Black + Decker Pump Schedule
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There are so many different potential configurations for pools, plumbing pipe sizes (and number of pipes) as well as the pool size, pool features...this is one of the reasons why it is difficult for a swimming pool owner to look up generic advice on the internet. Similarly advice which you get may not be suitable for your specific pool situation. The article that you are reading now looks at the (new) Black + Decker variable speed pumps, specifically the 1.5 horsepower model, operating on a large swimming pool. Additionally in this example we are testing with 1.5" pipe sizes which represents somewhat of a worse case scenario for a large swimming pool being that small pipes move water very inefficiently and large pools require a lot of filtration.
Normally with a variable speed pump schedule I like to endorse a few hours at higher RPM's, about double that time at medium RPM range, and the rest of the 24 hour day at a relatively low RPM. In total the goal would be to filter at least three times the volume of your pool over a 24 hour period, resulting in approximately 95% of the water in your pool being filtered at least one time. In the case of a large pool and especially when combined with small plumbing pipe size there is just not much opportunity for cost savings. Instead your challenge will be to filter enough water at all. A 20x40' pool with a deep end is going to be in the 30k to 35k gallons range which means the filtration goal of three turnovers per day means you will need upwards of 100k gallons of filtered water per day. So instead of cost savings as the primary goal we are looking at reducing the operating costs as much as possible while still meeting our filtration goals for this pool.
Filtration goals - Three turnovers of the pool volume daily will result in approximately 95% of the water in the pool being filtered at least one time. The first turnover nets 63% and the second nets 86%. The third 95% and a fourth turnover will result in approximately 98% of the water being filtered at least one time. A 20x40' pool with a 3.5' shallow end and 8' deep end might have an approximate volume of 30,000 gallons depending on the wall, floor and slope profiles. This means your 24 hour filtration goal should be in the 90,000 gallons range. Yes you can filter less. Many residential pool owners do, but if you can have the best of both worlds in more filtered water but for less cost then perhaps it is worth considering. In the case of a large swimming pool with 1.5" pipe size like this example we will operate the pump near to maximum speed for the duration of the 24 hour day. Notably we run at less than maximum RPM since even a small reduction in RPM, and subsequent linear reduction in flow, will experience a dramatic and non-linear drop in the amount of power consumption that the pump needs.
24 Hour filtration example
Pipe size = 1.5" PVC
TDH = 35'
Filter pressure = 14 PSI @ 3450 RPM
Pump = Black + Decker 1.5hp (BDXBTVAR150)
Filtration total = 95,160 gallons
Electrical use = 22.86 kWh
24 hour cost = $2.97
The point of major efficiency loss in PVC pipes is water velocity above 6 feet per second. In 1.5" PVC this represents about 38 GPM. This means that past this point there will be a sharp increase in efficiency loss due to friction and turbulence in the pipes. Also 6 feet per second represents the maximum safe suction line water velocity as stipulated by the VGBA anti-entrapment act. This means you should never have a suction line in your pool (any pool) with more than 6fps of water velocity. Ideally a large pool should have multiple suction lines (multitple skimmers, main drains) which usually means multiple suction line pipes to share the total flow between. For this reason if you have multiple 1.5" suction lines you might want to consider upgrading the equipment pad plumbing and suction side manifold to 2" pipe to minimize friction losses on the equipment pad.
24 Hour schedule
5am - 12pm = 2500 RPM
12pm - 6pm = 3200 RPM
6pm - 1am = 2500 RPM
1am - 5am = 3450 RPM
After 24 hours we have a total of 14 hours at 2500 RPM, six hours at 3200 RPM and four hours at 3450 RPM. This provides a total of 95,160 gallons of filtered water for a total 24 hour cost of approximately $2.97 which is very lean for a pool this large. In this schedule example the period of time where we run the pump at maximum speed, 3450 RPM, is in the middle of the night. If you live in an area with variable electricity rates usually the middle of the night is when rates are the cheapest. Since the pump uses the most power at maximum speed you would experience the most significant savings by running the schedule with the highest power consumption during the time of day (or night) when electricity costs are the cheapest.
Filtration totals
2500 RPM (58 GPM) = 48,720 gallons after 14 hours
3200 RPM (75 GPM)= 27,000 gallons after 6 hours
3450 RPM (81 GPM) = 19,440 gallons after 4 hours
Total filtration = 95,160 gallons / day
Electrical consumption totals
2500 RPM (634 Watts) = 8.88kW after 14 hours
3200 RPM (1270 Watts) = 7.62kW after 6 hours
3450 RPM (1590 Watts) = 6.36kW after 4 hours
Total cost (22.86 x $0.13) = $2.97 / day
Lowering the RPM down from maximum speed, 3450 RPM, has a large and beneficial impact on the cost to run the pump while only having a minimal impact on the amount of flow the pump is able to generate. This is one of the pump affinity laws and the basis for why variable speed pumps are so much more energy efficient than any single speed pump options. This large pool is a perfect example of this as we need the maximum flow but the cost to run the pump 24x7 on maximum speed would work out to be 38.16 kWh of power consumption for a total cost of approximately $4.96. This would nearly double the cost of the 24 hour pump schedule while only providing just over 20,000 more gallons of filtered water daily. A clear win for the variable speed pump. Reduces cost to operate by half while only reducing flow by about 20%.
It is important to understand that this page and this pump schedule for the Black + Decker variable speed pump is just an example. There are many variables to consider and this information should be used to help you better understand your own unique situation. The power consumed, flow achieved and total filtration requirements of your pool will be unique to only you and definitely different than the value you see in this example. This is intended to help you understand the relationship between flow and power consumption better so that you can make better informed decisions about your own pool filtration situation.
Watch this same schedule on a system with 2" plumbing: Black + Decker filtration for large pool (2" pipes)
Watch this same schedule tested on a 1.5hp Hayward variable speed super pump: Hayward Super Pump VS - large pool filtration schedule (1.5" pipes)
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Swimming Pool Steve is an award winning, second generation swimming pool and spa specialist from Ontario Canada. With over 10,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the 2018 Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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