Pipe size, layout, and heat loss questions

Pulse

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!

JohnNY

For delivering 44.3MBH, 1" copper will be fine.

Pulse

I do not need to take into account my longest runs or anything else?

hot_rod

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?

Pulse

I want everything you see in the above picture to be in the boiler room.

Brewbeer

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.

Pulse

@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

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.

Pulse

@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

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.