Friction Head Loss (Ft) Calculation for Closed Loop Systems

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 7:16 am

I have made a down and dirty (simple) spreadsheet for calculating a "wild guess" (no guarantees, please don't flame me too hard for making a wild guess) of a closed loop systems friction head loss in feet. Written in LibreOffice using Linux, but I believe that it should work just fine in Excel. Let me know please.

Comments are welcome (including mild flaming I guess). The more accurate the data/numbers are that you input, the better the results should be. Pay particular attention to the loops total run length, your actual pipe ID, and nominal pipe coefficients of friction. See attached spreadsheet file.

Attachments

Friction Head Loss Pipe.xls
.XLS | 16.4KB | Friction Head Loss Pipe.xls


 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 7:44 am

Practical application:

The friction head and GPM of flow at which the output of this spreadsheet intersects your circulators specific pump curve line (see its chart for this) is (on first approximation/guess due to much potential for variability in actual system vs. calculated) the GPM of flow that your system is operating at.

If you are not seeing an intersect for both head and GPM with your pump on its pump curve chart, you have not yet input the correct GPM of flow into the spreadsheet.

Pumps (unless variable speed, which is vastly different from multi-speed) absolutely do not run off of their pump curve, so you must find (or plot) the intersection point. Only when they intersect will you know your GPM of flow.

PS: Not to toot my own horn, but I have some level of confidence in my wild guesses. The level of which you will need to guess. :P

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 9:55 am

Once you have printed out the "pump curve" for your circulator, plotting your systems flow vs. head characteristics onto the chart you have printed out is as easy as:

1) Enter the total loop distance in feet on the spreadsheet
2) Enter the pipes actual diameter
3) Enter the pipes friction coefficient value

Then enter a range of 5 to 10 different GPM flow values into the spreadsheet (perhaps starting with 0.5 GPM increments, beginning at 0.5 GPM), and for each GPM entry plot a dot onto the pump curve chart that corresponds to the spreadsheets output for the closed loop head loss value. Then draw a curved line (beginning at 0 head and 0 flow) through the dots you have just plotted.

That's it! Where the line you have just drawn crosses your pumps (and also any other pumps) curve line, that is (or would be if you have some other pump) your systems flow in GPM for that loop.

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 6:52 pm

For multiple zones with zone valves and a single circulator you must calculate the combined open loops "effective diameter" and their combined length.

For "effective diameter" you sum the cross sectional areas and then solve for the diameter of a theoretical single pipe that would have a diameter that yields that same summed cross sectional area value. This value goes into the spreadsheet.

Combined loop lengths are simple addition. This value goes into the spreadsheet.

When I plotted the results on my Taco 00R, 3-Speed circulators pump curve chart I got the following flows for my system:

Slow Speed
-----------------
1 zone valve open, flow ~= 3.8 GPM
2 zone valves open, flow ~= 4.9 GPM
3 zone valves open, flow ~= 6.2 GPM
4 zone valves open, flow ~= 6.9 GPM

Medium Speed
----------------------
1 zone valve open, flow ~= 5.0 GPM
2 zone valves open, flow ~= 6.8 GPM
3 zone valves open, flow ~= 8.1 GPM
4 zone valves open, flow ~= 9.6 GPM

I did not calculate for fast speed. Slow is where I run it and 6.9 GPM of flow with all zones calling delivers plenty of heat to satisfy my heating needs.

If I ever replace my circulator, an AquaMotion AM5-FV1 (with a pump curve that lies between a Taco 005 and a Taco 007) seems to have the perfect pump curve to fit my needs. AquaMotion makes the lowest electricity consumption circulators available today. Only 0.54 amps for the AM5-FV1.

AM5-FV1 (in my system)
-----------------------------------
1 zone valve open, flow ~= 4.0 GPM
2 zone valves open, flow ~= 6.4 GPM
3 zone valves open, flow ~= 8.2 GPM
4 zone valves open, flow ~= 9.8 GPM
Last edited by lsayre on Mon. Dec. 07, 2015 5:56 pm, edited 1 time in total.

 
Mikeeg02
Member
Posts: 244
Joined: Sat. Mar. 09, 2013 7:28 am
Location: Milroy, PA
Stoker Coal Boiler: Axeman Anderson 130
Hot Air Coal Stoker Stove: Old Alaska Kodiak Stoker II
Coal Size/Type: Rice/Pea

Post by Mikeeg02 » Sun. Dec. 06, 2015 8:27 pm

Larry,

Had you considered the difference in temperature and percentage of propylene glycol in the water? Or is your info based on pure water? When I was picking circulators and doing all that I used the link below. And they do have a variable for % propylene glycol and estimated water temperature. I know not everyone uses propylene glycol ( I did just in case, plus I got a steal on it. ) But maybe its not factor enough to consider. I didnt use yours yet to see how it compares to my calculations. But again, when I was sizing, I used the link below from Taco.

http://www.taco-hvac.com/uploads/FileLibrary/Sele ... lators.pdf
Last edited by Mikeeg02 on Sun. Dec. 06, 2015 8:44 pm, edited 2 times in total.

