Why is elevation gain not calculated in head loss?

learnitdaily · July 2019

Im having the hardest time calculating my pump needs for my first multi-level home. The owner is doing an addition and wanting to upgrade the boiler and heating system. Its a 3,000 foot home, the main house is two storied 32'x32' making each level 1024ft and the total 2048. The addition is 750'. The upstairs Baseboard run is the longest (not including the infloor heat) at about 210' of 3/4" copper. Not knowing the exact amount of fittings is stressful but, I've found a few general estimation guides. My biggest headache is nothing tells me how to add the elevation from the lowest point to the highest, or if it's even necessary to calculate? Im running a lochinvar knight, my plan was to run a main loop with each of the 4 BB zones having its own pump and the 4 infloor runs (2 zones, 2 thermostats) on its own pump with closely spaced tees, mixing valve 4zone manifold with 4 actuators. Ninety percent of the posts I've read say you can run an entire heating system with one pump. Which makes me believe im over pumping the zones, and I'd prefer not to. Im having hell calculating if I can run all the baseboard zones off the supplied Pump. Or if there is better way of running the manifold other than my initial drawings of the closed loop with supplied pump, 4 bb each having grundfos pump with check, and the infloor low temp having its own grundfos and a 4 actuators. I know Im asking many questions with little info provided.but, im willing to get any info needed, and im looking for new knowledge moreso than just answers.
I appreciate any help and direction.

Zman · July 2019

You don't need to figure any vertical head. It is like a ferris wheel. It does sound like you need some help with the design. Do you have a sketch?

Jamie Hall · July 2019

Zman said:
You don't need to figure any vertical head. It is like a ferris wheel. It does sound like you need some help with the design. Do you have a sketch?

Ferris Wheel is a good analogy! The ups and downs of a pipe are of no concern to the pump circulating the water in it. The only time you need to worry about the elevation of the highest point is when you're figuring the static pressure to put in the expansion tank.

hot_rod · July 2019

Rarely on small residential work do you need a circulator on every zone. A single ECM, delta P circulator with zone valves is the best option to explore.

You have lowest power consumption, and the circuit will adjust to rpm requirements as zones open and close. Plenty choices on the market for ∆P circulators.

A load calculation and design to determine required supply temperatures and sizing of equipment is always a good first step.

delta T · July 2019

I would highly recommend you read some of the Caleffi Idronics journals. No. 16 specifically deals with circulation in hydronics systems and will give you a good rundown of how all this works.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_16_na_0.pdf

Basically there is a common fundamental understanding about head in hydronic systems. The unit of head is actually (lb*ft)/lb and is a unit of energy. because the lb units divide each other out, you can simply deal in ft. This is different than the static head pressure produced by a vertical column of water, also expressed in ft of altitude, which can be directly converted to psi.

HomerJSmith · July 2019

There's static pressure and dynamic pressure. Static pressure is the weight of the water pressing down on the boiler. Dynamic pressure is the force (head energy) that the pump imparts to over come the friction loss (pressure loss) of the system. Since you have a supply pipe and a return pipe on the boiler the weight of the water (static pressure) at the boiler is the same on both pipes. To move water thru the system you just need a pump (dynamic pressure) to over come the resistance in the piping circuit. The water moving up will balance with the water moving down just like Iman says, a Ferris wheel.

Static pressure (weight of the water) is of concern with pressure relief valves and bladder expansion tanks.

By all means, go to You Tube and read Caleffi's Idronics series, it's FREE. Thank you, Caleffi.

EBEBRATT-Ed · July 2019

@learnitdaily
and you in most cases don't need to stress about the fittings. Make a sketch or drawing and use the fittings the sketch shows. add a few for fudge if you want and go with it. A few fittings one way or the other doesn't make a huge difference.

Wellness · July 2019

I second Hot Rod's recommendation. Besides the energy efficiency, zone valves have fewer moving parts and lower maintenance costs.

HomerJSmith · July 2019

Sorry Iman, errr I mean Zman, fat fingers on the keyboard.

"the 4 infloor runs (2 zones, 2 thermostats) on its own pump with closely spaced tees, mixing valve 4zone manifold with 4 actuators."

If I understand this correctly, this is what I would do on the infloor. One single ECM pump, manifolds with actuators and visual balancing valves on the manifolds. You have to balance the flow (GPM) thru the individual circuits if they are more than 10% variation in length, beside I want the flow on all the circuits between 1-2 GPM and balancing valves do that. The ECM pump will adjust to the flow settings. If you plan on having a pump at each manifold station, I would go with something like the Caleffi mixing station.

How to make the connections and where to make the connections is up in the air as there isn't enough information on the physical layout. Read the YouTube Caleffi Idronic series or at least look at the diagrams. It is a whole course on Hydronics, do's and don't's. I don't know your level of expertise. learnitdaily as a moniker, isn't exactly reassuring.

Dave H_2 · July 2019

Remember that the pump is in fact a circulator instead.

A pump will typically move water from point A to point B.

A circulator moves water in a circle, so to speak; what goes up one side of the house, comes back down on the other side.

When the circulator shuts off, the water stays at the upper level; we don't need to pump it back up there.

If you want to ballpark the headloss, here is a quick calculation without doing that much work.

Get an estimate of the amount of pipe in that loop.
Multiply that by 1.5 to account for all fittings in the loop (elbows, valves, couplings....)
Then multiply by .04.

You'll be high with the head loss, but safe.

Here is a link to a few different video's for sizing circs.

Enjoy, Dave H.

Why is elevation gain not calculated in head loss?

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