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Pipe size, layout, and heat loss questions

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Pulse
Pulse Member Posts: 78
edited October 2019 in Radiant Heating


I am switching from an all electric house to a gas boiler. I plan to run this system @ 120 degrees. The above image is my planned piping layout. If there are any changes I should make, please let me know.

My specific questions are regarding pipe size.
1) The boilers inlet and outlets are 1". Is there a formula I can use to determine what the main supply and return should be? Should I keep it say 1" until after the hydraulic separator, then increase to 1.25-2", or what?
2) The home run manifolds available seem to only come in 1" or 1.25" trunk, so that makes choosing the pipe size off of the main supply/return either 1/1.25", once I have the formula, correct?
3) Once at the home run manifolds I plan to transition to 1/2" Uponor expansion pex. Again based on what is sold, it seems that 1/2" pipe size is already decided for me. Only option would be to decrease the size to 3/8", which does not seem appropriate in any situation.

My delta T/temp difference is 63 degrees, using 7 degrees as my outdoor temp and 70 as my indoor temp. The 7 degrees was used based on the 99% rule. (This is one variable needed for pipe sizing?)

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I drew my house floor plan, you can take a look here: https://imgur.com/a/p9TT3IV
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I am currently calculating my room by room heat loss, but heat loss is a tricky beast for someone doing it for the first time. I currently have a total loss of 44,384 BTUs calculated, however, I am not exactly sure all my calculations are correct, especially my air infiltration and slab loss calculations. I have an entire excel spread sheet I attached to this post.

Appreciate any help, thanks!

Comments

  • JohnNY
    JohnNY Member Posts: 3,230
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    For delivering 44.3MBH, 1" copper will be fine.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
    STEVEusaPA
  • Pulse
    Pulse Member Posts: 78
    edited October 2019
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    I do not need to take into account my longest runs or anything else?
  • hot_rod
    hot_rod Member Posts: 22,131
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    3/4 mag be adequate to run out to the manifold
    It’s based on gpm or byu’ that each zone requires

    Are the manifolds located near the boiler, or remote?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Pulse
    Pulse Member Posts: 78
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    I want everything you see in the above picture to be in the boiler room.
  • Brewbeer
    Brewbeer Member Posts: 616
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    I pulled out a dead forced air system and installed a high efficiency HWBB system a few years back, used a spreadsheet heatloss calc, had slab challenges, etc. Check out my design thread linked in my sig, I got good advice on treating the slab heatloss.
    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
    Pulse
  • Pulse
    Pulse Member Posts: 78
    edited October 2019
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    @Brewbeer Nice! Seems we are doing something very similar. I plan to install Lochinvar as well. I will read through your post right now.

    I attached my current heat loss spreadsheet to this post
  • hot_rod
    hot_rod Member Posts: 22,131
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    From the boiler to the sep 1", secondary side piping "headers" 1", The tees and piping off to the manifolds could be 3/4 since the 44K total load is divided among the 4 distribution manifolds.

    It may not be a big cost difference between 3/4 and 1" on the branches if those piping runs are short.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Pulse
  • Pulse
    Pulse Member Posts: 78
    edited October 2019
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    @hot_rod ..if 1" is all I need, making everything 1" will be a lot easier. The runs to zone manifolds are short. Would you mind taking a peak at the heat loss spreadsheet I made to see if I am doing anything incorrectly(I added it to the main post)?
  • hot_rod
    hot_rod Member Posts: 22,131
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    You should be fine with all 1".

    With oversized piping flow velocity drops and air removal can be more troublesome, we like to see 2- 4 feet per second in hydronic designs so air is carried along with the fluid to the air removal device.

    With a top quality sep or microbubble type air purger you should be up and running air and noise free within an hour of firing up the system.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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