Circulator Pumps

Thanks I just ordered a k6 boiler. I ran 60 feet of 1 inch pex al pex outside where I will be building a very insulated 10x14 shed. I plan on running a closed loop with two heat exchangers one to heat the return water into the 125000 btu propane boiler and the other to heat dhw. Size of household is 2 adults and 2 daughters that seem to leave the hot water running until they re enter the shower the next day or so it seems. Thanks Brian

What's the specs on the heat exchanger? Manufacturer? P/N? etc.

I'll 'wing it'.. a Taco 007 or 0011 will do.. or buy one of the three speed Grundfoss pumps... for my 150' run of 1" pex into two plate excahngers.. one 40 plate [propane boiler], one 30 plate [DHW] I use a Grundfoss 26-96.. the equivalent to a Taco 0011.. works great, no noise in the pipes..

Greg L

Taco also makes a three speed pump that is only $10 more than the 007 Scott

What I am looking at is a GEA flatplate Brazed 40 Plate FP 5x12 Heat Exchanger and a GEA Flateplate Brazed LP 20 Plate 5x12 Heat Exchanger. The 20 Plate is for DHW and I believe that LP stands for low pressure. The house has 3 zones but might add a 4th. All suggestions welcome. Thanks Brian K6 is ordered 6 weeks.

There is a good collection of radiant hydronic heating information on Taco's web site. See:

http://www.taco-hvac.com/en/products/Ra ... egory=170#

Of special interest to this thread is info about circulator pumps. It tells you how to select a circulator. See:

http://www.taco-hvac.com/en/products/Ra ... d_id=16246

It doesn't tell you how to determine your piping resistance. If you want to do that I can give you some design methods.

Selecting a circulator pump for a hydronic heating system is a straightforward procedure of matching the water pumping capability of a pump to the flow resistance of the piping. In a closed hydronic system, i.e., one not open to atmospheric pressure there is no need to consider the height of the water in the boiler, radiators or piping. That’s because when the pump starts all the water in the closed loop starts moving. There is no “static head”. The only thing the pump needs to do is overcome the resistance to water flow. Small sized fractional horsepower pumps are more than capable of doing the job.

You must know several items to make an intelligent selection, the desired flow rate, the piping or equivalent piping resistance and the pump curve. The pump curve plots pump capability (feet of head) vs. flow (gallons/min). These pump performance curves are available from all pump manufacturers. The Taco brand pumps curves are shown in Figure 1.



FIGURE 1

Notice the wide selection and the fact that the slopes of the curves are all negative, i.e., more flow means less head. Later I’ll use the Taco 007 pump, a very common pump in residential applications, in an example. The equation of this pump is:

H (circulator) = 10.88 – 0.206(f) – 0.00971 (f)^2

H is head in “feet of head”; f is flow in gallons per minute.
The equation is derived from the manufactures published pump curves using simple polynomial curve fitting techniques.


Fluid flow in piping is described by the equation

H (pipe resistance) = acL(f)^1.75

H is head in “head of feet”, a (alpha) the fluid flow properties, c is a constant based on the size of the pipe, L is the length of the pipe and f is the flow in gallons per minute.

Notice the flow is raised to the 1.75 power. Observation of the equation shows the obvious, the longer the pipe (L) the more the resistance (H) and the larger the flow (f) the greater the resistance. In fact the resistance increases much more as the flow increases because of the 1.75 power.

The equation is a special case of a widely used Darcy-Weisbach equation for fluid flow and the Moody friction factor for turbulent flow in smooth piping. Don’t be overwhelmed it’s fairly easy to use. Derivation of the equation is way beyond any need here.

The fluid properties factor a (pronounced alpha) is based on the fluid’s density and viscosity. c is a constant base on the size of the pipe and is read from a chart based on the pipe type and size. L is the length of the pipe in feet. f is flow rate in feet per second.

