Replies

1. 
   charlie_sullivan | Apr 07, 2016 10:08pm | #1

   I am a big fan of ECMs, but I think this is an application where it matters relatively little. Most importantly, the number of minutes it runs a day is small, and even if it were a lot of minutes, real energy hogs run for hours. Secondly, the biggest benefit of an ECM is the rapid reduction in energy consumption when you reduce the speed. If there were days when you decided you weren't in a hurry, and could wait a little longer for the hot water, and so turned the speed down to half, you would get that benefit, but somehow I don't think that is likely to happen.

   If I were to guess I'd say a conventional single phase motor would use 80 W and an ECM 40W, but that is just a guess. If you want to translate that into kWh, you could estimate how many times a day it is used and calculate how long it is on each time, but I don't think it will amount to much.

   It might be worth checking on the standby power of the control system ... That might actually be the dominant energy use, especially if uses 24 VAC.

2. 
   PAUL KUENN | Apr 07, 2016 10:53pm | #2

   Chris, we've had the D'mand with their Taco pump for over 12 years and it works great and is super efficient. Came with a small push button switch that I installed under the counter lip next to the sink. Easily pushed on and never seen. 30' run from water heater to front faucet where we wanted hot water fast for washing dishes after passing through a cold basement. PK

3. GBA Editor
   Martin Holladay | Apr 08, 2016 04:56am | #3

   Chris,
   I agree with Charlie Sullivan's analysis. These circulators have a single type of load, so the motors don't have to ramp up and down (the type of application where ECMs shine). Moreover, the usage doesn't add up to many minutes per day, as Charlie pointed out.

   For more information on this issue, see “Hot water circulation loops.”

4. 
   jcstratton | Apr 08, 2016 10:34am | #4

   Thanks Charlie, Paul, and Martin. Your responses help put the energy consumption of the pump in perspective. It sounds like the D'Mand system might be the best option for my situation. Good point Charlie about the standby power; maybe two switches, then: one to turn on the outlet the controller is plugged into, and another to activate the pump.

5. 
   bennettg | Apr 08, 2016 03:33pm | #5

   I'll pile on. In this sort of application, where the pump is full-on for maybe a minute or so for each use, an ECM isn't going to pay off. I offer an additional option for the under-sink on-demand recirc pump: the "chilipepper" http://www.chilipepperapp.com pump - another atrocious name. These guys must be related to hair salons... I have had two of the older models for years. They have low voltage wired switches. They've performed flawlessly. I see the new ones have a wireless fob, likely a water + 120vac safety thing, which would be good. I have no affilliation with them.

6. 
   jcstratton | Apr 18, 2016 04:40pm | #6

   Thanks everyone again for your help. Just wanted to provide a quick update. I went with the D'Mand base model pump and it's working well. The standby load is 1 watt and it uses about 50 w (on the medium setting) while it's running. For our household that's likely to be about 9 kWh standby and 18 kWh active use consumption annually -- 27 kWh total or about $4 at local retail rates. A small price to pay for instant hot water and thousands of gallons of water saved annually (in Los Angeles no less).

7. 
   charlie_sullivan | Apr 19, 2016 06:46am | #7

   Thank you for reporting back and for the measured power consumption! I'm glad to hear that it worked out well.