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Hydronic retrofit - circ pump and low loss header sizing

moosepucky
moosepucky Member Posts: 29
edited December 2015 in Radiant Heating
I have a 1950's monoflow hydronic system I need to replace the boiler on.

Sq footage to heat is around 1400 sq ft

Monoflow "race track" is 1 1/2" iron

overall length is around 110' with 15 Beacon-Morris convectors, 3 slant fin baseboards, and a single Beacan-Morris under cabinet kicks space unit

I've chosen a Bosch Combi 100 (89k btu DHW/boiler). This is the correct size for my home's size, age, and climate zone.

The new boiler has 1" supply and return (race track is 1 1/2")
  1. I need a low loss header (preferably with an integrated drain) that will work with the boiler and existing supply/return.

  2. I need to size a variable speed circulator pump (1 1/2" flanges)
I've been banging my head around this for a few weeks and like a marry-go-round I always come back to the same place (dizzy but with no answers).

I have come across this site that gives the flow rate of various sized hydronic piping and for 1 1/2" it says 25 gpm

http://highperformancehvac.com/boiler-piping-flow-pipe-sizing/

I cannot find any info on my existing circulator pump to give me an idea of its size.

For some reason the sketch that was in one of my responses gave up the ghost on photobucket so this is the existing piping layout




Some pic of the pump and motor plate below






«13

Comments

  • delta T
    delta T Member Posts: 863
    So a couple of things. That link is just....well, wrong. Mostly. Some correct stuff in there, but mostly not. For one thing, laminar flow happens when the flow rate is too low, not too high, and you cannot size a pump based on pipe size, it must be sized to the demands and limitations of the system. Their head loss formula is an old one from the Bell and Gossett company and was intended mostly as a rough guess for figuring a bid more than anything else. While I will be the first to say it does work surprisingly well a good amount of the time on larger commercial apartment buildings and the like, it tends to way overestimate smaller residential systems. 25 gpm seems pretty high.

    Okay it seems REALLY high for a residential system with a boiler that will put out ~87,000 buth (an optimistic number based on the boiler running at 180 supply water temp for your emitters)

    Some questions:

    1. Was a detailed heat loss actually performed? if so what was the number?
    2. Why the variable speed circ and what kind (delta p, delta t)? Do you have different zones? (see no. 4, if you do have zones then you probably do want a variable speed pump. on the system side only please!!)
    3. How the hell do you have still have the original motor on that old B&G pump!?? seriously cool to a lot of the nerdy wet heads here! (unfortunately to get an accurate curve on an older pump like that you would really need to disassemble and measure the impeller, as well as find info on that specific volute which can be tricky in my experience. Best bet is to size based on what the system actually needs, not on what was there before.)
    4. Why the LLH? if this is monoflow in a house that is only 1400 sq ft, I would be surprised if there were different zones, which would mean you don't really need a LLH. If there are different zones then yes you should have LLH and I would recommend getting a Caleffi product that will do air and dirt separation as well, they make several different ones and we can chose one once we know more about the system.
    5. Can you post some more pics of the piping near the boiler please?
    6. How many feet of slant fin do you have? What are the sizes of the BM convectors, and the toe kick.
    7. Can you post a picture of one of the diverter tees? there are two styles, and they have different properties.
    8. Can you get a rough schematic drawing of the layout of the system side (convectors, baseboard w/ lengths etc)
  • moosepucky
    moosepucky Member Posts: 29
    #1) No. Could not find anyone who was interested other than replacing the existing 190k in 144k out boiler with the same thing. Way too much boiler as it never reaches shut off temp until heat call ends. I set it down from 180 to 160 and now the boiler cycles while the pump keeps circulating

    #2) single zone, monoflow. Crane venturi T return with standard T supply (I am assuming the monoflo is a Crane but only the standard T is marked Crane).

    Variable speed pump was recommended by Bosch tech support for that boiler.

    #3) Original pump is a bruiser. Wakes me every morning when it fires up. I keep it WELL oiled and it has never given me a day's worry in the 25 years I have lived here.

    #4) Bosch tech support recommend a LLH, no not recommended, they said it was necessary based on what I told them the old system was (1.5" monoflow).

    #5) Pic of boiler below. Tell me if you need to see more specific areas of the piping. New boiler will be relocated as I do not want to pump condensate.

    #6) B&M convectors are original to the system and varying sizes most common is 4 foot x 6 inches and 3 foot x 6 inches all of them are three tubes and are 1/2" feed (pic). If you need a survey of all convectors and room sizes they are in I can do this (I already know the answer).

