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\"Smart\" VS Circulators, Mod-Cons & Delta-P Modulation

Yes, they are currently available in the US and Canada via Wilo. Not sure if any other any other mfgr. distributes them in North America.

Probably not yet a "stock" item except at the largest distributors.

For a number of very good reasons, specific prices are not mentioned here. All I can say is you can almost expect a comma in the list price...


  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    For months now I've been trying to figure out if these expensive but highly efficient VS circulators have much use in "American" hydronic heating systems.

    Aren't they coming from Europe (especially Germany) where TRVs are the norm?

    Try as I might, the only way I can see where they could modulate effectively is in a multi-zone system using zone valves--even then only when modulating on delta-p.

    They may be "smart" but I believe they are ignorant regarding the what's on either side--the boiler and the emitters.

    The worst thing I can imagine is attempting to modulate a VS circulator on the secondary side of a mod-con system via fixed delta-t.

    Why? Mod-con efficiency is all about maintaining the lowest possible temperatures--supply and return--to meet the current load on the system. Set a high (but fixed) delta-t in the 30F-40F range based on design conditions and you're screwed when system load is low. If it does somehow manage to maintain such a high delta-t during low load conditions, the supply temp will be FAR higher than required and not only will boiler efficiency drop, but your emitter output will be FAR greater than required to meet loss and the mod-con will be forced to cycle--even when it could have supplied the demand at minimum input and lower delta-t.

    If you're going to modulate via delta-t, I believe that it must be at a variable delta-t which can only be determined by the interactive communication between the boiler, the circulator and the emitters.
  • hot rodhot rod Member Posts: 7,059
    I believe that IS the intent

    TRVed systems or systems zoned with ZV's.

    I have a panel rad system, home run with TRVs at every radiator running with a Grundfos AlphaPro, and my own shop office with 3 ZVs.

    On my own system the readout runs from 7- 49 W depending on which ZVs are opened.

    But even on a single zone, single circ system the more efficient motor technology moves the load with about a 40% electricial energy savings. Compared to a equal sized non ECM circ.

    Put 'em up against a 3 piece, series 100 for example, imagine how many of those are out there moving 100K or less loads, and the savings look real nice.

    hot rod

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ALHALH Member Posts: 1,790
    VS Pumps

    I do agree that low flow rates and small dT's achievable in low temperature systems can conflict.

    In my opinion, the most bang for the buck in the average residential system is still an appropriately sized circulator with a dP bypass. The Grundfos 15-58 3-speed circ goes a long way toward making this happen. People get nervous about sizing pumps smaller, but as long as there is always speed 3 to CYA it's not so scary. How many zone-pumped systems could be running 15-58's on speed 1?

    There's nothing I like more than saving energy, but we have bigger fish to fry with reducing fuel consumption rather than saving a 60W light bulb's worth of electricity at design conditions. I dont think we have reached the pinnacle of fuel efficiency yet, and I think that's a lot more important. Better circs can always be retrofit into existing systems later without disrupting the piping significantly.

    In larger commercial systems the situation is completely different.

  • hot rodhot rod Member Posts: 7,059
    Not knowing how much more $$$

    a smart circ would cost....

    Is it possible to have a more efficient ECM based circ without all the delta P or T functions. Just a more efficient motor at maybe twice the price of a typical wet rotor circ. Ihat seems like a good compromise to start saving energy.

    From what i can tell the soon to arrive Laing e (electronic) series looks like a fairly simple efficient circ, without an expensive microprocessor attached. It is standard equipment on many of the Vaillant boilers.

    Maybe Wilo Steve Thompson or Mark H could set us straight on ECM options?

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Mark HuntMark Hunt Member Posts: 184

    Here is how I see it.

    We design systems to meet the max required demand at an assumed load. Heat loss of the total structure with an indoor temp of X and an outdoor temp of Y. That makes sense as long as we remain within reality. Let's face it, no one wants to under-size something. Subsequently, everything gets "SUPER SIZED". A heat loss may determine that a structure requires 40k btu's but the contractor has never installed a heating plant under 100k. He never got an "Insufficient heat" call with the 100k heating plant so that is what gets installed.

    Sad but true.

    The industry has made HUGE advances on the combustion side of things. We now extract maximum btu's from the fuel. The HX designs maximize heat transfer from fuel to transfer medium more efficiently than ever before. That is a good thing.

    So now we are "all in" as far as combustion and transfer efficiency is concerned, but where do we stand with delivery?

    ANY fixed speed pump works along the pump curve. As flow requirements diminish, head pressure increases. It doesn't matter what the highest head zone required is, as zones shut down, head increases and flow drops. Why? Because fewer zones require less flow. Isn't that backwards?

