water heating and pumping

Re: water heating and pumping

1. Can I hook the inverter to the batteries direct or do I need a 2nd c60 controller to go between the battery bank and inverter ?
2. How many batteries and what type would be the best.

It’s my understanding that the C60 can be configured for PV charge control, diversion control or load control, but only for one mode at a time. Accordingly, I believe that you’ll need one C60 for a PV controller, and a second one for the diversion controller.

For the PV application, the basic block diagram would be 24 V PV array -> C60 controller #1 (configured for PV charge control mode) -> 24 V battery bank -> 4024 inverter -> AC loads. For the diversion application, the additional connections would be 24 V battery bank -> C60 controller #2 (configured for diversion control mode) -> diversion load (i.e., water heater element).

The Morningstar TriStar controller might also be worth considering for your application.

For your 520 W STC PV array configured for a 24 V system, a 24 V x ~260 Ah battery bank should be appropriate. One configuration would be four 6V T-105 (“golf cart”) batteries wired in series for 24 V x ~225 Ah. Another solution would be a pair of size 8D 12V batteries wired in series for 24 V x ~250 Ah. Both battery types are available in either flooded-cell {cheaper but require equalization, maintenance, ventilation and are ~80% efficient (Wh out / Wh in)}, or VRLA (AGM or gel) models (more expensive, but don’t require equalization, typically don’t require much maintenance or ventilation, but are ~90% efficient).

For your Michigan location, you’ll probably need remote battery temperature sensors for the controllers.

HTH,
Jim / crewzer

Re: water heating and pumping

Could I just run it at 120 or 240 from the 4024 and with the inverter set up to stop at low battery level and not heat again till the batteries were fully charged? Instead of using a dc element in the water heater. Any comments on which would be better?

This will work technically. You’d just to make sure the water heater element is 4,000 W or less.

Whether this is a practical solution for solar energy is another matter. For example, roof-mounted solar water heaters can be as much as 80% efficient. However, considering that PV modules are but ~12% efficient and that the effective system efficiency is but ~67% efficient, that makes PV-based water heating ~8% efficient.

Another issue is that heating water is energy intense. Assuming ~96% efficiency, a 40 gallon electric water heater requires ~3,414 BTU’s (1 kWh) to raise the water temperature by ~10 F. Assuming 2,000 W heating element and 90% inverter efficiency, the batteries will be supplying ~93 A at 24 V. This load will discharge your batteries (~180 Ah at 2 hours rate) by ~50% in one hour.

I suspect that I’d use a second controller and a DC diversion water heater if I were faced with this situation.

Thanks again for the information. Wont be too long and I hope to be getting the system put together. Placement of the panels probably will be on the south end of my house Im still in contruction in the basement so Im going to build a closet for it all on south end of the basement. Ill then run 240ac to the other end of house where the well hook up and water heater will be. about 75 feet I would think. Any suggestions on wire size?

The SW4024’s manual recommends #6 AWG wire for AC cable in conduit between the inverter and the AC subpanel. See page 132. Wire sizes from the subpanel to the loads will depend on the breakers and loads… I’d recommend consulting the NEC.

I checked on these batteries SunExtender PVX-2240T 224 Amp Hour, 6 Volt. 4 of these for around 900 shipped to Michigan,Would I need 4 of these?

These are AGM versions of typical “GC-2” golf cart batteries. They are apparently very good batteries. Four of ‘em in series will work fine as a 24 V x 224 Ah battery bank. AGM batteries are sensitive to overcharging, so I recommend you carefully follow Concorde’s charging and maintenance instructions when configuring your charge controller. If possible, measure the charging voltages at the battery terminals to confirm the controller’s settings. Don’t forget the remote battery temp sensor for the controller. An alternative battery consider is the PVX-2580L… you’d need two in series.

Note that I had a battery-to-battery voltage imbalance problem with my 12V AGM batteries wired in series/parallel. I solved the problem by installing a pair of PowerCheq battery “equalizers”. More info about the problem and the solution is available here.



HTH,
Jim / crewzer