    All convectors have separate loops for each unit

    -slant fin #1 is 3 sections in a bay window (two 3' and one 5') they are 3/4" feed
    - slant fin #2 is one 4 foot and one 5 foot 3/4" feed (forgot about this one in the OP)
    - B&M toe kick is M-84 1/2" feed that chokes the 3/4 down at the unit then back to 3/4 after it leaves,

    The slantfins and toe kick are all on a single long loop with the toe kick the last one on that loop (see below) and always stone cold

    #7) pic of Ts

    #8) I'll do a sketch but most runs on main floor are very short @ 3' in to convector then 3' back. second floor is obviously longer.

    the original system is VERY well balanced as there are no hot or cold rooms, all seem to be exactly the same room temp.

    Cape Cod original house is 35' x 25' x 1.5 o r 1312.5 sq ft.

    Addition is run by a single monoflow T LARGE loop with all of the slantfins and the toe kick and is stone cold (long story but MANY air loops and NO bleeders......) Addition is dining room and kitchen with a bath and hallway above kitchen which all get hydronic. These rooms also get air to air heat and AC from a Carrier Infinity that is in another/seperate section of the house so I did not calculate them in too heavily.

    I need to redo all of the addition hydronic heating. Add 2 more monoflo loops for the 2nd floor and for the kick (keeping the bay window on the existing loop) I will get rid of all the up and down loops AND put bleeders on everything.

    Contractor on the addition had the plumber do the heating. I remember him saying "I've never done this before but it can't be that hard" OY.....

    Let me know what additional info I need to provide to you.

    Convectors



    Monoflo Ts





    Old boiler




    New Bosch sitting on palette for the past 3 weeks.



  • delta T
    delta T Member Posts: 863
    Awesome, let me do some digging, I will see what I can come up with, and will let you know if I have any more questions. I will get back to you tomorrow, Others may beat me to it!

    LLH may be necessary for that boiler depending on boiler flow requirements, I am not intimately familiar with that product. Did Bosch say why they want a variable speed pump? I can see a delta t pump maybe, but with a single zone system without TRVs or anything on it a delta p pump makes no sense. outdoor reset can usually do a good job of regulating proper system output without a delta t pump. It worked before right?

    Those old B&G pumps can be trouble free for 50 yea rs if properly maintained. Industry standard for many many years. Built to repaired too. Almost every part in that pump can be replaced or rebuilt in the field. Not the most efficient things by today's standards though... :smile:
  • SWEI
    SWEI Member Posts: 7,356
    delta T said:

    Those old B&G pumps can be trouble free for 50 years if properly maintained. Industry standard for many many years. Built to repaired too. Almost every part in that pump can be replaced or rebuilt in the field. Not the most efficient things by today's standards though... :smile:

    But they could be, if someone built an ECM replacement motor. Build it on a 1/4 HP platform and programmable firmware and you could repower dozens of models spanning multiple manufacturers' lines.
    delta TRich_49Gordy
  • delta T
    delta T Member Posts: 863
    @SWEI thats brilliant. Love your thinking.

    @OP I apologize for not getting back to you got tied up in a boiler last night until about 10. Today *should* be an easy day, so I should be able to get some answers to you tonight.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,367
    Don't those tees need to be a minimum of 18" apart??
  • GW
    GW Member Posts: 4,330
    Not a great pic yet you can see the 2" jumbo header we use on all wall hanger installs. This is Alberta Tee stock.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • GW
    GW Member Posts: 4,330
    Hat, this is a combi, more btu is needed.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • moosepucky
    moosepucky Member Posts: 29
    My understanding is the boiler is variable burner and if combined with a variable speed pump all should be well.

    the combi 100 is the smallest combi boiler Bosch makes. They list it at 79k btu max output

    http://www.bosch-climate.us/products-bosch-thermotechnology/boilers/residential-boilers/greenstar-gas-condensing-boilers/greenstar-wall-mounted-combi-condensing-boiler.html

    I am looking at LLH units with 1.5" connections and these seem to be 26 gpm flow which is why I am looking at a 0-28 gpm variable pump.

    I am trying to run a heat loss profile but since I have never done this before it is a little daunting.

    This online HL calculator is the one I am working with.

    http://www.loadcalc.net/

    they do not have a selection for cement block construction only brick and frame. Closest would be brick but not really as most brick is over 2x4 framing, mine is 1x2 furring as the block is structural.

    is there something I could use that would be closer to the type of home I have?

