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Community and Q&A

Circulation pumps

Trevor Lambert | Posted in Mechanicals on

Hoping there’s some people who know a lot about circulation pumps here. I’m about to buy one for my HRV pre-conditioning loop. I was planning on getting a Grundfos Alpha2, as that was what was suggested and supplied by the company I got my in-floor heating stuff from. They said it used 50-75% less energy. They’re also pretty pricey. I’ve done some reading on these things, and I’m wondering whether they will actually perform any different than any other pump in a simple on/off application like mine. It seems the big feature, Auto Adapt, depends on the system having some automatic method of changing load (e.g. thermostatic valves). Without that, I’m having a hard time picturing what this thing would be adapting to. Am I correct in thinking this thing is overkill for both my in-floor heating and the ground loop?

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  1. Yupster | | #1

    ECM pumps are fantastic. At a recent project we used one for a fixed speed primary pump, it sat there sipping 8 watts while a conventional pump would have been gobbling 80+ watts. Unless your ground loop won't be running often, an ecm pump is a logical choice for an energy efficient house. As far as the radiant system goes, you definitely want an ecm pump if you have a zoned system. The logic in these babies is brilliant. Basically, it can see holes in the system and as these holes (zones) open, it increases the pump speed to fill them. So it's always operating at the lowest output possible for the load. Cuts WAY down on watt usage. With high Ontario hydro rates, payback will be short and the control aspect is fabulous for the designer of your radiant. The Auto Adapt feature is awesome, but the real gold is in the low power draw of the unit.

  2. Trevor Lambert | | #2

    My floor system has one pump per zone, so there's never more or fewer "holes" open. But it's good to know that the ECM function was worth it. I have the option of buying the previous generation Alpha1 for $100 less, and the only difference is the Auto Adapt, so that's what I'll get for the ground loop. Thanks.

  3. User avatar
    Dana Dorsett | | #3

    Taco's 007e- Fx series and other fixed speed ECM drive pumps are a lot cheaper than the auto-adapting/variable speed versions. If you can spec the pump, there's probably a fixed speed version that will fill the bill.

  4. Trevor Lambert | | #4

    I'm not sure how to spec it out, so a variable speed pump is probably best. The Taco 007 series seems to be limited to 10' of head, which I'm guessing is the height differential(?). My loop is about 7-8' below the floor, and needs to get about the same amount above the floor so that wouldn't cut it.

  5. Yupster | | #5

    Head is the power the pump has to overcome the head loss, which is the frictional losses caused by the piping and fittings, similar to friction loss in ductwork. 10' of head is usually plenty for any reasonably sized residential system. You might want to reconsider using individual pumps to zone your system, it's expensive and not necessary. Instead, consider using zone valves to separate manifolds or you can even put it all on one manifold and use loop actuators. The variable speed pumps work really well for this application, ramping up and down as zones open and close.

  6. User avatar
    Dana Dorsett | | #6

    A single programmable/responsive variable speed ECM drive pump + zone valves is the most common configuration for multi-zoned systems.

    I can't image that the flow requirements or pumping head of the preconditioning coil is very high, and probably doesn't "deserve" a pump of it's own, if the heating loops are being operated at a high duty cycle. Plumbing it in parallel with the floor heating loop and with a ball valve for tweaking the flow to the coil back is probably good enough.

    The ground loop is for a ground source heat pump, or something else?

  7. User avatar GBA Editor
    Martin Holladay | | #7

    Trevor described the ground loop as his "HRV pre-conditioning loop" -- it sounds like the type of system I described in this article: "Using a Glycol Ground Loop to Condition Ventilation Air."

  8. Trevor Lambert | | #8

    Martin is correct. That system has to have its own pump.

    If I had to do the floor heating all over again, I'd use just one pump. Given that it's already complete, it's probably not worth re-doing it, even if it provides me with a free pump for my pre-conditioning loop. Seems like a fair amount of work, and not without its own added cost. A couple of zone valves looks to cost similar to another pump.

  9. Yupster | | #9

    I'm definitely no expert when it comes to electricity, but considering that 24v transformers required to run the zone valves consume some power 24/7 and when they are active consume as much power as a Grundfos Alpha on it's lowest setting (around 8 watts, dependent on the valve of course), there may not be any/many electric savings from switching to zone valves anyway.

  10. Calum Wilde | | #10


    I find it shocking that those transformers are still in use. There are plenty of solenoids that run on 120Vac. Even more concerning is door bells. Not every house has solenoid zone valves, but just about every house has a door bell. The transformer for mine was hot to the touch all year long. I recently disconnected it as I realized the only people that ring it are the kids when they're having some annoying fun. But, how hard could it be to make a door bell system that ran 120Vac and didn't use any power when it's not ringing, and solenoid valves that only require power to move, not to stay in either position?

  11. User avatar
    Jon R | | #11

    A careful reading of page 3 below indicates that these zone valves don't use 100% power (22W) when on (they just have to keep some wax warm). No idea what the resulting average watts is.

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