1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

What controls variable speed pumps?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Tennman, Aug 22, 2014.

  1. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    Currently our circ pump between boiler barn and the house is a fixed speed Taco 0013, sized per the Taco datasheet. It's done the job but I have no idea if it's over or under sized.... it's just worked. I've read about variable/multispeed pumps but don't understand what part of the control system decides when or why to use first, second or third "gear". Since our system is forced air and the fan is turned off when the thermostat is satisfied is there any benefit to using a variable speed pump? We're redoing the boiler barn plumbing to add the storage so if there's any advantage to upgrading to the latest, greatest pump, now's the time.

    Another dumb question.... are folks with forced air/storage systems turning off the demand circ pump when the blower's not on? It seems possible the electrical energy to get that big slug of water (~350' round trip) moving again every time the fan turns on may be greater than the wasted thermal energy lost circulating all the time. I guess that depends on the time duration between the tstat calling for the fan. I can see keeping the circ pump running all the time could hurt storage energy.

    Finally... if most systems stop circulation during fan downtime, having the circ pump in the house vs in the barn makes sense but our Taco is quite noisy. Has anyone found the Grundfos or others quieter?

    Thanks guys. Almost looking forward to winter... almost. Certainly looking forward to football and deer season!

    Helpful Sponsor Ads!





  2. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,981
    Loc:
    Nova Scotia
    I love my Alpha. Whisper quiet, can't hear it. For any system with multiple changing loads, it is a no-brainer to use one - it ramps up & down with zone valves opening & closing.

    With an Alpha, you don't even have to contol it. You can just plug it in, set the speed curve you want, and it will keep itself there. It can sense when a zone valve opens, and ramps itself up automatically. For example, if you put a zone valve in the line that feeds your HX, and control it so it opens when the HX needs heat, the pump will do the rest. When the zone valve is closed, the pump will just go to zero speed, but stay active. Then ramp up when the valve opens. Same thing with multiple zones. I've got 5, and as each zone opens, it speeds up a little more. And it also is conducive to tuning in your zone flows by throttling ball valves. It slows down, whereas a normal pump will keep on pumping at the same speed trying to force the same amount of water through a smaller opening. It somehow senses the pressure differential between the inlet & outlet, and maintains it. It might do it by measuring the amperage changes, or how hard the pump is working. But however it does it, it's like pump magic.

    Plus they simply use less juice than a non-ECM pump, all else being equal. Maybe 1/3? Forget now.
    arbutus likes this.
  3. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    Huh.... well, I just have one water-to-air HX so don't have any zone valves. Just the 0013 that for the last 4 years would run from Nov to March when the boiler provided 100% of our heat. Pretty crude but I was saving so much vs propane I ignored it. I really love the sound of putting a zone valve in my house then I could place the Alpha out in the boiler barn? That would give me the best of both worlds, the zone valve in the house near the fan controls controlling the pump out in the barn where it's currently mounted and wired. Then even if it did make a little noise, so what. If the Alpha is that quiet I could mount it in our root cellar, but if it would work ~150-160' from the zone valve out in the barn, I'd rather keep it there.

    Maple, this sounds really sweet. I'm gonna wait to see if anyone throws rocks at this before I order a zone valve and Alpha. This wonderfully solves my screw up of not running a data line between the house and the barn when I did my underground to provide control between the buildings. Because of the distance and pressure drop calculated, the datasheet said I needed Taco's biggest pump, the 0013. I'll be checking the gpm capacity of the Alpha products. Who's zone valve did you buy?

    Hoping others will chime in and say this is a great idea. I've never heard of this used with forced air but it sure solves a bunch of problems! Geez I want to click the "Like" on this!
  4. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    BTW, I was no kidding researching wireless relay systems to solve this.
  5. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,981
    Loc:
    Nova Scotia
    I'm also hoping others will add to this.

    I'm no pro - if there's misunderstanding in anything I say I'd like to know about it too.

    I just bought an off-the-shelf honeywell zone valve for my DHW loop. My heating loops had honeywells installed 18 odd years ago & they've been good, except for the odd end switch going bad (last two I didn't bother replacing since they are on upstairs zones where I get convection flow anyway), and I think one motor. There might be better choices though - like maybe some that don't need constant power to hold a valve open like I think the honeywells do.

