New TACO with a nice set of curves

Oh C'MON..........not those kind of curves.............


I like the 2400's because most of them are designed to function with less Net Positive Suction Head (NPSH) than other circs moving the same amount of fluid require. Note that these are medium to higher flow circs that in wood boiler use would be put into place for main loop work or pushing water through up to a few hundred feet of underground tube. They have a seal made for handling less than optimum quality water as often found in open systems and/or neglected sealed systems. Note that the 2400-10 and 20 are probably the models that are going to be most widely applicable for residential jobs and they are standard flange dimensions along with the 45 and 50. They would be a poor choice for zone circulation unless you had a single zone calling for 10-15 GPM. Looks like a good product to me.

http://www.taco-hvac.com/uploads/FileLibrary/100-72.pdf

Heaterman

I was thinking of trying to figure out my total head loss in my system. My big unknown is my heat exchanger. The pump that I have works fine, but I sometimes hear it cavitate when the water is really hot. I would like to measure the flow rate and then I can figure out the head loss based off of the pump curves. Do you know of an economical way to measure flow rate in my supply lines from the boiler to the house? I would like to have a spare pump on site because o'l man murphy will always pay a visit in the most inconvenient time. Looking at the link in your post, I might be inclined to explore these pumps more, but would like to know my actual total head loss first.

Hello Heaterman. I am proposing to use Taco 2400 series pumps in a soalr water heating application. You mention the NPSH of these pumps is low. Do you have any NPSH curves or data on that? Thanks.

I bought a 2 in. flow indicator with thermometer for $156 plus shipping. Most of the hot water meters I looked at were over $1000

http://www.ppe.com/11cat/0500.pdf

Heaterman, would this be a better route for my set up? I did not change it last year. The pump survived another year but your right It is always blowing steam out of my air purge.
http://www.hearth.com/talk/threads/1-pump-or-2-that-is-the.66222/#post-66222

Taxidermist,

It was my pleasure helping you out with the calculations (believe it or not, I actually enjoy doing the math !)

However, I wanted to clarify one of the figures you posted:

13.6 GPM @ 77 ft. of head is not actually correct for your EKO60.

The correct number is actually 20 GPM due to your boiler being an EKO60 which is rated at 206,000 BTU/HR and not an EKO40 as I originally thought and calculated for.

206,000 / (500 x 20) =20.6 GPM

Also, below are the assumtions and calculations that I used in determining this pump sizing:

PUMP CALCULATION FOR EKO60 SYSTEM
01.17.09

QTY ITEM DESCRIPTION

348’ 1” Pex 348'
38’ 1” Black Pipe 38'
13’ 1-1/2” Black Pipe 13'
8 1-1/2” BP elbows x 4.03 32.24
6 1-1/2” BP tees x 2.68 16.08
6 1-1/2” ball valves x 6.50 39
2 1” Shark Bite elbows x 2.62 5.24
8 1” BP elbows x 2.62 20.96
7 1” BP tees x 1.75 12.25
2 1” Ball Valves x 1.80 3.6
1 1-1/2” Danfoss loading valve 16.4

TOTAL (Equiv. length pipe) 544.77

HL= k x c x L x (f1.75) where:

k=0.00223 (1” Pex) x 348’ = .776
k=0.00036 (1.5” Pex) x 348’ =.12528
k=0.0001(2” Pex) x 348’= =.0348
(notice this # drops significantly due to the larger diameter Pex, 1” dia. = .785 in2 area,
1.5” Pex =1.76 in2 area, 2” Pex =3.14 in2 area- more than double !)
k=0.000845 (1” copper/black pipe?) x 38’ = .032
k=0.000146 (1.5” copper/black pipe?) x 13’ = .002
c=.933 (water @ 180 degree)
L = 545 (equiv. length of piping circuit)
f1.75=101.327 (based on 13.6/14 GPM desired flow rate)
f1.75=189.148 (based on 20.6/20 GPM desired flow rate)


USING 348’ OF 1” PEX
HL=(.776+.032+.002) x .933 x 189.327 = 143 feet (based on 20 degree temp drop & 20.6 GPM design flow rate)

Because of the extra long length of 1” Pex the head is very high and thus not even a Taco 013 can provide 20.6 GPM at 143’ of head (a 014 is rated for a max of 8 GPM at 6’ of head). Even at a flow rate of less than 1 the Taco 014 has a max head of 35’.

When doing the initial calculation of target flow rate (Page 1 of Taco TD10 bulletin):
F = Q/(500 x∆t) where:
F= flow rate
Q=rate of heat transfer (BTU/Hr)
∆T=temperature drop of circuit (supply temp – return temp)

F=206,000 BTU/HR/ (500 x 20) = 20.6 GPM ( the EKO 40 is rated at 206,000BTU/HR)

When looking at table 1 on page 2 of the same bulletin, it shows that a 1” Pex has a minimum flow rate of 3.8 GPM and a max flow rate of 7.5 GPM. Thus, the 1” Pex is not large enough for this application. The proper size Pex would be 2.0” which has a min flow rate of 13.4 GPM and max. flow rate of 26.8 GPM.


Running the same calculation but using 1.5” Pex vs. 1” Pex results in the following:

USING 348’ OF 1.5” PEX
HL=(.12528+.032+.002) x .933 x 189.148 = 28 feet (based on 20 degree temp drop & 20.6 GPM design flow rate)

STILL QUITE A BIT OF HEAD ! (a Taco 013 is max. rated at 20 GPM @ 18 ft. of head, possibly a 014 might get the job done)

Running the same calculation but using 2.0” Pex vs. 1” Pex results in the following:

USING 348’ OF 2.0” PEX
HL=(.0348+.032+.002) x .933 x 189.148 = 12 feet (based on 20 degree temp drop & 20.6 GPM design flow rate)

THIS IS MORE LIKE IT ! This scenario can be taken care of with a Taco 011 pump which is rated at 20 GPM @ 13 ft. of head (a 013 would probably be best).

I have used the data listed for copper fittings/pipe when calculating the k value of the black pipe items. I’m assuming these are pretty close to the same but will investigate this further to verify.

The bottom line is something we've all heard before:

PAY ME NOW (FOR THE LARGER PEX) OR PAY ME LATER (FOR THE ELECTRICITY OF THE SUPER LARGE PUMP THAT IS REQUIRED WITH THE SMALLER PEX AND ALSO HAVING AN IN-EFFICIENT SYSTEM FOREVER!)

Warning to all - keep the Pex large when running it in long lengths !

Sorry to post all the details but I figured this might clarify things.


Rob

I got to thinking....... when figuring my head pressure with storage should i include my piping to my HX and my DHW? I would since they are doing their own pumping from storage I should have only totaled the piping to and from my boiler to my storage only????

Rob

http://www.taco-hvac.com/uploads/FileLibrary/100-68.pdf

and this in the future:



SK