Burning up on-demand 12v pumps

We've been burning out a lot of pumps. I suppose my first question is how does a pump that is rated to operate at 16 amps max wind up drawing enough amps to blow a 20 amps fuse. Ive burned up a lot of these pumps but can't figure out why. These are on-demand pumps with pressure switches. Hopefully someone can ask me the right questions to help solve the riddle. Thank you in advance.

Well, the motor in the pump will draw its maximum current when stalled: starting or otherwise prevented from moving physically. If you are trying to cycle the pump on and off too quickly, you'll be drawing a lot of current.

That said, is the 16A rating for continuous current draw or current spikes? If it's continuous, then you have your answer: the motors are creating a huge current spike, blowing the fuses.

I pump needs to come on speed to reduce its current.
So if you have a series of burn outs, then check the following.
1. liquid is to thick as a result its speed is to low.
2. input is to small or blocked filter.
3. output is to high or blocked, yes i know that you have a pressure switch still you can be on the border in that case install a lower pressure switch.

Also keep in mind that a lot of pumps have specifications that are tested in a laboratory and in real live it does not work.

As a last step what is your power supply and is it stable a under rated battery can drop voltage and again give problems, a switched power supply not made for this current draw will give extreme high start up current in PWM.

I hoop this helps

Can you post up link to pump spec sheet and or email it?

The best I could find was this here http://www.delavanagpumps.com/powerflo/5800.htm.

Here's a pdf of some specs http://www.delavanagpumps.com/powerflo/5800.htm. I believe 16 amps is the start-up draw. My retailer swears they're great pumps but need specific installation. He suggested 12-3 wire because the wire strands are fine making better connection, crimped connections- no wire nuts, short wire runs to the battery, biggest marine battery possible fully charged.

The spraying nozzles cannot be too small or it will cycle like you stated. The pumps will always run smooth at ground level. But I believe once the hoses reach the 2nd or 3rd floor of a roof, the fluid in the hose is creating a head pressure which pushes back to the pump and cause cycling. So it a fine line of using a hose big enough as to not create restrictions and cause cycling, but also not to large as to hold more fluid and create more head pressure.
My batteries are 600 ca or higher and are new to 2years old. They hold good charges from 12.2 to 12.8 volts. The only thing I havent check is the voltage drop when there's a load on.

Thanks for the reply. My reply to Peter is also for you. I am no electrician by any means, but my pump retailer has me feeling stupid. We run 4 trucks with these pumps. Sometimes the pumps last for months, others have crapped out rather quickly.

I understand these are marine pumps. We run chlorine through them for which its not intended, but that should not matter. Theyre not really designed to pump 2nd floor but allegedly Im the only one having these problems.

P.s. If I do not solve my problem in this forum, I am grateful that you guys quickly responded to offer assistance. Really good stuff, much appreciated.

I suspect that you are exceeding the duty cycle of the pumps. The responders here need to realize that some of these pumps are designed to pump water in recreational vehicles. The normal usage is a few minutes on and long periods of off time. The longest normal usage would be a shower and many RVs don't have a shower so many of these pumps have duty cycles that are quite short. Good news is that there are many of these type pumps that are higher durability and may have up to 100% duty cycle. I did notice you mentioned nozzles in your note so I suspect that when the pump is turned on there will never be enough pressure built up to turn it off so the pump is probably running continuously. The manufacturer recommends not letting the surface temp of the pump exceed 180 degrees. Check, carefully, the temp of the pumps in service and see if they are hot. If they are hot then I think you have found a smoking gun. Don't hesitate to use a larger, gpm, pump as well as one with a longer duty cycle. A higher flow pump will be more likely to build up enough pressure to shut off periodically and even if it's off only 10% of the time it will run cooler and be less likely to burn out.

Fair enough Chuck. I suspected this model pump is not up to the task. I do have the option of running pumps with internal fans and thermal protection. These pumps were fairly cheap and others have claimed to have good success with them. I suspect we may be cleaning more roofs than the average.

Thanks everyone for the help. Look me up for any questions regarding exterior cleaning of every nature.

Ed from New Jersey
Thompson Roof Cleaning and Powerwashing

Chlorine is a bad chemical for pumps. It eats iron even stainless steel.
As soon as that one off the valves stops working correct you start over loading the pump a second one and your pump will start over heating and it does not have protection.
Next to that Chlorine is thickening under heavy motion, like a pump.
These pumps are also not designed to pump to height As stated they are for RV and Boot use.

Seeing on your email you use them for your work.
Go to a farmers store they have pumps for spraying chemicals.
It will give the easy the pump height that you need and if you take care for the oil in the gear box it will live longer than your truck.

Hi Ed,
You could determine the current drawn by the pump at any particular time by connecting (preferably by someone electrically qualified) an ammeter in series with the pump, then have someone watch it and note the values while the job is being carried out (or simulated).

Then see how the results compare with the maker's heat rise graph, which (if I read it correctly) shows that a constant current of 13 Amps (or an equivalent duty cycle) should be indefinitely sustainable.

The pump's maximum pressure is rated 100 psi, so you could calculate its suitability for the pressure required for your purpose, from the density of the fluid being pumped and the height it has to go to.

Is it possible to fit an output pressure gauge on the pump ? Or even a flowmeter ?

Apart from that, may I suggest you use the "Contact Us" button on the maker's webpage ?

Give them full details of your usage, duty cycle (time on to time off)(as the pump will cool when its off).
(As this pump is non-ventilated, its duty cycle at higher currents will be limited.)
Tell them the substances you use and the height pumped to.

I would expect their technical department would give you all the information you need to determine whether this is a suitable pump for the purpose, or if you need a more powerful or special purpose unit.

Thanks Frank. Hooking an ampmeter should not be a big deal, and technically there should be a gauge in-line to make sure the pump is not exceeding recommended pressure. We pump a mixture of chlorine, water, and a surfactant which technically voids the warranty of the pump, but would also destroy such objects such as gauges, etc. I'm going with a bit larger pump to see how I fair.