Any advantage of having multiple inverters?

[josefaz]

If I was in a high ambient heat situation, I would oversize the inverter by at least 20%

I would avoid one with an internal fan, and opt for a cheap desk fan on a timer to just stir the air around.
I feel internal fans would be ON a lot, and eventually require replacement which would not be easy.
$30 for a new desk fan, as I did.
My garage is closed days, and the south facing stucco wall is not insulated, and soaks up a lot of heat.

Maybe mount the inverter on a insulated plywood board (rigid foam insulation, foil backed plywood) to help reduce heat gain.
polyisocyanurate rigid foam insulation is a brownish color, and rated for high temps

Moving air removes more heat than stagnant air.

If your garage interior runs 130F, you need more venting in it, roof vents, floor intake vents.... something.

Thanks for the ideas. So far this year, my recorded peak temp in the garage is 116F with two cars just parked and the hottest part of the year is yet to come. So we'll see how hot it really gets inside. The garage is already vented outside but no fan. Just 2 vent grills that really don't do much.
I was thinking about placing a fan in the vent facing out or in to circulate the air but I changed my mind because occasionally we get a huge dust storm here. When that happens I really don't want all that dust sucked in the garage. I made a mistake once leaving my car window slightly open and the dust storm came. That was an expensive detailing to get the dust out.

[Naptown]

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With this panel orientation, I am told that the supplier's choice of (1) Fronius inverter is identical to two PowerOnes and that change of the inverter brand and model number is not possible at this stage of the project, without
affecting the quote substantially (note that I have the old pricing from June). So it seems that I am toast and have to go with the one Fronius. It would be interesting to make a calculation, how the "several percents" difference
mentioned to me will affect me monetarily over the long term (= missing on peak hour production).
The only change I was able to get was moving the inverter out of the garage on the east wall. No comment on the dust rating of the Fronius and how it can be affected outside.

You have an instance where the power one would serve you better as you have essentially 2 arrays facing in 2 different directions and the power one will track to arrays independently. Depending on the pitch of the roof this could mean a nominal loss of production to a great deal of loss.

[josefaz]

AZstar, I signed my lease last week. Didn't you sign yours last week as well and the installer already identified your equipment? I know we signed up from different companies but I was told it depends on the site audit engineers assessment. I was asked for equipment preference and I named a couple. I'm still debating with the PowerOne inverters but with two of those, I'm not sure how much that changes there quote. The original equipment they have me filled out with the APS rebate was for 3 SMA's which I found out was inferior compared to either the Fronius or PowerOne.

[AZstars]

Add about 30^oC to the ambient temp and you will get pretty close.

Hmm, I would think that the black color will make the temp differential higher..
Can't you cook eggs on the pavements in Phoenix now ?

[AZstars]

You have an instance where the power one would serve you better as you have essentially 2 arrays facing in 2 different directions and the power one will track to arrays independently. Depending on the pitch of the roof this could mean a nominal loss of production to a great deal of loss.

I agree but was denied in this way:
Fronius has performed experiments comparing east-west systems using one inverter versus two and found the maximum difference in yield to be under 5%. This occurred when the sub arrays were 180deg different and the roof pitch was very high close to approx. 45deg . In your case the orientation difference is 90deg and your roof pitch is less than half of that in the experiment (19deg). Given these circumstances paying extra for another inverter wouldn't be worth the
marginal, if any, gain in yield you might see.

So if I would agree with this justification and have let's say 2.5% difference on guaranteed 21kWh production, how does this translate in monetary loss I may have, compared to potential higher cost of having 2 Power Ones Aurora 6.0 inverters..
Can some board member give me SunPower inside pricing of 2x Power One Aurora 6.0 compared to SPR-11401f 11.4 inverter ?

[AZstars]

AZstar, I signed my lease last week. Didn't you sign yours last week as well and the installer already identified your equipment? I know we signed up from different companies but I was told it depends on the site audit engineers assessment. I was asked for equipment preference and I named a couple. I'm still debating with the PowerOne inverters but with two of those, I'm not sure how much that changes there quote. The original equipment they have me filled out with the APS rebate was for 3 SMA's which I found out was inferior compared to either the Fronius or PowerOne.

No, I signed earlier like end of June, just enough to get the old prices. So this may be the justification why I am being told take the Fronius quoted in the offer, or...
I had the site visit not until a week ago. I am wondering what would be their response if the site visit would discover facts necessitating changing the quote..
Can you ask your supplier for quote comparison of two PowerOnes vs. the Fronius ?

[josefaz]

No, I signed earlier like end of June, just enough to get the old prices. So this may be the justification why I am being told take the Fronius quoted in the offer, or...
I had the site visit not until a week ago. I am wondering what would be their response if the site visit would discover facts necessitating changing the quote..Can you ask your supplier for quote comparison of two PowerOnes vs. the Fronius ?

Yup, I signed my lease at the same time but not getting the site audit for another month. Your installer seems to move fast. I can only assumed that the 3 SMA's was part of my quote. Checking the prices through Amazon shows, the 3 SMA's (sunny Boy)~$7100, Fronius 11.4 ~$7700 and 2 Aurora 6000 ~$6600. It's not the installers price but it gives you an idea of prices. My prefered inverters seems to be the cheapest but nothing is final until the site visit.
In my lease, if the final price exceeds 10% of the initial lease, I have the option of revoking the lease.

[AZstars]

Yup, I signed my lease at the same time but not getting the site audit for another month. Your installer seems to move fast. I can only assumed that the 3 SMA's was part of my quote. Checking the prices through Amazon shows, the 3 SMA's (sunny Boy)~$7100, Fronius 11.4 ~$7700 and 2 Aurora 6000 ~$6600. It's not the installers price but it gives you an idea of prices. My prefered inverters seems to be the cheapest but nothing is final until the site visit.

