Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

need pump guru..

Kal Row
Kal Row Member Posts: 1,520
only the non-bypassed flow is actually going to move past the boiler header close-t’s –that’s why the 8 stages – I wish I had even more, because one stage of one boiler IBR is 250KBTU – a lot more than the trv’d load on a mild day if the hall is not being – thank god, the tekmar takes care of short cycling too – I recommends that instead of two huge boilers – in order not to have a single point of failure – to put in 5 Weil McLain ultra 310’s fully modulating – which could handle cold water return – and would match the loads better and faster – and they would save a bundle on gas – well, talk to the flue pipe….

Anyway, keep asking – this way we both learn


  • Kal Row
    Kal Row Member Posts: 1,520
    need pump guru for problem after the fact...

    was asked to do a boiler room layout on a new building - that has unfortunately already been piped and they don’t want to do it over –( don’t you just hate those..)

    they are using slant-fin JR-14 baseboards, that put out apx1200btu per ft at 180f@3ft per sec,

    the heat loss on each floor is 167,000, or 84,000 per outer wall, but they put in too much radiation, 5x16ft jr-14’s (with trv’s)–

    problem is that they zoned it out, by building sides – so I have three floors, or 15*16ft baseboards in the zone, 15*16*1200 or 288,000btu – though, I am only expecting to ever need about 240,000btu out of that on a design day, (the boilers are a pair of 4 stage mightytherms, each sized for 75% of load IBR, driven with a tekmar 268, with outdoor reset)

    problem – there is only an 1-1/4 pipe getting to the boiler room on the roof – and you cant get that many btu’s through a 1-1/4 pipe with normal circulators, and they wont re-pipe or even tee in extra pipe for the last two floors
    (moral of the story – never trust an architect’ pipe sizes )

    now, if I had 2.5” pipe, a Grundfos 43-75 would give me the required gpm, but with the 1.25 pipe, should I put two of them in series, (oh the noise!!), or walk away??

    The only saving grace is that those slant fin units – require 3ft per sec instead of the customary 4ft per sec – anyone have a pipe size to gpm table, for 3ft per sec? (ziggi’s formula makes my head hurt)

    attached is slant-fin's spec sheet for those baseboards - real nice!!!
  • bigugh_4
    bigugh_4 Member Posts: 406

    You'd need 1.75 X's the normal flow thru a 1-1/4" pipe for that load. and Ziggi's formula most likely takes in the extra head loss that will occur. So my best guess is to use it. Otherwise, just use Dan's comment in his "Golden Rules of Hydronic Heating" page #78 . "I'll get back to you on that" bigugh
  • Jed_2
    Jed_2 Member Posts: 781


    So, Kal, are you saying there are 2 zones, each including one side of the building and three stories? Where's the T'stat? The ratings you suggest conclude 3/4" element. But you are not providing total equivalent length of the zone. You need this to continue any pump selection scenario, futile as it seems. I didn't look at the 43-75 curve, but how did you arrive at this pump(whoops, circulator)? 3/4" copper pipe @ 4gpm @20^T= 40mbh. You obviously don't have that. I suspect you have quite a long circuit length, and with accurate head loss data, you might be aghast at the pump you really need, and the resultant velocity.

  • Kal Row
    Kal Row Member Posts: 1,520
    the pump is of course wrong...

    it would be right with 2" pipe

    the baseboard are piped with a 1" reverse return feed on each wall and floor, and each 16ft section of baseboard has a TRV,

    they are then tied together in the riser which increases to 1.25 after on floor,

    i begged them to just give me 1" risers of each wall and floor and i would give them a bunch of cheap zone circs and stats - the answer... "NO"

    i could get the flow with two pumps in series to overcome the resistance - but it will make a racket and eroded the pipe

    in sizing pumps for trv'd radiation - one tries to get pumps with flat curves – so you can skip the differential pressure bypass valve – flat curve circs have small diameter but wide impellers, – high head circs have large diameter but narrow impellors

    this is a mixed load job with a bunch of fin-coil air handlers also

    attached is what I laid out for the boiler room design so far
  • Kal Row
    Kal Row Member Posts: 1,520
    of course the selected pumps are wrong...

