Help figuring AH/Day for my water pump.
I’m trying to figure out how much AH of battery storage per day I will need to run a Red Lion RL12G05-2W1V submersible pump. I should start by saying that this pump will supply water to a four bedroom cottage, located on a lake in Ontario Canada. I plan to pull water right from the lake at a depth of maybe 10-15’ and the floor level of the house is probably 20-30' above the top of the water, so 30-45' of head height. Now the pump I want to use states that at 40' of head height, it will pump 13 GPM @ 50 PSI. I am thinking about pairing the pump with a 40 gallon pressure tank and a regulator to keep the tank pressure between 30-50 PSI. Even though I have not chosen a specific model of pressure tank, the draw down specs for a Wellmate 40 gallon tank states that it will deliver 12.5 gallons of water between 30/50 PSI. So to me that would mean that the pump would cycle on for 1 min every time the tank drops bellow 30 PSI to bring the tank back up to 50 PSI.
Using this information, if I figure a shower head will put out around 2 GPM and if each shower lasts 10 min. that would be a total of 20 gallons used for the entire shower and the pump would cut on after the initial 12.5 gallons of the 20 gallon shower have been used. Now, it would make sense to me that if the pump supplies 13GPM that 2 of those gallons would go to the shower and the remaining 11 gallons would go to fill up the tank. So the pump would run around 1.2 minutes for one complete 10 minute shower. If my logic is correct, then at 8 showers a day, The pump will run around 10 minutes a day for all the possible showers that could be taken in a day.
Now to the washing machine. I have not picked out a model yet but I plan on using a newer model front loader so that it plus a dryer can be stacked. According to info I found online, high efficiency washers use 15-30 gallons per load. I’m guessing based on my current washing machine, that there are at most 4 fill cycles per load or at 30 gallons, 7.5 gallons per fill. That would mean that the pump would cut on maybe 2 times per load at around a minute each time. So that’s 2-3 minutes the pump will run per load. At 3 loads a day, that’s 6-9 minutes total.
Other than that, there will be a kitchen sink and vanity. I would guess both of those would run at most an hour combined each day. At 2 GPM per faucet, that’s 120 gallons total. It would be impossible for me to guess how many times the pump will cycle on and off so I’m just going to divide the 120 by the 12.5 gallon draw down which is 9.6 times. I’m sure that’s way high but it’s probably good to figure worst case scenario. So we are talking 10 min of pump time for the kitchen sink and vanity.
So we have 10 + 9 + 10 for a total of 29 minutes the pump will run each day. The pump I chose runs at 10 Amps at 115V or 1150 watts x .5(30 min.) = 575 WH/Day. Using the formula for figuring AH/Day that I got from Bill, 575 x 1.18 = 678.5 x .04(24V)= 27.14 x 2 = 54.28 x 2 = 108.56 AH/Day.
So my question is, does this sound right? If not, what do you think would be the correct AH/Day?