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1/2" Pex-Al-Pex to 3/4 baseboards

voronvoron Posts: 10Member
Good day everyone,
I am working right now to add few Stant Fin 30 baseboards to heating system. I would like to use Pex-Al-Pex 1/2" pipes. My concern, that this type of baseboards has 3/4" pipe. Longest run will be 35-40 feet. Cam i just use regular 3/4 to 1/2 connector?
Also , s anything wrong if i will use this actuators
https://www.supplyhouse.com/Bluefin-HMACT4-4-Wire-Thermal-Actuator-for-Bluefin-Manifolds?gclid=CjwKCAiA9efgBRAYEiwAUT-jtM63PGRTn36bY06MkC34CNLYI-CfDBHdjrtXe-idKCZFwX33FW7DEhoCvV4QAvD_BwE
I am really appreciate any help.
Thank you

Comments

  • NY_RobNY_Rob Posts: 1,369Member
    edited December 2018
    You risk underflowing your boiler if one of the 1/2" piped zones comes on by itself without any other zones being open. And, the 1/2" fittings reduce flow even more.
  • 30 feet x 500 BTU's per foot = 15,000 BTU's which max's out the 1/2" pipe.

    So, if you go over 30 feet of baseboard you might not get full baseboard output.
    Often wrong, never in doubt.

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  • voronvoron Posts: 10Member
    edited December 2018

    .

    Thank you for your respond Alan. I think i was not clear enough. When i talk about 35 feet run, i mean whole loop. It will be not more than 12 feet of baseboard in the loop. Each room will have it's own loop. Is it possible to use 1/2 PAP pipes or i need to go with 3/4 PAP pipes?

  • voronvoron Posts: 10Member
    edited December 2018
    NY_Rob said:

    You risk underflowing your boiler if one of the 1/2" piped zones comes on by itself without any other zones being open. And, the 1/2" fittings reduce flow even more.

    It will be "navien" NCB-240
  • NY_RobNY_Rob Posts: 1,369Member
    The NBC-240.... is a mod-con boiler with a minimum output on lowest fire of 18,000BTU's.

    A fin-tube radiator only puts out 260 BTU's/ft with 130deg Average Water Temp (assume 140F Supply Water Temp), so your 12' length of fin-tube is only putting out 3,120BTU's and your boiler can't supply less than 18,000BTU's.
    Somethings got to give.... your boiler will short cycle it self to death with tiny 3K BTU zones.

    You will need to combine zones to get close to the minimum 18K BTU figure or use a buffer tank.
  • voronvoron Posts: 10Member
    NY_Rob said:

    The NBC-240.... is a mod-con boiler with a minimum output on lowest fire of 18,000BTU's.

    A fin-tube radiator only puts out 260 BTU's/ft with 130deg Average Water Temp (assume 140F Supply Water Temp), so your 12' length of fin-tube is only putting out 3,120BTU's and your boiler can't supply less than 18,000BTU's.
    Somethings got to give.... your boiler will short cycle it self to death with tiny 3K BTU zones.

    You will need to combine zones to get close to the minimum 18K BTU figure or use a buffer tank.

    Thank you very much for your respond.
    It will be 2 floor.
    First floor will have 6 loops(each room will have it's own loop). It will be 45 feet of baseboards.
    Second floor will have 3 loop 45 feet of baseboards
    Lines will be 1/2 PAP.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,802Member
    1/2 inch will feed 12' of baseboard without an issue. @Alan (California Radiant) Forbes is correct
  • BrewbeerBrewbeer Posts: 576Member
    Do you have any other radiation in the house other than the 90 feet total of baseboard? I wouldn't expect 90 feet of slant fin 30 to put out more than 50k BTUs/hr connected to a mod con. That's only about a 1/4 of that boiler's maximum rated output.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
  • GordyGordy Posts: 9,264Member
    Are you home running each baseboard section to a manifold location?
  • voronvoron Posts: 10Member
    Brewbeer said:

    Do you have any other radiation in the house other than the 90 feet total of baseboard? I wouldn't expect 90 feet of slant fin 30 to put out more than 50k BTUs/hr connected to a mod con. That's only about a 1/4 of that boiler's maximum rated output.