Indeed, I have just checked for myself. I thought there may be a financial reason why they are pushing the Fronius one one me, but unless SP has a big discount on them from Fronius, this does not seem to be the case.

[KRenn]

Indeed, I have just checked for myself. I thought there may be a financial reason why they are pushing the Fronius one one me, but unless SP has a big discount on them from Fronius, this does not seem to be the case.

There shouldn't be a financial reason, using the Power-One's would up the cost by a few hundred dollars at most but what they said was correct from everything everyone has told me, once you locked in the old price, no amendments could be made to the system without affecting the entire system's pricing. You'll be fine with Fronius, just make sure they put it on the side of the home that has the least amount of direct sun exposure.

[Ian S]

In all this discussion, one factor's been missed...

the highest ambient temperature of the day tends to occur mid afternoon which is long after the PV production has peaked. By 3 PM, my production is typically down by 15-20% from its peak. Unless you have an undersized inverter, you shouldn't have a problem with it being in the garage even in Arizona. I just checked: shortly after 1 PM, the temperature in the garage in the vicinity of the inverter was 101F - this on a day where the high will be 110F. I suspect the garage temperature will peak even later than the outside ambient.

IIRC, the Fronius is rated NEMA 3R which suggests it's not suited for dusty areas. And, unless it is mounted in all day shade, the intense Arizona sun is going to bake that cabinet and all the electronics therein. Keep it in the garage.

As for the 2.5% drop using a single inverter with differently oriented strings, your system sounds like it's oversized so the excess will be sold back to APS at $0.06/kWh. So based on what I assume is actually 21 MWh per year production, that 2.5% loss will amount to about $32 per year.

[inetdog]

Thanks for the ideas. So far this year, my recorded peak temp in the garage is 116F with two cars just parked and the hottest part of the year is yet to come. So we'll see how hot it really gets inside. The garage is already vented outside but no fan. Just 2 vent grills that really don't do much.
I was thinking about placing a fan in the vent facing out or in to circulate the air but I changed my mind because occasionally we get a huge dust storm here. When that happens I really don't want all that dust sucked in the garage. I made a mistake once leaving my car window slightly open and the dust storm came. That was an expensive detailing to get the dust out.

If temperature in the garage ever actually becomes an issue, you might consider putting together a photo-electric dust detector in the vent which would shut off the fan until manually reset.

[AZstars]

..
IIRC, the Fronius is rated NEMA 3R which suggests it's not suited for dusty areas. And, unless it is mounted in all day shade, the intense Arizona sun is going to bake that cabinet and all the electronics therein. Keep it in the garage.

I may give it a second thought for the reason you mentioned (dust and radiant heat) , the HOA request to have items outside painted to house color (I would need to devise some perforated shade around it not restricting airflow) and the easier time inside to develop some fan contraption for cooling the inverter and ventilating the garage itself (the latter maybe saving more $$ as the house is from 1996 and I suppose the insulation between garage and house itself is not perfect)

[Ian S]

I may give it a second thought for the reason you mentioned (dust and radiant heat) , the HOA request to have items outside painted to house color (I would need to devise some perforated shade around it not restricting airflow) and the easier time inside to develop some fan contraption for cooling the inverter and ventilating the garage itself (the latter maybe saving more $$ as the house is from 1996 and I suppose the insulation between garage and house itself is not perfect)

I think that's wise. In the garage, avoid a west wall mounting as that will heat the most. Ideal would be a northern wall or one shared with living space. On the record setting hot summer days, just avoid putting hot cars inside before 3 PM. That's not usually a problem. Don't worry about putting a hot car inside after 3 PM - PV output is way down then so max inverter power is not needed.

[KRenn]

the highest ambient temperature of the day tends to occur mid afternoon which is long after the PV production has peaked. By 3 PM, my production is typically down by 15-20% from its peak. Unless you have an undersized inverter, you shouldn't have a problem with it being in the garage even in Arizona. I just checked: shortly after 1 PM, the temperature in the garage in the vicinity of the inverter was 101F - this on a day where the high will be 110F. I suspect the garage temperature will peak even later than the outside ambient.

IIRC, the Fronius is rated NEMA 3R which suggests it's not suited for dusty areas. And, unless it is mounted in all day shade, the intense Arizona sun is going to bake that cabinet and all the electronics therein. Keep it in the garage.

As for the 2.5% drop using a single inverter with differently oriented strings, your system sounds like it's oversized so the excess will be sold back to APS at $0.06/kWh. So based on what I assume is actually 21 MWh per year production, that 2.5% loss will amount to about $32 per year.

It's not just the heat, its the lack of airflow in the garage. Unless you have a dedicated ventilation source, air circulation is non-existent. I would never recommend putting an inverter in the garage anywhere in the hotter area's of Arizona. Even with the Fronius lowered NEMA rating I would still want that inverter sitting outside as long as its not facing due south.

[Ian S]

It's not just the heat, its the lack of airflow in the garage. Unless you have a dedicated ventilation source, air circulation is non-existent. I would never recommend putting an inverter in the garage anywhere in the hotter area's of Arizona. Even with the Fronius lowered NEMA rating I would still want that inverter sitting outside as long as its not facing due south.

West facing would be just as bad and even east would present a problem. The Fronius has an internal fan so I don't see why air circulation would be a major problem indoors but it would be far easier to set up some extra garage ventilation than protect the inverter from the sun and dust outdoors. Having considerable experience installing electronic instrumentation outdoors in Arizona, I'd want something like this in all-day shade like a north wall under an overhang. We also don't use anything other than an airconditioned NEMA 4 rated enclosure outside here but then our electronics are not rated for above 105F.