    it would be right with the correct pipe size

    the baseboards are piped with a 1" reverse return feed on each wall and floor, and each 16ft section of baseboard has a TRV,

    they are then tied together in the riser which increases to 1.25 after one floor,

    i begged them to at least give me 1" risers off each wall and floor and i would give them a bunch of cheap zone circs and stats - the answer... "NO"

    i could get the flow, with two pumps in series to overcome the resistance - but it will make a racket and eroded the pipe!

    in sizing pumps for trv'd radiation - one tries to get pumps with flat curves – so you can skip the differential pressure bypass valve – flat curve circs have small diameter but wide impellers which don’t stall when you block the flow, – high head circs have large diameter but narrow impellors, huge centrifugal force – but aerodynamically stalls on the least bit of back pressure, (or should I say hydro dynamically), and also cavitates on the least bit of low inlet pressure

    this is a mixed job with a bunch of fin-coil air handlers also

    the ceiling are only 8 ft, the building is 100x77 – so to follow dan holohns’s worst case pipe length rule – up, to-back, across, return = 2x(100+77+24+3ft) = 408ft
    half of it is ¾ baseboard at apx 9ft of head and the rest 1.25 L at apx 7ft of head

    ziggi’s flow rate formulas make my head hurt

    told the plumber to leave room for series or parallel pumps – cause this will be a tough one

    attached is what I laid out for a boiler room design so far - cept for the pipe size screw-up it's such a simple system

    thanks for listening – I knew, there was no clean solution to this mess – I will be using the new tekmar tN4 system zone managers and Tstats – hoping the trv’s and the electronics will cover the sins
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Counfused About Your Heat Loss

    You say, 167 mbh loss per each of three floors = 501 mbh total loss.

    Then you say they "put in too much radiation". 5 x 16' b/b per floor. At 1,200 btu/ft that's 96 mbh but the loss is 167 mbh??? For the three floors that's 288 mbh for the radiation with a 501 mbh building loss???

  • Kal Row
    Kal Row Member Posts: 1,520
    per side...

    5x16 on one side and 10x8ft'ers on the other side
    total per floor 192000 against a load of 167k

    the tekmar's outdoor reset is almost a waste cause the trv's will be mostly closed, that's why i wanted a high flow but flat pump curve, the 1.25 riser kills my whole show

    told him he is going to get high head pumps and just have to listen to the noise - or re-pipe the risers, tough
  • bigugh_4
    bigugh_4 Member Posts: 406
    OK what if ?

    You timed each floor to come on only after the one below was heated to say, 67*F. That way the flow would be full for the time it was on for each floor. and lowering the floor ambient would mean it would heat up quicker. I know of no parameters other wise that would allow the use of the higher flow in that "dumb" main riser. The flow could be taken to five (5) feet per second. That is just at the noise and turbulent flow speed. Maybe even if there was extra flow above that needed for one floor, it could be "leaked" to the next,untill the one below was satrisifed. Just brain storming here!
  • Kal Row
    Kal Row Member Posts: 1,520
    Too complicated..

    He is getting a pair Grundfos 43-75 or equivalent in series – and have a nice day…

    I was just looking for someone that’s been through the same scenario, trust me, the amount of systems out there with properly sized circulators is probably less than 25%
  • Jed_2
    Jed_2 Member Posts: 781
    Still not clear

    on sub-system #6 detail piping. Your description does not clearly describe the 1¼" piping,i.e. 1-pipe, 2-pipe, P/S, with parallel reverse return. I hear you on small pumps/t'stats, vis-a vis "load match". You ran into a "stone wall". They get what they get, and live with it.

