New Tesla Solar; wattage calculation.

[qdeathstar]

I’m pretty sure this is a easy question to answer, but I got 8.8kw of solar installed by Tesla. But only a 20 amp inverter, which says on it will never put out more than 13 amps….

13amps x 240v = 3000w

I understand that panels don’t put on their max rating, but 5000w seems like a large difference.

What am I missing?

 

[qdeathstar]

The other this is the Tesla scheduled the city inspection without telling me and the inspector passed the inspection but was not able to get access to the inverter or panel because they are inside my house and no one was there to provide acceess…

 

[Redhill_qik]

I’m pretty sure this is a easy question to answer, but I got 8.8kw of solar installed by Tesla. But only a 20 amp inverter, which says on it will never put out more than 13 amps….

13amps x 240v = 3000w

I understand that panels don’t put on their max rating, but 5000w seems like a large difference.

What am I missing?

Something is wrong here, what inverter model was installed?

 

[jjrandorin]

I have never heard anyone say "20amp inverter" here. Inverters are normally mentioned as kW. You have 8.8kW of solar, but a X.X kW inverter. Tesla inverters are usually (I think) either 3.8 or 7.6, and if you got "8.8kW of solar" I am going to guess you should have a 7.6kW inverter, which should be fine, from a ratio standpoint.

Perhaps they installed a 3.8 kW inverter by mistake?

 

[qdeathstar]

I have never heard anyone say "20amp inverter" here. Inverters are normally mentioned as kW. You have 8.8kW of solar, but a X.X kW inverter. Tesla inverters are usually (I think) either 3.8 or 7.6, and if you got "8.8kW of solar" I am going to guess you should have a 7.6kW inverter, which should be fine, from a ration standpoint.

Perhaps they installed a 3.8 kW inverter by mistake?

I will investigate further. The inverter is fed into the panel with two single pole 20 amp breakers. And on the cover of the inverter I’m pretty sure it says max output 13.4A written in pen.

 

[Redhill_qik]

I will investigate further. The inverter is fed into the panel with two single pole 20 amp breakers. And on the cover of the inverter I’m pretty sure it says max output 13.4A written in pen.

You should have received and approved installation plans that included all of the information on the equipment that was to be installed.

 

[yblaser]

Look on the side of your inverter. There should be a little white sticker showing which version it is:

 

[qdeathstar]

It is the 7kw inverter… but still 7kw at 240v is more than 20 amps. And higher than what the sticker on the front says…

Is that the input current at a higher voltage that would still only be about 4000w…

But also what about the 20 amp breakers…

 

[dareed1]

The placard shows the output characteristics of the solar panels, which is one string of input to the inverter. This tells you that the highest power string of your solar panels will provide 10.7A at 371V, if it is operating at standard conditions (25C, 1000W/m^2, etc) and the Maximum Power Point. A 7.6kW inverter can have up to (I think) 4 strings, but will start to clip if the output power goes over the nominal 7.6kW.

I would however expect 30A breakers rather than 20A.

 

[qdeathstar]

The placard shows the output characteristics of the solar panels, which is one string of input to the inverter. This tells you that the highest power string of your solar panels will provide 10.7A at 371V, if it is operating at standard conditions (25C, 1000W/m^2, etc) and the Maximum Power Point. A 7.6kW inverter can have up to (I think) 4 strings, but will start to clip if the output power goes over the nominal 7.6kW.

I would however expect 30A breakers rather than 20A.

10.7A at 371v is only 4000w…..

 

[yblaser]

Yes it should be a 30A breaker. I would call Tesla and tell them your concern. I would also request a copy of the detailed plans.

10.7A at 371v is only 4000w…..

That's the highest power string. There are multiple strings. Get a copy of the plans.

 

[qdeathstar]

Yes it should be a 30A breaker. I would call Tesla and tell them your concern. I would also request a copy of the detailed plans.

That's the highest power string. There are multiple strings. Get a copy of the plans.

I will ask for detailed plans.


I opened up the inverter, and It looks like there are three strings.

I also opened my panel and even though the stickers are on two 20 amp breakers on the bottom, the wires the breakers are connected to have nothing to do with the solar system. Instead the wires from the inverter are attached to the main service wires with clamps. Is that kosher? I’ve seen it in panels before but I thought maybe the code requirements have changed.

Also there is some kind of amp meter in the panel… I suppose that is for monitoring? Looks poorly installed to me, they used cascading wego connectors and one of the wires is barely making it…

I attached pics.

 

[yblaser]

I will ask for detailed plans.


I opened up the inverter, and It looks like there are three strings.

I also opened my panel and even though the stickers are on two 20 amp breakers on the bottom, the wires the breakers are connected to have nothing to do with the solar system. Instead the wires from the inverter are attached to the main service wires with clamps. Is that kosher? I’ve seen it in panels before but I thought maybe the code requirements have changed.

Also there is some kind of amp meter in the panel… I suppose that is for monitoring? Looks poorly installed to me, they used cascading wego connectors and one of the wires is barely making it…

View attachment 780043View attachment 780044


View attachment 780045


I attached pics.

Is there a box between the inverter and the splices in the picture with a breaker in it? I'm not familiar with this type of install.

Maybe @wwhitney or @Vines have better insight here.

 

[qdeathstar]

Is there a box between the inverter and the splices in the picture with a breaker in it? I'm not familiar with this type of install.

Maybe @wwhitney or @Vines have better insight here.

There is a disconnect on the exterior of the building.

 

[jjrandorin]

Instead the wires from the inverter are attached to the main service wires with clamps. Is that kosher? I’ve seen it in panels before but I thought maybe the code requirements have changed.

Maybe I am mis remembering, but I thought you were a practicing electrician yourself. I dont know codes, but would imagine that you have access to what codes should be etc in your area, and if something is not "to code" in your own install would be able to escalate that back to tesla with the appropriate code citation, etc.

 

[qdeathstar]

Maybe I am mis remembering, but I thought you were a practicing electrician yourself. I dont know codes, but would imagine that you have access to what codes should be etc in your area, and if something is not "to code" in your own install would be able to escalate that back to tesla with the appropriate code citation, etc.

I am a master electrician but I do not do solar panels and I am not familiar with the ins and outs, which is why I am asking people who are more familiar.

Gynecologist vs Neurosurgeon….

 

[qdeathstar]

Also, right now I have this meter, is is a net meter or just a normal meter?

https://www.itron.com/-/media/feature/products/documents/spec-sheet/101381sp03-c1sr-r400-centron_web.pdf

I’m thinking it is a standard meter but not sure.

 

[Ampster]

What does the meter say when you are generating and add loads? I could not download the PDF but maybe it offers a clue. What does the PDF say about the meter?

 

[Vines]

From what I see that is a line side/load side tap. I cannot tell which because you didn't include pictures of the service.

The disconnect on your wall is probably a fused 60A unit, so there is overcurrent protection to otherwise too small wires connected to your 200A wires.

The "do not relocate" label is inappropriately applied to the breaker that powers your monitoring system. Unknown if the inspector or the installers didn't understand the requirements there.

 

[qdeathstar]

It is a line side tap and there are fuses in the disconnect. The monitoring wires are tapped on to a different breaker….