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Feedback on pump vs. valve mini-tutorial

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Nofossil, Jan 29, 2008.

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  1. Nofossil

    Nofossil Moderator Emeritus

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    I'm assembling a series of mini-tutorials on my site intended for people who are starting down the path towards a wood heating system. I have all the appropriate disclaimers, and it's not intended to be a complete how-to for heating system design. Basic format is brief discussion, pros and cons, then what we did and why.

    I'm doing a section now on circulator vs. zone valve based systems, and I'd like some feedback on the content. In particular, I'd like to make sure I've captured the 'pros' - the advantages of pump based systems. There will be another section that talks about supply/return vs. primary/secondary loops. Here's the content:

    Circulator based or valve based zone control?

    There are a near-infinite variety of plumbing approaches, but one useful distinction is pump-based vs. valve-based zone control. In a pump based system, each heating zone has its own circulator pump which runs when there is a demand from that zone. In a valve based system, there is one circulator pump at the boiler and each heating zone has a zone valve which opens when there is demand from that zone. If there's more than one heat source, each source typically has its own circulator.

    In a pump based system, each zone thermostat goes to a controller which controls the pumps.

    In a valve based system, each thermostat is wired directly to the corresponding zone valve. Contacts in the zone valves provide a demand signal to the boiler when the valve is open.

    Circulator pumps and zone valves cost about the same, so there is no significant cost difference. Both are reliable and easily repaired.

    Pump pros: Pumps can be sized to the flow requirements of each zone. Flow rates can be better controlled.

    Pump cons: Pumps consume more power than valves. Pumps do not provide positive isolation - water will flow forward through a pump even if it has a chack valve. It can be more difficult to understand what's happening in a system with multiple pumps.

    Our choice: We went with a valve based system, in part because that's what our plumber had recommended for our initial oil boiler installation. The lower power consumption is also a factor, and our installation is designed so that there is only one active heat source and one pump running at any time. That make it easy to understand what's happening with the system. We are upgrading to a multiple speed pump for the wood boiler to provide better control of flow rates.

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    Very good resource, nofossil. When you get a chance, can you post the link in the "Resources" sticky?
  3. Nofossil

    Nofossil Moderator Emeritus

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    Yeah, but I'd like people to comment and criticize before I post it rather than after. I'd like to feel that it was more complete than it is now, and there are certainly plenty of areas where I don't have enough knowledge. I can go with pure fabrication and arrogance as a last resort ;-)
  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    It's a "check" valve not a "chack" valve. Maybe you can discuss the difference between standard cast-iron flow-checks and the kind that come with some pumps. In a power outage, for example, you can open up a conventional flow check and get some benefit from convection. To do that with an integral flow-check, you need to unbolt the pump from the flange and pull the check valve out of the pump outlet. I don't have any zone valves on my system, but I assume there is a way to manually open them if the power goes out. Maybe that's all beyond the scope of your discussion.

    As you know, I rely more on anecdotal information than number crunching for a variety of reasons, including laziness. When I was making the decision posed in your original question, the guy selling me the boiler and helping me design my system said that he had recently replaced all the zone in his house with pumps, which he said are much more responsive than zone valves. I don't know how to put a number to that observation, other than I believed him and designed my system accordingly. Maybe somebody can explain why that would be.

    These mini-tutorials are a great idea, nofossil. I can see a time in the not-too-distant future when we can point the newbs (seems like we get more and more all the time) to a resource or set of resources that gets them up to speed quickly and reliably with a minimum of confusion. This looks to me like a good start.
  5. sled_mack

    sled_mack New Member

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    There has to be something to do with the installation regarding reliablility.

    When I put my system in, pumps were recommended and that is what I went with. So far, 10 years into it, I haven't had any zone pump failures. I've got 9 zones, including DHW.

    I worked with a guy who ended up ripping his out and putting in a main circ and zone valves because he would have to replace several pumps each year. He had 4 zones. All better after the change.

    A good friend of mine has 3 zones valves. He seems to have to replace 2 of them each year, sometimes all 3.

    Each of these guys have had multiplel plumbers try to figure out why so many failures. So far, no luck.

    My ancedotal observation is neither one is more or less reliable than the other. But, something about these applications, or the sizing of the pump, or whatever, has caused many problems for these guys. Maybe some of the heating contractors can add some other "rules of thumb" to go along with this? I've looked at both installations, and I can't figure out what the differences are.
  6. Nofossil

    Nofossil Moderator Emeritus

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    Part of my approach to all of this is to try to cut through the fog of 'everybody knows...' and get to real data.

