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Here is what goes on in a zone valved system

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Bob Rohr, Feb 5, 2008.

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  1. Bob Rohr

    Bob Rohr Minister of Fire

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    or any system that uses a single circ to try to cover various, ever-cheanging loads. like 3 way thermostatics, etc.

    With a fixed speed circ you chose the pump that matches your system requirements, typically at design day with all loads calling. You try to select a circ to work on the "knee" or middle third of it's curve. Typically that is the highest efficiency point of the circ.

    The red line is the pump curve from the manufacturer. The blue lines are from a system curve overlay sheet, or calculated on the HDS program. where the system curve touches the pump curve is the actual operating point. There is no such thing a a circ with a flat curve.

    Now look what happens as zone valves open and close. the pump is running all over the curve. on the high end you get high velocity, noise, and potential erosion corrosion. High pressure can squeeze by the closed zone valves and create ghost flows, overheating or un-controlled output in some zones. possibly inadequate flow through the boiler or heat source. On the low end.... slow flow, poor air removal, possible in-adequate heat distribution, and the pump running 15% or less efficiency.

    A differential bypass valve can correct to a degree, but it is a parasitic valve and just sheds away pump head.

    As I mentioned before the ECM variable speed delta p pumps will correct this issue, at a cost.

    I am a fan of zone valved systems and most of my jobs are ZVs. Design around a flat pump curve pump, keep the loads down to where one pump can handle no more then 4 ZVs or design around a PAB pressure activated bypass.

    The graph is from a 2001 article in PM Engineer by John Sigenthaler.

    hr

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  2. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Personally, I try to balance zone valves and pumps. When it is realistic to do so, I limit it to no more than four zone valves per pump, which helps to prevent the gap between "one zone open" and "all zones open" from being too large. In actual use, it depends on the actual zones - a single kickspace heater cannot realistically be paired with a dozen cast iron radiators on one pump, if reasonable performance is expected.

    I'm definitely hoping that the variable-speed technology comes into its own. It will make my life easier and my customers happier.

    Joe
  3. Nofossil

    Nofossil Moderator Emeritus

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    Is it fair to say that:

    1) Zone-based is good for systems with 4 or less zones, where the flow characteristics of the zones are similar.

    2) Pump-based is good if there are more than 4 zones or if there are zones with significantly different flow characteristics.

    3) If zone based control is used with more than four zones, some control mechanism should ensure that no more than four are active at one time.

    In my case, I open additional low-priority zones as the boiler output gets closer to my desired upper limit.
  4. Andre B.

    Andre B. New Member

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    You can have it now. Just takes the right amount of $$$$$$$.

    Ever parallel up multiple pumps in a binary progression?

    Like pump #1 is 2gpm, pump #2 is 4gpm, pump #3 is 8gpm etc..
    Then depending on which ones you turn on you can have 0, 2, 4, 6, 8, 10, 12, and 14 gpm system.
    You also have redundancy for when a pump stops turning.
  5. Bob Rohr

    Bob Rohr Minister of Fire

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    Exactly, gentlemen.

    Perhaps the nicest feature of hydronic heating systems is the ability to zone to infinity. Often bathrooms, even micro loads like towel bars will be zoned by themselves. Loads of 5,000 btu/hr, even smaller are not uncommon. Yet on the same pump you may have a great room zone with a 40K load and larger. Or a large master suite with high loads due to glass walls, etc.

    That's exactly the common challange fixed speed circ face. For years, decades really, we used the good old B&G;100 series. My dad and me installed, and oiled :) those pumps inn the 1960's! Long lasting, very flat curve, great for zone valved systems. Very high current draw and expensive now a days.

    With the advance of wet rotor circs and radiant we started to see higher head circs to "shove' small diameter long lop heating distribution. at this point circ manufactures are scrambling to build an "everyman's" pump. We still need a 15- 20 GPM circ at 5 feet of head for primary loop applications.

    Wet rotor pumps solved many issues, quiet, inexpensive, small, wide selection, etc. But by nature they are very inefficient. Spinning a rotor in water has it's drawbacks:) They have become throw aways where the old series 100 could be rebuilt for years and years. a terrible waste of resources consider most end up in landfills not scrap barrels.

    But the next generation of circs with ECM motors will again change the picture. Moving heating loads with as low as 1W consumption. Incredible starting torque with DC motors, low cost polymer volutes, speed and output controls. delta T and P functions built in.

    This type of circulator is service, and have been for years. Some were developed for the auto industry like that 1W Wilo we keep seeing. orginally developed as a coolant pump for BMW. I've held some fine mini circs built by Panasonic, Laing, and Grundfos. Seen the Delphi name on them.

    Some contractors I know can't wait and shop globally, online for these high tech pumps.

    The biggest plus with zone circs is the ability to move EXACTLY the flow you need regardless of changing conditions. The ability to read and react to changing temperature requirements with indoor and outdoor feed back. Redundancy should one circ fail. The ability to go online anywhere and read and adjust you pumps real time. And possibly the ability to move fairly large residential loads with under 80W total power consumption! Off grid heating, or cooling with DC circs is another real possibility. Someday soon we may all want to generate and sell back our own electric. Low power consumption PV and battery pumps will be a plus for those systems.

