Water Pump Wiring

HARG Hunter

Solar Enthusiast
I am designing my water system, and just want to figure out the best option for wiring the water pump.

Looking at hooking a tankless water heater and 12v water pump up to feed the cabin with water from a rain collection barrel.

What is the best way to hook up the water pump?
It is a 12v DC pump.
I know Will is not a fan of hooking up the 12v DC to the charge controller directly.

So....Do I?:

A) Wire it directly to the batteries?
B) Have bus bars that come off of the batteries to connect the charge controller/inverter/12v pump together?
C) An option not above (Please describe)

Also - is there a wire preference for running the DC from the area to the pump?
Is running standard 12/14ga Romex OK?
More Info: Distance from the batteries/charge setup to the pump will be approx. 30 ft.

Thanks in advance for the help.
 

gnubie

Photon Sorcerer
Is the pump float or pressure controlled? Does it have a run time limit or will it simply pump away until the trigger is satisfied?

What sort of battery are you talking about? You want some way to prevent the pump from over-discharging the battery. With a lithium battery the internal BMS will disconnect should the cells ever be discharged too low. With a lead acid battery you normally don't have this level of protection. If you have lead acid and the pump start up and run current is lower than the charge controllers' output load limit you could hook it directly to the load output terminals. If it's more you can use a slave relay on the load output to remove power from the pump on low battery voltage.

The gauge of wire will depend on the current the motor draws and the acceptable voltage drop. Voltage drop will make the pump run more slowly and if severe enough, not be able to start at all. Do you know the running amp rating of the motor?
 

HARG Hunter

Solar Enthusiast
Pump I'm looking at is the Camplux 12v Water System Pump.

Specifications
Model: JK-3206
Voltage : 12V
AMPS:6.0A max
DC Flow capacity : 1.6 GPM/6.0LPM
Water pressure: 65PSI
Item size: 7.4 x 3.9 inch
  • Self-priming allows it to be mounted above tank; able to run dry.
  • Built-in 65 PSI pressure switch, it automatically turns on and off as you turn your tap or nozzle on and off.Adjustable CUT-OFF Pressure : default 65 PSI, MAX 80 PSI. It doesn't mean 6.0L/min jet at 65 PSI
  • 1.6 gallons per minute (6.0 liters per minute). 1/2" male hose thread.
I hope this helps answer your questions.

My battery bank is made of SLA's.
 

PHoganDive

Solar Addict
FYI, Most pumped water systems have an accumulator, so the pump doesn't come on every time you crack a faucet. It pumps water into a pressurized container holding a few gallons, then the container supplies water under pressure until nearly empty and the pressure drops enough for the pump to come on and refill the accumulator again.
 

gnubie

Photon Sorcerer
OK, you definitely want low voltage cut off so you don't nuke the batteries if something goes wrong with the pump control and it stays on. If your charge controller can handle 20A on it's load output terminals that should be OK to run the motor. You can then use the SCC's low voltage setting to remove power from the pump if the batteries are low. If you want to isolate the motor from the SCC you can use a relay connected to the load output terminals, and in turn switch the pump through that. The relay will always draw power when the SCC says the voltage is OK, maybe 3 watts. You could also use an external low voltage cut off device, plenty available on ebay etc, and not have the SCC involved in it at all.

10 AWG over 30' should be OK IMO. Voltage during pump start up should go down to around 10.9V, assuming the motor peaks at 18A, and that should be fine. Listen to what other people say about this, I'm only making educated guesses as to how much current your pump will draw at start up. You could even contact Camplux and ask them what they have found the start current to be, and then we can use that to see if you can use lighter wire.

handy voltage drop calculator
 

HARG Hunter

Solar Enthusiast
All of my components are finally arriving.
I am indeed hooking up an accumulator so the load on the pump and batteries is eased a little bit.

Going to wire it directly to the batteries and install a switch on the positive line near the pump so I can turn it off when we're not there to prevent an unnecessary draw from the batteries.
 
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