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Circulator selecting

Member Posts: 72
Hi guys I have a cast iron baseboard radiant loop just trying to put the right circulator there are 8 ten foot radiators and about 20 feet of three quarter piping not sure if I'm doing the math correctly but it's coming out to 23. Something feet of head at 4 gpm does that sound right?

• Member Posts: 6,561
No, that doesn't sound right. Typically, CI baseboard has very little flow resistance. You'll have to see if the manufacturer has any info on it to confirm what the head is per lineal foot @ 4 gpm, but it should be pretty low.

I would think that a Taco 007 or a Grundfos UPS15-58 on low or medium speed would be more than sufficient.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
• Member Posts: 72
Thanks for the Quick response i was calculating the baseboards as straight pipe and each one has four elbows which o think came out to a total of 180 feet I'll upload my calculations when o get home
• Member Posts: 6,561
edited December 2014

You'll notice that an 8 foot section has a flow resistance of 2.68 INCHES of water column, not FEET of water column @ 4 gpm. 28 INCHES = 1psi (actually it's 27.72 inches). 10x2.68 = 26.8 / 28 = .9571psi. There's 2.31 FEET of head per psi. .9571x2.31 = 2.21 FEET of head for 80 lineal feet of BaseRay @ 4 gpm.

Of course there are 12 inches in a foot, and you could do the math that way.

Either way, the Grundfos UPS15-58 on low speed would be sufficient.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
• Member Posts: 72
Would This be the correct formula to figure out the head loss for 200 feet equivalent three quarter inch pipe?
• Member Posts: 72
For a total of 14.5 feet of head
• Member Posts: 72
Also where did you find the head loss at 4 gpm the chart only has 1 gpm on it?
• Member Posts: 6,561
The head loss for 200' of type L copper pipe is 8.7 @ 4 gpm.

The second chart in the BaseRay manual gives you inches of head @ 2000 lbs. of water per hour. That's 4 gpm.

You said that you had 20 feet of 3/4" piping in your first post.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
• Member Posts: 72
Thanks I sized the circulator based on 8.7 feet and it's working great so far if you don't mind to just break down how to figure out the head because every time I calculate it I get a different answer I'm obviously doing something wrong