Zone Loop Friction Head and Circulator GPM Calculator

 
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lsayre
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Post by lsayre » Fri. Nov. 02, 2018 12:36 pm

I hope this will be a useful and very simple tool to utilize when designing a hydronic zone system and trying to figure out if your zones pipe diameter (ID) and your circulator will be proper and adequate for the task.

I originally placed copies on swyman's LL AA-220 thread, but this likely needs a thread of its own. The version seen here is the latest update. Newer than those spreadsheets seen within the swyman thread (which should probably be deleted by a moderator, perhaps with instructions to find it here instead).

On the main page, user input is made in cells that are colored blue. Should be easy and straight forward. The only required (or possible) inputs are: 1) Total length of run in feet for your systems single longest zone. 2) Coefficient of friction (value choices are supplied). 3) ID of the zones main pipe. 4) Number of zone loops (which will almost always remain at "one" unless you have zone valves and a single circulator, and even then it will mainly be left at "one"), and lastly: 5) the friction multiplier for your system (for which suggested values and guidance are provided, and this value is also discussed below). There is literally almost nothing to it. A child could do it. The spreadsheet is internally juggling all of the math. The days of tossing Taco #7's at everything and then praying should be over. Many (if not most) of us will find that we are way over-pumped, and some will discover the opposite.

Be sure to visit the chart page for a graphical display.

Page switching is done at the lower left of the spreadsheet.

General insight and Instructions: The friction head pressure of the entire boiler system is generally found to be highest for the longest single zone loop, and it is generally assured that if a circulator can function properly within the environment of the multi-zone system for the case whereby only the single longest zone is open and circulating, then it will also handle additional added zones without question (since the systems friction head progressively falls as additional zones open to flow). The biggest trick for any system is going to be dialing in the correct friction multiplier value for the system. Hot water baseboards and conventional radiators generally call for this multiplier value to initially (as a first best guess) be set to 1.5, and in-floor radiant generally calls for this value to initially be set to 2, but beyond this the sky is the limit as to getting this multiplier value dead on. The 1.5 and 2 multiplier values are likely a bit conservative to the high side, and this is generally a good thing, and a safe place to start. 1.4 for HWB/Radiators and 1.9 for in-floor radiant are probably more likely to be correct for many if not most systems. All user input is in blue only. All else is calculated. After entering your data in this spreadsheet your remaining task will be to locate where a valid spreadsheet offered friction head (as found in spreadsheet column M) matches up with a valid GPM flow (as seen in column G) along your circulators pump curve chart (supplied by the manufacturer). Where spreadsheet friction head and GPM flow both simultaneously intersect the manufacturers pump curve chart, precisely there will be your zones actual flow in GPM. A circulators GPM flow always resides somewhere directly along and on its pump curve, and will never deviate from the pump curve unless it is a new-fangled variable speed circulator type. Variable speed is not multi-speed. Pumps are most efficient in the middle range of their "pump curve".

Sometimes it is easier to just time the flow of a single loop by feeling the pipe while running a stopwatch to calculate GPM flow (from the time of circulator start to first feel of a warm pipe at the return end of the loop), so below the main calculator is one that does this. And where all data matches up confidence of having discovered the zones true friction head and also its flow in GPM is very high.

Don't miss the chart (graph) page... Enjoy!

Edit from 11/5/18:

Thanks to Rob, I now know how to provide you with the most currently updated version of this spreadsheet via Google Drive. The image seen below will take you to my spreadsheet on "Google Drive" by pressing the "pop out" button in the upper right-hand corner, where it will always take you to my most current version. After you have popped it out onto "Google Drive" you can open it from "Google Sheets", scale it to fit your screen properly, and then run it directly within "Google Sheets" via clicking on the "Open With Google Sheets" button at the top center without even having Microsoft Office (or an equivalent office suite) installed on your computer, and also without any worry of me accidentally and unintentionally sending you any viruses. And lastly you can download it directly from "Google Sheets" also if you desire to have a personal copy.



 
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lsayre
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Post by lsayre » Fri. Nov. 02, 2018 5:32 pm

I would like to hear some observed zone Delta-T figures for in-floor radiant heating. For 0.485" ID PEX I'm guessing (with the aid of this spreadsheet) that GPM flows are likely only between 0.5 GPM and 1 GPM for each zone, and that Delta-T's may be on the order of 40 degrees (give or take) for each zone. For continuous heat that should be fine, even on the coldest day of the year.

The program initially predicts that a 600 ft overall length zone loop using 0.485" ID PEX would require a circulator capable of delivering 0.7 GPM into a calculated 20.6 feet of friction head for a selected (and quite likely worst case scenario) friction multiplier of 2.0.

At 40 degrees of Delta-T and 0.7 GPM of flow the BTUH's being delivered to this zone are: 0.7 x 40 x 60 x 8.33 = 14,000 BTUH

4 of such zones heating a home would total to 4 x 14,000 BTUH = 56,000 BTUH, and that amount of honest output heat should be sufficient for adequately heating a good number of homes. A 2,000 sq-ft home would be receiving a quite respectable 28 BTUH per sq-ft. (the equivalent of 8.2 Watt-hours/sq-ft.) for this 4 zone scenario.