    1950 built cape cod. Block with no insulation. 1x2 furring and drywall. Single glass wooden double hung windows with old aluminum storm windows. Solid wood doors with store doors. Minimal to no attic insulation (yea I know....), no insulation between roof and cape walls on 2nd floor. Convectors on outside wall with maybe 2" between convector and outside.

    I would say heat loss would be above average but still working on a #
  • moosepucky
    moosepucky Member Posts: 29
    running what I have through that online heat loss calculator comes out around 39k btu loss but I am sure that I missed a few things which might take it a tad more.

    When I spoke to Bosch tech dpt before ordering the boiler they felt that the unit I got would be "close" to what I would require.

    I would like a little "wiggle room" as someday I would like to add a 2nd zone in addition to the monoflo in the old part of the house. this zone would be around another 1300 sq ft. I doubt this will ever happen as last year I had to replace the air furnace because of a bad heat exchanger that was allowing flue gas inside. I have been so happy with the infinity that running a 2nd zone hydronic does not seem viable any longer, even though I have 3/4" copper running from the boiler up to where I need to install the baseboards (NONE of it is hooked up to the boiler).

    Don't ya just hate working with people who can't make up their minds.

    I need to get past the LLH and pump so that I can start dry fitting things as there is NOT a lot of room where the new boiler is mounted and it will be a TIGHT fit with N/C DWH, gas, electric, supply/return, LLH, and pump.




  • Gordy
    Gordy Member Posts: 9,514
    The LLH does not need to be sized to the 1 1/2" piping it needs to be sized to the required flow rates to delivered the required btus to the system. Along with the circulator.

    1 1/2" piping can deliver 225,000 btus
    1 1/4" 145k
    1". 72k
    3/4" 42k
    1/2" 15k
  • GW
    GW Member Posts: 4,330
    Moose, just becasue it's 1 1/2" certainly doesn't mean you need to pump 15 gpm. With that large piping your head loss is minimal, just install an Alpha or equivalent. Remember your ZWB has an internal pump, so you could simply use close space tees. Use a LLH if you feel the need. It's good to use a cleaner on the system before draining down the old boiler.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • moosepucky
    moosepucky Member Posts: 29
    @Hatterasguy

    The mono flow piping is existing and original to the house (black iron).

    The "old/original" monoflo system is well balanced.

    there was a "tear down" of an enclosed porch which had 2 convectors in it that were added to the original piping using 3/4" in/out T + venturi. the porch was enclosed about 2 years after the house was built (early 50's). The monoflo system is 1 1/2" race track with 1/2" in/out T + venturi to the convectors.

    the contractor who did the tear down of the enclosed porch and new addition for us, "reused" the abandoned 3/4" T + venturi in the monoflo system to run 3 slant fins in a new dining room bay window (11' total) then up a wall to a hallway and bathroom on the "new"second floor (9' of slant fins), then down the wall to a under cabinet kick space radiator in the new kitchen, then back to the front of the house to the old/existing venturi connection.

    this may be confusing as it "exists now" but the new boiler work will include reworking this large loop

    This long loop has never worked.

    I plan to keep the 11' in the dining room bay window on the original/existing T + venturi loop. this would be 4' to the baseboards then back to the main race track monoflo

    I plan on cutting in 2 additional T + venturi loops (one for the 2nd floor another for the kick space radiator).

    This will eliminate the "too much" large loop and make things more balanced.


    @GW

    I plan on using a Fernox Boiler Commissioning Kit cleaner/conditional through the old boiler before taking it off line.

    __________________________________________________________

    Would this smaller 1" Spirotherm LLH be a better fit for my needs? The 1" model is 10 gpm (1 1/4" flow is 15 gpm) the 1 1/2" LLH I have been looking at is 30 gpm

    http://www.spirotherm.com/sites/default/files/Quad-3.pdf

    Bosch boiler is 1" supply/return.

    Thanks

    Das Moose

  • Rich_49
    Rich_49 Member Posts: 2,627
    Your wall assembly has an r value of 2.6 . 8" block , no insulation in cavity , 3/4 air space inboard , 1/2 Drywall .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • GW
    GW Member Posts: 4,330

    GW said:

    It's good to use a cleaner on the system before draining down the old boiler.

    I love that idea Gary. Any reason not to put the cleaner in the old system and let it run for one week?

