alpha circ in series

[weiland13]

Just curious if anyone has tried to run 2 alpha circs in series and if so, what was discovered. Does it work?

 

[jebatty]

Based on my experience in running 2 Taco 007 in series, there is some but not much advantage in achieving an increase in flow rate from a series installation. If I assume your goal is to increase your flow rate, then it would seem the better route would be to install a circulator that has that ability based on your system pump head at the desired flow rate.

 

[thecontrolguy]

If you need to overcome a particular head (pressure loss) restriction, it might be better to up-size the pump so the new pump exhibits the flow rate that you need and the pump is in the efficient portion of its pumping curve. If you are pumping out to a to remote heat source (or load), and the tubing is the correct size, you might get by putting one pump in the supply side and one in the return. This might work in a (closed) loop system where the supply pump overcomes the losses in the supply piping and fittings, and part of the pressure loss of the remote load or source, and the return pump overcomes the losses in the return piping and the local load or source. This setup might also reduce differential pressure across the pump(s) and reduce the likelihood of the pump cavitating if your loop pressure becomes too low. Anyone elses thoughts on this?

 

[ewdudley]

Just curious if anyone has tried to run 2 alpha circs in series and if so, what was discovered. Does it work?

Without having some idea what the circuit head loss curve looks like all anybody can do is speculate about your situation.

That being said, in the case of circulating pumps where there is no net lifting of water, two pumps in series could rarely be better than than a single pump with a more appropriate taller steeper curve. Probably the only time it would make sense is if the outlay for the two pumps is cheap enough to overcome the increased cost of electricity over the life of the pumps.

For instance a $100 Taco 008 might be the right pump, but two $10 Taco 007 pumps off craigslist might do the same job while using twice the electricity. There are cases where the 008 would be the better choice and other cases that would prefer the pair of 007s.

You want a pump to operate in the middle third of its curve. The right pump with the right power and the right curve is what you want. Taco has a good paper you can get to from the stickies above:

https://www.hearth.com/econtent/index.php/forums/viewreply/453833/

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

But as you increase flow through the circuit the head loss curve gets steeper and steeper, and at some point there can be no 'right' pump, or combination of pumps, because the power required become prohibitive. At some point you have to go with a fatter pipe, or get by with less gpm by increasing deltaT or by reducing the heating load.

--ewd

 

[in hot water]

You might need to bump up to the Grundfos Magna series or the new "mini" Magna. I'm not sure how the delta P function would work with two Alphas in series.

I have installed an Alpha with a Grundfos 15-58 in series on my drainback solar. The concept is the two pumps start and run together for about 3 minutes, to overcome the lift head. once the siphon is established then the 15-58 drops off. This allows me to run the solar with a very low power consumption Alpha pump, about 25 W. I did lock the Alpha in one of it's 3 fixed speed modes, no need for delta p on a fixed flow loop.

Pumps in series all but double the head, there is some friction loss in the volutes. Pumps in parallel double the flow, like this "Dolly Parton" pump assembly from Grundfos.

hr

 

[weiland13]

Thank you for the comments. I did not run any calculations yet as far as what may be required or what the proper size circ would be. I am just looking at the system in our home (we just bought a house with a very nice system done by a good friend in it) and looking if there were any ways to improve. I am not a master with system design or anything so everyones experiences on this board are and have been very helpful. Currently the system is set up with zoning circs. I was toying around with the idea of zoning with valves. Not really a need for it but after lurking around this site for a few months, you kind of get the urge to change things just because!! Thank you for the comments regardless.