    But even if I got something wrong about the Alpha - I'm still in love with it. :eek:
  6. Bob Rohr

    Bob Rohr Minister of Fire

    Joined:
    Jan 9, 2008
    Messages:
    769
    Loc:
    SW Missouri

    The pump should always be sized to the job, or work it needs to accomplish. The trick is knowing what the job is exactly. Ideally you know the GPM (flowrate) and the pressure drop, or the resistenance the piping presents at the flow rate you require. This is usually expressed in head.

    So look at a pump curve sheet and find that flow rate and pressure drop to select the best pump or pump speed. The pump should operate in the middle 1/3 of that pump curve.

    To size a pump for an unknown piping circuit, a flowmeter could be installed, calculations could be done if you know all the piping size, fittings, etc. or a pressure gauge could be used to read the pressure difference across the pump that is installed and running. Use that data to go back to the pump curve sheet and determine what the system is actually doing.

    Not all systems need or benefit from delta T or delta P circs, although they do save energy even is a fixed speed mode.

    I doubt the Alpha has enough "fizz" to move the load that 0013 moves, but one of the above methods would help determine that.

    There are more and more larger ECM circs hitting the shelves, price is still a bit high on those larger sizes.

    This You Tube explains how Auto Adapt works on systems with changing flow requirements.



    The pump curves for variable speed circs are a bit more complicated. Note for this Alpha the sweet spot around 10 gpm, in fixed speed 3, read to the left axis to see the head at that flow rate, or vice versa if you know head, read right to see the gpm it will flow.

    Attached Files:

    BoilerMan likes this.
  7. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    Bob, unfortunately my Taco datasheet Spreadsheet is at work. But, as I recall the energy and deltaT gave me the gpm and I added up all the fittings and distances to get the reqd head. The pressure drop from the fittings wasn't huge but the distance and required gpm in our 1 1/4 pex really drove the head up. Flow velocity was higher than ideal. I'd hate to go down in capacity from something that works. No idea if the 0013 is oversized but it's what the calcs called for.

    So what do you think of Maple's idea of a zone valve near the HX and the alpha in the barn? Assuming the alpha can provide the head and gpm does the approach sound good? I've never heard air/water HX's systems mentioning zone valves but it sure would solve my problems. Am I correct assuming most don't run the circ pump all the time, just when the fan is on? I guess turning the circ on and off is so obvious it's never discussed here but I've never needed or could control it until now. Really appreciate the feedback. I read about the alpha and watched the video. I'd love to use one if I can.
  8. ewdudley

    ewdudley Minister of Fire

    Joined:
    Nov 17, 2009
    Messages:
    1,680
    Loc:
    Cayuga County NY
    In your circuit (using 400 feet as an estimate to account for some fittings and the WAHX) an Alpha 15-55 would push over 6.5 gpm and generate about 10 feet of head. The 0013 is probably running about 10.5 gpm at over 25 feet of head. So if you can get the job done with the lower flow you'd be using less than a quarter of the power. And as you say, if you could switch the pump off when there's no call for heat you can save even more. (For the 0013, 120 days times 2 amperes time 120 volts times 0.15 dollar per kilo-watt-hour is $103.)

    A zone valve would have to be pretty big and expensive to be free-flowing enough not to add considerable restriction to the circuit. Can't you just put the pump in the house?

    Do you have an idea of what your deltaT is with the 0013? What percentage of the time is there a call for heat in the dead of winter?
  9. Bob Rohr

    Bob Rohr Minister of Fire

    Joined:
    Jan 9, 2008
    Messages:
    769
    Loc:
    SW Missouri

    How many GPM are you trying to move to that heater? Or how may thousand BTU/hr? You need one of those numbers plus that circuit length of @ 400 feet of 1-1/4 to get your answer.

    That Taco 0013 is a high head, high flow pump. The Alpha is no where close. The Alpha is more like a 007, good for about 9gpm at 9' at the mid curve range.

    You can see both pump curves on this chart.

    I'm guessing you would need something like a Magna from Grundfos to move that load. Maybe not.

