Hot Water Recirculation with ECM Circulator?

WaterSensible

I am wondering about the benefits of an ECM circulator pump used in a domestic hot water recirculation system.
Other than the ECM having higher efficiency compared to an AC induction motor, does the ECM circulator run at variable speed/load at any point, except when someone uses hot water in the system?
In hydronic heating systems with multiple zones, I see the benefit of using an ECM for its ability to vary the flow depending on the number of open zones, but what about hot water recirculation?

Rich_49

Answers would be dependent on how the recirc system is controlled (run time) . Are you asking if the ECM unit would pay for itself if you chose it over a PSC unit .

What type house are you inquiring about , off grid homes really benefit from low power consuming things ?

If a PSC circ runs for one hour a day total and uses 80 watts the ECM circ may use 9 , 14 , 20 watts . Let's use 80 ( 4.09 annually) and 20 ( 1.02 annually) or .46 annually if it used 9 watts , based on what I pay for electric , YMMV . If using 75% less energy interests you then you have your answer . Not everyone uses an ECM for it's variable speeds , some just use it to feel good about themselves and help the planet .

My opinion is that using the ECM taking into account how most re circ systems are controlled now is not worth the investment in anything other than a renewable or off grid project . Not to say that this country doesn't go completely totalitarian and mandate them in an effort to be like Europe .

WaterSensible

Thanks Rich,

My main concern is to understand whether a variable speed circulator with automatic control (dP, dT, constant pressure, etc) is actually used at variable speeds in a hot water recirc. system.
My understanding is that the different control schemes that affect runtime (aquastat, timer, demand control, or other) turn the circulator on and off only, they don't vary the circulator's speed.

SWEI

DHW recirc control covers a fairly wide range of strategies. Timers and "smart" learning voodoo work up to a point, and also complement variable speed pumping. ΔT and setpoint control both work quite well when paired with a master mixing valve.

hot_rod

The best first step is to calculate the actual pumping requirement and do everything to keep the heat loss of the loop to a minimum.

Then the smallest possible circulator should be chosen.

On a small residential loop generally you need very small flow rates, choosing an ECM, properly sized, will reduce power consumption, if that is a goal.

Timers and thermostats can limit run time also. On a small, less than 1/12 hp record pump application, I doubt ∆T cost would add enough value of savings.

ECMs are here to stay which is why one of the largest US pump manufacturer recently went to Europe for ECM technology.

Regardless if the government mandates it or not, soon only ECM technology will be offered.

Gordy

If there is a defined usage pattern a timer would probably be more economical for piping losses. Laing made some nice ones with thermostat, or timer.

I have found that with pilot water heaters the btu losses seldom impact enough to fire the WH between usage. Pilot is probably off setting losses, and it's always on anyway.