Hey Folks... I'm planning my next project. A small Stand Alone Power System (SAPS) for my remote Bore Pump. It will run a small 240VAC 800W submersible bore pump, and some 24VDC loads (lights, timer, maybe a DC surface pump in future, etc...).
I've drawn it up as attached (no masterpiece, but it should suffice for this discussion) and I'm happy with most things (e.g. panels, wire/breaker/fuse sizing, AC distribution panel) all spec'd out to relevant AS/NZS standards/CEC Guidelines. But there were several points where I found the standards lacking in detail &/or little help on the Interwebs.
So here goes... I'd appreciate any advice at all, especially from those with a 'downunder' perspective! If I need to clarify anything just let me know!1. DC Combiners/Distribution
- I've seen DC PV Combiners & Load Center's/Distribution Panels from Midnite Solar and Rainbow Power Company, but they tend to be pricey (Midnite) or hobbled together (RPC). I've used Auto/Marine blade fuse blocks before, but I want a more professional job this time round. Does anybody see any problems using;
a. standard Surface Mount Enclosures (e.g. 8 or 12 pole) to hold DC MCB's/SPD's/Fuse Holders?
b. the included Neutral Link to combine/distribute DC - loads. They copper bars seem 'chunkier' than many Auto blocks I've used. I think they're 63A 240VAC rated?
c. the included Earth Link to ground DC SPD's?
d. a Single Phase Fork Style Insulated Busbar to string the DC + Sub Load Panel DIN mount fuse holders together? Again fairly chunky and they tend to be 63 to 80A AC 240VAC rated.
Or if you know of a better way to do this let me know!2. DC SPD's
- worth it or not? Thoughts/Suggestions/Experiences? I'm planning on Class II DIN MOV SPD's for the incoming PV, and the 24V loads. I'll probably do the 240V board too, but my focus is DC right now.
And before you ask - yes I've done the AS/NZS 1768 risk calculation and it was bugger all, but... My neighbours regulator was blow and I had a cheapie regulator on an exhaust fan pop by close lightning strikes. So thats why I'm considering this stuff.3. Inverter Earthing
- The Power Jack Inverter has the 240VAC outputs earth wired to a ring terminal thats screwed down inside the bottom half of the aluminium chassis. It also has a "CHASSIS GND" screw point on the powder-coated steel backplate that holds the DC power terminals. What should I do if anything with this GND point? For my money it wouldn't be very conductive for starters, and if I did anything I would have thought earthing the top half of the aluminium chassis to the AC earth would be more effective (I don't think the anodised? paint/coating would bond the two chassis halves very well).4. DC Earthing/Fault Protection
- I'm happy with bonding/earthing of PV array's as per AS/NZS 5033, but I found AS/NZS 4509 SAPS somewhat lacking with respect to the DC side of things in general. Basically all it has to say is this...
3.6.6 Battery overcurrent protection
The output conductors of the battery bank shall be protected against overcurrCllt, by HRC
fuses or d.c. rated circuit breakers, as follows:
(a) Where the battery bank is electrically floating (i.e. neither side of the battery is
earthed), protection shall be provided in both positive and negative battery leads.
(b) Where one side of the battery bank is earthed, protection shall be provided in the
unearthed battery lead.
I've never earthed SAPS batteries before. I'm perhaps overly cautious using HRC Fuses AND DC Breakers for the PV and Battery connections (the DC Main Distribution Panel does also serve as my DC lockout/emergency shutdown box) , and fuses breakers protect from overloads/short circuits, but what about DC earth leakages? Is there such a thing as a DC RCD/RCCB? Would a DC MEN link work? If not, would it be safer if I doubled down and fused both + & - for DC loads?
So I'm keen to hear others thoughts/experiences with regards to DC Earthing/Fault Protection. Who floats or earths their batteries, + or -, why, pros/cons either way? How do you protect your DC Loads from overloads/surges and how do you protect yourself from possible DC earth leakages... if at all... maybe you're from the "bird on a wire" camp and prefer not to give those electrons a return path, through you?
Why the 101 questions I hear you asking? Well I just want to ensure the ELV part is as safe as reasonably possible. Thats all. I'd rather not see smoke coming from that end of the paddock.
Plus I think discussion is generally lacking on this stuff anyways, so it'd be good to have a chin wag about it.
I look forward to hearing what y'all have to say.