12v dc water pump wiring question

[DAVEHOLMAN]

My Thomas HDX has, basically, a sub panel under the dash by the front door. Is there any reason no to connect the pump to the + and - terminals there? It would be a shorter run than the batteries which are in the back on the other side.

It's a 3.5gpm demand pump. Shouldn't stress the starting batteries much.

Also, is 12gauge wire adequate for a 10 foot run? Or should I get something bigger?

[peteg59]

Are those terminals live with ign. off?
As far as draining the start batt., it shouldn't drain too much as long as you don't take half hour showers a couple times/day...

[DAVEHOLMAN]

Ha! Guess I better go check that right now.

And 1/2 hour showers are not likely with a 4 gallon water heater. 🙃

[Danjo]

I think that it’s preferable to use a circuit that’s always live, but I’d take it to a switch before the water pump so you can turn it off during storage.

[ol trunt]

definitely use a switch because if your water system springs a leak the pump will happily drain your tank into the bus. Also, be sure to use a switch rated for 12 volts and the appropriate amperage. The less expensive 120 volt switches will work for a while but their contacts will eventually fail under the 12 volt load.
Jack

[DAVEHOLMAN]

See, this is why I love this forum. I hadn't even thought about the need for a switch. Thanks!

[Danjo]

Originally Posted by ol trunt

definitely use a switch because if your water system springs a leak the pump will happily drain your tank into the bus. Also, be sure to use a switch rated for 12 volts and the appropriate amperage. The less expensive 120 volt switches will work for a while but their contacts will eventually fail under the 12 volt load.
Jack

Haha! I’ve been living dangerously secretly hoping for a clean floor!

[kazetsukai]

I initially ran a 15ft-20ft run of 10ga (12V) to our water pump. I was having issues with other 12V devices when the pump kicked on- lights would flicker, etc. When I measured at the pump while it was running, I was getting 10V at the pump, 13.8V at the panel.

I tried a capacitor to even out the surge load at first. This helped with lights flickering but I still had low voltage at the pump. So then I took the same 10ga line and switched it to the 48V circuit- and put a 48V -> 12V converter at the pump itself. Night and day difference in performance. 13.8V at the pump, on or off. Later, I switched to using a Square D pressure switch instead of the dinky built in one, that was also a massive improvement. The pump runs for much shorter periods, much faster, and it will also last longer since it is pulling less amperage.

If you have a 24V or 48V system, my advice is to do as I did above, run your native voltage to the pump and convert there. If you have a 12V system, my advice would be to run the largest cables you practically can and put another DC fuse block right at the pump. It may be useful later for wiring other stuff in, I have a few of them throughout our rig.

[Danjo]

Originally Posted by kazetsukai

I initially ran a 15ft-20ft run of 10ga (12V) to our water pump. I was having issues with other 12V devices when the pump kicked on- lights would flicker, etc. When I measured at the pump while it was running, I was getting 10V at the pump, 13.8V at the panel.

I tried a capacitor to even out the surge load at first. This helped with lights flickering but I still had low voltage at the pump. So then I took the same 10ga line and switched it to the 48V circuit- and put a 48V -> 12V converter at the pump itself. Night and day difference in performance. 13.8V at the pump, on or off. Later, I switched to using a Square D pressure switch instead of the dinky built in one, that was also a massive improvement. The pump runs for much shorter periods, much faster, and it will also last longer since it is pulling less amperage.

If you have a 24V or 48V system, my advice is to do as I did above, run your native voltage to the pump and convert there. If you have a 12V system, my advice would be to run the largest cables you practically can and put another DC fuse block right at the pump. It may be useful later for wiring other stuff in, I have a few of them throughout our rig.

What’s the pump? Sounds big

[kazetsukai]

Originally Posted by Danjo

What’s the pump? Sounds big

Its the Seaflo 55 series with the accumulator tank:
https://www.amazon.com/gp/product/B07QN8D18H