  • Kal Row
    Kal Row Member Posts: 1,520
    sub #6 is not being done by this contractor...

    it's being done by the city itself as they rent that floor, and they are just tying into our heat source, they also only just have a 1.25 pipe going down there - so they are going to have fun too...

    as for the #3, the 540kbtu air handlers, I recommended that instead of putting in an expensive pump where 54gpm is at the knee of it's curve, they should rather extend the passive system loop to the first floor where the air handlers are, reverse return and all, and use small circulators by the air handlers themselves

    with the advent of a staging boiler heat source, close-t'd into a passive system loop, it's like the loadmatch system - with one better - because of the reverse return piping of the passive system loop, each zone can get the same temp water - as opposed to close-t zones where the later ones get cooler water, and you can always use injection or mixing valve for a radiant zone, or do remote zones via minitube approach – and I’ve eliminated the bottleneck, limitations, and the “single-point-of-failure” of a system pump – it’s a beautiful thing – and long as the passive system loop is big enough for all the loads and piped “reverse” !! – hey, I recommended that instead of 2 big mightytherms sized for 75% of total each IBR, that they use 5 or 6 Weil McLain ULTRA310’s – will give them the same 1.47 million btu – for a fraction of the cost to buy and run – was like talking to the wall – theses idiots cant project the rising price of natural-gas – as they say, “you can lead a blond to Vasser, but you cant make her think!!!”
  • Kal Row
    Kal Row Member Posts: 1,520
    One more rule for a passive sys loop…

    Each pump must be able to pump it's zone plus it’s pipe sized and gpm share of the sys loop

  • Kal Row
    Kal Row Member Posts: 1,520
    another (but wastefull) way to get a flat pump curve...

    Any pump run backward has .25 to .40 the performance but is flat curved
    Take a 50gpmX30ft pump and run it backward and you get a 20gpm 10ft pump and that wont complain even if all the trv’s close down – though if water cooled – might overheat
    Also wont cavitate on low suction head - but it's wasteful, a forward small diameter but wider impellor is a better way

    A lot of air handlers use back-curved blowers if the filter is downstream from it, so that it don’t stall and overload the motor if the ac coils freeze over solid, if the filter is clogged upstream, it’s creating a suction and will actually un-load the motor, because there is less air to centrifugally spin, ever notice how the pitch of a vacuum cleaner goes up when you clog the inlet – pitch goes up cause there is less air mass to spin thus it turns faster
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    240,000 expected maximum load, right?

    288,000 output ability at 180° average temp, right?

    You're presuming a 20° delta-t, right?

    You're worried about moving 24 gpm @ 20° delta-t through a 1¼" pipe when 14 gpm is considered "safe", right?

    BUT YOU HAVE TRVs!!!!!!


    Forget about that darned 20° delta-t rule-of-thumb! It's almost meaningless with TRVs!

    With a 34¼° delta-t AT DESIGN CONDITIONS you need to move 14 gpm (e.g. the "no problem" rate).

    The radiation is already oversized based on 180° output so you never needed 180° average temperature to begin with.

    I'm not doing all the math for you here, but it would seem that the engineer did a very good job of sizing.

    Use your "standard" 190° max supply temp at design.

    Select a pump that can deliver 14 gpm at your head loss.

    Let the TRVs do the rest!!!!!!!

  • ALH_3
    ALH_3 Member Posts: 151

    Sometimes the usual assumptions lead us to do strange things.....simply to force those assumptions to be true.

  • Kal Row
    Kal Row Member Posts: 1,520
    thanks mike, i was thking along the same lines...

    just don’t have as much trv experience as you do... also it's a commercial building, and it’s setback to 55 overnight for freeze protection – so I was worried about the delivering those British guys on a cold morning with the trv wide open – I was even considering one large high flow/head and one small flat curved pump in parallel switched either or by the return water temp – because the differential pressure bypass valve, while it protects the pump it’s still wasteful – why run a 400watt pump when a 90watt pump will maintain the temp just fine when the trv’s are mostly closed

    there is a real need for a variable flow and head pump
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Setback Recovery

    How are you controlling the setback?
  • Kal Row
    Kal Row Member Posts: 1,520
    actually 2 ways...

