Power Consumption: Cycle Stop Valve vs Large Hydro Tank
Using an actual flow graph from a city with 150 connections we have cut by two thirds for a city of 50 connections. This graph is during winter so we have added in the irrigation demand as calculated by the engineer. Flow rates for an average day are as follows.
|Irrigation used same time as average domestic for 6 months per year.|
|Total gallons per day in summer 6 months||86,520|
|Total gallons per day in winter 6 months||14,520|
Large Hydro Tank
A 350 GPM pump model 275H30-7 drawing 32.46 HP and a 40 GPM pump model 33GS30 drawing 3 HP are used. A pressure tank with 1900 gallons of draw down would give 8 cycles per day if the irrigation were set up for 314 GPM without cycling. A pump run time of 4.62 hours at 35.46 HP during summer months.
4.62 x 35.46 = 163.83 HP
1 HP = .746 Kwh
163.83 x .746 = 122.22 Kwh
Estimating 5.5 cents a Kwh x 122.22 = $6.72 per day or $1,229.76 per half year.
Using a 350 GPM pump model 275H30-7 and a 40 GPM pump model 33GS30 with a pressure tank with 1900 gallons of draw down that would be 8 cycles per day and a pump run time of 37 minutes at 35.46 HP during winter months.
.62 hrs x 35.46 = 21.99 HP
1 HP = .746 Kwh
21.99 x .746 = 16.40 Kwh
Estimating 5.5 cents a Kwh x 16.40 = $.90 per day or $164.70 per half year.
Total year electric bill $1,229.76 + $164.70 = $1,394.46
Cycle Stop Valves
Compare to a 3 HP pump model 33GS30 in one well and a 30 HP model 7WAHC-3 in another well. Both pumps have a Cycle Stop Valve and use a tank with 25 gallon draw down. The 3 HP is shut off anytime the flow exceeds 40 GPM and the 30 HP comes on to handle the load. For five hours during minimum flow the 3 HP pump runs 8 minutes and is off 12 minutes making a total of 15 cycles per day. Anytime the flow is above 5 GPM the 3 HP runs continuously. There are two times during the day when irrigation is permitted so the 30 HP pump will cycle twice per day.
|Flow Rate||Hours/Day||Pumping Hours||HP Load||Kwh/day|
|Irrigation used same time as average domestic|
|Total Kwh per day in summer 6 months||122.13 Kwh|
|Total Kwh per day in winter 6 months||34.10 Kwh|
Summer estimating 5.5 cents a Kwh x 122.13 = $6.72 per day or $1,229.76 per year.
Winter estimating 5.5 cents a Kwh x 34.10 = $1.87 per day or $342.21 per year.
Total year electric bill $1,229.76 + $342.21 = $1,571.97
Using the two pump system with Cycle Stop Valves and an 86 Gallon tank the power consumption is $1,571.97 per year.
Using the two pump system with a 7,200 gallon pressure tank the power consumption is
$1,394.76 per year.
$0.49 difference per day or
$1,571.97 - $1,394.76 = $177.21 difference per year.
At 5.5 cents a Kwh it will cost $177.21 more per year to use Cycle Stop Valves on this system than a large Hydro Tank. The 7,200 gallon hydro tanks cost about $30,000.00 more than the 86 gallon tank and the Cycle Stop Valves.
$30,000.00 divided by $177.21 = 169 years to save enough energy to pay for the large Hydro Tanks. (Not counting interest, maintenance, etc..)