24V to 12V 20A DC DC Converter 20AMP 240 Watt Voltage Step Down Module

I recently saw a thread that mentioned this step down module and not to wire a panel directly to it.
My seasonally adjustable panels, wired to 12v bilge pumps in a goldfish pond, and have the step down module in between the panel and pump, (with a standard enclosed (so spiders don't nest in it) switch). I was wondering why this admonition? why not to wire it directly from a panel?
I have also had a 12v digital timer post module to occasionally turn the pump off/on automatically. I believe the timer also limits the output to 12v.
I often burn out pumps! Sometimes I have two pumps wired from a single step down module. I think that if I disconnect one pump without turning off all power from the panels, that there is a surge to the other pump, burning it?
I have a seasonable adjustable array with 4 - 20w panels wired parallel, and a 175w panel. with switches at a switch box where the step down and the digital timers are located. I've sometimes wired all 5 panels parallel through a single step down.
Any comments?

If you have a step down converter and see only 12v at the pump, burning out pumps could be.....
1. What happens when the voltage is less than 12v because of clouds? Does the pump try to run at 8v, for example?
2. Pump working too hard (in general). Is the pump pulling more than the normal/rated amps?

Having only recently found this forum, I’ve wondered re what you’ve asked!
I’ve naively never included a fuse but will add one. Should it be near the panel or near the load? Does it matter?
I’ve often wondered also about the impact of less than 12v on the pump(s).
In addition to limiting more than 12v, is there a way to switch off if less than?
Really appreciate your response.

If you could post a wiring diagram/drawing, that would be helpful. Draw what you have today.

Fuses are normally used to protect from major faults, like short circuits. Fuses can be part of a good design but I don't think will help in regards to pump problems that you mentioned.

You might consider getting a small 12v battery and a 12v solar charger that has an "output" connection. These are low cost and with a battery will help keep your equipment running if a cloud passes over. The can also turn off the output when the battery is low or with the built in timer. Here is an example of one. The output is not made to run a lot of amps, so read the instructions on the output's limits. If you need more amps, use the output to control a relay and let the relay carry the greater amp load. A charger like this will replace the 24v/12v step down converter. The battery will allow solar energy to be built up for the time when you run the pump, if the day is somewhat cloudy. The charger also has a low voltage turn off for the output, so you don't drain your battery too low and don't try to run the pump on low voltage.

I’ve always been under the illusion? that it’s either powering the pumps OR charging a battery. Could the charge controller be used without a battery and used to switch off the pumps when voltage is low?

SillasMarner said:

I’ve always been under the illusion? that it’s either powering the pumps OR charging a battery. Could the charge controller be used without a battery and used to switch off the pumps when voltage is low?

Click to expand...

The charge controller's electronics are powered from the battery. So you connect the charge controller to the battery and configure it,
1. to charge the battery, know what voltage to charge to, etc.
2. for controllers with "output" you can configure the output features, low voltage cutoff, when it can power the load, timer, etc.

A solar charge controller without a battery, no use at all. (in this example)

Given 4 - 20w 17v 1.17a panels, and one 175w 17v 10a wired parallel, can I charge a battery AND power pumps?

I’m understanding now that the simplist solution for bilge pump in goldfish pond pump longevity, being directly connected to my panels, is a way to turn them off automatically when they’re made to strain due to insufficient voltage when the sun is not at apogee. I have a step down 24/12 module. Anyone know of such a controller? Thanks for any suggestions. I’ve burned out at least a dozen pumps over the last 10 years.

Not sure how robust they are, but this buck converter has some protection features that can be enabled (ie. under voltage protection)
wuzhi WZ5020L
review on youtube

SillasMarner said:

I’m understanding now that the simplist solution for bilge pump in goldfish pond pump longevity, being directly connected to my panels,

Click to expand...

I use $5 XH-M609 Low Voltage Disconnect Switch Cut Off for a lot of things.
The only issue in your case is that they need a constant battery source to keep them running.
One controls a external relay that switches 6 X 6w led lights directly from the PV side (Voc 22) when B reaches 13.8v and switches off at 12.6v.
This would suit your pump if a 24v relay is used between pump and pv and you up the voltage settings. .
Edit- just realised this runs off system voltage and there may be times the panel voltage being controlled may not be there so you will be still in the undervoltage situation.....works for me but probably not all the time in your case.

I have another row of led lights direct off the panels, no control. Low voltage doesn't effect them. They start coming on a 4v , just get brighter at 22v