    An ECM pump sees the reduced demand and reacts much like a mod/con boiler. It reduces it's output AND energy consumption.

    Case in point. I was on a job in Long Island last week where a contractor replaced TWO 7.5 horse power, fixed speed pumps with two 1.25 horse power Wilo Stratos pumps. Each of the 7.5 HP pumps were drawing 60 amps when running. HE measured this, not me. I'm no electrical guru, but when I shot the Stratos pumps with our IR meter, they were drawing 37 watts and they were heating the building.

    Yes, the entire system was over sized. Happens all the time.

    Isn't it time we had pumps that were as smart as the boiler they were hooked up to?

    BTW, smallest Stratos made will bottom out at 6 watts dead headed. That is the commercial line.

    Our residential ECM line solves many issues.

    Mark H

    **Edit** My mistake. Only one of the Stratos pumps was running and it's actual power consumption was 370 watts, not the 37 that I posted. I spoke to the installing contractor this morning (he monitors The Wall) and his last reading was 1.75 amps being drawn by the Stratos. Amps x Volts = watts so the Stratos was drawing 385 watts.
  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    From the one price I was quoted think list price with a comma for the smallest Stratus...

    ECM based circ without all the delta P or T functions. Just a more efficient motor at maybe twice the price of a typical wet rotor circ

    Exactly what I was thinking. In most cases I see the brain of these circulators at odds with typical North American heating systems--and even working against the designs of fine hydronic engineers who aren't using TRVs.

  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    That's where I see them as marginally useful--modulating at a fixed delta-p in poorly engineered/poorly controlled/poorly operated multi-zone systems using on-off zone valves. Don't forget that the better engineered your multi-zone system and the more efficient your mod-con's reset curve the more all of the zones tend to call simultaneously and constantly. Design it well and the slight benefit you'll get from delta-p modulation will likely never justify the cost above that of a "dumb" but highly efficient ECM circulator...
  • vanvan Member Posts: 20
    Availabillity of new circs

    Are these new circulators available yet for residential applications? If so, who stocks them and how much are they?
  • vanvan Member Posts: 20
    Availabillity of new circs

    Are these new circulators available yet for residential applications? If so, who stocks them and how much are they?
  • Mark EathertonMark Eatherton Member Posts: 5,584
    TOTAL system modulation makes sense...

    We have modulating boilers.

    We have modulating non electric control valves...

    Why would we leave the circulator running full out with all the other components modulating? THAT does not make sense.

    In order to have the ultimate in energy efficiency, all links of the chain SHOULD be of the same ilk.

    As it pertains to the older gravity conversions, electronic interface can be as simple as providing a 1 to 10 volt DC signal based on system delta T (system supply versus return), outdoor temperature reset (0 degrees OSA = 10 VDC, 60 degrees F = 1 VDC), or simply allow the pump (with one additional input sensor, one is already built into the circulator) to modulate flow based on delta T.

    How does one justify the additional expense? In overall increased performance, less wasted electrical consumption, less wear and tear to the system, and less noise in the operation of said system. At YOUR cost per KWH, it might be hard to justify, but with electrical cost ever increasing, it becomes easier to justify.

    The Europeans have a Blue Angel rating system for circulators. Most American circulators fall into the C and D category, and the Stratos line are in the A category. I think that in the very near future, all systems (residential and commercial) will be REQUIRED to utilize the MOST efficient circulators available, that being a circulator whose energy consumption is proportionate to real time demand.

    Just my humble opinions...


    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    Bless you Mark.

    "Total system modulation" is exactly what the dead men did their best to incorporate into their solid-fueled, variable draft systems be they hot water or steam.

    Of course such still depended greatly on a good superintendant, a loyal servant or a great wife--all of which are HIDEOUSLY substituted by an on-off wall thermostat or worse yet a "smart" thermostat with multiple daily setbacks in a fruitless attempt to save energy while maintaining comfort.
  • What

    You got a few numbers mixed up there.
    120 amps to less than an amp. Not.
    Regardless if its 3 phase or single.
  • Availability of Residential ECM Circs

    Hello Van. Ok - here's the scoop...

    We're at the final stages of having the Stratos ECO (residential ECM circ) ready for a North American launch but it's difficult (and somewhat dangerous) to suggest a firm launch date (the apporval process is going very well but I am a believer in Mr Murphy!).

    To give us a little "wiggle room" let's say sometime during the first quarter of 2008. We'll have technical documentation prior (I'm actually proofing this tonight!).

