Feet of head

Paul_28

The head of 100 feet of 3/4" copper pipe.

Dave Landy_3

head

I'm not trying to be a wiseguy, but don't you need to know what direction the pipe is going? Like up 100 ft. or up 6 ft and sideways 94 ft? Ithought head and rise were the same.

Mark Eatherton1

The one correct answer to ALL hydronic questions...

It depends... In the case of pressure drop on flow, it depends on the flow rate, fluid type and temperature of the fluid. In the case of height or static head, it depends on how high you are above the system. They're both called "head", but they are different heads.

It also depends on the smoothness of the pipe for flow pressure drop.

Roughness of the pipe has no effect on static head, which is the head required to over come atmospheric pressure conditions.

So, in order to answer your question, we need more information. What is the fluid, what is the temperature and what is the flow rate?

Answer these and we can answer your question.

In the case of vertical, or static head, it requires 2.307 feet of head to equal 1 PSIG, or stated inversely, each foot of water column will exert .434 PSIG at the BASE of the water column.

ME

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Mike T., Swampeast MO

Head loss is the restriction (friction) to flow in the system. Elevation doesn't matter as it takes the same amount of pressure to raise 100' of water in a drinking straw as to raise 100' of water in a water tower.

In a closed circulating system it is your static fill pressure that does the job of lifting the water.

PJO_3

That's only half of it...

Like ME said, you have to account for the static AND dynamic head.

The static head is the vertical pressure from non-movement at a certain elevation...0.434 psi per foot of height.

The dynamic head is the friction loss from the (moving) water as it moves along, and this is the one with all the variables...gpm, pipe size/smoothness, fluid type, etc.

Take Care, PJO

Gordy1

If one has a pressure gauge on the return side of the circulator, and a pressure gauge on the supply side of the circulator. Can pump head be determined by the difference in the gauge readings?

I only ask because in my existing system I have about a 6 psi difference in readings.Circulator on the return side of the boiler. I just wonder if there is any correlation between the pressure difference in psi that can also be used to determine pump head of the system.

Mike T., Swampeast MO

Dynaimics

Presuming the gauges are accurate, that's the head loss across the pump at the pump flow rate as limited by the friction in the piping.

Notice that there are TWO variables. Without knowing one, you cannot calculate the other.

That's why we have pump curves that given a head loss in the piping you can calculate flow and more importantly choose a pump of proper size.

Bill Nye

G.

Did you ever have chance to read this text written by our esteemed host? Dan Holohans "Pumping Away, and other cool piping options"?
Try this link:


http://www.heatinghelp.com/shopcart/product.cfm?category=2-16

Gordy1

Pumping away

Bill while I have not read Dan's book "Pumping Away". I have read other material relating to that very topic and I understand the benifits. Keep in mind this is a 50's ceiling radiant system with new boiler and circulator installed in 1993. Evidently the installer did not know the benifits of pumping away from the expansion tank. Though the system works fine.The topic seems to be debated as I have asked about moving the circulator, during my seasonal inspection and I have had two different people tell me to leave it where its at.

Gordy1

Dynamics

Mike, I understand, I did go through the pain of tracing down pipe lengths elbows sizes ect. and using Bell and Gossets system syzer calculator to calc out the head of the system I have. I just wondered if there was a correlation there with the PSI difference.

Mark Eatherton1

Gordon...

Assuming that the pressure gauges are relatively accurate, you can calculate the head of resistance with the pump running. The math is 2.307 feet of head per PSIG, and once you determine that, using the manufacturers performance curve, you can see how many GPM the pump is moving under THOSE conditions. Remember, conditions change as a function of the number of zones open and close.

I used Siggys wonderful software to calculate how many GPM the pump on my system should be moving, and it came in EXACTLY as predicted (I have an in line flow meter on the closed loop portion of my system)

If unsure as to the accuracy of the different gauges, a person could pipe both the suction and discharge ports through one gauge, and open and close branch isolation valves to read the pumps pressure differential. This way, if the one gauge is off a bit, its inaccuracy applies to both readings, so the readings would be relatively accurate.

