Help choosing a circulator

[kuribo]

Really? I calculated a bit over 8 ft of head at just under 5gpm with 1" pex. It looked to me like I was right on the 007 curve....???

 

[ewdudley]

Really? I calculated a bit over 8 ft of head at just under 5gpm with 1" pex. It looked to me like I was right on the 007 curve....???

With 180 degF supply, 100 degF return, 250 ft, 5 gpm, nominal 1.0" PEX (0.878" actual) I'm getting 9.73 ft head using:

(broken link removed to http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf)

which is about 0 gpm on the 007 curve.

The Taco formula agrees closely with the FostaPex table:

http://www.viega.net/cps/rde/xbcr/en-us/Viega_FostaPEX.pdf

  gpm   head
 3.00   3.98022
 3.10   4.21530
 3.20   4.45613
 3.30   4.70267
 3.40   4.95488
 3.50   5.21272
 3.60   5.47614
 3.70   5.74511
 3.80   6.01959
 3.90   6.29953
 4.00   6.58492
 4.10   6.87570
 4.20   7.17186
 4.30   7.47335
 4.40   7.78014
 4.50   8.09221
 4.60   8.40953
 4.70   8.73206
 4.80   9.05978
 4.90   9.39266
 5.00   9.73067
 5.10  10.07380
 5.20  10.42200
 5.30  10.77527
 5.40  11.13357
 5.50  11.49688
 5.60  11.86518
 5.70  12.23845
 5.80  12.61666
 5.90  12.99979
 6.00  13.38783

 

[kuribo]

If I look at 0 gpm, the 007 curve crosses the Total Head axis at about 11feet. If I follow a horizontal line to the right from 9 feet of head on the left, vertical scale, I hit 5 gpm on the 007 curve....Am I doing something wrong?

I am also wondering if it is a bad idea to use pex and a 190F supply temp? Maybe I should be limiting to 185F?

 

[ewdudley]

If I look at 0 gpm, the 007 curve crosses the Total Head axis at about 11feet. If I follow a horizontal line to the right from 9 feet of head on the left, vertical scale, I hit 5 gpm on the 007 curve....Am I doing something wrong?

I am also wondering if it is a bad idea to use pex and a 190F supply temp? Maybe I should be limiting to 185F?

That interesting. Sounds like you're doing it right, but your curve is different than mine. Here's the curve from Taco's Submittal Data Information for 007 circulators Effective: June 6, 2011:



I would assume there's some rules about having PEX too close to the boiler, and you'd want to make sure your overheat logic sends flow only through metal to the overheat radiation device and not through any pex. Most all brands are rated for 80 psig at 200 degF, but it can turn into bubble gum somewheres up over 250 degF.

 

[kuribo]

Here's the graph I am using from the Taco circulator selection document....Indeed, seems the graph is different....Guess another call to Taco is in order...

I'm planning to use copper around the boiler and for the overhead. The rest, pex...I suppose since it is rated to 190F I will be alright with it.

 

[kuribo]

Technical support at Taco said to use the submittal document info...

 

[kuribo]

Since I would be at the far end of the curve with 20gpm (with a 20F delta T through the boiler), I am looking at 16 gpm with a 25F delta T. The 005 looks good for the job..