    In the systems I'm aware of, I've seen one pump failure and two zone valve failures. That's out of about 120 pump-years and 90 zone valve years. All cases were easily repaired without unbolting or unsweating anything. Clearly, both approaches can yield systems that exhibit satisfactory performance.

    To your specific question, here are some things I've picked up that seem reasonable and might even be true: pumps can have their lives shortened many different ways - improper orientation (shaft / bearing loading), operation at excessive temperatures / pressure drops (localized boiling), installation that doesn't allow air bubbles to be purged, and so on. Valves that cycle too often can get failures of the geartrain. Very little discussion of these issues, and way too much 'this is the right way and everything else is wrong'.

    Some people will advocate an approach because they're familiar with it or have had good luck with it. While that's good data, it doesn't help very much in figuring out the important questions: What are the basic advantages and disadvantages of each approach? What are the specific circumstances that would suggest that one approach is clearly superior? What are the special considerations that I need to be aware of with a particular configuration?

    Many professionals with lots of experience can't answer those questions. I figure I can't do too much worse, especially with the help of folks here ;-)
  7. Buck1200

    Buck1200 Member

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    I'm sure HR will weigh in on this... and perhaps this is telling of the other forum I spend my time lurking in, but I would (and will) use a single pump for the entire distribution system with Thermostatic radiator valves on each radiator. These systems are silent, comfortable, and room by room adjustable (and I'm speaking from experience after many long trips to germany), and with only one pump, a lot less complicated to maintain. Of course that's single point of failure, but at least you'll know what failed.

    That's the distribution side, but as for the delivery side, with multiple heat sources, buffers, and subdry other repositories, the jury is still out with me anyway. So I'll be reading your tutorial as soon as I can later tonight, nofo. Thanks a lot for this valuable information.
  8. Bob Rohr

    Bob Rohr Minister of Fire

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    That sounds like good info to offer, thanks nofossil.

    I look at the load size to help determine pump or zone valves. Typically I favor zone valves, as a single inexpensive 80 watt multi speed circ can easily move 150,000 btu or more. Really no need to use 6 zone circ all consuming 80 watts to move a load like that, for instance.

    The beauty of hydronic or wet heat is the ability to zone inexpensively. This is great not only for optimum comfort control but energy saving potential for seldom used spaces.

    There are many brands of dependable easily serviced zone valves no on the market. Issues relating to sticking or stuck zone valves can usually be traced to water quality issues.

    I am looking at zone circ more closely these days, however.

    ECM circ are making their way into the US market. They typically consume 40% less power then then what we currently use. The pump manufacturers have banded together in Europe to develop an efficiency standard for pumps (Europump) I expect to see that standard being used over here in the near future.

    I have heard figures as high as 30% of the electricity consumed in the world is used to spin pumps. So that 40% efficiency boost could be a huge number.

    But the other nice feature of these high efficiency pumps is the ability to easily change their RPM and as such their output. I'm not an electronic pro but them change the AC current to a pulsating DC. You end up with a lot more torque in addition to the energy savings. also there are many controls on the market to control that type a motor with a floating signal.

    My shop solar uses a Laing ECM circ that modulates it's output with the intensity of sun hitting the 20W pv panel. So the thermal panel output tracks nicely with the pump speed for using the very least amount of energy to get the job done.

    The Grundfos Alpha Pro I have on my shop heating system consumes 38W at full load. it replaces an 80W circ.

    Wilo pump is hard at work on a 1W circulator! It will be used to replace zone valves and modulate based on an external signal. Slowing down for instance as the room nears the thermostat setpoint.

    So the list of pump "pros" is getting better all the time.

    Check valves should easily be able to handle any ghost flow potential. Thermal drop traps are another non-mechanical means to prevent unwanted flow. A properly placed cold slug of water works. Usually an 18" underslung drop will be sufficient.

    I'm not ready to retire my zone valve option, but I'm liking the direction pumps are headed.

    Remember most zone valves are powered by a 24v power source. Transformer loss needs to be accounted for when comparing power consumption.

    Pumps lend them self to off grid PV power nicely also. just as we watch and count burner or wood boiler efficiency numbers, we need to watch electrical "wire to water" efficiency numbers.

    hr

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  9. jebatty

    jebatty Minister of Fire

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    Thanks, nofossil. In addition to tutorials, I have thought that it may be appropriate to open a new forum or a resource site for other energy saving ideas. In particular, not exactly the "insulation" idea, but other ideas which deliver big bang for the buck, almost any dummy can do it, and a little outside the box. My recent post on energy savings for hot water heaters is an example.

