Taco 007 Circulator Replacement Sizing? Undersized even though working ok?
The 16ish year old 007-F5 on my EK1 boiler has started to sound a bit angry of late, which lead me have a premptive look at replacement options.
I did some measuring, and ran some numbers, and arrived at the following observations:
- House has 3 zones. A single pipe for the kitchen, and split parallel loops on both the first floor and second floors.
- The longest run (which is one of the two 2FL loops), including fittings and elbows and such, is ~130ft equivalent length of 1/2" copper.
- In order to maintain the best practice of <4fps flow rate, I selected 3gpm to calculate head loss. That comes out to ~13.5ft.
- This is beyond the 007's pump curve. Does this mean that the current 007 is actually flowing more like 2gpm at max head output?
- If that be the case, does that mean (pretending the parallel loops are actually balanced… they are fairly close) I am really only seeing ~1gpm down each of the two parallel loops? Meaning below the ideal lower bound of 2fps for air removal.
- On the flip side, does this mean that to achieve ~3gpm down each of the split parallel loops, the correct sized pump is actually closer to one that can produce 6gpm at ~13.5ft head?
I realize that the 007 is good for many/most small to medium sized residential applications, however I feel like if my calcs are correct I should be looking at something more like the 0015 running on Medium or High speed.
Thoughts?
Comments
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What is the boiler BTU output?
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Standard fired EK1 at 0.85gph, so 104k BTU I believe. It has no problem heating the house. This is more of a best practice for air removal and not overtaxing the pump question.
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the pump curve from the manufacturer tells you what the pump is capable off.
A system curve that you develop based on the math you have done goes on top of the pump curve to show you where the pump is actually running.
Best practice is to run in the middle 1/3 of the pump curve for a healthy life.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
I get a considerably higher number: about 34 feet for 3 gpm in half inch copper 130 feet long. I get a flow for the 007 series around 1.5 gpm in that setting.
For the two loops in parallel, to have 3 gpm in each, you want something which will produce around 34 feet of head at 6 gpm.
Now I have to ask… are you sure about the half inch copper? Because if it's 3/4 inch the head loss at 3 gpm is only about 5 feet… which is easily within the range of the 007.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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@hot_rod I'm not sure how any pumps would operate in the middle of their curve when running long lenghts of 1/2". Head loss rises so fast in 1/2".
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I measured hte pipes I can see and they are indeed 1/2". I can look closer to see if they size up somewhere. Feels odd that they would mix and match sizes mid-zone.
I used the equiations in the Taco design handbook and Caleffi idronics handbook and both came out the same numbers.
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when you see a wall covered with zone pumps, pretty good chance none are running at the bep.
Ideally you run mid curve, doesn’t mean that you are:)
Run the lowest flow rate that will get the job done. Long 1/2” runs will be the gpm limitation
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Those basically cost as much as a full new unit. Also not convinced it is sized right as noted. Unless the system does indeed size up to 3/4 somewhere I havent seen.
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True. The cost for the material is around the same. But the headache, the labor involved is much less when using a cartridge. Unless of Course you can isolate the circulator with valves, then replacing the entire circulator is fine.
And as for convincing. Im sure you are weighing your numbers accordingly with the fact that it has been running well for some 16 years. If it aint broke don't fix it may sound silly, but may apply here.
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I am certainly weighing that. I just wonder if the occasional air I seem to be getting is actually because the 007 is actually out of its league.
I'd like my numbers to make sense so I may poke around and see if the builders did actually mix in some 3/4 with the 1/2 piping. It wouldnt totally shock me based on some other construction "choices" they made, but I didnt think to actually look.
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Is this a zone valve installation? If so and you do want to upgrade the pump, look at one of the electronic versions with delta P, zone valve settings.
You don't want to oversize a pump and end up with zone valves that bang off.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Yes, the one circ and three zones valves.
I dont have a DirtMag or similar product installed and I beieleve the ECM pumps require one yes?
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I would always add a magnetic separator with any ECM. May as well get dirt and magnetite removed.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Alright, I checked all the baseboards and all but two are indeed 1/2".
Two smaller ones on the kitchen loop size up to 3/4" but that doesn't matter for the head loss calcs.
I really think it's 13.5ish feet.
So would the consensus be to go with what I know (007) when it takes a crap, or step it up a bit?
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here is a table that shows pressure drop at various flow rates From Engineering Toolbox. Com
1/2”copper Type M?
2 gpm would be a safe design flow, 2.5 fps velocity
Use the factor times the EL, the number is in psi multiple X 2.31 to get ‘ of head
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Id been using the H=a*c*l*(f)¹.⁷⁵ from the Caleffi idronics #16 publication. That landed me on the 13.5ish (including the larger return pipe length) at 3gpm. At 2 gpm as you mention it looks like 6.8ish ft total. A 007 could swing that.
But then it comes back to the fact that in the parallel loops, 2gpm out of the pump is really only 1gpm down each loop.
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Except that you must remember that as the head pumped against drops, the flow picks up — the 007 has a pretty flat curve, and if that pump can manage 2 gpm into one loop, it will be much more like around 1.5 gpm into two. Maybe more.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
I guess the best proof of concept is that the current 007 gets the job done
If anything I would use a pump that adjusts to the required output of the 3 zones as the toggle in and out, a delta P circ pretty much flattens the curve across the operating conditions. It also consumes less power doing so
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
What would cause the head to decrease though? Sorry, going on two decades since I've taken fluid dynamics.
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Less flow resistance in two loops than in one…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
If I know the head of each individual loop or zone, and let's pretend they are all balanced, how do I calculate the cumulative head if 2 or 3 are flowing at once?
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By far the simplest way to handle two or more loops which are piped in parallel is to replace them with an "equivalent" single pipe which has the same hydraulic characteristics as the combined pipes. If all the pipes are the same material, it is sufficient to simply use an equivalent pipe with the same cross-sectional area as the sum of all the pipes in the loop. You can then calculate the head loss/flow curve in the usual way for that equivalent pipe. Then the flow in each individual pipe can be back calculated from the head loss.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
You can try the following test to see if there are major flow issues, but realize that the output of baseboard at 1 GPM is only about 5% less than flow at 4 GPM. So if the flow is anywhere near similar, you probably will not be able to tell.
If you know the piping circuit for your split loop, you can measure how much fin tube is in each side of the circuit (loop A “shorter” and loop B “longer”). Measure the supply water temperature where it enters the start of the baseboard the loop A, and measure the temperature at the end of that loop. Do the same for loop B, but measure the temperature after a similar amount of fin tube as you did in loop A (or find a nominally equivalent length if possible). The inlet (supply) water temperatures should be the same, but the outlet will tell you which side has more flow (lower temperature drop), or even if one side is air bound with very little flow (very high temperature drop). You can do the same in other baseboard zones to see how they compare.
Robert W.
Energy Kinetics
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Just know in the 1/2" fin tube that 4 gpm is going to cost you quite a bit more flow resistance. 1- 2 gpm is what I would design around
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Alright I went ahead and did it the right way.
Calculated the head loss values/curves for each zone and plotted them against (what I back calculated to be the best fit for the Taco 007 pump curve.
Red is my most used first floor zone (split loop)
Purple is if my first and second floors are both calling (2fl is also a split loop)
Blue is if all zones are calling (mudroom/kitchen is single pipe)
With just the first floor running it'll be at right around 3fps through the pipes and with the two main zones it'll be around 2.6fps.
Seems I'm to the good with the 007 after all. I was just not thinking about the additive effect of loops and zones right.
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