    Any preferences for manufacturer?
    I guess longer the merrier if it's all getting yanked out, I haven't heard of 'too long' being a problem, but i can not see the smarts in letting it sit there for weeks on end. I have the Fernox in stock, yet the Rhomar is its equal I understand.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • moosepucky
    moosepucky Member Posts: 29
    @Hatterasguy

    I like the specs on the Taco variable speed pump you recommended. 18 gpm should be more than enough from what every one has said based on the existing B&G pump (if I can get the Taco in 1 1/2" flange). Thank you for this recommendation!!!

    As far as restricting other loops, I would need to do this at each radiator as all of the radiators get fed from a single 1 1/2" race track pipe that runs in a circle around the basement (there is only 1 loop and all radiators feed in/out off of this single loop, even the newer 6 radiator loop is nothing more than a badly designed feed off of the monoflo).

    It's the monoflow that has thrown most of the HVAC folks around here. Almost all would rather tear it out and run manifold and separate radiator supplies and returns rather than deal with a single feed monoflo

    Low Loss Header:

    Will I get in trouble using the 1 1/2" Spirotherm LLH ?

    I'm not sure I want to get into running from 1" at the boiler to a 1 1/4 LLH (15 gpm flow) then up to the existing 1 1/2" race track

    Transitioning from 1" up to 1 1/2" at the boiler (after a union) then sticking with 1 1/2" from there onward "seems" to be logical as long as the 30 gpm (max flow) LLH will not throw a gremlin into the system but what I know about hydronics would fit in a small half empty beer can.

    I'm just stuck at the LLH and pipe sizing. I do not want to tear out the entire feed loop and put in something smaller even though it looks like this would be the best thing to do (efficiency wise).

    I "can" use 3 different size feed and return piping from the boiler, through the LLH and pump then to the existing single monoflo feed if it is necessary.

    the only parts I have not purchased for this are the LLH and the pump. the rest is pretty straight foward, 2 new T out and venturi back into the monoflo.

    I will have to remove a 25' section of 1 1/2" iron and replace it with copper where the 2 new feeds will go. this is OK as I am relocating the boiler at the same time so new monoflo at one wall was in the cards anyway.

    I've read about close Ts and even using 2 venturi (first one reversed) to force more flow though a long supply run and my 2nd floor hall/bath slant fins is 20' out, 10' up a wall then back. It will be the longest feed on the loop.

    Has anyone used 2 ventur Ts in this manner outside of forcing water down to a radiator? If I use 2 ventruri Ts do they need to be separated more than a standard T and venturi combination?




    I don't want to foo bar this up as redoing it would not be in the cards. I'm not big on soldering large copper and the thought of putting a wrench on that 65 year old iron is giving me the willies.
  • moosepucky
    moosepucky Member Posts: 29
    edited November 2015
    Here is a sketch of the existing boiler and feed layout and a photo of the old boiler with the monoflo pointed out.

    I will do another sketch with what I want to do in the way of breaking out the large feed/return that does not function (the green one in the sketch)

    for now this is what exists (original boiler/piping)

    Each radiator has its own individual feed/return with the exception of the green (bad one) which has 6 radiators on it.






  • moosepucky
    moosepucky Member Posts: 29
    Here is a sketch of how I want to change the system

    New boiler location

    Add 2 additional 3/4" T + venturi for the rad feed/returns that don't work as a single large feed/return


  • tbrooks
    tbrooks Member Posts: 100
    Interesting, and sorry for the mess you are trying to figure out. I just wanted to point out what Hatterasguy is trying to tell you, if you haven't figured it out, is that the more gpm, the less heat is being lost by the water as it passes through the various emmiters. Slow the water down and it will release more heat, and with it all balanced properly (the right flow for each emmiter), you will get the heat you want from each emmiter
  • Paul48
    Paul48 Member Posts: 4,470
    I'd bet a DT circ doesn't work with a monflo system. The one reason series 100's work is flow. You slow the circ down for a certain DT and you will have problems with uneven heat.
  • Paul48
    Paul48 Member Posts: 4,470
    edited December 2015
    We've seen many folks come here that replaced a series 100 with a 007, and wonder why their system doesn't work anymore. I hope you have good luck with yours.
  • moosepucky
    moosepucky Member Posts: 29
    all of the old/original convectors in the system have bleeders and an inflow valve that I did not notice before. the bleeders are at the top of a copper "tower" Is this so that they do not need to be bled as often or are these mini expansion tanks?




