Electrical Panel Upgrade for Solar Panel Install

[Explorer]

Hi -

I am looking at having a 8477W CEC rated system installed. I currently have a 100 AMP panel that has a rating sticker of 125. One of the contractors states this will handle the load with the new solar system. Another contractor states we need to upgrade to a 200 amp panel (in fact he said we may need a 400 amp panel at one point). What is true? I am definitely clueless in this arena..,.,.

[megalo]

You can typically go up to 120% of the bus bar rating, provided the solar breaker is placed at the opposite end of the box from the main feed. That means on a 125A bus bar with a 100A main breaker, you could have 50A of solar. That array size "should" be ok.

That said, that's a small box to be stuffing a lot of things into.

(also, I am not an electrician)

[Sunking]

You need a 200 amp Main Breaker panel.

[megalo]

^ Nevermind, then.

[Explorer]

You need a 200 amp Main Breaker panel.

Thank you Sunking. Any reason you think they talked about a 400 amp?
Also, can they cheap out on other things, ie wiring?

[Sunking]

Thank you Sunking. Any reason you think they talked about a 400 amp?

Whoever told you 400 amp, stay away from them. A 150 would work but they are an odd ball size, and 200 amp panel is pretty standard and can handle up to about a 2500/ft2 home with heat pump, electric kitchen, and electric hot water heater. 400 AMp is for one very large luxury home, all electric with swimming pool.

Also, can they cheap out on other things, ie wiring?

Certainly to many ways to count. They can start with the panel and breakers, use aluminum wiring, low grade receptacles.

[Longstreet]

I don't know much about these kind of things, but there is one thing I don't get.

How can you need a 8.4kw system for a house that only has 100 amp service? A house with that small of a service couldn't possibly draw enough power to need that size system, right?

I'm curious, I'm not trying to be rude. I've looked at 5kw system for my house to offset almost all of my power use and I have 150 service.

[Sunking]

How can you need a 8.4kw system for a house that only has 100 amp service?

A 100 amp Service can deliver up to 24 Kw. However I do agree it does not sound right but if the OP is a Yankee in the north or in a trailer is plausible and normal.

When it comes to panel size all the service amp size really means to a consumer is the number of Breakers Positions they have available . A 100 amp panel only has 20 slots in them. Those can be filled either with single of double pole breakers. Total demand cannot exceed 125 amps. A Solar system requires 2 positions for a double space 240 volt breaker. A 200 amp panel has 42 positions.

[Naptown]

and no one mentioned a line side tap which would not require a panel upgrade.
If his panel is a 100 A main breaker and 125A buss bars he could certainly backfeed it.
he could potentially backfeed an 11KW inverter into it.
125x1.2=150 amps
150-100=50 left for the solar
The first guy was right that it will handle it.

[Sunking]

and no one mentioned a line side tap which would not require a panel upgrade.
If his panel is a 100 A main breaker and 125A buss bars he could certainly backfeed it.
he could potentially backfeed an 11KW inverter into it.
125x1.2=150 amps
150-100=50 left for the solar
The first guy was right that it will handle it.

Good catch Rich, but that is not how an inspector looks at it in my experience. An inspector looks at a Line Side Tap as a Load. The solar system is a Source in our book with power flowing in only one direction, and with that in mind is subtractive. However an Inspector sees it both as a Source and a Load. If seen as a Load the power or current in this case is additive.

At least that is my experience with Inspectors interpretation and the two golden rules of Inspectors being right.

[Naptown]

Good catch Rich, but that is not how an inspector looks at it in my experience. An inspector looks at a Line Side Tap as a Load. The solar system is a Source in our book with power flowing in only one direction, and with that in mind is subtractive. However an Inspector sees it both as a Source and a Load. If seen as a Load the power or current in this case is additive.

At least that is my experience with Inspectors interpretation and the two golden rules of Inspectors being right.

Here we are required to install a separate disconnect for the line side tap. Since panels here are generally inside and meters outside tis requires 2 disconnects one by the meter and one by the panel.
You are right about the inspectors though.

[Sunking]

Here we are required to install a separate disconnect for the line side tap. Since panels here are generally inside and meters outside tis requires 2 disconnects one by the meter and one by the panel.
You are right about the inspectors though.

Understood Rich. Just my experience Inspectors see Line Side Taps as loads. I understand that reasoning because there is nothing to prevent someone else down the road to use the new tapped panel/disconnect as a load in the future. As you can tell I lost the argument.

[Explorer]

Good catch Rich, but that is not how an inspector looks at it in my experience. An inspector looks at a Line Side Tap as a Load. The solar system is a Source in our book with power flowing in only one direction, and with that in mind is subtractive. However an Inspector sees it both as a Source and a Load. If seen as a Load the power or current in this case is additive.

At least that is my experience with Inspectors interpretation and the two golden rules of Inspectors being right.

Thank you the information. I really appreciate it.

[Explorer]

Here we are required to install a separate disconnect for the line side tap. Since panels here are generally inside and meters outside tis requires 2 disconnects one by the meter and one by the panel.
You are right about the inspectors though.

I would like to PM with you and Sunking but have not posted enough. I am hoping this puts me at 10.