[RE-wrenches] How to isolate the array DC

[boB at midnitesolar.com]

The inverters' input capacitors may be charged and so that must also be 
isolated near the inverter.

A grid operated contactor will not work for a battery-back up system.

Also, 600V DC  can weld contacts closed and if this happens and there is 
no feedback to show that
the contacts definitely opened, this can ruin a firefighter's day.

Otherwise, a system of contactors from AC grid could work in a grid-tie 
only system.

The new UL rapid shutdown specifications are supposed to be released 
very soon now.
Maybe within the month ?

boB Gudgel
K7IQ
MidNite Solar


On 2/2/2015 1:23 PM, Mark Frye wrote:
> In order to clear up the conversation...
>
> I you put a relay in a box within 10 feet of the array on the roof, 
> you can use an relay with a DC rated Normally Open contact to open and 
> connect/isolate the array DC voltage.
>
> You can drive the coil of that relay with either AC or DC, but either 
> way, if you lose voltage to drive the coil, the contact opens and 
> isolates.
>
> My point is, for simple grid-tied system, there is no need for a 
> "stop" switch anywhere in the system. It doesn't matter whether the 
> contactor coil is driven by the premise AC or by a DC power supply 
> connected to the premise AC, when the the main is opened or the meter 
> pulled, the array Dc will become isolate.
>
> Therefore, there is no need for the "stop" switch and yet as I 
> understand it, such a switch is now required by the Code. The switch 
> is not needed but is required.
>
> Mark Frye
> _______________________________________________