    Attached Files:

  10. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    Guys, got my spreadsheet yesterday. My pump sizing assumptions were 180 kbtu/hr for the 60 class boiler with a HX deltaT of 30F. Back in those days (5 years ago) many distributors were saying " just use 1" pex and this pump". From the research here I learned to ignore my distributors advice which then left me to my own calcs but based on no direct experience. Given the above the Taco data sheet computed 12 gpm to transfer the 180kbtu with a 27' head. Again, this site was my best/only source of knowledgeable experience. Never looked at a Grundfos but am now. So given that choice I have a noisy pump which is why I'm reluctant to put a pump in the house. AND zero local professional experience to consult with here at the Tenn/Alabama line. I'd love to put the pump near the HX but if my gpm is right i'm concerned about pump noise in our home. Within reason, pump and possibly zone valve cost is not relevant for this upgrade of our system. Bob, I'll google larger ECM pumps to find out what ECM means... Variable speed? I'd really like to use an Alpha type pump and don't mind using a zone valve if it will assure quiet service. Really appreciate the help. I'm on my own down here.
  11. ewdudley

    ewdudley Minister of Fire

    Joined:
    Nov 17, 2009
    Messages:
    1,680
    Loc:
    Cayuga County NY
    Again, with the current system what is your actual deltaT with the 0013? Does the heat exchanger fan run 100% of the time during you coldest days or does it run more like 30% of the time?

    Need do get some idea of what your actual heat load is as opposed to what the original design heat load might have been. Once you have a better idea of how much heat you need then you can decide if the need can be met with 7 gpm as opposed to 11 gpm.
  12. alaskawild

    alaskawild New Member

    Joined:
    Aug 18, 2014
    Messages:
    80
    Loc:
    Fairbanks AK
    ECM stands for (Electronically Commutated Motor). Look here for details. http://www.marsm-a.com/images/ECM Technology Overview.pdf
    You could also run two Alpha's in parallel to obtain needed pump curve since they are Delta P controlled. Have done several setups like this in the past.
    The Taco Bumble Bee's could possibly also be used in parallel but it would be a little more tricky since they use a Delta T setup. In my experience the Alpha's are the quieter than the Bumble Bee's if noise is a concern.
  13. alaskawild

    alaskawild New Member

    Joined:
    Aug 18, 2014
    Messages:
    80
    Loc:
    Fairbanks AK
    Just my two cents on zone valves. Make sure to understand what the CV rating is for the valve you choose. You need to know the flow rate needed. If you need a huge amount of flow the White-Rogers valves are your choice hands down. Almost unrestricted. Their biggest issue is they are powered on opening and closing unlike almost everyone else's. This requires a little more thought in wiring as most zone valves are either normally open or normally closed. (most normally closed) I guess White-Roger biggest advantage is power is not always on during operation and huge flow rates.
  14. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    EW, remarkably the HX maker pretty much nailed it. I gave him plenum cross section, fan cfm, and I guess btu output. He then sized the thickness. When about 180F is sent return is in the neighborhood of 150F. I sorta guessing but when it's cold in the 30's I'd say the fan's on about 50% of the time. That's just from memory. This winter I'll monitor that to get a better picture of demand. Just never thot of it. It worked so I never paid attention. I guess 50% fan on implies about 90kbtu/hr demand sizing all for 180kbtu output?

    Alaska, yes I really like what the Alpha offers. I'll be looking to see if they make a bigger one. I'm inclined to get a big variable speed pump. Yes I could do 2 Alphas. BTW, I looking forward to coming to Fairbanks in 2 weeks! I'm coming up to the University for a conference!! Jazzed.
  15. alaskawild

    alaskawild New Member

    Joined:
    Aug 18, 2014
    Messages:
    80
    Loc:
    Fairbanks AK
    Teenman...

    Grundfos does have a new line of ECM pumps just hitting the market but you will not like the cost!!! Parallel Alpha's are the way to go for now. If you have time while you're up contact me and I'll give you the nickel tour of the biomass industry here. There is already a chill in the air. Bring a coat! LOL!!!
  16. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,654
    Loc:
    Sand Lake, NY
    This is the pump curve from a manually adjustable Bell & Gossett ecm pump, the Ecocirc Vario that I got. They also have an automatic version, plus some other more powerful advanced pumps that involve wifi even. I think parent company ITT bought out a European firm and is putting its stuff under the Ecocirc name. I'll put the Grudfos Alpha next to it, mostly for my own purposes to compare the two.