 
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lsayre
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Post by lsayre » Wed. Nov. 07, 2018 3:15 pm

The image below is a plot of data from my spreadsheet for my system. Mine is a 4 zone system with a single circulator and 4 roughly equal in length zones. As I bumped the number of zone loops zone valves open (simultaneously) for evaluation from 1 to 4, I plotted each on the pump curve I got from Taco by taking data directly from the spreadsheet output. This pump curve chart has two pumps on it. An 00R 3-Speed and an 0010 3-Speed. Mine is an 00R, and I have it set to low speed. The 4 circles seem along the 00R's L (low speed) line are where the data from my spreadsheet intersects the pumps low speed curve line. The GPM's (and friction head) are read at the intersections. 1 zone open = ~4.2 GPM, 2 zones open = ~8.0 GPM, 3 zones open = ~10.3 GPM, and 4 zones open = ~11.5 GPM. This for the conditions of 132 ft zone length for my systems single longest zone, 20 degrees Delta-T, 3/4" copper pipe (ID = 0.811"), and the friction multiplier set at 1.50 for a hot water baseboard system.
Taco OOR 3 Speed.jpg
.JPG | 118KB | Taco OOR 3 Speed.jpg
My system also has a DPBV (differential pressure bypass valve) installed, and the horizontal line I drew across 3.5 ft of head represents the friction head pressure that I have dialed into the settings of the DPBV. Thus my actual GPM flows are seen where the horizontal DPBV line crosses the 4 zones lines, which happens at 2.2 GPM for 1 zone open, 6 GPM for 2 zones open, 10.3 GPM for 3 zones open, and lastly when the DPBV is wide open my 4th zone open flows at its original 11.5 GPM. I placed asterisks (*) next to these.

 
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lsayre
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Post by lsayre » Wed. Nov. 07, 2018 4:36 pm

The bottom line is that I'm way over-pumped and a far less output circulator would have suited my system just fine and placed less wear and tear upon it as well. The DPBV kludge is like applying the breaks to a circulator that is running like a high output sportscar (even on its low speed setting). I suspect that most of us are in the same boat.

Even the Taco 005 is overkill for me. And the 007 that everyone recommends would probably be worse than what I have now. It would be a massive overkill. And I'm running a single circulator feeding 4 zones no less.

A Taco 006 would have been a way better selection for my system. But I don't believe it is made in a cast iron HVAC suitable version with flanges. If it is, it may be my next circulator.

It appears that the end user customers want them big and powerful, so the circulator companies deliver to meet their demands. Illogical as the demands are.... And the HVAC experts don't ever want to undersize a circulator and look stupid so instead they wave their magic wand (calculator) and way oversize them, and then they can be seen as geniuses deserving the big bucks.

Only the advent of the variable speed circulator has assisted in making things right.

 
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Post by Rob R. » Sat. Nov. 10, 2018 9:34 am

lsayre wrote:
Wed. Nov. 07, 2018 4:36 pm
The bottom line is that I'm way over-pumped and a far less output circulator would have suited my system just fine and placed less wear and tear upon it as well. The DPBV kludge is like applying the breaks to a circulator that is running like a high output sportscar (even on its low speed setting). I suspect that most of us are in the same boat.

Even the Taco 005 is overkill for me. And the 007 that everyone recommends would probably be worse than what I have now. It would be a massive overkill. And I'm running a single circulator feeding 4 zones no less.

A Taco 006 would have been a way better selection for my system. But I don't believe it is made in a cast iron HVAC suitable version with flanges. If it is, it may be my next circulator.

It appears that the end user customers want them big and powerful, so the circulator companies deliver to meet their demands. Illogical as the demands are.... And the HVAC experts don't ever want to undersize a circulator and look stupid so instead they wave their magic wand (calculator) and way oversize them, and then they can be seen as geniuses deserving the big bucks.

Only the advent of the variable speed circulator has assisted in making things right.
That is the big advantage of the new variable speed circulators like the Grundfos Alpha, or the Taco Viridian. You can set them pretty much exactly where you want them, and use less power at the same time.

 
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Post by nepacoal » Sat. Nov. 10, 2018 9:38 am

FYI, Supply House does sell the 006 in cast iron. I used one with the IFC for the loop between my two boilers. I still have the 007 for my house loop. They cost double what the 007 costs, but have the low flow i wanted for the boiler loop.

 
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Post by lsayre » Sat. Nov. 10, 2018 9:49 am

nepacoal wrote:
Sat. Nov. 10, 2018 9:38 am
FYI, Supply House does sell the 006 in cast iron. I used one with the IFC for the loop between my two boilers. I still have the 007 for my house loop. They cost double what the 007 costs, but have the low flow i wanted for the boiler loop.
Does it have flanges?

I discovered just yesterday that the B&G NRF-9 has very close to the identical pump curve as the Taco 006, is cast iron with standard flanges, and is very inexpensive.


