What's the max BTUs delivered through 1\"?

Brad White_26

But the basic thing to know is how much flow a given pipe size can handle. Once you have that in your head, you no longer need a chart.

Here are my guidlines (conservative I admit; many will allow more water per size) for maximum allowable flow in gallons per minute:

1/2" = 1.5
3/4" = 3.0
1" = 5.0
1-1/4" = 9.0
1-1/2" = 18.0

Next factor is the temperature drop, ("delta-T"). Conventionally this is 20 degrees in many systems, could be higher, 30 or 40 degrees, could be less, 10 or 15. 20 is a good balance of heat output without moving too much water.

At a 20 degree delta-T, every gallon of water per minute will carry the potential for 10,000 BTU's per hour (BTUH).

The shorthand calculation is:

GPM x 500 x Delta-T (degrees F) = BTUH

If you use glycol anti-freeze, the 500 number will drop by about 10% depending on concentration. But for discussion let's stick with water.

Thus if you have a 5 GPM flow rate at 20 degrees Delta-T = 50,000 BTUH. (Your 1-inch pipe)

If you have a 30 degree Delta-T you can get 75,000 BTUH, 40 degrees, 100,000.

But 20 degrees does make the math easy, doesn't it?

Hope this helps.

Brad

Fred Almeida

What's the max BTUs delivered through 1\"?

Searched through some of my old studying material and just couldn't find the ratings of max BTUs delivered through hydronic piping.

Can anyone refer where to find this material?

Empire_2

Great explanation

I would add that although you can increase or decrerase your "delta T" the idea is to keep to a minimum, velocity noise from excessive flo and poor performance from the lack of flow. That is why we have given BTU and GPM ranges for a given pipe size.

Brad White_26

An excellent reminder, Mike

It is all within a range (why we were given judgement and free will I suppose? Yeah, that's it! For hydronics!)

Thanks!
Brad