  • moosepucky
    moosepucky Member Posts: 29
    @GW - Remember your ZWB has an internal pump

    This is what Bosch says about the internal pump:

    "Bosch
    :Greenstar Internal circulator
    can support a single zone loop
    not to exceed 4 gpm at 12 feet of
    head. See pump curves in
    manual for pump capacities at
    alternate flow rates.
  • Gordy
    Gordy Member Posts: 9,514
    edited December 2015
    question is what will the convectors do with less than .25 gpm on average. if the 4 gpm goal is achieved. 4 gpm / 15 convector loops. Counting future additions.
  • GW
    GW Member Posts: 4,330
    tbrooks said:

    Interesting, and sorry for the mess you are trying to figure out. I just wanted to point out what Hatterasguy is trying to tell you, if you haven't figured it out, is that the more gpm, the less heat is being lost by the water as it passes through the various emmiters. Slow the water down and it will release more heat, and with it all balanced properly (the right flow for each emmiter), you will get the heat you want from each emmiter

    T, I don't quite get the general logic on this, won't the emitter be hot if the flow is higher than necessary? The convection process doesn't know how fast the water flow is, it just does its thing naturally. Gary
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • GW
    GW Member Posts: 4,330

    @GW - Remember your ZWB has an internal pump

    This is what Bosch says about the internal pump:

    "Bosch
    :Greenstar Internal circulator
    can support a single zone loop
    not to exceed 4 gpm at 12 feet of
    head. See pump curves in
    manual for pump capacities at
    alternate flow rates.

    Yes, as a habit i have been adding a second pump for the distribution. We did one install a while back where we 'just' used the internal pump for the distribution (a small AHU 20 feet away). You certainly need a second pump
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Rich_49
    Rich_49 Member Posts: 2,627
    @GW
    Stacking heat in an emitter faster than it will allow natural convection to transfer it to the reservoir is self defeating . That process will only take place as fast as it will at varying conditions . When trying to get the RWT to the boiler as cold as we can while still heating the space adequately makes stacking heat in the emitters the worst thing we can do .

    Some in the industry have mistakenly perpetuated the idea that we need more flow or turbulence throughout the entire operating range . This is just not so . Just because the math works does not mean we should do it , example ,
    4 gpm = 16,000 / 8 x 500 . Maybe we can stop perpetuating this myth and start designing properly and recognizing the age old statement , " You can't fool Mother Nature " . There are no mechanical solutions to natural problems that will save or use less energy .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • GW
    GW Member Posts: 4,330
    Thanks Rich, I didn't say it was 'good' to overflow, I'm just saying the heat will still work. If you increase the flow but decrease the dT, the math will be pretty similar. I haven't sat on a test bench to test these points, but you're right, you 'can't fool mamma nature', that i agree. But mamma does allow the math the change and get the same result.

    Same with a warm air furnace. the btu's don't change much if you increase air speed and decrease the temp rise.

    The gpm x dT x 499.8 is iron clad. the gpm and the dT is not.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • SWEI
    SWEI Member Posts: 7,356
    Just think AWT.
    GordySuperTech
  • Paul48
    Paul48 Member Posts: 4,470
    My mention of flow was only related to the presence of monoflo tees in the system. It had nothing to do with the thought that greater flow means more heat transfer. Only that the tees may not function desirably at the reduced flow created by a DT circ. Operative word is "may".
  • moosepucky
    moosepucky Member Posts: 29
    I am completely lost now.
  • GW
    GW Member Posts: 4,330
    Moose, yes we have big gun syndrome, the shorter we can make our messages the bigger we feel, and that means acronyms galore.

    So, what system pump are you going with?
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • moosepucky
    moosepucky Member Posts: 29
    I am at a complete loss on the pump and LLH.

    there was a sale (blanket % off all orders) at one of the suppliers I have used but it is off in a few minutes. I have a few more "bits" in the cart that I may get (flush/venturi/bits)

    I'm thinking I may just hook the boiler up to flue, gas, DHW and electric. then drop back and punt on the heat supply/return, just hooking it as a short loop in/out using the internal pump until I understand what I am doing a LOT more.
  • GW
    GW Member Posts: 4,330
    I feel you bro- my head hurts when i talk to my financial adviser people, the terminology just kills me (not that i do much with them people, just IRA stuff). The boiler has 1" taps, just use a 1" LLH. If you want to humor yourself and go larger, have at it, you're not doing any harm but spending a bit more $.

