hey ME

[Deleted User]

so far, i've had no takers on this problem? that i think i see. and my interest is in furthering my education if that's what it takes

here goes

please go to the w-m link below, and scroll to pg 15, and/or, just follow what i have below

http://weil-mclain.com/downloads/ug3_boiler_manual.pdf

paragraph 5, Sizing system water piping

2. ........To use this table, select a pipe size with a flow rate just larger than that required. ........

3. ........(For type M copper piping, this means flow rates of: 1-inch — 5.5 to 10.9 gpm; 1¼” — 8.2 to 16.3 gpm; 1½” — 11.4 to 22.9 gpm; 2” — 19.8 to 39.6 gpm.)......

now look at fig13. a problem; do you see any of the above values in the chart?

and now, look at their 'note' and 'examples'

Note: Total head loss for a piping circuit equals the loss per 100 feet times the TEL (total equivalent length) of the circuit in feet. TEL includes head loss for valves and fittings in equivalent feet of piping (i.e., how much straight length of piping would cause the same head loss as the valve or fitting). ok, no problem

For example, if a piping circuit has a measure length of 250 feet, and includes valves and fittings with a total of 175 equivalent feet, the TEL for the circuit = 250 + 175 = 425 feet. again, no problem

Examples: Consider the circuit given above, with a TEL of 425 feet. If the flow rate required for the circuit is 21 gpm, as in the example at left, select a pipe size from above.

example from left: FLOW = 210,000/(20 x 500) = 21 gpm

Using 1½-inch pipe would cause a head loss of 4.0 feet per 100 feet of piping. Since TEL is 425 feet, head loss would be: Head loss = 4.0 x 425 / 100 = 4.0 x 4.25 = 17.0 feet

Using 2-inch piping would cause a head loss of 2.5 feet per 100 feet of piping. Since TEL is 425 feet, head loss would be: Head loss = 2.5 x 425 / 100 = 2.5 x 4.25 = 12.3 feet.

so, from the 1st example, the math equates to 17, which is less than 19 AND 23

and in the 2nd example, while their math is incorrect @ 12.3(it should be 10.63) but either value is less than 19 AND 23, but not, "a flow rate just larger than that required." the values, 19 and 23 are, by comparison, much larger than 12.3(10.63)

so, is that the point? a value that closer/lower than the 19 and 23? and if so, if we needed 38gpm, then the 2" pipe would be our choice?

weil my guitar gently weeps, i'll patiently await an answer

MIke_Jonas

I'm not ME

It seems you are comparing flow numbers with head loss numbers??

On second thought, if you had 1 1/2", you would want something between the 19 and 23. Lower would give you less than desirable fpm, higher would give you problems related to high velocity. So, what you're looking to do is, shoot for a gpm between the numbers listed for each pipe size.

For 38 gpm (multiple boilers? commercial building?), 2" copper would be OK if your head loss is less than or equal to 2.5 ft/hd per 100 feet of copper.

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[Deleted User]

not ME?

no big deal. thanks for the response

am i comparing flow rates and head loss? not really, even though they're related. w-m's own figures don't match, and that's part of what i'm scratching my head about. or maybe i'm simply lost.
example: their paragraph says; ........(For type M copper piping, this means flow rates of: 1-inch — 5.5 to 10.9 gpm; 1¼” — 8.2 to 16.3 gpm; 1½” — 11.4 to 22.9 gpm; 2” — 19.8 to 39.6 gpm.)......
but their chart in the manual says; 1" - 7 to 9gpm;
1-1/4" - 12 to 16gpm; 1-1/2" - 19 to 23 etc
why the discrepantcy between their own figures?

"shoot for a gpm between the numbers listed for each pipe size."
yes, that's what i was understanding, and i'd simply used the 2" as an example of my understanding

so, with their examples of flow not matching, and incorrect math, do you see anything else that's incorrect?

Mark Eatherton

Their math is wrong....

but so is yours.

They calculated the head pressure required to maintain flow, and you were using THAT number in their charts for FLOW in G.P.M. The two are different from each other, but related. As you increase flow, the head of resistance increases.

Their recommendations of maintaining flow between certain values is based on three factors.

One is to maintain a velocity that can sweep entrained air in a downward flow consideration. This is critical on small residential systems, not so much on commercial systems that are bottom filled, top vented.

The 2nd factor is to maintain a velocity flow rate that is not so high that it can either eat pipe (hydraulic erosion corrosion) or create velocity noises that can be obnoxious. Hydronic heating systems are SUPPOSED to be virtually silent.

The last factor is being able to choose a pump of reasonable head and GPM capacity. You can choose to go with the higher head requirements, but will chew up more watts of energy to keep the water moving, and in todays energy aware consumer market, that is not a good idea.

Head = pressure generated and or burned.

GPM = flow in gallons per minute.

HTH

ME

bob_46

A suggestion for mike

go to B&G's web site and look for Syzer. With Syzer you can play "what if"and learn a bunch.