    [​IMG][​IMG]
    Last edited: Aug 24, 2014
  17. Bob Rohr

    Bob Rohr Minister of Fire

    Joined:
    Jan 9, 2008
    Messages:
    769
    Loc:
    SW Missouri

    If in fact the boiler has an output of 180,000 BTU/hr, you need to flow about 16- 18 gpm to move all the energy it can product. Looking at these pump curves, really none of the small circs lile 007, 15-58, Wilo 16 or the ECM style Alpha, Vario, or Bumblebee will come close.

    It is possible to put two pumps together, but until you know the pressure drop, you cannot determine that.

    If you have a 400 run of 1" pex, you will probably need a fairly high head circ, like the 0013 you have. To replace that with a high efficiency style you are probably in the $400. plus range.

    Only if you have multiple zones, controlled with zone valves would you need a variable speed circ.
  18. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,654
    Loc:
    Sand Lake, NY
    Hey, I did a search on that xylem smart pump and came up with a lot of publication, but no sales. I guess, call the distributor. There were a couple of videos. The other one had a lot of info in German. The original company name is/was Lowara. This video is kind of basic. Who doesn't need a circ pump that can talk to your phone? :)
  19. ewdudley

    ewdudley Minister of Fire

    Joined:
    Nov 17, 2009
    Messages:
    1,680
    Loc:
    Cayuga County NY
    I think perhaps now we have enough information to estimate answers to your questions.

    First, here's a load table of gpm vs. head for your system. First column is gpm and the other two columns are for loop resistances for 1.25" PEX equivalent lentghs of 350'and 400'. (Using inside diameter of 1.013".) Don't know how many elbows and other fittings there are, plus the WAHX, but I'm guessing the 400' column would be closer to your actual load resistance.
    Code:
    gpm      350     400
    
     6.00    7.37   8.42
     6.25    7.95   9.08
     6.50    8.55   9.77
     6.75    9.16  10.47
     7.00    9.80  11.20
     7.25   10.46  11.95
     7.50   11.14  12.73
     7.75   11.83  13.52
     8.00   12.55  14.34
     8.25   13.28  15.18
     8.50   14.04  16.04
     8.75   14.81  16.93
     9.00   15.60  17.83
     9.25   16.42  18.76
     9.50   17.25  19.71
     9.75   18.09  20.68
    10.00   18.96  21.67
    10.25   19.85  22.68
    10.50   20.75  23.72
    10.75   21.68  24.77
    11.00   22.62  25.85
    11.25   23.58  26.95
    11.50   24.56  28.07
    11.75   25.55  29.20
    12.00   26.57  30.36
    12.25   27.60  31.54
    12.50   28.65  32.75
    
    
    
    The 400' load table intersects the Taco 0013 pump curve at about 10.75 gpm and your deltaT is verified at about 30 degF, so your HX is putting out on the order of 160,000 to 170,000 btu per hour for real, as measured, on site, and close to as designed. Nice.

    According to the pump curves above the Alpha 15-55 would flow a little over 7 gpm and the B&G would do about 8.25 gpm.

    So to your first question, is your 0013 oversized? The design gpm is fine coming in at 4.3 feet per second, which A-OK. The pump itself is somewhat mis-applied because it is operating outside the middle 1/3 of its curve; but considering price, performance, and availability the 0013 is still arguably a very good choice, assuming of course that you actually need about 11 gpm.

    Second question, is there any advantage to a variable speed pump? If you had a variable speed pump that was too big at max speed then you could dial it back for your application to save energy. And in your situation a self-activating variable speed pump would be nice because it would shut itself off if the circuit was controlled with a zone valve. Plus modern ECM variable speed pumps offer substantial power savings, but that's an advantage of ECM pumps, not variable speed pumps.

    Third question, would it be possible to burn more electricity turning the pump on and off as opposed to running constantly? No, on and off will burn less electricity assuming on and off times are more like tens of seconds as opposed to half a second.

