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Sun Volt Solar

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Photovoltaic system details

30 Jul 09 | Solar Electric

Every installation is different, that is the number one lesson I have learned.  Those that try to get into the cookie cutter mentality often get into trouble.  This is a PV installation we are currently working on:

5 KW DC Photovoltaic array mounted on a standing seam roof.

5 KW DC Photovoltaic array mounted on a standing seam roof.

It is a 5 KW PV system attached to a standing seam roof. This system takes up about 420 square feet of roof area and consists of 24 Sharp ND-224UF1 PV panels.  We use Sunwize pre-packaged systems because it eliminates a lot of the minutiae involved in installing grid connected PV systems.  They produce well thought out systems complete with engineering drawings.  This speeds the permit process along nicely.  That being said, even Sunwize grid tied systems occasionally need some different parts than what is supplied.

First, all grid connected PV systems installed in New York state must have a lockable disconnect switch that is accessible to the utility company for safety reasons.  Because this is a pretty large house, the wire runs between the utility room and the disconnect switch are quite long.  I had to up size the wiring to stay below 2% voltage drop.  The larger wire would not work with the NEMA 3R switch provided with the pre-packaged system, so I needed to install a larger switch.

Second, this house has a backup generator with an automatic transfer switch for emergency power.  With that configuration, there could conceivably be a time when the generator is running that the inverter tries to come on line.  If the house was using less than 5,000 watts of power, the excess power from the PV array would be fed to the generator windings causing the field coils to melt.  This is a long shot because in all likely hood, the generator frequency would change dramatically when the inverter came on line causing the inverter to drop out again.  Never the less, in order to avoid any possibility of this happening, a generator running relay is installed between the inverter and the power panel.  This way if the generator is running, the inverter is forced off.

Third, because this is a standing seam roof, the traditional Unirack PV mounting racks that come with the Sunwize grid connected systems could not be used.  Instead, we used S5! standing seam mounts (S5! U mini) with PV clamps (PV anchor kit, 41-60 MM).  These worked out very well.  I used to of the S5! mini clamps to mount the combiner box at the top of the array.

S5! PV mount holding down two Sharp ND-224UF1 panels

S5! PV mount holding down two Sharp ND-224UF1 panels

We are waiting for the roofer to make an ingress port at the top of the array to make the final connection between the PV array and the inverter.  Once this is done, the system can be inspected and turned on.

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30 Jul 09 | Solar Electric | Comments (0)