DAB E.sybox and Electricity Usage

Finding the Right-for-you balance of cost, space, maintenance, and features.

Finding the Right-for-you balance of cost, space, maintenance, and features.

Two energy-conscious options:

  1. DAB E.syBox and no pressure tank
    1. smaller footprint in the utility room
    2. less maintenance/ fewer parts
    3. possibly longer pump lifespan
    4. lower maximum power draw required (more ambiguous on total power draw)
    5. wi-fi capabilities
  2. Small pump, big pressure tank: Get a big enough pressure tank to only run the small single-speed pump once or twice per day to refill it.
    1. Cost of pump, pressure tank, pressure switch, and extra valves and fittings vs. the DAB. A single speed, submersible, on-demand pump is a less expensive pump, but needs to have a pressure tank to limit the number of starts and stops on the pump. 
    2. Bigger tank = fewer pump start-ups = less wasted electricity. The larger pressure tank needed for an energy-efficient system is not cheap.
    3. Provides a reserve supply of water for use when the pump is not running and/or during times of high demand.
ENERGY USE

Variable speed pumps are usually more energy-efficient. However, they are not magic.

  • (Pro) DAB VFDs incorporate a "soft start" for the motor, reducing how much power is wasted starting up the motor.
  • (Mixed) They adjust operational speed to meet demand, speeding up and slowing down to match the input power to the motor to the load on the motor (kind of like a multi-stage furnace).
    • If the motor needs to run at 100%, you're still going to be putting in about the same amount of power with or without a VFD. (image below)
    • Where VFDs really shine is on lightly loaded motors, where you can reduce the speed based on less demand for water flow. In this case, a VFD *will* reduce the power drawn at any given time. (lower maximum draw)
    • If you have a constant pressure system, a VFD might help cut down on average power.  
    • Compared with a typical on/off cycling pressure tank system, savings are more ambiguous in the total/net daily power use for pumping, because you're still pumping the same volume of water. Essentially, a fixed speed pump front-loads the energy used to fill the pressure tank all at once, several times a day. The VFD spreads out the usage.
  • (Pro) Because variable speed pumps usually do not operate at full capacity continuously, they often experience less wear and tear, potentially increasing their lifespan.


The below performance curves for the E.sybox Mini 3 demonstrates its electric usage (typical household usage is around ~40 psi and flowing 1 to 6 gpm). 



SOLAR 

Not all systems are a good fit for solar. VFD will lower the maximum power draw required. It is more ambiguous on total power draw vs a small pump and large pressure tank. 

Consider this article: Evaluating Energy and Cost Requirements for Different Configurations of Off-Grid Rainwater Harvesting Systems.  by Heather S. Rose,Charles R. Upshaw andMichael E. Webber.  The goal of this analysis was to evaluate energy and cost requirements for different configurations of a rainwater harvesting (RWH) system in conjunction with a solar PV and energy storage system for an off-grid house. A special issue of Water 2018 (ISSN 2073-4441).

UV

To save more energy, skip UV disinfection and instead use Clairify Disinfection, which uses no energy, no chemicals, and requires no maintenance. 

Hope this helps!

 

Variable Speed Pumps