    Fourth question, what about putting pump in the house? I would expect a smaller modern ECM pump operating at lower head would easily be quiet enough to be in the house, but the big problem in your case might be the high head circuit. With high head it is important to 'pump away' immediately from the expansion device to prevent cavitation, so you would need to move the expansion device to the house also.

    Fifth question, how big a pump do you really need? Since at max load you're only running the fan 50% of the time it would seem possible that you could run the fan closer to 100% of the time and only flow half as much water. But having the fan run nearly all the time in the dead of winter only to deliver air that is 'half as hot' is probably not what you want. To do it right you would need to slow the pump down and also slow the fan down as well.

    That said, a pump like the B&G Auto (not Vario) would deliver more than 80% of the flow of the 0013 and would use less than one third the electricity (even if it was running when the fan was off), which would probably be plenty since your WAHX was designed nicely to be plenty big.
    Last edited: Aug 25, 2014
    maple1 likes this.
  20. Tennman

    Tennman Minister of Fire

    Joined:
    Mar 4, 2009
    Messages:
    673
    Loc:
    Southern Tenn
    Bob, Sorry, I ignored the advice of the distributor and per the Datasheet 1.25" pex was really on the edge of recommended flow rate so that's what I installed. If I had to do it over I'd go 1.5" given the length of my runs to reduce head. Also the BioMass 60 is rated at.... I think 205kbtu/hr max. I assumed 80% of that rating for max normal output to come up with the 180kbtu for sizing everthing. Got that from guys here way back when. If I could get a Alpha type pump with a max output of my 0013 Taco, I'm good with $400. I save that in propane in about 2 weeks! What excited me about the Alpha is it's automatically sensing the opening of a zone valve, I guess by the drop in pressure. I'm leaning towards plumbing the upgrades to install the pump in the house and if the noise is annoying then I'll move it to the barn.

    Alaska, I just may take you up on the tour and yes I'll pack a jacket! I have no idea what I'll do there for 4-5 days, but it would have to be in the evening. Days are full. Thanks on the pump suggestions.

    Velvet, I'll look into the B&G but also going to research the new, bigger pumps from Grudfos. I watched that Alpha video and now I'm hooked.

    EW, Your simulation nailed what the Taco Datasheet gave me. When I estimated the ells, tees, length, etc on my paper system it came out right at your line for 11.25 and 11.5 gpm to pump 180kbtu/hr. As I recall, our propane forced air furnace was rated at 165kbtu and did ok... but cost a fortune just to keep the house livable in the low to mid 60's.That's why I shot for 180kbtu output.

    Question 1 - Yes.... "Assuming I need 11gpm..... Seems like if I get a BIG ECM or variable, I can slow it down and experiment to see if I can get by at less than 11-12 gpm. But, really don't mind feeding the 0013 compared to propane costs. Electrical savings is just a big plus.

    Question 2- Yes, I'm inclined to get a big variable speed or ECM (I need to study the difference, thot they were the same). That way I can experiment with reduced gpm. If I start out small, I'm screwed. Again, several hundred bucks more for a bigger pump is in the noise of my storage upgrade expenses.

    Question 3 - Yeah I thot so. I all my reading here I don't recall it ever mentioned. I guess kinda like someone asking if fish swim. Yes, definitely off for minutes except for those very rare days of single digits. A once every five or so year event for us.

    Question 4 - Yeah, I think I'll try the pump in the house to see. If I put the unions in the barn for it, moving it will not be a big deal and will avoid the zone valve. Yes, I have space for at least one of the expansion tanks. Have two big ones. It could be I poorly placed my expansion tank with the 0013 which could be the cause of it's noise. I never read an expansion tank should be immediately upstream of my pump. Thot just anywhere would handle expansion.

    Question 5 - We're satisfied with how the boiler keeps our old place warm. I'm sure my wife wouldn't want to go backwards in comfort.

    Thanks all..... I'm on travel, but will try to research Grudfos products bigger than the Alpha while on the road. So I'm learning that an ECM pump and a variable are different technologies with the ECM being the latest and greatest. Correct?

    So I think from ya'll experience my system may require less than 11-12 gpm, but without doing some flow measurements I'm best off getting something with the same gpm capacity. ECM is the preferred technology (the Alpha is an ECM?). Our storage system will add at least 40-50' of line to the overall system. So I don't want to go down in capacity since I'm somewhat in the dark and what I have works.