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 8:34 pm

Mikeeg02 wrote:Larry,

Had you considered the difference in temperature and percentage of propylene glycol in the water? Or is your info based on pure water? When I was picking circulators and doing all that I used the link below. And they do have a variable for % propylene glycol and estimated water temperature. I know not everyone uses propylene glycol ( I did just in case, plus I got a steal on it. ) But maybe its not factor enough to consider. I didnt use yours yet to see how it compares to my calculations. But again, when I was sizing, I used the link below from Taco.

http://www.taco-hvac.com/uploads/FileLibrary/Sele ... lators.pdf
My simple spreadsheet considers only water. The Hazen-Williams equation is at its heart. You are free to modify the equation to suit any level of propylene glycol percentage that you choose.
Last edited by lsayre on Sun. Dec. 06, 2015 8:44 pm, edited 1 time in total.

 
Mikeeg02
Member
Posts: 244
Joined: Sat. Mar. 09, 2013 7:28 am
Location: Milroy, PA
Stoker Coal Boiler: Axeman Anderson 130
Hot Air Coal Stoker Stove: Old Alaska Kodiak Stoker II
Coal Size/Type: Rice/Pea

Post by Mikeeg02 » Sun. Dec. 06, 2015 8:44 pm

I looked again, the straight run friction head is within a foot of what I calculated. But where does the 1st guess of estimated closed loop friction head value come from? What does it mean?

Is that a fudge factor assuming bends, bows, etc?


 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 8:49 pm

Mikeeg02 wrote:I looked again, the straight run friction head is within a foot of what I calculated. But where does the 1st guess of estimated closed loop friction head value come from? What does it mean?
Closed loops have bends and elbows. Per some old Bell & Gossett literature that I came across a good number of years ago, the typical (average) head loss of a closed loop system is a factor of 1.5X greater than the loss for straight line pipe alone. The 1.5X factor for closed loops is why my spreadsheet is only good for guessing. It yields merely an average head loss. Your (anyone's) actual systems head loss may be higher or lower than the average system.

As for straight line, it should (as you have discovered) be highly accurate.

 
Mikeeg02
Member
Posts: 244
Joined: Sat. Mar. 09, 2013 7:28 am
Location: Milroy, PA
Stoker Coal Boiler: Axeman Anderson 130
Hot Air Coal Stoker Stove: Old Alaska Kodiak Stoker II
Coal Size/Type: Rice/Pea

Post by Mikeeg02 » Sun. Dec. 06, 2015 8:58 pm

Ok that makes sense. Though when I calculated mine originally (Ill have to find where I wrote it down) Taco has suggested pipe lengths to add for each 90, 45, etc. Effectively making it look like one straight line for friction head/gpm/circulator calculations. Not saying its any more correct. Just how I did all my calculations. I think your suggested 1st guess is very close to my total calculation. Though your suggested first guess calculation was only based on my 200' underground insulated PAP (Each way so 400 total) I have an additional 50' of Pex, and a little copper for P/S loop separation at the house which is all made of copper. I believe my system calculated friction loss was around 25-26' of head for my house loop. And your 1st guess based solely off the 200' of PAP comes to 27.66' head.

Either way I did the math several times, using several methods to come up with my final answer, which settled me on the Taco 0011. Which does cost ~300 but keeps me warm. Thanks for the additional resource!

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sun. Dec. 06, 2015 9:03 pm

Mikeeg02 wrote:Ok that makes sense. Though when I calculated mine originally (Ill have to find where I wrote it down) Taco has suggested pipe lengths to add for each 90, 45, etc. Effectively making it look like one straight line for friction head/gpm/circulator calculations. Not saying its any more correct. Just how I did all my calculations.
No one can make one closed loop equation that is so simple to use actually fit all cases, and most people will not go through what you went through, so I had to settle for an equation that yields results that the average system can use. In the end I'm merely a Sayre. I'm not a soothsayer.

 
Mikeeg02
Member
Posts: 244
Joined: Sat. Mar. 09, 2013 7:28 am
Location: Milroy, PA
Stoker Coal Boiler: Axeman Anderson 130
Hot Air Coal Stoker Stove: Old Alaska Kodiak Stoker II
Coal Size/Type: Rice/Pea

Post by Mikeeg02 » Sun. Dec. 06, 2015 9:14 pm

lsayre wrote:
Mikeeg02 wrote:Ok that makes sense. Though when I calculated mine originally (Ill have to find where I wrote it down) Taco has suggested pipe lengths to add for each 90, 45, etc. Effectively making it look like one straight line for friction head/gpm/circulator calculations. Not saying its any more correct. Just how I did all my calculations.
No one can make one closed loop equation that is so simple to use actually fit all cases, and most people will not go through what you went through, so I had to settle for an equation that yields results that the average system can use. In the end I'm merely a Sayre. I'm not a soothsayer.
Well I didnt use your method for the loop thats in the house, its much more complicated. (1.25 black iron in line with a little 3/4 copper to a radiator and back to 1.25 black iron) and lots of fittings. But I didnt design it, it worked, so why fix whats broke. I did replace the circulator with a quieter B&G one, but I just compared curves. Either way, Im staying warm, and if I remember right, when I was watching temperature differential vs approximated flow rate things added up. Either way, nice work!

