Help with Panel sizing for brushless DC bore pump

[BigfootBushy]

Hi all, I am hoping for some guidance with regards a screw type brushless solar bore pump I have installed.

The pump is rated at 24V 150W. The manual recommends 2 panels 100W 15.5V connected in series. All controlled by an MPPT pump controller.

Now when purchased as a kit, 2 panels were supplied. A 100W 23V and a 120W 19.5V.

The seller advised that they would work fine and to still connect them in series. The seller has since been unwilling to assist in helping get system running properly.

The pump does run with this connection but stops on voltage error with the slightest of shade on the panels.

With that story in mind, what would be the solution to keeping the pump running longer? For instance, with light cloud.

I had in mind replacing the 100W panel with 3 panels 120W 14V or 12V and having 2 pairs in parallel then in series to feed the controller.

Am I on the right track or have i missed something completely? As a complete novice with solar I would welcome any advise or ideas

Cheers Tyson

[inetdog]

Hi all, I am hoping for some guidance with regards a screw type brushless solar bore pump I have installed.

The pump is rated at 24V 150W. The manual recommends 2 panels 100W 15.5V connected in series. All controlled by an MPPT pump controller.

Now when purchased as a kit, 2 panels were supplied. A 100W 23V and a 120W 19.5V.

The seller advised that they would work fine and to still connect them in series. The seller has since been unwilling to assist in helping get system running properly.

The pump does run with this connection but stops on voltage error with the slightest of shade on the panels.

With that story in mind, what would be the solution to keeping the pump running longer? For instance, with light cloud.

I had in mind replacing the 100W panel with 3 panels 120W 14V or 12V and having 2 pairs in parallel then in series to feed the controller.

Am I on the right track or have i missed something completely? As a complete novice with solar I would welcome any advise or ideas

Cheers Tyson

1. Since you do not have batteries to stabilize the DC source voltage and supply current when the sun is momentarily blocked, you need a pump controller that can automatically restart. I hope you have that and are just trying to get more running time total.
2. When you get partial shade on a panel, it does not just cost you a little current, proportional to the shaded area. It costs the entire voltage output of anywhere from one third of the panel to the whole panel. One way to work around this is to put three panels in series so that when there is some partial shade on one panel you still have enough voltage to run the pump and controller. Assuming that your controller will accept the higher voltage.
3. If your MPPT pump controller cannot boost the voltage but only buck it down, increasing the current in the process, you must keep the panel string voltage above the pump cutoff voltage as much as possible.
4. In general you are better off putting four panels into two strings of two instead of a string of two panel sets in parallel. But in your case the need to keep up a minimum voltage may make the uncommon configuration you described better for you.
5. If a cloud goes over all of the panels, the pump will stop unless your system includes batteries. No way around that unless the pump and controller can keep the pump working in a very low current mode. An inverter type pump motor can do that, a straight DC motor cannot.
6. If the controller can take it, all four panels in series would probably be even better.
7. Your 120 watt 19.5 volt panel can produce as much current at 19.5 volts as your 100 watt 23 volt panel, but the extra power it has when used at its best power point is just going to be lost because of the lower current capability of the 100 watt panel.
8. A 100 watt 23 volt panel will not be able to deliver as much current to the controller as a 100 watt 15.5 volt panel could, but IF it is truly MPPT that should not matter. If it is not really MPPT, then you do not have as much current at the pump manufacturer recommends.

[BigfootBushy]

Thanks for that great explanation inetdog.

Yes the pump controller shuts the pump off at low power and restarts 3minutes after power is high enough. At present it only takes a slight wispy cloud to cut power and then by the time it restarts another cloud is across. The pump can be heard slowing and the mppt light comes on just before it stops.

The pump is a brushless DC three phase screw type.

I cannot find any maximum input voltage rating on the controller so I'm not sure how much will be safe. But if I stay around the present input capacity there shouldn't be a problem.

On that basis and from what you have explained, would you agree that replacing the 100W 23v with two 120W 14v connected in series with exsisting 120W 19.5v would be a sensible starting point.

Then next step if still unsuccessful would be to go to replace 120w 19.5v with a further two 120W 14v and have four of them in series.

I hope this reads ok, I'm on an iPhone while traveling to work.

Cheers Tyson

[Texas Wellman]

What is the pumping level?

Thanks for that great explanation inetdog.

Yes the pump controller shuts the pump off at low power and restarts 3minutes after power is high enough. At present it only takes a slight wispy cloud to cut power and then by the time it restarts another cloud is across. The pump can be heard slowing and the mppt light comes on just before it stops.

The pump is a brushless DC three phase screw type.

I cannot find any maximum input voltage rating on the controller so I'm not sure how much will be safe. But if I stay around the present input capacity there shouldn't be a problem.

On that basis and from what you have explained, would you agree that replacing the 100W 23v with two 120W 14v connected in series with exsisting 120W 19.5v would be a sensible starting point.

Then next step if still unsuccessful would be to go to replace 120w 19.5v with a further two 120W 14v and have four of them in series.

I hope this reads ok, I'm on an iPhone while traveling to work.

Cheers Tyson

[BigfootBushy]

What is the pumping level?

110 Feet with 1" poly. According to pump chart flow is approx 400L/hr

[Texas Wellman]

That's about 100 gallons per hour, or about 2 gallons per minute. That's a pretty deep water level also for that amount of power.

What is the brand of the pump?

110 Feet with 1" poly. According to pump chart flow is approx 400L/hr

[BigfootBushy]

The pump is a Shilushi brand.

I have got the pump performing noticeably better at this point.
As a trial a borrowed 100w panel has been connected in parallel work my existing
100w panel and these are connected in series with the 120w panel.
When funds permit I will set up array of 4 120w panels. 2 parallel pairs connected in series.