 
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Post by nepacoal » Sat. Nov. 10, 2018 10:11 am

Yes, normal cast iron flanges... But $158 versus $75 or $80 for an 007.

https://www.supplyhouse.com/Taco-006-F7-IFC-006-T ... ck-1-40-HP

 
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Post by mikeandgerry » Mon. Dec. 10, 2018 1:01 am

:lol: These were exactly the same exercises I ran through 12 years ago in designing my system. At the time, I concluded that it was more cost effective to “throw Taco007s at the problem”.

To maintain a delta-T of 20degF and stay below 4gpm for noise reduction and optimal heat transfer, I needed a Taco 007 for my two longest loops, a taco 006 for the mid size loop and taco 003s for each of four bedroom loops.

After reviewing the pricing and availability of Taco circulators, I realized that all the pump curves were shifted way too far outward to accommodate my low friction head and low flow rate requirements.

I researched the downside of “over-pumping ” and found that the major drawbacks in heating
hydronics were: wasted electricity and laminar flow causing inefficient thermal transfer.

Electricity consumption between a 1/25 hp and a 1/40hp may seem like a large factor but, in practice, small $$$. (.7 vs .5 amps). So, I thought it might not really be worth the price difference. Also, Taco003s wre scarce as hen’s teeth when I was searching for them.

That left laminar flow as the other potential problem in evaluating thermal transfer. As I discovered, it just isn’t a big issue in plumbing at this magnitude of pumping and the home heating application.

Slower is certainly better. But, sInce the Taco 007 wouldn’t cause laminar flow in the average home heating situation, the Taco007 became the only choice.

I re-sold the one in-needed kick-ass Grindfos pump I had bought on eBay before properly crunching the numbers. (And I made some nice money on it bc when I bought it at auction on eBay the seller misspelled “Grundfos”!)

I have not regretted my final decision. The longer loops have a 20DegF Delta T. The short loops do have a much higher than desired DT but bc I have a steel boiler, and therefore greater protection from thermal shock, it hasn’t been a problem. “Right sizing” would have cost an additional $1000 at a time when the checkbook was pretty well drained for the project!

 
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Post by lprince » Mon. Jan. 07, 2019 9:46 pm

I am installing an Axeman Anderson and tying it into my existing oil boiler. Since I do not have a specific heat load I can not use a delta t to calculate my required flow rate at a specific btu. In a normal situation you would use F=Q/(500*delta T). Where Q is BTU requirement and F is flow rate in GPM.

The existing boiler has about 70 feet of baseboard broken up over 4 zones with one circulator and zone valves.

My pipping between the 2 boilers is about 200 feet total equivalent of 1 inch pex al pex.

So my question is how do I go about correctly sizing my circulator to ensure I have enough flow to the oil boiler to keep it at temperature if I do not have a known constant for my delta T?

Do I base it off the total heat load of approximately 40,000 total BTU of baseboard and use a 20 degree delta T for that heat load and then use that flow rate to calculate my head loss?

As always any help is appreciated

 
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Post by lsayre » Tue. Jan. 08, 2019 4:55 am

Begin with the "Hot Water Baseboard System Design Assistant" spreadsheet to uncover the parameters which are presently missing.

After that:
When designing a system for a single circulator and zone valves, if all zones have the same ID for their piping, you only need to look at the single zone with the highest friction head when using the "Zone Loop Friction Head at Circulator GPM Calculator" spreadsheet. If the system can heat this zone it will easily heat the others without need for their consideration. All else being relatively equal, the longest single zone loop will generally be the one with the greatest friction head.

But for the case of an existing oil boiler, as well as an existing 4 zone piping and zone valves system with circulator, didn't someone already solve for all of the requirements years ago? Or do you intent to completely re-design and re-do the system in conjunction with adding a coal boiler to it?

 
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Post by lprince » Tue. Jan. 08, 2019 7:16 am

So a picture is worth a thousand words
boiler pipping.JPG
.JPG | 95.1KB | boiler pipping.JPG
Basically this what I have except it is not a wood boiler on the left it is an axeman anderson. The oil system is to stay in place as a backup or in the event we go away on vacation and I cant get someone to empty the ashes.

The existing boiler system and circulator works flawlessly with adequate heat for all zones.

I am trying to figure out how to size the circulator between the stoker and oil furnace

 
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Post by lsayre » Tue. Jan. 08, 2019 7:24 am

I can only provide you with the tools I have devised. I can not design your system for you. I am not a licensed HVAC provider, and I have no knowledge of your homes heat load (demand). But you should be able to determine your own needs via the tools I have provided. It is then up to you to either go it alone, or to seek professional assistance.

If you have only ballpark 40,000 BTUH of radiators, might I ask why you decided to install a 260,000 BTUH coal boiler?

 
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Post by lprince » Tue. Jan. 08, 2019 9:49 am

When I purchased the boiler I was told it was a 130. After I drove 3 hours I found out it was a 260 and the price was right. Eventually it will heat the garage that will be built. So for now it will barely break idle.

 
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Post by hotblast1357 » Tue. Jan. 08, 2019 10:05 am

Why not isolate the oil boiler with ball valves? Why heat it for nothing.


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