    Same with a wood boiler, nice to have a 12v DC circ with a battery or two back up for power outages and overheat protection in power outages. A 20 PV panel to keep the battery topped off. now you have free fuel and free distribution energy.

    hr
  6. Willman

    Willman Minister of Fire

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    hr

    Should we give the local beemer dealer a call for 12v pumps? Any other manufacturers (Euro of course) that use 12v coolant pumps. They work with glycol and high temps. I wonder how water pumping stacks up against miles driven with these pumps.
    Will
  7. eekster

    eekster New Member

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    Master of Sparks, my brother uses varible 3 phase pumps for irrigation systems and fountains for golf courses in Florida.
    This subject REALLY interests me and can"t wait to learn and hear more about them. This will be the wave of efficience coming into the future!
    Keith
  8. Nofossil

    Nofossil Moderator Emeritus

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    Being a major league skinflint and hopeless tinkerer, I'm modifying a $60 Grundfos 3 speed pump so that it will be under computer control - poor man's variable speed pump. I'll post the schematic. Needs 2 discrete inputs - 12V relay drive type. That'll have to do me until the real variable speed pumps get cheaper.
  9. Jim Post

    Jim Post Member

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    We were disappointed in the power consumption of our series 100 pump last fall when we were trying to see how low our overnight power consumption could go. We shut off everything even unplugged the refrigerator but soon realized the series 100 pump was sucking as much power as our electric water heater in 24 hrs. These new pumps sound pretty cool thanks for the heads up. I was planning on replacing the b&g;series 100 with a grundfos 3 speed pump this summer. Sounds like I will probably be priced out of the newer circs for a while.
  10. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Yeah, that's what I meant by "comes into its own." Most customers won't pay the extra for it. Particularly given that it comes with higher repair costs, as well.

    But it won't take many years for it to sort itself out, I expect.

    Joe
  11. mtfallsmikey

    mtfallsmikey New Member

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    Also HR, you should reference the article about circ. sizing in this month's PM mag by Siggy. As I have finished the basic design of my new HW system, I'm going to try to get a Wilo ECM to run my secondary BB loops (3 zone, with TRV's) instead of using a circ. running constantly with a diff.. press. balancing valve. I just don't like the idea, don't want to get into zone valves, etc, keep it simple. I also grew up with the B&G;100, rebuilt many of them, have 30 HP B&G;'s in both of the buildings I manage, and they are virtually indestructible. Keep up the good work! :p
  12. Eric Johnson

    Eric Johnson Mod Emeritus

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    Thanks for the website mention over on The Wall, Mikey. I'm glad you guys are helping us out by participating here.
  13. Bob Rohr

    Bob Rohr Minister of Fire

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    Do you have any connections with Grundfos? On good terms with the local rep? They are trying to get a bunch of prototypes out in the field for feedback. I have 3 in my shop and on jobs. Rumors are 50 more arrived or will be arriving soon for demo purposes.

    Let me know maybe I can get some demos out to you.

    hr
  14. Jim Post

    Jim Post Member

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    I had some contact with grundfos after a discussion on The Wall indicated there may be a prototype available for the alpha pro model....
    Here's the response I got.

    Not sure where that leaves me but I haven't heard anything since. I'd be very interested in any demos that may be available. Reducing our electrical consumption is a high priority for us. Thanks.
  15. Buck1200

    Buck1200 Member

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    I have to ask- what are the ramifications of ordering these circ's directly from any of the UK or German online stores and bypassing Grundfos altogether? Is it the lack of a UL listing and potential insurance problems/
  16. mtfallsmikey

    mtfallsmikey New Member

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    I'd be interested in beta-testing the Grundfos..let me know if it pans out...Eric, you are quite welcome as far as the mention goes, but HR and others deserve the credit; they were here before me...I'm just a worn-out former P/HVAC contractor, 3rd generation, who took the good job in the Big city, similar to what HR is getting ready to do!
  17. Bob Rohr

    Bob Rohr Minister of Fire

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    The Alph Pros do have a CE listing, meaning it meets the requirements of the European Directives. I suspect it is plenty safe, and possibly more scruntinized then UL requires?

    The manual included with the samples I have is printed in 26 languages. Make me think there are plenty in operation, safely, across the world.

    There was talk about bring them in with out UL? Not many manufacturers like playing the waiting and money game with UL :)

    Rumors I have heard indicated the long awaited Wilo ECO may in fact arrive without UL? it's been at least 2 years now that that circ is "on it's way here"

    I suspect Grundfos may be waiting to see how Wilo does with the sales of the ECO. I have received mixed signals from Grundfos as to when and if the Alpha will be available.

    Actually the Viessmann Vitoden uses a 15-62 VS Grundfos, 230V that I suspect is a close cousin of the Alpha pro. Does it have UL?

    hr
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