Calculating Head - Loss from Boiler and fittings

peedee360

I am looking to change from zone valves to circulators, so in calculating each zone I have had no problem figuring out the required flow rate, but I am having trouble calculating the head loss. One way I have seen is to calculate based on equivalent feet. This makes sense to me except that I can't seem to find equivalents for many fittings. For instance sharkbites (yes I know, I am getting rid of them soon). Also my Buderus G115, what is the pressure loss though the boiler? And with a mix of pex and copper and Propress and etc... Am I over thinking it?

hot_rod

I think an ell is an ell regardless of the connection. Long sweep ells are a small bit lower pressure drop.

This Idronics issue takes you through an exercise on EL.

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_16_NA_Circulation in hydronic systems.pdf

peedee360

Hot Rod, I was thinking that the size of the fitting would make a difference, for instance a pex crimp fitting has a much smaller inside diameter than a pex expansion fitting. But again, maybe I am getting too granular here and I dont need to be so specific.

hot_rod

peedee360 said:

Hot Rod, I was thinking that the size of the fitting would make a difference, for instance a pex crimp fitting has a much smaller inside diameter than a pex expansion fitting. But again, maybe I am getting too granular here and I dont need to be so specific.

Maybe if you had 100 of them in a system it would add up. But the pex id should be used, not copper tube size

EBEBRATT-Ed

@peedee360

It can be kind of crazy. I have never seen anything that has every possible available fitting. Basically you count the pipe footage for every pipe size you have but you have to know the expected flow in each pipe to calculate the feet of head. The fitting manufacturers will give you the head loss through the fittings or you can usually find it on line. I have found all sorts of different charts to convert fittings to feet of pipe and the #s vary quite a bit.

Some fittings like couplings and unions have very little resistance so for those you just throw something in to cover those.

That leaves elbows. Two ways to handle that. Calculate all the elbows or do what most do and use a "rule of thumb" They calculate all the head loss for all the pipe and when you get the total for that you ad 50% of
that figure in to cover the fittings. Boiler loss is probably negligible for cast iron. Some Mod Cons have a very high-pressure drop depending on the heat exchanger.

You can download B & G System Sizer. You input the information and it spitz out the number.

peedee360

@EBEBRATT-Ed Thank you, this is helpful. As for the B&G System Syzer, Seems like all the downloadable programs are windows based and I am on a mac, but I can figure something out.