Energy audit question: Shallow Well Jet Pump

rjpear

New Member
Hi Folks. In starting an energy audit i started with the most important (and problematic ) part of my needs..and that is my water well pump. It is a Shallow Well Jet Pump with the following Specs: 115/230v 3/4hp 8.0/4.0 Amps ..per the label. How would you calculate the pumps needs if it is generally random usage for 30 seconds or so? It is part of a pressure tank system so only kicks on when the pressure is dropped past a certain level.

Thanks..
 

rjpear

New Member
Heh... I guess "it depends" is not a great answer. Lets say 2x an hour on average. I figure after 10 PM it may kick on only 1 or 2 times all night/AM due to no usage.
 

MisterSandals

Participation Medalist
115/230v 3/4hp 8.0/4.0 Amps
Lets do some math!

I will go with runs 30 per day. Thats 15 minutes.
.25 h x 120V x 8A = 240Wh per day

For a 24V bank thats 240Wh / 25.6V = 9.37Ah

The tricky bit will be the surge current which can be 10x the 8A run current.
 

rjpear

New Member
Ok..thanks.. so I had a "light bulb" moment when looking at your math. Since I am at 120V I have to use the Higher Amps (8) but if it was run at 220 then would it only use 4 amps? And does this kinda play into the more efficiency of a 48 volt vs 24 volt system.?
Math can be fun! ;-)
 

Northernchateau

Solar Enthusiast

Supervstech

Administrator
Staff member
Moderator
Ok..thanks.. so I had a "light bulb" moment when looking at your math. Since I am at 120V I have to use the Higher Amps (8) but if it was run at 220 then would it only use 4 amps? And does this kinda play into the more efficiency of a 48 volt vs 24 volt system.?
Math can be fun! ;-)
Yes, lower amps, same watts though. Startup watts are still 10 times running watts, so 2500W to start, 240 to run…
 

MisterSandals

Participation Medalist
Since I am at 120V I have to use the Higher Amps (8) but if it was run at 220 then would it only use 4 amps? And does this kinda play into the more efficiency of a 48 volt vs 24 volt system.?
The power use is pretty much the same, especially when just doing the math (real world has to be different)
4A x 240V = 960W
8A x 120V = 960W

Lets say you have 16 100Ah LiFePO4 cells at 3.2V

24V battery bank (either 2P8S or 8S2P) = 16 x 3.2V x 100Ah = 5120Wh
48v battery (16S) = 16 x 3.2V x 100Ah = 5120Wh
 
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MisterSandals

Participation Medalist
Or how you might be expecting to see the numbers:

Also assuming your battery bank is made up of 16 3.2V 100Ah LiFePO4 cells...
And will use 25.6V for the "24V battery" since its correct (8 x 3.2V):
25.6V x 200Ah = 5120Wh

And will use 51.2V for the "48V battery" since its correct (16 x 3.2V):
51.2V x 100Ah = 5120Wh
 
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sunshine

Solar Enthusiast
Maybe a energy audit should look at the efficiency (power & labor) of shallow well jet pumps compared to submersibles.
From my farm experience, 20 - 30ft down , the arrival of submersibles meant the end of the jets.
We also realised that pumping into a overhead tank for a few hours with a smaller pump was a lot better than constantly stop starting a larger pump and also avoided the starting requirements needed for larger pumps.
The arrival of cheap pumps from China made the decision easier!
 

rjpear

New Member
Maybe a energy audit should look at the efficiency (power & labor) of shallow well jet pumps compared to submersibles.
From my farm experience, 20 - 30ft down , the arrival of submersibles meant the end of the jets.
We also realised that pumping into a overhead tank for a few hours with a smaller pump was a lot better than constantly stop starting a larger pump and also avoided the starting requirements needed for larger pumps.
The arrival of cheap pumps from China made the decision easier!
I agree..but I don't have access to the well head at this point (under a Cement foundation of an addition). So it's a new WELL and then the new pumps. Plus the Jet is noisy!
 
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