Whose pump do you have on your system?

Also, as it pertains to the pumps location in regards to the boiler/expansion tank package, if the pump is placed so it pumps away from the expansion tank, the chances of air binding and air related noise problems cease to exist.

One thing I've noticed about hydronic heating systems in the 30+ years I've been doing it is that you can have a whole bunch of parts in the wrong place, and the system will still put out heat. Heat is but one component of "comfort", but it's still heat. I've witnessed systems that according to industry standards should not work, and they still put out some heat. That said, if a person only wants heat and doesn't care about comfort and convenience, why not grab a 55 gallon drum and connect a smoke pipe to it and burn your wooden furniture. It puts out "heat" doesn't it? ;-)

Just because it's not done perfectly doesn't make it right. Done correctly, the system will be virtually silent and relatively maintenance free as it pertains to air in the system.

I have most of the performance curves for residential pumps here in my basement office if you need the information.

How do you like your radiant ceilings? Have you ever experienced the "cold legs under the table" syndrome that many radiant floor providers talk about?

TIA

ME

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Brad White_2

AND...

if speaking of dynamic head, is it type K, L, or M copper? I mean, if you want to be precise.

Simple answer if vertical (Landy's Corrollary) is "100 feet"

:^)>

Gordy1

ME

ME,Just a little system info. to get in the the frame of mind. The system is powered by a Weil Mclain CGM series 7 150,000 Btu IBR rating with auto damper and intermittent electronic ignition.The circulator is a B&G series 100 HV return side plumbed . Near boiler plumbing is bypass piping:( with a mixing valve,have to keep supply temps at 120* max. usually runs 115* at design temp. and a steel compression tank. The radiant is ceiling in the upstairs (2300 sq.ft ranch)imbedded in the 1 1/4" plaster and radiant floors in the basement. This is all parallel piped from a main supply 1 1/2" and return 1 1/2" all copper, panels are 3/8" copper 6" o.c. and floors are 1/2" 12"o.c. all controlled by a single central located t-stat.

If I go with the 2.307 feet of head applied to the Psi difference of 6 which is 75* temp for fluid that puts me at 14.25 feet of head which translates to an off the chart reading as the head on that pump tops out at 12 feet.If I do it the Bell and Gossett way taking the length of the supply and return mains add 50% for fittings and the highest head loop I'm still off the chart for head at around 15'. I suspect this parallel piping configuration may be throwing me a curve except the psi difference does not lie. I'm doing something wrong in my calcs.

As for the radiant ceilings they are wonderful even heat ceiling to floor only about 2* difference, the old boys even did the bay window ceilings. You don't have floor covering issues or furniture taking away from the radiation of the floor. Floors are nice also nothing like warm concrete, slate or tile throw the slippers away, combine the two superior. As for shadowing effect under the table for ceiling radiant, its not that noticeable could even be the power of suggestion,buy glass table tops if a problem

My system is a jewel still have the chase copper brochure. I only wish Icould have met the men who installed it over 50 years ago to thank them for a fine job still providing comfort to those that dwell in their liquid sunshine. My hats off to you all for being the next generation of hydronists to do the same. Humans control every aspect of their enviroment no matter where they are. You all have picked the right trade to satisfy many, though I'm sure there are those days that it does not seem to be that way.

But with that said hydronics has come along way since then and I beleive this system could benifit greatly from some optimization. Moving the circulator to pump away,Primary secondary pumping to prevent boiler shock, outdoor reset. My only problem is finding the right person. No one listed on the Wall with in 75 miles. The only people I would trust are right here on this site. I have had 2 area pros take a look and no one seems to want to take the initiative or is not up to modern standards or they don't need the work. I have learned enough to ask the right questions and I know what I need maybe that was intimidating to them.
Gordon