    The pump, you can get dizzy with engineering figures or install an Alpha, they always seem to move the water in almost all 'normal' sized residential systems. The cool thing with the Alpha is you can simply push the mode button to get more or less flow. That way you can dial in some temp drop figures as you run the system. I don't have any experience with other ecm pumps for residential heating (I have installed a few Wilo Stratos pumps, for bigger jobs/ geothermal, etc)
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • moosepucky
    moosepucky Member Posts: 29
    I added the 1" (10 gpm) LLH to the order. From what I have found out it should be fine

    I found the info on this page helpful but I am still lost

    http://jbblog.flopro.taco-hvac.com/flow-rate-head-loss-chart/

    GPM = BTUH ÷ (ΔT x 500)
  • Gordy
    Gordy Member Posts: 9,514
    There you go learn it well.
  • moosepucky
    moosepucky Member Posts: 29
    It seems when I throw in the large pipe monoflo everything I read does not apply.

    Does anyone do large supply monoflo systems in residential anymore?

    All I am reading is manifold + home run supply/return with zones.
  • Gordy
    Gordy Member Posts: 9,514
    @moosepucky

    Think of the pipe as a conveyer belt to deliver btus to the emitters. If you pipe it with a LLH then there are two conveyor belts.

    So your at the quarry and there is a guy with a back hoe loading the 1st conveyer belt with btus that the boiler makes. It's dumping into the second conveyer belt (LLH) going out to the system. At the end of the system there are dump trucks hauling away btus as needed to the emitters when the thermostat calls for heat.

    The most efficient operation is when the conveyer belts are at the right speeds to deliver the btus to their different unloading locations as demand is needed. The belts don't run to fast using more electricity than necessary or to slow keeping the trucks waiting for btus. The goal is to deliver exactly the amount the trucks need for the btu order they get.

    If the conveyer at the boiler is running slower than the boiler makes btus the guy in the back hoe ends up with a huge pile of btus building up because he cant get them out to the second conveyer fast enough because the first one is moving to slow. The boiler shuts down until the back hoe catches up.

    If the conveyer at the boiler is moving faster than the second conveyer then the btus pile up in the low loss header, and go back to the boiler ending up in a big pile again. Boiler shuts down.

    Ideally what you want is to deliver, and use the exact amount of btus being produced, and used out in the system. If anything need be sacrificed the second conveyer for the system should always run at the same speed, or faster than the one at the boiler.

    If you pipe the boiler direct same analogy applies except there is only one conveyer. But the conveyer is directly tied to the btu producer so conveyer speeds are even more relevant. To slow the btus back up boiler shuts down. To fast the comveyer spins at a speed not necessary to distribute the btus being produced wasting electricity.

    Now the pipe size same thing it's the conveyer belt. To small it can't carry enough btus to satisfy the demand. To big well you spent more money than you needed to for a bigger conveyer than necessary to deliver the peak demand, but it still works.

    To indirectly answer your question no mono flo systems are a thing of the past. But it's still a delivery system that follows the same principles as the hydronic formulas dictate.

    Personally I think there is a fine line between flow rates, and deltas verses varying loads. We embrace the formula differently with variable speed pumping, and trying to hold a delta through the whole range of demands. Where before the delta t applied to peak demand (design day) and from there down the delta was what it was, narrower because the fixed speed circulator was selected for that peak load, and no one cared, and the technology was not there. So flows were more than needed on less than design load days.


    Sorry if I confused you more.
  • GW
    GW Member Posts: 4,330
    Yes, my brain does better with remembering the other direction, gpm x dT x 500 = btu.

    If math isn't your cup of tea them it's time for a beer or some other refreshment. Here are some pointers to try to simplify this.

    Your heat loss can be plotted out via heat loss programs but it's just theoretical. Virtually no one knows there true infiltration in their home. To know that you need a blower door ( I have the esteemed Retrotec blower door). And we rarely know the exact r value in walls. Glass U factor is often a good guess. Do you see my point? Don't do back flips in a smaller home. Your boiler had a Modulating burner. So.... don't get crazy with gpm numbers. If your boiler can ramp up and down, and a good modern pump can do the same (manually adjust it), why kill yourself trying to chase these moving targets?

    I have a Viessmann Vitodens 100 in my home. The supply and return connections are 3/4". The piping inside the boiler looks more like 3/4 OD. Do I get funky and worry about how much heat the 91000 btu boiler can move through its heat exchanger? Heck no, I just drop the puny 3/4" lines to a 2" jumbo header.

    Don't over think this stuff, life is too short.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
    Bob Bona_4