Comparing two installers

rrs26ja

I am comparing two solar installers for a 9.7 kW DC system.

First installer wants to use:

• Forty-eight (48 ) SUNTECH STP 200-18/Ub-1 PV Modules
• One (1) Fronius IG Plus 10.0-1UNI Inverter

The other installer wants to use

• Fifty Four (54) Schuco MPE MS05 180w Modules
• One (1) Sunpower SMA 4000US inverter
• Two (2) Sunpower SMA 3000US inverter

Not sure why the 2nd installer is using 3 inverters?

The prices are basically the same, both companies have provided references that seem to check out.

I did see an install that the 2nd installer did, it was very neat and the people seemed very pleased. The 2nd installer is also local, the first installer is about 100 miles away but have done > 2000 installs compared to 400 for installer #2

I would like people's opinions of the components used.

Solar Guppy

Re: Comparing two installers

There have been posts reporting issues with the Fronius inverters that Fronius has not resolved. SMA is the number one brand of GT inverters, I think it would be something to consider

solar_dave

Re: Comparing two installers

Make sure your service entrance can stand the added Amperage from either installer. My 200 Amp service was inadequate of a 10.4 kw system. The total inverter max output was rated @ 46AMPs and the buss bar of the service would have been over rated Max + 10%.

This required a expensive service entrance upgrade all the way from the transformer to the home. While a cursory look at the panel was done by the salesman, the engineer providing the drawings for code approval failed at least 4 times before the "final solution" of upgrading the service entrance. Once you decide on a contractor, pay them minimal monies to pull the permits first and only then provide a real money draw to start work.

Make sure you do the project on a draw basis for a percent of monies on the contract for stages of completion. Make sure they will only get the last draw after everyone accepts the configuration as installed. In my case that was the Local Building code guys, and the Local Utility. This required the electricians to be on site with the inspectors to fix and correct issues to get the final approval. It got rejected a couple times until we got them all together.

Braden

Re: Comparing two installers

I'm surprised installer #2 is using 11kW of rated power for the inverters for a 9.7 kW system. Seems like a somewhat inefficient use of inverters. You can check on the inverter spec sheets for max dc input power, but generally its 10%+ ABOVE rated power. This is because various factors affect voltage prior to even reaching the inverter, so the panels are almost never putting out their STC rated power, AND inverter inefficiencies.

Re busbar connection. If your local authority having jurisdiction is using the up to date NEC code ( 2008 ), then the 120% rule is applied. That means the total sum of all circuit breakers running into a service panel (in most cases that's the array input and the grid input) can be 120% of the bus bar rating.

Other than that, SunPower is often seen as the premier US made solar panels, with SChuco not far behind. Sunnyboys ARE better inverters than Fronius, though Fronius is number 2 or 3 in the market.

There are a couple advantages to a multi inverter system, however.

1) array output will improve slightly as you'll have 3 separate max powerpoint tracking systems running
2) depending on your monitoring system, having 3 inverters may provide more granularity in information
3) if an inverter goes down, you only lose a portion of your array as opposed to the whole thing

Energy Efficiencies

Re: Comparing two installers

solar_dave wrote: »

Make sure your service entrance can stand the added Amperage from either installer. My 200 Amp service was inadequate of a 10.4 kw system. The total inverter max output was rated @ 46AMPs and the buss bar of the service would have been over rated Max + 10%.

Why not just use a fused AC disconnect and line side tap the system???;)

solar_dave

Re: Comparing two installers

Energy Efficiencies wrote: »

Why not just use a fused AC disconnect and line side tap the system???;)

That was my first attempt at this without the panel upgrade.
My local code and permit and local utility refused such a connection on a residential install.
"Want a permit boy? Do it our way!" pretty much.

It worked out OK in my case as I added a 700 sq. ft building (Man cave) which would have required a service upgrade anyway for the 125 AMP service to that structure.

Jburgess

Re: Comparing two installers

solar_dave wrote: »

That was my first attempt at this without the panel upgrade.
My local code and permit and local utility refused such a connection on a residential install.
"Want a permit boy? Do it our way!" pretty much.

It worked out OK in my case as I added a 700 sq. ft building (Man cave) which would have required a service upgrade anyway for the 125 AMP service to that structure.

To expand on this a little, here in the Phoenix area, almost all the homes use a "All in One" service entrances. Usually it's modifying this assembly they object to rather than the idea of a line side tap.

russ

Re: Comparing two installers

"Want a permit boy? Do it our way!"

That is the purpose of permits and inspections isn't it?

They should provide a safe manner/scheme that all have to adhere to. When the inspector has too much leeway in the field and or has to determine just exactly what different method the installer has used is where trouble comes in.

ASTM/NEC and all similar are not suggestions normally - they may allow some flexibility but within specified bounds.

solar_dave

Re: Comparing two installers

Jburgess wrote: »

To expand on this a little, here in the Phoenix area, almost all the homes use a "All in One" service entrances. Usually it's modifying this assembly they object to rather than the idea of a line side tap.

Actually no, the city of Glendale said they would not approve a line side tap for any residential. Never have and never will under any condition. The only conditions that they will approve a line side tap is commercial. APS would "prefer" no line side taps as well but defer the final decision to the local code officials.

I found my code agency a bit stuffy but better too tight than too loose. I went through a bunch of this with other code requirements when doing this building. Concrete, Framing, Drywall and electrical were all better if well within code rather than right up against the limit. The only part we stretched bit was the set backs and they were right on the limit and they did check it and told the GC so.