Best way to run to Water pumps for a pond?

[Alber]

Please help, have not found any threads on this as yet and I am new to solar
I have purchased 2 x 275 Canadian Solar panels and are looking to make my water pumps work directly from the panels.
I have 2 x Water Pumps:

Specifications:
RD-DC 12V is a submersible pump with stainless steel casing
Voltage:12V
Power:120W
Caliber:25mm(1")
Capacity:26.4US.GPM
Max Lift: 5-7M
Main applications: Water
Cable Length: 2.5M

and 2 x Canadian275w Solar panels.
Specs:
Pmax - 275w
Vmp - 31.3 V
imp - 8.80 A
Voc - 38.3 V
Isc - 9.31 A

Please what do I need to get these water pumps working from these panels. The Panels will be south facing.
I will not be having batteries as its only for day time pumping. ( for my fish pond).
What size controller would I need and should i be parallel or series?
Can I wire both pumps together or best separate with 1 panel for each

Thank you in advance for all your help and support.

 

[DerekH]

The cheapest and simplest way is to wire the two pumps in series and your two panels in parallel and then connect them directly. That will bring the load demand voltage of the pumps to 24V and keep your solar panel system's voltage in the ~31.3V ~38V operating range minimizing the discrepancy between pump operating voltage and the voltage that your panels supply. The concern I have with this method is the longevity of your pumps. You'd be running them above their recommended operating voltage by a small enough margin that immediate catastrophic failure is very unlikely and they're submersible so the risk of fire is negligible, but they will run at increased temperature and the overheat is likely to decrease your pumps' lifespans.

EDIT: At the minimum, you'll want to place an on/off switch between your panels and pumps. This will allow you to leave the panels off while you wire them to the pumps and until you can get the pumps submerged. Otherwise, connecting the panels and pumps in daylight would cause the pumps to turn on immediately which seems problematic.

If you want the pumps to run safer and last longer you should consider putting a component between the pumps and panels to step the panels' supply voltage down to 12V per pump or 24V for the two pumps wired in series. I'm new to the solar game myself, so I can't recommend a specific component, but I'm sure something that performs this function exists at this point.

Hope that helps.

 

[Alber]

The cheapest and simplest way is to wire the two pumps in series and your two panels in parallel and then connect them directly. That will bring the load demand voltage of the pumps to 24V and keep your solar panel system's voltage in the ~31.3V ~38V operating range minimizing the discrepancy between pump operating voltage and the voltage that your panels supply. The concern I have with this method is the longevity of your pumps. You'd be running them above their recommended operating voltage by a small enough margin that immediate catastrophic failure is very unlikely and they're submersible so the risk of fire is negligible, but they will run at increased temperature and the overheat is likely to decrease your pumps' lifespans.

EDIT: At the minimum, you'll want to place an on/off switch between your panels and pumps. This will allow you to leave the panels off while you wire them to the pumps and until you can get the pumps submerged. Otherwise, connecting the panels and pumps in daylight would cause the pumps to turn on immediately which seems problematic.

If you want the pumps to run safer and last longer you should consider putting a component between the pumps and panels to step the panels' supply voltage down to 12V per pump or 24V for the two pumps wired in series. I'm new to the solar game myself, so I can't recommend a specific component, but I'm sure something that performs this function exists at this point.

Hope that helps.

WOW thank you, that was very helpful, would I need a controller? as when looking at the videos about solar they all have controllers?
I found this:
Step-Down DC/DC Voltage Converter - 36/48V (36-60V) to 12V Power Reducer - 10 or 20 Amp - 10 Amps

Step-Down DC/DC Voltage Converter - 36/48V (36-60V) to 12V Power Reducer - 10 or 20 Amp - 10 Amps

This DC-to-DC voltage converter allows you to use 12V LED lights with your vehicle's 36V or 48V DC system (36-60V). The waterproof converter is rated for 10 or 20 amps and is constructed of durable die cast aluminum with 7" wire leads. Surface mount the converter with screw holes on both sides...

www.superbrightleds.com

So based on this can I use each panel separately? linked to each pump, then I could use 2 converters one for each?
I also found this item? not sure if its what we need?
Specifications:
Load: Light Control
MPN: RBL
Model: RBL-30A,RBL-60A
System Voltage: 12V 24V
Max Solar input(Solar Panel):36V(24V battery) 18V(12V battery)
Max input power: 390W(12V system); 780W(24V system)
Equalization: 12.6V(sealed) 14.2V(Gel) 14.6V(flood)
Float charge: 13.7V(default,adjustable)，12.0-15.0V
Discharge stop voltage: 10.7V(default,adjustable)，9.0-11.5V
Discharge reconnect voltage:12.5V(default,adjustable)，11.0-13.0V
Rated current: 30A,60A
Self-consume:<10mA
Batteries:Only fit for OPEN, AGM, GEL
Operating Temperature:-35℃~60℃
USB output:5V/2A Max
Dimension:13.4*7*3.3cm

 

[DerekH]

That device looks like it would work nicely with the two pumps wired in series and connected to the "light" output and the panels in parallel connected to the "battery" input of that device. Your pumps will draw about 20 amps in series so that puts you comfortably under the 30A rated current. Looks like a good solution to me.

 

[jones26]

The easiest way is to wire the two pumps & two panels in parallel and then connect them directly. That will bring the load demand voltage of the pumps to 24V and keep your solar panel system's voltage operating range minimizing the discrepancy between pump operating voltage and the voltage that your panels supply. Operating voltage by a small enough margin that immediate catastrophic failure is very unlikely and they're submersible so the risk of fire is negligible, but they will run at increased temperature and the overheat is likely to decrease your pumps' lifespans.

 

[rudra11]

When you run water pumps for a pond, you should determine the size pond pump, first, You need to calculate the volume of water in gallons, simply multiply the length x width x average depth x 7.5.