Well pump for fire supression sprkinklers

[gambieroffgrid]

Hey Everyone...first time poster. I've gleaned a lot of info from people on these forms over the years and finally have a question that I don't think has been answered.

I have a Goulds well pump that pumps water into a 1000 gallon holding tank. I previously had a 1/2HP little giant pump (with Franklin motor) pumping from the cistern, via a pressure tank, into my off-grid home. Unfortunately that pump placed too high a load on my system and generator during start up and occasionally tripped the generator. It was well within specs, but my honda 7000 didn't seem to like the start-up surge.

I replaced my little giant submersible pump (that tripped my generator during start-up surge) with a 24v dankoff pump. The 24v pump is working great, though I am still worried about the noise and whether that means the pump will wear out prematurely...time will tell. The lower power draw and minimal surge has made a big difference to my off-grid setup.

I've just moved the little giant 1/2hp pump to a seperate 2000 gallon cistern that is only be used in case of a fire to run our rooftop sprinklers in an emergency.

I hope to have the pump be turned on by a simple 20A electrical toggle switch rather than a pressure switch. I may, in fact try to source a smart switch that will allow me to turn the pump on and off via wifi in case we are away during an emergency.

I am unsure, however, if I can run the little giant without a pressure tank or a pressure switch (i.e have the pump run to our 4 rooftop sprinklers which draw 1.5 gallons each). Will this work? Will the pump simply hit a certain PSI and stay there or will it damage the pump (or pipe). I am trying to have the system as simple as possible in the event of a fire. I guess without a loss of prime pressure switch I would also need some sort of run-dry protection for the pump. Any thoughts? Do I need a pressure release valve? Can I simply use a loss-of-prime pressure switch with a very high "off" setting to stop the pump from cycling?

Thanks in advance!

Also, curious to know if anyone else has used Dankoff booster pumps. I was really surprised by how noisey mine is. I went through tons of troubleshooting with Dankoff (i.e temp remove pre-filter, use a bigger / shorter intake line) but nothing reduced the "buzz".

 

[Valveman]

A 7000W generator should be able to easily start a 2HP pump, so 1/2HP on 230V should not be a problem. Three wire motors with the capacitor start box will start easier than a 2 wire without a control box.

Rotary vane pumps are noisy and usually don't last long.

Yes you can just turn on a submersible with a switch while having 6 GPM sprinklers opened up. The pressure will probably settle around 90 PSI at 6 GPM. A pressure relief valve is only needed if there is anyway the sprinklers could be closed off.

A loss of prime switch would mean you need to be there to start the pump. No pressure switch needed if you turn the pump on with a light switch or even a Wifi switch.

 

[Sponsor]

 

[gambieroffgrid]

A 7000W generator should be able to easily start a 2HP pump, so 1/2HP on 230V should not be a problem. Three wire motors with the capacitor start box will start easier than a 2 wire without a control box.

Rotary vane pumps are noisy and usually don't last long.

Yes you can just turn on a submersible with a switch while having 6 GPM sprinklers opened up. The pressure will probably settle around 90 PSI at 6 GPM. A pressure relief valve is only needed if there is anyway the sprinklers could be closed off.

A loss of prime switch would mean you need to be there to start the pump. No pressure switch needed if you turn the pump on with a light switch or even a Wifi switch.

Thanks, Valveman. Yeah, I'm not sure why the generator was having trouble (it seemed to get worse over time...maybe the pump was failing) but it was a bit of a blessing taking the high surge draw off my inverter so I didn't have to worry as much about making coffee, running the well pump, and triggering the cistern pump all at the same time. I'm bummed to hear about your thoughts re. the rotary vane. I was searching for a 24v pump and somehow it rose to the top of the list. Any thoughts on a reliable 24v submersible pump to run from my cistern to the house? Max head is about 20 feet (bottom of cistern to shower) that can provide about 4gpm at 50psi?

I hadn't thought about the fact that my loss of prime would need to be manually reset. Good catch, and important to know in case of fire. I guess a "normally open" float switch would be the best low-tech solution to avoid having my pump run dry.

 

[Valveman]

Don't know of a 12 or 24V pump that would work. But the SQ has a 5 second soft start that makes it easy on an inverter or generator. One this size would be good, and they do make it in 115V. https://aquascience.net/grundfos-10...60140-3-stainless-steel-submersible-well-pump

A pump down float switch at the bottom of the tank or a Cycle Sensor are better ways to protect the pump from running dry.

 

[Reach4]

Whatever submersible you use in a tank/cistern, you would want a flow inducer. Those are cheap and easy to make.

If you use a Grundfos SQ pump, for 3 inch pipe selection, see https://terrylove.com/forums/index.php?threads/franklin-c1-cistern-pump-mated-with-csv.95826/ #18 and #5

 

[Fitter30]

Softstart for pump

 

[Chad D.]

I’ve used a Honda EU7000i to power my entire house, including a 1/2hp 3-wire pump motor. My guess is something is haywire if that little pump is making your genny angry.

I just installed a 2hp 3-phase pump and the max load I see with it is about 2,000 watts when I’m moving a ton of water. A little over 8A. It does have soft start, but my old one didn’t.

 

[gambieroffgrid]

I’ve used a Honda EU7000i to power my entire house, including a 1/2hp 3-wire pump motor. My guess is something is haywire if that little pump is making your genny angry.

I just installed a 2hp 3-phase pump and the max load I see with it is about 2,000 watts when I’m moving a ton of water. A little over 8A. It does have soft start, but my old one didn’t.

Yep, something weird going on for sure, the pump worked fine with the EU7000 for about a year, then began protesting. It still works fine directly off the batteries and inverter. The EU7000 powers my 1/2 goulds pump in my well without any issues, so the Franklin / Little Giant pump is probably the culprit (maybe a wonky starting capacitor).