    The Wall is not the best venue to announce pricing. Again, please hang tough - as we get closer we'll have a better idea of costing etc. 2 to 3 times the cost of a standard circ will be at least in the ball park.

    If anything firms up prior I will fire out a post - OK?

    To those that are asking about applications, if our North American systems are not applicable with VFD circs why do we use pressure compensated by-pass valves (required when constant speed circs build pressure at low flow)? Others have addressed the applications far better than I can - but it seems to make sence that if flow is modulating in a system it is a VFD application. And as almost if not all heating systems have varying BTU loads they are almost 100% vary their flow somewhere in the system.
  • bobbob Member Posts: 813
    Mike T

    Not trying to be a smart### but I would like to here your definition of a " typical" american heating system. bob
  • Andrew HagenAndrew Hagen Member Posts: 236
    Energy Savings

    I think far more electricity could be saved in residential systems through the application of good design principles that reduce pumping requirements as well as proper pump selection. If I have a 15-58 running on speed 3, how much would be saved by using a VS pump? I think VS pumps in small applications are at the margins of energy savings in well designed heating systems.

    Once these VS pumps are a few hundred bucks, I could see one running on dP. I'm still having a hard time wrapping my mind around what's going on with dT control. I tend to think it could waste more energy than dP control.

    I would love to see affordable small VS pumps.
  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    One whose final control is on-off wall thermostat(s). Nothing more--nothing less.
  • hot rodhot rod Member Posts: 7,059
    Steve, what about just

    an ECM circ without all the bells and whistles? Is it possible to just build a more efficient circ without any of the delta features? A more efficient single or 3 speed motor in the $200 plus or minus range, for single zone or zone pump applications.

    Or is it all or nothing when you switch to the ECM technology.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Mark HuntMark Hunt Member Posts: 184
    The Stratos Eco

    is the stripped down version of the Stratos. ECM technology, delta P operation, no bells and whistles. Well.....almost no bells and whistles. The Eco, like the Stratos, does have a "set-back" function built in but you can choose whether to use it or not.

    Hope this helps!

    Mark H
  • Kal RowKal Row Member Posts: 1,518
    this rings a lot like the talk when modcons first arrived...

    and were expensive and imposable to get, etc, - they got so much negative press, sure, the stratos and alpha's are hard to get and expensive - but with time it will change - it simply has to, like i told the wilo regional sales manager, "you will start making money on these pumps - when all your competition has them also and supply houses start having them on shelves - you cant make an economical go out of selling one'zy two'zies - it's got to move – just like modcons – now that just about everyone makes them and supply houses have stock"

    with copper being so expensive, we are starting to do a lot of cascading pex manifolds – ie a manifold with zone valves in the boiler room driven by a delta-p vari-pump, injecting to the floor manifold pairs each of which have a delta-t vari-pump - trouble is, that the remote vari pumps would be too expensive, so they are going in “el-cheapo” fixed speed for now to be changed out later – when delta-t pumps become reasonable

    also controls- controls -controls – integration for wall stats, slab sensors, outdoor, and vari-pumps as well as easy integration with building automation systems and remote internet gateway

    ps: the stratos has a combo delta-p/t mode where it maintains pressure diff yet slows down still more if the delta t shows that few btus are is being used by the open zones

  • Joe MattielloJoe Mattiello Member Posts: 547

    After reading some of the treads about variable speed pumping, I thougt I would add my input. One of the greatest attribute of VS pumping is the increase in confort level. Taco offers the variable speed setpoint, reset, and variable voltage. You can use these pumps with a modulating boiler already using an outdoor reset control, and do a mulitible temperature system, or a non condensing type boiler and run a variable speed pump, with outdoor reset. You might want to use the variable speed setpoint version for a mulitple temperature system. The variable speed pumps gives us more opportunities to design systems that run more efficient, and more dynamic. Taco, also has other products to help system design engineers offer their customer the best product for their money. To reference some of these other fine products visit
    Joe Mattiello
    Application Field Service Engineer
    Taco, Inc.
  • Yeah

    To quote Andrew Hagen the following:

    I think far more electricity could be saved in residential systems through the application of good design principles that reduce pumping requirements as well as proper pump selection.

    And a big roar went up from my peanut gallery. Skip the trinkets and get to the basics.

    Edit: that was with my utmost admiration Andrew.
  • MacMac Member Posts: 6
    Smart Circs

    I think the original postings comments were right on the money. If you simply install a smart circ. are you doing more harm then good. If the circ can't communicate with or assist the boiler and emmitter to operate closer to their best performance points have you really accomplished anything.