For any piping-pumping system an operating point balance is created where the pump curve and the piping resistance curve intersect. It’s called the operating point. See Figure 2. The piping resistance is fixed and the pump operates with exactly enough output (Head) to overcome the piping resistance. The water flow rate is determined by reading from the graph the flow rate (gal/min) along the horizontal axis. In this example the flow rate is 2.42 gallons per minute. Without making piping changes you cannot change this flow rate. To increase the flow rate you must lower the piping resistance by making the pipes larger or select a more capable pump. This is an important concept to understand.




FIGURE 2

Yanche,

Have you seen this new ECO pumps by Wilo? Apparently this is the company of choice in Europe. These pumps seem VERY energy efficient copmared to the traditional wet-rotor circulators like the TAO 007s

These pump actually adjust to varying head pressure and increase/decrease the pump speed based on what's actually going on in the system.

Read this thread: http://forums.invision.net/Thread.cfm?C ... &un=6ka6fz

And I've attached a spec sheet for them.

I have a pump question. Cast iron is for boilers, bronze is for drinking water. What's the purpose of stainless steel?

Freddy, Stainless is also for potable water. Usually more expensive than bronze.

beatle78, I'm not familiar with the ECO pumps other than there is a new European Union energy standard for electrical efficiency improvements that is requiring a redesign of many items. Energy losses that were once acceptable no longer are. In the US Calif. is leading the way with new efficiency standards on the "wall warts", the little power units that power all our electronics. In total a big waste of electrical energy. Efficiency will improve and the units will no longer get hot. In addition the power factor will be 1.0 or close to it. This is a little understood term by the public which greatly impacts the electric utilities. Having less than unity power factor causes the current to lag the voltage, wasting power that the utility has to generate but you can't use. It's a big problem with electric arc welders which on occasion will cause a electric utilities pole mounted transformer to blow up.

I ran across this site and thread while searching for some info on circulator pumps and repairs. I am a trustee at a church and do some repairs when I feel that I have enough information, experience, and tools. There are two questions I have regarding the same pump set up. Unfortunately, I don't have all of the information so far as the pump capacity, or motor size at hand but can update it if it's needed. The first question is something that I just want to double check before proceeding. I did a re-build on the pump seal/bearing setup. This is one of those commercial set ups with the motor mounted to a flange in which the bearing/seal unit is in, and then has an impeller on the end of the shaft. It's an 8 hole mounting to the pump housing. The problem: I did a "boo boo" and snapped a bolt off when trying to clean out the rusted threads on the housing. (The motor is on a small slab that's raised about 8" off the ground, and the bottom hole is just at the right position to not allow getting a tap into the hole for the job. The setup is with a paper gasket and I was wondering if it's possible to just reassemble it with only 7 bolts holding it in place and not worry about problems, or should I do it "the right way" which involves un-bolting the pipe flanges on both intake and output and the pipes and housing, etc., to get access to the one bad hole to get the rest of the bolt out. (If a tap wouldn't go in, I can't very well get a drill, or bolt extractor in there to get it out where it is.) (The machined side of the pump housing is about 3/8" give or take from the slab.)

The second question involves some information that may help solve the problem of inadequate heating in parts of the building. This is a building that was built in the early to mid 60's so there was no concern with energy conservation. Our biggest problem is not easily solved as there are a large number of single pane windows in the church so we're losing a lot of heat that way. From what I can get from some of the older folks in the church, while it took a long time to get things warmed up, they don't remember having so many problems with it not getting warm enough inside. This of course seems to have changed when they replaced the old single unit furnace with a 3 stage 3 boiler system which brings me to my question. I'm wondering if part of the problem may be that the new circ pumps are adapted to the original piping. The old pipes are 2 1/2" pipes, the inlet to the pump is 1 1/2" and the ouput is 1" going to a reducer to the larger pipe. I"m guessing that the old pipes are part of a convection circulation system, but am not sure. I'm wondering if that 1" outlet on the pump is restricting enough flow that it's affecting the ability of the system to heat the building. The length of restriction is only 2 - 3" if that.

now dassa sommmaa pumpaa huh?

Is that from the Pioneer Tunnel/Museum? I was there this fall and saw a pump display very similar.

-Rob

yes exactly!