    the tekmar 268 boiler control has outdoor reset and the zones will be wire with the new tekmar tN4 system with networked stats with setback program and outdoor reset -

    but i hear what ya thinking, "just let the tekmar ramp up the system in time - and don’t worry about ever having full flow”, - except, that i don’t like a system that cant go home to "momma" when the electronics dies and all hell breaks loose!!! - i always design my systems so that with a flip of one switch and a few ball valve moves, the system will revert to a one zone, boiler limit controlled show – “fail operational” – all Buderus systems come with such a switch – I call it the “run home to momma mode"

    where is Joe Mattiello when I need him, hey joe, don’t be insulted that I speced out Grundfos pumps, I have their data readily avail on my desk, the contractor will be using taco’s anyway probably a 012 – the original architect speced out B&G’s, and the boiler rep is pushing Armstrong’s – as the communists would say, “ke-pe-tah-liz-im – vot de-ka-dense….”
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    [Am confining myself to your TRVd areas here and I do assume that they will have constant circulation during occupied periods.]

    Actually, was hoping you'd say it was using the TRVs with integral setback ability...

    With t-stats you're relying on setback via "starving" the TRVs by either eliminating firing and flow altogether or keeping flow and reducing the supply temperature below the point they need to maintain setting. That's where your description of the piping should actually come in handy. Flow should be tolerably (but not ideally) balanced with the TRVs wide open. With boiler room on roof and downfeed through a single 1¼" main, flow should actually favor the top floor (where you have the roof loss) a bit. You're not going to get a lot of flow through any given baseboard, but you should get some at all.

    Regarding recovery, what you need to do is raise the supply temp to the max during the recovery period. Hopefully you'll start recovery some amount of time before the building opens. Am guessing that those are "smart" stats that can both calculate time required for recovery AND provide the necessary boost to the supply temp.

    You might not be able to get the maximum possible output from the b/b during recovery (because of the lower total system flow rate and thus lower average b/b temp) but you'll still be getting at least the amount required to heat the building in the coldest weather. In really cold weather such deep daily setbacks may well have a negative impact on comfort with little (if any) fuel savings.

    As to your fail-safe in the event of control failure/problems all you have to do is flip a switch that removes the electronics and operates the boiler up to high limit.

    In the fail-safe mode, flow will be really slow through the rads but as long as you haven't over-pumped for the size of the pipe, that sizing will again become your "friend". Your differential pressure bypass valve will start to bypass some of the water thus keeping your return temp reasonably high. Without the differential pressure bypass and running at high limit you could easily get return temps near ambient in really mild weather.


    If you utterly insist on using more circulation power, here's an idea:

    1) Pump with ability to move 18-20 gpm at your head loss.

    2) VERY near boiler in 1½" with a 1½" differential pressure bypass valve.

    3) Flow meters both before and after the bypass would come in VERY, VERY, VERY handy.

    4) Temp gauges for return in the TRVd areas and right by the boiler should be considered a MUST!!!!!

    4) From a cold start, adjust the valve for just a touch of bypass. (By indication if you have meters, by ear if not.)

    5) Over the season, train someone to "tweak" the differential pressure bypass such that maintenance flow through the radiation loop is NEVER above 14 gpm and return temps are within your "comfort level" for the boiler used. If it's someone who will really pay attention and do some calculations, they'll find they can actually adjust fuel economy via the bypass...

    By doing this you'll get higher-than-recommended flow ONLY when recovering from deep setback. Why? Because many of the TRVs will be wide open and there won't be sufficient head loss to further open the bypass.

    Your oversized pump will be happy as it will be moving water to its ability.

    Your TRVs will be happy because they won't have to "hold back" the force of an oversized pump.

    Your conventional boilers will be happy because you're keeping delta-t within reason regardless of your supply temp and current flow requirements of the TRVs.


    From what you've written, it seems you want to eliminate the differential pressure bypass valve.


    When properly adjusted, it has MULTIPLE functions in a TRVd system! Not only do they prevent circulator problems during extremely low (or no) flow conditions, but with conventional boilers like the Mightytherm, they help keep return temperatures up! With condensing boilers they help to keep boiler flow up during periods of low demand.

    Again, in your "fail-safe" mode where reset is deactivated you can easily get VERY, VERY low return temps through the TRVd circuits.


