## ft head loss (7 Posts)

when determining the head loss of a radiant zone...for example zone has 5 loops do i take longest loop in feet x 1.5 x .04= x . ?. thanks PAUL S

Paul,

Your design for infloor radiant will not have to be 1.5 gpm. Most systems will run just fine with .7-1.0 gpm.
If you look up 1/2" pex at 1 gpm at 140 degrees you get 3.22' per 100.

A system with 5-200' loops will  need 3.22x2 =6.44 feet of head. Since you have 5 loops you will be shopping for a circulator that will push 5 gpm at 6.44 feet of head. if you have significant feeder lines or boiler room piping you need to figure that in as well.

Taco flow pro university does a great job of explaining this.

Carl

But how did you find that 3.22 ft hd...when I find head loss I use loop length X 1.5X.04= head loss...
• ### Finding flow rate

The pivotal point is the flow rate the heat loss requires.

Carl was quoting a flow rate of 1 gpm.

Once you know the flow rate and water temp dictated by a heat loss then you can refer to the chart with accuracy.

Your formula is a rough guess.

Paul,
The head loss for any piping system is a curve. It will vary based on a number of factors.
The temperature and percentage of glycol are minor factors.
The length of the pipe and the amount of GPM you are trying to push is a huge factor.
There are some vary long formulas in 'Siggy's books that will allow you to get these numbers right on.
Uphoner has already done the math and have published tables to make it easy.
I found the 3.22 on the Uphoner tables..
Your formula will give you a rough idea of the head loss through copper pipe based on 4 ft per second. Pex has a different inside diameter and coefficient. Not to mention you would need a huge circulator to push 4 ft per second through a 200' radiant loop.
Carl
• ### sorry

thanks guys...im sorry for all these stupid basic questions....ive been expanding my business and doing lots of radiant heating but they are very basic sytems ....no outdoor reset , a 3 way mixing valve thats all no real comfort control....Are they any heat loss calculators specifically for radiant heating....i would like to know how to find the design temp for the system...flow rate(gpm=btuh/TDx500)???what delta T do i use?etc...etc...thanks Paul S
• ### Design

Paul,
http://www.uponor-usa.com/misc/cdam-request-page/default.aspx

Once you find your BTU loss per square foot of you project, use this manual to figure out the rest.
If you start around page 270 you can figure out the water temp required for your assembly, floor covering and required heat output. Then you can go down and figure the flow requirements. Once you have your flow requirements you can calculate the head loss.
Carl
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