Pipe sizing question WW

Wayco Wayne_2

to remove 2 boilers on a primary secondary loop and replace them with 2 new Munchkins. The primary loop supplys a large radiant floor. I figure the vision 3 control will simplify things. The 2 original boilers had 1 inch lines up to the primary loop. I installing a 140M and a 199M. The lines are very short, maybe 8 feet up and 8 feet back. How do I size for such short runs?? I know I would be safe running 1.25 and 1.5 respectively, but feel I could probably downsize with the shortness of the runs taken into consideration. Any help would be appreciated. WW

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You could actually

pipe them with 1" if you spread the delta t.

The 140 could be run at a 30° delta t with 1"

9.5 gpm, 4.3" per 100 feet of pipe, 3.5 fps

The 199 would squeak by with a 40° delta t on 1"

10.1 gpm, at 3.7 fps

I'd check with HTP for their opinion on the acceptable delta t through the HX, before getting too creative..

What is this connected to? If it is a low temp radiant that may work. If you need 180° supply the wide delta t may not work out, as the 140 low (boiler on) side may hamper the heat output.

Ever look down the throat of those 1-1/4" nipples comeing out the side of the Munch? Pretty sure you will see a 3/4" connection into the headers That and the small diameter HX coils are the reason for the high head primary pump requirement. Pressure drop through a cast iron boiler is zilch, compared to small diameter coil HXers.

You mean to tell me you don't have Siggys HDS software yet! You could run all sorts of what if pipe sizing with the pipe sizer module

hot rod


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Wayco Wayne_2

Spreading the delta

tee should be no problem. The heat emmiter is a large concrete slab for a warehouse. They don't want to heat for comfort, just keep things from getting too cold. I'm guessing 100 degree water would be acceptable for a lot of the Winter. The old cast iron boilers only lasted 10 years. The munchkin is better adapted for the cold returns. I'll contact HTP just to be safe. Thanks for the input. WW

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