    The point of comparison of a circ to an 80W light bulb seems also on target. Using the 40K and 100K boiler sizes mentioned these units when operating at full load would equate to 12,000 W/hour and 29,000 W/hour respectivly. How much time and money should be spent chasing the light bulbs?

    If we are concerned with cost, and in particular the operating costs of a system over its life, the reliability and call back costs should also be considered. Adding intelligence to a circ also adds lots of additional components many of which are sensitive to moisture and heat. If you don't think this could be an issue talk to someone who works on furnaces with variable speed fans.

    Don't get me wrong I love electronics and do believe we are headed that way. That said I think the biggest opportunities still lie in promoting and teaching good design practices
  • tktk Member Posts: 36

    Arn't we still concerned with flow of 2 fps. Are we achieving this with the VS circulators?
  • That is when we

    pitch the proper design theory out the winder. Then we start inventing new ideas to fix the problems we just created.
  • Darin CookDarin Cook Member Posts: 298
    VS Circs

    Circulators just like everyones boiler are oversized except for a few days out of the year. There is considerable money (energy) to be saved for individuals and our country in utilizing this technology. Yes, in residential systems we are talking light bulb wattage in power consumption, but now times it by millions of American homes. We could power towns or even cities with the electricity saved for a long time.

    How many houses have you been in or even piped in that had a big bank of circulators. I have seen houses that had up near 20 circs for zoning. Multi zone systems whether it is electric zone valves or non-electric thermostatic heads utilizing a VS circ can save a customer quite a bit on their electric bill. Why would you design a multi-zone system, use a high efficiency boiler to save fuel but then increase their electric bill with a multiple pump install??? It does not make any sense!!!!

    The new pumps will force alot of people to really start doing their homework when it comes to sizing a pump but so did mod-cons when it came to boiler piping.

    As far as circs with ECM motors and no frills, if enough people want them they will be made. The market will step up and meet a demand if money can be made.

    It will be interesting to see what else the heating future holds for us.


    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Kal RowKal Row Member Posts: 1,518
    i am expecting the power companies to subsidize...

    ecm pumps - because the cost of putting more copper into the street is soon going to be orders of magnitude greater than helping us out with the ecm pumps - like they do with compact fluorescents

    eg - a laptop computer with a 17" lcd draws 1/3rd of a desktop with a 17" lcd and 1/6th of an older desktop with a 17" CRT - that’s a lot of street copper!!! - if you live in nyc and your fridge is more than 10yrs old - it's stealing apx 20$ a month from you!!! - when they start charging rate of demand for residential like they do for commercial - the ecm pumps will start flowing

    what bugs me is that while the cast iron volute is cheaper to make in the usa, the multi-phase winding and permanent magnet rotor, and ckt board, is cheaper to make in the far east – we will loses labor over here - grundfos brought manufacturing from Germany to here because it was a lot less here – now we will be sending them to china like wilo – sucks... :(
  • zekezeke Member Posts: 223

    Quote"As far as circs with ECM motors and no frills, if enough people want them they will be made. The market will step up and meet a demand if money can be made."

    Not if the mfrs keep the commas in their designs. No way should a no frills motor cost that much. Seems the mfrs want to get their R & D money out and then some immediately for their bottom line. And by the way, ECM technology has been around for better than 2 decades (control theory has been known since WW2) and should have been well developed for HVAC by now. What was/is their problem?

    Case in point. If I have say three zones, I can get 3 007's for a fraction of the price of the ECM, so why bother since the additional cost of electricity is peanuts compared to the cost of amortizing that capital investment.

    I think the mfrs should step up to the plate and do some serious marketing, starting with REASONABLE pricing. Maybe then they will find a market.
  • Taco DT & DP

    And, you can get those 007's in a delta-T or delta-P. From what I've been told, you can juice up just about any of their pumps with those options - including built-in outdoor reset.
  • Kal RowKal Row Member Posts: 1,518
    hear, hear...

    for the cost of a 007 you can buy a 250gb hard disk - made in a clean room env with a lot more labor, and an amazing ECM motor that does accels/brake/decels on the fly many times in one revolution to balance out the drive, and all, at 5200+ rpm!!!

    - "give me sweat shops!!!" - if taco doesnt get with the program - we should take the pump business to hitachi!!!

    another eg: for the cost of a lexmark color print cartridge - you can buy a vcr!!! - now, what is there in that print cartridge that there insn't orders of magnitude more of in the vcr, from technology to labor??? it simply bogles the mind

  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    If you zone with valves--or better yet TRVs--and use a single ECM circulator modulating on delta-p, I see some genuine benefits. Not only greatly reduced electric consumption, but more consistent flow in each zone no matter how many others are calling.