    Now to critique your tutorial. I have a three zone, one pump set-up on a LP boiler which operated for 10 years before I had one zone valve fail, and since we bought that house with the system installed, the zone valve worked for some years before that. I agree that reliability and cost are important. Anyway, pumps fail too.

    As to one pump with zone valves, you might want to mention that controllers are available to run a variable speed pump, depending on demand. This helps to solve the situation that can arise where one zone gets a lot more heat than another zone.

    Also as to pumps, efficiency is making ground here to, and some models of newer pumps use much less electricity than older pumps.

    Everything on the table, if it is a DIY install by a non-professional, and because most people do not have endless cash, simplicity and economy may trump other options.
  10. sled_mack

    sled_mack New Member

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    I don't think my point came across clearly. And after reading HR's post, maybe I can clarify.

    In addition to pros and cons, maybe there are limiting factors to be considered? For example - if you've got really hard water, maybe you need to consider pumps instead of valves, or else plan on treating the water in the system. I don't know if that statement is valid or not, just an example of what I am thinking. I don't know what else can affect the decision? Number of zones? Types of emmitters? Use of primary/secondary loops for mixing down radiant floor temps?

    My point is for your comparison to get people thinking deeper about their setup. If they have really hard water, maybe they want to do something about that knowing the consequences to their heating system. Or, if they are planning on long runs of 3/8 inch pex for radiant floor heat, maybe that zone isn't going to get enough flow with only one pump. Now they can think about the value of upsizing the pex, shorter runs in parallel, etc. I think you are on the right track. But some of these issues may not be apparent when planning the system to someone new to the whole process.

    Taking it to the next level would be a list of "best practices" for each solution.
  11. Nofossil

    Nofossil Moderator Emeritus

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    Thanks for the encouragement. I'll probably add a few words about pump evolution. Jim, can you pass along a manufacturer / model number for a variable speed pump controller? It's of direct interest to me, and it would be good to add to my writeup.

    MOS / HR, could I use some of your post as part of my site content? It's a good summary of the topic, and something I've been following. I couldn't find US resellers for any of the new breed pumps last time I looked, though.
  12. jebatty

    jebatty Minister of Fire

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    nofossil - take a look at this, which I stumbled across yesterday. Anyway, this is what I was thinking when I mentioned variable speed pump control.

    Ebay listing: search "tekmar 4" and you will see a controller listed: TEKMAR 4 STAGE BOILER CONTROL 353* (58610)

    For more controllers, search "boiler control" in Business/Industrial -- HVAC

    Tekmar literature for this control: this control is discontinued, lit is available, and Tekmar has many other current controls. I have no experience with or opinion regarding Tekmar. Here is link for lit for the Ebay listing.

    http://www.tekmarcontrols.com/literature/acrobat/disc/a353.pdf
  13. Bob Rohr

    Bob Rohr Minister of Fire

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    Here are a couple of my favorite pumps and controllers. tekmar makes variable speed controls for many of the radiant suppliers. Taco uses their control as does Grundfos, Uponor, Watts and many more.

    The basic control can run any brand of wet rotor circulator.

    The Grundfos MixiMizer has the control built right onto the pump. This is an excellent choice for a boiler pump/ return protection device in all one package approch.

    Taco also offers a mixing pump with or without a heat exchanger with this variable drive. i like that assembly for my Aquatherm wood boiler jobs for radiant mixing.



    hr

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  14. Bob Rohr

    Bob Rohr Minister of Fire

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    Here is the tekmar control only for variable speed.

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  15. Nofossil

    Nofossil Moderator Emeritus

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    Thanks for the references. I'm thinking of adding another section to the site describing the 'ultimate system' with a few variations. These variable speed pumps / controllers would have to be included.
  16. Sting

    Sting Feeling the Heat

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    I like it

    Bravo Nofossil!
  17. Buck1200

    Buck1200 Member

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    HR- are the Wilo and Grundfos variable speed ECM pumps actually available in the US yet? It seems that maybe a few lucky contractors such as yourself have them, but I cannot find any outlet for either other than some online stores in the UK and Germany. I will likely enlist a plumber for the installation of my system when the time comes (hopefully before next winter), but I want to be able to push for the use of some of this appropriate new equipment with whomever I use, and that means being able to read the instruction manuals, get pricing and leadtimes, and line up knowledgeable support as needed.

    Can you tell us about the distribution schedule? Condensing oil boiler from Veissman and Buderus released to the US is my other significant curiousity these days, but that's a subject for a different thread.
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