Garn and 1 1/4" Pex vs 2- 1" Pex?

[Sawyer]

Sorry if this has already been discussed but I have read everything I can find by searching the archive and still can't find the answer. Why isn’t everyone using two 1” pex rather than one 1 ¼” pex since two 1” pex have more internal volume than a single 1 ¼” pex, and the fittings and 1" pex installation are much less expensive?

I have to order my pex for the Garn 2000 which I have to run 175” to the house. I calculated the 2300 sq./ft house, with finished basement to need 90,000 Btu which may be a little high as I have Applegate blown insulation in the walls and ceiling and Slant Fin does not allow for this insulation.

Thanks, George

 

[Willman]

Hot Rod discussed this a while back. Can't remember it all but I think the 1 1/4 was the preferred method. Try searching posts by member. He posted this under his old id, master of sparks.

 

[pybyr]

Here's the series of discussions on it, where I'd asked a similar question:

https://www.hearth.com/talk/threads/19503/

there's also some useful stuff here on tubing sizes and how they interact with circulator choice at

https://www.hearth.com/talk/threads/18383/

Somewhere, I remember someone pointing out that two parallel 1" pipes don't really flow the amount that you'd think if you added the cross-sections, because in addition to the additional cross section, you're picking up more relative wall surface than you would if you just went with a larger single pipe. I can't re-find that set of discussions, wish I could, because I think it also had some interesting idea from someone on how you tie the "duals" together at each end in a way that flows OK and isn't too bulky or fitting-intensive. But on your basic point, I do think that Hot Rod basically "blessed" running equal length paired 1 inch tubing as an OK work-around instead of 1 and 1/4

PS a Garn 2000 sounds like a _honkin_ big boiler for the size house and heat loss you're talking about- I understand some of the reasons why a Garn is attractive with the built-in storage, but why did you move to the 2000 over the 1500?

 

[pybyr]

here was the other one- and it also confirms that a parallel pair of equal length 1 inch PEX lines is "close enough" (although slightly shy of) a single 1 and 1/4

https://www.hearth.com/talk/threads/19559/

 

[Sawyer]

Thanks for the leads and links, if anyone has additional information to digest it will also be appreciated. I will start reading as soon as I finish hauling my lumber to the kilns. With the heat requirement for the house I would think I could make the dual 1” work and save a bundle of money. Being 80 miles from a “big box” store makes things a bit more expensive locally.

Trevor, I chose the 2000 because I also heat my 1200 sq./ft workshop also. I wanted to heat both at –20* without re-firing for ten hours. The 2000 gives me that storage capacity and the ability to replace the stored heat rapidly while still providing 125k to the buildings. I hope my reasoning is not flawed.

 

[pybyr]

Trevor, I chose the 2000 because I also heat my 1200 sq./ft workshop also. I wanted to heat both at –20* without re-firing for ten hours. The 2000 gives me that storage capacity and the ability to replace the stored heat rapidly while still providing 125k to the buildings. I hope my reasoning is not flawed.

makes sense- similar to why I picked an econoburn 150 over the 100- so that I can charge up my storage quickly and also have the option to use a new fire/boil to start heating the house and maybe start recharging the storage at the same time