I provide the charger)

System configuration

200A Main Panel 
  (100A breaker) ----  100A Sub-panel 1 (Existing in house -- unchanged)
  (60A breaker) (New)  ----  125A Sub-panel 2 (New) ----- 2 breakers (15A) (New) -------- 2 Panel strings (9 panels each)
                                                                             ----- 40A breaker   ----  AC
                                                                             ----- 40A breaker (New)  ---- EV charger in Garage.

Cost : $3.4/w

Time frame:
- sign contract and sent via mail on 9/5 (deposit 1k)
- permit approved : 9/8
- equipment order : 9/8
- equipment received : 9/10
- installation started : 9/21 (Paid 10k)
- frame and electrical inspection for solar: 9/22
- move frame 3 feet to the right as inspector wants to have the whole frames are 3 feet from everything on the roof (both side), not from the edge : 9/22
- 2nd frame and electrical inspection :9/23 - passed
- Panel and all electrical completed a long with all labels ... : 9/26
- final inspection for both electrical and solar permit : 9/28
- inspector requests special label to state that the solar sub panel is on the right of my main panel and over the fence, roll back the change I want for electrical to the original plan, smoke detectors and carbon dioxide detector ...
- the special order of label arrive and final change on all inspector request on 10/3
- 2nd final inspection : 10/6 -- Passed
- PTO application : 10/7
- EV car charger installation : 10/8 ( Paid the rest)
- PTO approval : 10/12 --

All solar completed -- 5 weeks