res. panel upgrade? for solar

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bohl1076

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southern california
my friend wants to install solar at his home and is trying to do it him self. his total amps for each leg from the inverter to his panel is 15a.
he currently has a 240v-40a a/c unit.
4-120v/20a general circuits
4-120v/15a lighting/general circuits
and thats it can anyone help me with calculating this? he currently has a 100a/240v service. is he going to need an upgrade? having trouble remembering the formula/ steps to calculate this.

thanks
 
Check out 2008 NEC section 690

Check out 2008 NEC section 690

If you check out section 690 of the NEC you'll have plenty of information on what you are trying to calculate. Take a look and then post back.
 
bohl1076 said:
my friend wants to install solar at his home and is trying to do it him self. his total amps for each leg from the inverter to his panel is 15a.
he currently has a 240v-40a a/c unit.
4-120v/20a general circuits
4-120v/15a lighting/general circuits
and thats it can anyone help me with calculating this? he currently has a 100a/240v service. is he going to need an upgrade? having trouble remembering the formula/ steps to calculate this.

thanks
Click to expand...

He needs to get help. Is the inverter capable of 240V. I thought you needed 2 inverters to get 240V????? not sure but I was told that.
 
bohl1076 said:
he currently has a 100a/240v service. is he going to need an upgrade? having trouble remembering the formula/ steps to calculate this.
Click to expand...

I'm not sure what is being asked, either. Why would he need to upgrade his service to install a solar system?

Dennis Alwon said:
Is the inverter capable of 240V. I thought you needed 2 inverters to get 240V????? not sure but I was told that.
Click to expand...

240V inverters are available. Solectria Renewables is one that I have seen in the past.
 
bohl1076 said:
i just didn't want to overload the bus bars since thier only rated for 100a
Click to expand...

Now I understand your question. You aren't adding load to the panel by adding as solar system, as long as the rating of the solar system is less than the panel rating. For instance, if the house had a max load of 60A @ 240V, and the solar system could put out a max of 30A @ 240V at its highest output, then the house load would get 30A from the solar system and 30A from the utility for the 60A load. But the panel still only sees 60A.
 
david luchini said:
Now I understand your question. You aren't adding load to the panel by adding as solar system, as long as the rating of the solar system is less than the panel rating. For instance, if the house had a max load of 60A @ 240V, and the solar system could put out a max of 30A @ 240V at its highest output, then the house load would get 30A from the solar system and 30A from the utility for the 60A load. But the panel still only sees 60A.
Click to expand...

Check out 690.63. You are limited to supplying this panel to a max of 120%. If this panelboard is rated 100 amps with a 100 amp main your PV input may not exceed 20 amps.
 
OTT2 said:
Check out 690.63. You are limited to supplying this panel to a max of 120%. If this panelboard is rated 100 amps with a 100 amp main your PV input may not exceed 20 amps.
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OTT2, you are correct, if the solar is connected on the load side of the service disconnect. It can be connected to the line side of the service disconnect without the 120% limit, however.
 
I think many 100A panels have 125A busses. But depends on brand. Check the labeling in the panel and hope for a 125A panel. Still may work with a 100A.
 
Dennis Alwon said:
He needs to get help. Is the inverter capable of 240V. I thought you needed 2 inverters to get 240V????? not sure but I was told that.
Click to expand...

Dennis, I read his satement as 'both legs from the inverter is 15amps' to mean he has a 240v inverter.

All of the top inverter manufactureres make 240v inverters.
And with 120v inverters, you can run into trouble with MWBC's.

And I do agree, he needs to get help.
 
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