Looking for Feedback on a System Design

[ccasey487]

Looking to install a small off grid system at a rural health clinic in the next few weeks and thought it might be helpful to draw on the forum's collective computing power. I'm looking to use a tristar 30 mppt CC with a suresine 400W inverter. The loads are a few lights and a DC vaccine refrigerator. Attached is the line drawing I have, I'm wondering if there's anything I might be missing? Any help would be most appreciated. Thanks!

[zoneblue]

Obvious improvements would be midnite kid controller. And midnite SPD :-)

Im not big on DC GFIs. Prefer negative bonding. Otherwise things look generally ok. Have you determined your loads and battery sizing etc.

[Rybren]

Maybe I missed it, but how many panels are you looking at?  I see that you are planning on a 450AH battery bank, a general rule of thumb is that you'll want your PVs to be able to produce enough current to equal ~10% of your battery capacity.  In your case, that would be ~ 45 Amps.

I believe that the Suresine inverter only comes in a 300W version.  I don't know whether your planned loads would require the full 400W that you have listed for the inverter.

One thing that is missing from your diagram is fuses/circuit breakers.

How do you know that you'll need 450AH of battery?  Have you measured the appliances that you want to run or are you just guessing?.

Generally, the first step in off-grid is to define, as accurately as possible, the load
Then, calculate how much battery you'll need to support the load (to include the desired number of days that you can run before needing to run a genny)
Then, calculate how much PV you'll need to recharge the battery.

If you haven't been there already, I would suggest visiting the Solar Beginners Forum at NAWS. http://forum.solar-electric.com/forumdisplay.php?18-Solar-Beginners-Corner

[ccasey487]

Thanks for all the great feedback! Originally spec'd the Kid but have to work with some pre existing inventory down here. I had also thought to use 2 panels that have an ISC of 8.3A. My total load I've estimated at 199W, with about 2700 wh/day of usage and am looking for about 2 days of autonomy with a 50% DoD. The breakers in the Midnite MNDC-C  I have spec'd as 20A for the PV, 30A for the CC, another 20A for the DC refrigerator, 63 and 0.5 and a 125A main to the inverter.

[Westbranch]

A little more info will help us help you...where is this located and what is the weather/temps like there?

I would also add the WhizBang jr to the list of things to get  or a Midnite BCM depending on who will be doing the long term monitoring...

[vtmaps]

The breakers in the Midnite MNDC-C  I have spec'd as 20A for the PV, 30A for the CC, another 20A for the DC refrigerator, 63 and 0.5 and a 125A main to the inverter.

the 63 and 0.5 are ganged together and constitute the DC GFP that 'zoneblue' was referring to.  Do a little more research on DC GFP before you commit to that.

--vtMaps

[ccasey487]

Yes I've heard a bit about how much more effective the MSPD is for lightning protection unfortunately I've got to work within limitations of what's available down here. Would it be better to just forgo the lightning arrestor and breakers and bond the ground to neutral within the panel instead?