    The greatest benefit however will likely be when mod-con mfgrs work with the manufacturers of these circulators to develop a standard interface between the boiler and the circulator. Viessmann sort of did this with Grundfoss for the Vitodens 200, but the interface is proprietary and the circulator dedicated for use only in that boiler.
  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    Unless something has changed radically and recently, the drive motor of hard disks is a servo-controlled DC spindle motor that operates at a fixed and highly-controlled speed. The drive can't even read or write until it gets "up to speed".

    High-speed DC motors driving CDs do however vary their speed as they generally operate with constant angular velocity, meaning that as the read position gets closer and closer to the center of the disk the speed gets slower.
  • Supply House RickSupply House Rick Member Posts: 1,404
    250gb hard disk

    Won't move hot water to keep your grandma warm. It's not apples to apples.
  • Kal RowKal Row Member Posts: 1,518
    something did change...

    they gave up physical micro balancing and do it electronically - so the motors actually change speeds a "gzillion" (scientific term) times a second

    hard disks don’t move water - but the drive principles would make pumps smaller, cheaper, and more powerful - the starting torque of a permanent magnet rotor make a PSC motor look like a toy

    and the internal feedback is so sensitive that they can do real cool stuff like going imperceptibly slow and wait for a zone valve to open up – you wouldn’t even need end switches on a bank of zone valves, the motor would simply know when one open up, and would draw a negligible amount of power waiting
  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    Sorry to split hairs, but I think there's a big difference between adjusting the speed a gazillion times a second and correcting speed on a gazillionth of a second basis. The first implies that the speed can intentionally be changed in a gazillionth of a second; the latter implies that after one gazillionth of a second the speed is exactly the same as it was two gazillionths of a second before.
  • Kal RowKal Row Member Posts: 1,518
    Reminds me of a pilot friend…

    Trying to explain an Inertial Reference System on his jet, he said simply that it “measures the difference between where you aren’t to where you wasn’t, and where you wont be, to where you shouldn’t ”
  • Mike T., Swampeast MOMike T., Swampeast MO Member Posts: 6,928

    Call me a freak, but your pilot friends statement makes perfect sense to me.

    Submariners will say the same thing--when running submerged and silent they have nothing but an "Inertial Reference System" to both guide them and let them know where they are...
  • ConstantinConstantin Member Posts: 3,782

    Not sure I agree. As usual, it all depends on the circumstances.

    If you're running a zone valve system with one pump supplying multiple zones, the "old" correct approach was to fit a bypass valve. With a smart circulator, you can eliminate the bypass valve and save power at the same time. That most "older" systems didn't have those bypass valves is a completely separate matter.

    The beauty of a delta-P controller is that it doesn't have to communicate with the boiler. It takes care of the zones, the boiler takes care of supplying enough heat. Some mart boilers already have a smart circulator and then use a LLH to separate the house from the boiler of optimum performance.

    As for the additional components, I agree that putting a great circulator into the wrong location or heating system makes no sense. There is an additional cost of the electronics in terms of energy efficiency and materials. Otherwise avoid the variable-speed benefits and go straight to single-speed brush-less permanent magnet motors.

    However, for the right heating system such circulators not only save a lot of electrical power, they also allow for the elimination of a mechanical point of failure (the bypass valve), along with all the labor of installing it. With power now at $0.20+ per kWh in my region, the benefits of reducing the power footprint are rapidly expanding, while competition among circulator manufacturers is sure to drive the price of smart, energy-efficient circulators down.

    Sooner or later, I predict that we will see the adoption of such circulators just as widely as we see modulating, condensing boilers now. Perhaps not the majority of applications, but enough to make it not only a worthwhile technology to understand, but also a means of setting your operation apart from that of other installers/maintainers.
  • Mark EathertonMark Eatherton Member Posts: 5,584
    In a properly designed, installed and commissioned system...

    air in suspension is not an issue. That said, if the system is of poor design, poorly installed, commissioned and operated, you will have issues regardless of whose circulator is moving the fluid...

    Trust me, there are a LOT of systems out there operating at velocities of less than 2 FPS and they are doing just fine...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hot rodhot rod Member Posts: 7,059
    Status quo doesn't often

    serve up new and exciting ideas or products. It's those on the fringes, pioneers, grassroots type of hydronicians. Count me in. I'd rather be looking for way to advance systems and conserve energy then trying to find reasons why it shouldn't be attempted.

    I'm on my second week of heating my shop and office with a circ at 9-16W. I'm here to tell you it works just fine.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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