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How many BTU's

Member Posts: 710
What is the maximum amout of BTU's you can squeeze out of 3/4" pipe?

• Member Posts: 5,884
• Member Posts: 6,106
Depends!

Using the Pipe Sizer module of Siggy's Design Studio. If you want to push to the limit!

170° average water temperature, 20° delta T, 6.4 gpm, 4fps would move 62,000 BTU/ hr. (7.2' per 100' of tube pressure drop)

4 feet per second is the high side for velocity.

If you can spread the delta T the number increases.

hot rod

• Member Posts: 1,935
what length?

hot rod, what length of 3/4 are we talking about?
• Member Posts: 6,106
that is for

100 feet of tube. This Hydronic Simulator Module lets you build the circuit and include fittings and valves, as well as emitters. Only then will you get a complete pressure drop through the system.

hot rod

• Member Posts: 6,106
That's for 100 feet

The Hydronic Simulator Module allow you to build the entire piping adding valves and fittings. It also shows flow rate and pressure drop for the entire assembly.

This example shows 50' of baseboard, 100 feet of 3/4, 10 ells, 2 ball valves and a flow check.

hot rod

• Member Posts: 710

Sweet program HR! We'll have to look into that. I know it was such a broad question. I'm looking @ running HePex to a water coil about 100' away (oneway) from my boiler. The hot-water coil needs 8 gpm @ a .31 friction loss to provide about 85,000 btu's and we have to use a 30% glycol mix.

Jamie

• Member Posts: 6,106
A bit of difference between pex and CU

Regular pex has a smaller ID (SDR-9) than copper. You could proably squeeze by with 1" HePex

85,000, 20°delta T, 170°average temperature, 8.9 gpm, 30% glycol, 4" head per 100' at 4.7 fps, using 1" pex.

I-1/4" pex at 3.1 fps would be better but the 4.7 fpm proablby would not pose a problem. b4 fpm is generally max.

Generally the HePex would not have a lot of fittings, if any. I'd use the 1".

Be sure to insulate a long run like that. You could easily lose 15° before you hit the fan coil!

If you go to www.hydronicpros.com and download the demo you can try some options with the Pipe Sizer.

hot rod