    Not yet. Potentially i am planning to add basement - around 800sq ft radiant floor or another 45ft of baseboards and this Navien will be used for hot water. Also in future i have plans to install radiant floor oma first and second floor during reconstrauction. As i understand it's not a problem if this kind of water heater will be used to produce 60-80kBTU
  • voronvoron Posts: 10Member
    Gordy said:

    Are you home running each baseboard section to a manifold location?

    Not now. But i would like to use this design and install two manifold for each floor. Or do you think possible to use one manifold for 2 different zones?
  • voronvoron Posts: 10Member

    1/2 inch will feed 12' of baseboard without an issue. @Alan (California Radiant) Forbes is correct

    Thank you very much. Does it means, that if length of baseboard 12 and less, i can connect 1/2 pap to 3/4 baseboard with simple eccentric fitting 1/2x3/4 ?
  • KC_JonesKC_Jones Posts: 4,114Member
    > @voron said:
    > Do you have any other radiation in the house other than the 90 feet total of baseboard? I wouldn't expect 90 feet of slant fin 30 to put out more than 50k BTUs/hr connected to a mod con. That's only about a 1/4 of that boiler's maximum rated output.
    >
    > Not yet. Potentially i am planning to add basement - around 800sq ft radiant floor or another 45ft of baseboards and this Navien will be used for hot water. Also in future i have plans to install radiant floor oma first and second floor during reconstrauction. As i understand it's not a problem if this kind of water heater will be used to produce 60-80kBTU

    What is being eluded to here is, that choice of appliance is way oversized for what you are trying to do.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    https://www.facebook.com/media/set/?set=a.10202744301871904.1073741828.1330391881&type=1&l=c34ad6ee78
  • NY_RobNY_Rob Posts: 1,369Member
    Why don't we start this back at square one?

    Is the NBC-240 already installed and running at this time?

    If it is, please describe the zones it currently serves (length of fintube in each zone, zone valve or circulator for each zone, etc..).
  • BrewbeerBrewbeer Posts: 576Member
    @voron how do you plan to heat DHW?
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
  • GordyGordy Posts: 9,264Member
    The ncb 240 e is a combi
  • NY_RobNY_Rob Posts: 1,369Member
    Is it a NBC-240 or 240E?

    The OP only wrote ""navien" NCB-240"
  • voronvoron Posts: 10Member
    NY_Rob said:

    Why don't we start this back at square one?

    Is the NBC-240 already installed and running at this time?

    If it is, please describe the zones it currently serves (length of fintube in each zone, zone valve or circulator for each zone, etc..).

    II am still on a design stage. Right now i have forced air furnace.
  • voronvoron Posts: 10Member
    Brewbeer said:

    @voron how do you plan to heat DHW?

    Yes, water boiler is really old an i am planning to start use NCB-240E for this purpose. But looks like i need to look om 150e or 180e.
  • NY_RobNY_Rob Posts: 1,369Member
    Well the good news is that you haven't made any purchasing mistakes :)

    Have you done a heatloss analysis for the home yet?
    If not, slantfin has an app you can install on your phone that will allow you to estimate your total heatloss in BTU's so you can right-size your boiler as a first step.

    Once you have your total heatloss figure and correct size boiler calculated, you can start to size radiators, etc... to match heatloss.

  • GordyGordy Posts: 9,264Member
    If you are going with a combi then you will need to look at what combi fits your needs.

    Personally I think a nice boiler, and an indirect are a better option.
  • BrewbeerBrewbeer Posts: 576Member
    voron said:


    II am still on a design stage. Right now i have forced air furnace.

    I did a HWBB conversion In my house a few years ago, check out the design thread linked in my signature.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
  • voronvoron Posts: 10Member
    Thank you everyone for advice.. I will do a drawing,measuring and calculations and will present everything here in a few days
  • GWGW Posts: 3,406Member
    Don’t know if your question was answered—-yes you can run 1/2 Pex to 3/4 BB, no prob

    Put the reducing coupling wherever. Don’t overheat the BB tubing

    You might want to consider a heating only boiler with an indirect water heater
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
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