    Had I designed the piping system, I would have used larger tube for the main, but it would have diminished in size after each floors' takeoffs. NOT because higher flow was desired (or even needed) but to keep delta-p low and as consistent as possible when the TRVs are wide open...
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    While I've studied and observed the action of TRVs remember that I'm not truly in the trade.

    Will say that my recommendations will prove suitable provided your numbers are accurate.

    I "see" heat. God wired me to understand energy but not people.

  • Kal Row
    Kal Row Member Posts: 1,520
    most of what your saying is going in..

    the bypasses stay of course - using taco's with their procedure

    will probably be using 012 taco (flat with 25gpm at the knee of the curve)

    and the supply pipe steps down to 1" two levels down, but the return starts at level 5 then to 4 then to 3 then back to boiler on roof in reverse return fashion,

    the taco bypass set procedure is, to close the bypass, and run all loads at full open, then slowly open bypass until the it starts to get equally hot on the discharge side, then close it back one turn, and your done – since you bypass is now just closed, any load that closes will crack it open accordingly
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    The piping sounds better and better. Sure seems to me that the architect/engineer knew his business.

    Simple flat curve pump.

    Taco bypass setting procedure sounds good BUT, rather doubt that you'll be able to accurately determine when "it starts to get equally hot on the discharge side." 'Tis a point that must be observed when it happens yet it never seems to happen when you're closely watching...
  • Kal Row
    Kal Row Member Posts: 1,520
    the little piping fixes were my idea...

    the architect had everything in parallel, the biggest thing i still have to worry about, is cold returns, as these are not condensing boilers and the system is loop is passive I need a way to stop or bypass the zone pumps on themselves until the boilers come up to temp – though I daresay with the huge boilers and the reduced pipe sizes, it shouldn’t be that much of a problem,
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    And a good idea at that...

    Don't know if your staging controler is capable of this, but here's a way that I think would control them.

    Am still a bit confused about the system. Are those "anti-freeze" air handlers in the same space as the TRVd areas? e.g. used instead of the B/B during setback? Or in different space like a warehouse?

    Have you determined flow rates for the boiler circulators? Don't see them on your system drawing.
  • Kal Row
    Kal Row Member Posts: 1,520
    the boiler circulators...

    are then next to the little blurb with "b&g checktrol",
    those are for sure 0012 since the only resistance in that circuit is the boilers heat exchanger, i will get close to the full 45gpm out of each of them, which is inline with the architect’s spec of a 100gpm main loop pump is his old fashioned diag

    as for the air handlers, i intend to use tekmar tstats each with the slab sensor on the coil to protect from freezing and scorching

    as for boiler protection – because I am using the tN4 system from thekmar – I will probably have to add a mixing module with a mixing valve tn4 mixing module to protect the boilers and take advantage of the indoor feedback the new tN4 stats provide in their network
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    See the notation for the circulators now. Sorry I missed.

    But again are the air handlers in the same or different spaces than the TRVs?
  • Kal Row
    Kal Row Member Posts: 1,520
    in a diffferent space...

    4 space air handlers - 540 kbtu tot, and 4 over the door air curtains 180kbtu total – all on the ground floor in wedding hall, I did not do the heat loss over there, I am going with the architect’s, since his radiation for the other spaces was close enough

    no trv’s on those - as they will be running together
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Let me make sure I have the general primary (boiler) pumping strategy right.

    One, the other or both boiler circulators can be in operation.

    Say only one boiler circulator is operating and it's moving 43 gpm. Only the TRVd zones are currently being supplied with heat and they're drawing* 13 gpm. That means 30 gpm of the flow is heading back to the boiler via the connection in your 4" header. Correct?

    * By "drawing" I mean that while the TRV zone circulators are actually moving say 28 gpm, that only 13 gpm of that flow is heading through the radiation with [ideally] the other 15 gpm heading back to the system via the differential pressure bypass. If that flow through the radiation seems low, it's because I'm imagining moderate weather with the supply temperature somewhat inflated because you're using conventional boilers that can't be fully reset.

    Sorry for all the questions. I don't mind sticking my foot in my mouth occasionally, but try to avoid the entire leg.
This discussion has been closed.