Thread: Pool pumps and solar power

No way would you tap into a mains connected series panel set, DC voltages in a string can be quite high and dangerous. Panels are cheap, just run a suitable panel set for just the pump if that's what you want. Pump example:

500w Solar Pool Pump with MPPT Controller | eBay

Originally Posted by jx2mad

The house we are buying has an inground pool which has solar heater attached. Both the filter pump and the solar heater pump are 1 hp 240v motors. I will be having these replaced with 24 v DC motors run from solar panels. Now I am going to get a large capacity solar power system for the house. My question is....can I tap 24v off the solar power system to drive the dc motors or should I use dedicated panels? Jim

Why would you do that? Just get a large capacity solar power system for the house. The solar inverter will supply 240V AC. The surplus electricity above what you use directly in your house will run your existing pool pumps and any surplus above that (if any) will be feed back to the grid. You don't need to change your pool pumps.

Originally Posted by Ferret

Why would you do that? Just get a large capacity solar power system for the house. The solar inverter will supply 240V AC. The surplus electricity above what you use directly in your house will run your existing pool pumps and any surplus above that (if any) will be feed back to the grid. You don't need to change your pool pumps.

Agee 100% with above. Run all your heavy consuming electrical goods when the sun is shining, rather than feeding into the grid.

Thanks guys. A large solar power setup without changing the pump motors would be the easiest.

Yep. Bigger is better.

I install solar to the house the second year after installing the pool, run my pool pumps during the peak midday sun and It halved my electricity usage on average. So after I pay it off!!! Three year interest free on the install cost etc, so electricity cost will be the same if not smaller then before I installed the pool.

Can't remember what size my system is but I have 20 panels on the roof!

Cheers Lemo

A couple of things you need to be aware of - DC motors in that application won't last anywhere near as long as a 240 volt AC induction motor, even if you can buy such a beast. A 1HP motor has an output of around 750 watts, with the inefficiencies bought in, the input would be closer to 850 watts. That's around 35 amps continuous on a 24volt supply, so wiring will need to be quite beefy, but that's not your biggest problem - solar panels have absolutely zero ability to produce current levels above their manufactured rating, even for a millisecond, so starting a motor off them is pretty much impossible, even if you had enough panels - you'd need around 6,000 watts of panels to start a 1HP motor, it wouldn't work as the sun doesn't hit them in one shot, so you'd never get to a point where the panels would provide enough current to start the motor. You'd need to have a timer or something that will kick the pump in once the sun is fully on all panels and they are at peak efficiency (sun overhead). Even then, I doubt the motor would start.

If you go down this path, you'll need batteries to be able to do this - by the time you sort the panels and batteries, you could run the 240 volt pumps for 20 years on the money you'd spend doing it.

Lemo's got the best solution - put a decent home solar system in and run the 240 volt pumps during the day when the sun is out - problem solved as the grid is still there to start the motors. Once their running, the solar is taking care of business. Win/win as you then have solar to reduce your grid demands throughout the day as well saving you money.

Lemo, most solar panels used in home applications are around 200 to 250 watts, so between 4 and 5KW your system is - a cracking setup.

DC pumps designed to run directly off solar panels don't have any problems starting as they are electronically commutated and ramped up. I have a small one on my HWS as the collectors are above the tank and it has been trouble free and entirely automatic for the last 7 years. However they're not exactly cheap so you need to do your sums before lashing out on a solar pumping system. The loss of a low solar FIT by running ordinary AC pumps during the day will never get anywhere near the cost of a stand alone system. If one of the existing pumps dies however then you might consider the upgrade instead of simple replacement.