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Mon. Dec. 07, 2015 7:04 pm

I learned something today about my circulator. Somewhere around 2010 my Taco 00R 3-Speed was replaced by the Taco 0015 3-Speed. The cross-reference guides all show the 0015 3-Speed as its replacement, so I have always assumed (until today) that the 0015 3-Speed has the same pump curve for each speed as does the older 00R 3-Speed. Since I've just found the actual pump curves for the 00R 3-Speed I now know this is not the case. My data as seen above for the 00R on slow speed was derived from an 0015 3-Speed pump curve chart. Here is the real data when I plot my systems curve onto the "real" Taco 00R 3-Speed pump curve for slow speed:

"Real" Taco 00R 3-Speed on slow
------------------------------------------------
1 Zone valve open = 4.3 GPM
2 Zone valves open = 6.5 GPM
3 Zone valves open = 8.0 GPM
4 zone valves open = 9.1 GPM

This isn't even close to the replacement pumps curve for slow speed. But it makes me a lot happier.

Moral of the story: When a pump is discontinued, and its factory authorized "direct replacement" comes out, don't assume their pump curves will be the same.

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Fri. Dec. 11, 2015 5:58 pm

So what does the plotted output of this spreadsheet look like you might ask. Well, to answer that I plotted my 4 zones against the pump curve of the AquaMotion AM5-FV1 single speed circulator. And the image is attached here. I took a pump curve sheet with multiple circulators pump curves originally upon it and did my best (umm, ahem, choke) to white-out all but the circulator that I'm most interested in. You can tell from the sloppy work that I'm not an artist. Total system flow in GPM is where my system plotted lines (hand drawn) intersect the factory pump curve for each number of zones open. Click image to enlarge it.
Pump_Curve.png
.PNG | 1.7MB | Pump_Curve.png

 
User avatar
Rob R.
Site Moderator
Posts: 17980
Joined: Fri. Dec. 28, 2007 4:26 pm
Location: Chazy, NY
Stoker Coal Boiler: EFM 520
Hand Fed Coal Stove: Chubby Jr

Post by Rob R. » Fri. Dec. 11, 2015 6:26 pm

I learned something about circulators when I rearranged some of the boiler piping to connect the EFM. When you have two circulators in series, you basically double the amount of piping resistance that they can overcome. For those of you searching for a circulator to overcome a lot of friction, the cost of two "regular" circulators may be far less than a single large unit.

The way my system is setup, the circulator between the oil boiler and the EFM runs whenever there is a heat call....although the system is piped parallel, the zone circulators basically feed the EFM circulator. There is a noticeable difference in flow rate through the main zone when running on just the oil boiler, or when running the EFM and the extra circulator.

 
User avatar
lsayre
Member
Posts: 21781
Joined: Wed. Nov. 23, 2005 9:17 pm
Location: Ohio
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Lehigh Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75

Post by lsayre » Sat. Dec. 12, 2015 6:13 am

I mentioned earlier that for a multiple zone system using a single circulator in order to plot the associated multiple system curves you must determine your pipes "effective ID" for each additional zone that is open.

Example using 3/4" Type M copper pipe. ID = 0.811"

1 Zone open:

Effective ID = Actual ID = 0.811"

2 zones open:

step 1: single pipe cross sectional area = Pi*R^2 = 3.1416 x .4055^2 = 0.5166 square inches
step 2: two pipes cross sectional area = 2 x 0.5166 = 1.0322 square inches
step 3: 1.0322 / Pi = 0.3289
step 4: Effective R = 0.3289^0.5 = 0.5735"
step 5: Effective ID = 2 x Effective R = 2 x 0.5735 = 1.147"

3 zones open:

step 1: single pipe cross sectional area = Pi*R^2 = 3.1416 x .4055^2 = 0.5166 square inches
step 2: three pipes cross sectional area = 3 x 0.5166 = 1.5498 square inches
step 3: 1.4498 / Pi = 0.4933
step 4: Effective R = 0.4933^0.5 = 0.7024"
step 5: Effective ID = 2 x Effective R = 2 x 0.7024 = 1.4047"

4 zones open:

step 1: single pipe cross sectional area = Pi*R^2 = 3.1416 x .4055^2 = 0.5166 square inches
step 2: four pipes cross sectional area = 4 x 0.5166 = 2.0664 square inches
step 3: 2.0664 / Pi = 0.6578
step 4: Effective R = 0.6578^0.5 = 0.811"
step 5: Effective ID = 2 x Effective R = 2 x 0.811 = 1.622"

Short answer for effective ID using 3/4" Type M copper pipe:

1 zone effective ID = 0.811"
2 zones effective ID = 1.147"
3 zones effective ID = 1.4047"
4 zones effective ID = 1.622"

Remember to put the above effective pipe diameters into the spreadsheet along with the sum total of all "open" zones lengths.


Post Reply

Return to “Hand Fired Coal Boilers Using Anthracite”