    Great help guys Bob, EW, Alaska, Maple, Velvet. Any experience with a bigger ECM Grudfos or equivalent, love to have the input.

    BTW, anyone know why I can't reply here anymore from my iPhone? Something about cookies. Really appreciate the help. Sucks when on travel.
  21. alaskawild

    alaskawild New Member

    Joined:
    Aug 18, 2014
    Messages:
    80
    Loc:
    Fairbanks AK
    Hope you have a great trip! Not sure if we can send a private message on here but I'll look around. If I can I'll send you my ph#.
    Just a FYI. The new Grundfos pumps are called the Magna3. Very nice but you will not like the price!!! I looked at them at a trade show in Chicago this year. Lots of bells a whistles! Programming with smart phone, rotating motors, dual valute models, just to name a few. But the price!!! Dual or even triple Alpha's are the way to go if price is an issue. Very quite and efficient. My only other thought is do you really need to move all that heat? I know you are producing it just wondering if you need it? If you only had storage. Just found some more 1000 gallon LP tanks today. Wish we were closer! LOL. Anyway here are a couple of sites that will give you the skinny on the Magna3's.

    http://us.grundfos.com/products/find-product/magna3.html#overview
  22. ewdudley

    ewdudley Minister of Fire

    Joined:
    Nov 17, 2009
    Messages:
    1,680
    Loc:
    Cayuga County NY
    I think if your'e going to switch to an ECM pump it would likely work out well to go with the B&G Auto, which is a 60 watt max pump compared to the 200 watt 0013. In your circuit it would deliver over 80% of the flow of the 0013. An Alpha is probably too small, and a larger Grundfos would cost more than two smaller pumps.

    When installing the pump simply make provisions for adding another pump in series (not parallel in this case), and if you're not happy with the flow you can add a B&G Auto, Alpha, or Stratos to increase flow. (When using two pumps together the pump curves are added vertically for series and horizontally for parallel. If you plot the load curve for your circuit you will see that it intersects the series added curve much closer to the middle of the curve than it would for the parallel added curve.)

    I think with the advent of ECM pumps, using pumps in series or parallel is more viable these days because the smaller pumps are so efficient.
    Last edited: Aug 28, 2014
  23. alaskawild

    alaskawild New Member

    Joined:
    Aug 18, 2014
    Messages:
    80
    Loc:
    Fairbanks AK
    FYI. If you do go the series route with specifically Bumble Bees or Alphas watch out for pump chasing. If you are using both with their variable speed sensing function (Delta T or P). They are constantly trying to compensate for output in series. You can set the first pump inline to manual and allow the second pump to sense requirements and vary output. In essence you will have solved the issue then. The bottom line is that sometime ECM's are not the best choice. B&G is also a great circ!
    ewdudley likes this.
  24. goosegunner

    goosegunner Minister of Fire

    Joined:
    Oct 15, 2009
    Messages:
    1,275
    Loc:
    WI
    A little confused about your location of storage and how you will go from storage to forced air exchanger, But on demand pump will keep your storage from mixing. If you pump continuously you will end up with a tank at or near the same temp throughout and most likely significantly reduce the useable storage time.

    gg
  25. heaterman

    heaterman Minister of Fire

    Joined:
    Oct 16, 2007
    Messages:
    3,039
    Loc:
    Falmouth, Michigan

    Wrong target as far a flow rate is concerned.
    You size the pump for the heating load, not the boiler output. (Unless you're talking carrying all the heat output to storage)
    What's the design temp btu load in your house? That's what determines how many GPM you actually need to move. I'd be surprised if you actually need more than 6-7 flow rate.

    I'll put a $20 bill out there that says a much smaller pump will bring enough heat to your house Tenman. ;)
    If it was me, I'd get a variable speed that works on temp drop, dial it in for 20* and leave it run constant.
    When your furnace coil is pulling heat out of the flow the pump will ramp up. When the fan isn't running and there's less heat loss supply/return, the pump will ramp down.
    A Taco Bumble Bee comes to mind.

    http://www.taco-hvac.com/products/w...et_rotor_variable_speed_circulator/index.html
    Last edited: Aug 29, 2014
    alaskawild likes this.

Share This Page