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[schoppy]

Just curious if anyone has ever installed pumps in series in the same loop, say one at the back of the boiler and one in the house? Will it increase flow gpm?

I am wondering about using 2 Grundfos Alpha pumps instead of one higher capacity pump which would be about 1/4 the energy used.

[RSI]

It will double the head. The max GPM stays the same. Depending on what is in the loop it could gain just a little to quite a bit.

[slimjim]

I have done it a few times on very long runs from the boiler to house, I have one in Mass that we installed 2 years ago with 500 feet of Logstor, circ at the boiler and another at the basement wall, no complaints or failures as of yet.

[RSI]

Alpha pumps use about 1/2 the power of a normal pump so that is closer to the power savings you would be looking at. I am assuming you have long 1" pex that you need to 2nd pump. Each Alpha would be running at 43 watts on high. If you went with a single B&G PL36 it would have the same head but might move slightly more water than the two alphas. It would probably be running somewhere between 150 and 180 watts.

Depending on how your system is setup, a better option might be to use an alpha running continuous and a 15-58 that runs off a temp sensor after the heat exchanger. Then you would only have the high flow rate when needed and use less power than two alphas running 24/7.

[schoppy]

I have two B&G PL36's (set on high) as my primary pumps now on the back of the boiler with an Alpha as my bypass pump to have enough GPM's for the G400. The Alpha says it is drawing 43 watts on high and shows 7 GPM at the back of the boiler. The B&G's say they draw 270 watts on high but I have never put a meter on them. If two Alphas would do it that should be less than a third the usage which I could calculate the pay back at my electric rates. 

I have another Alpha for the reservoir tank for my Geo going through a 20 plate exchanger and it shows using 7 watts and 5 GPM on low which has worked out great.

After I get my unit changed out I will probably experiment with the Alphas to see what kind of GPM's I can get and still meet the flow requirement.

[RSI]

PL36 pumps are single speed. Do you have NRF36 pumps? Those use a lot more power.

[schoppy]

Yes, they must be the NRF36 since they are 3 speeds. The amp rating on my NRF36 is 2.3 for high and the PL36 is 2.1 so not a huge difference. I got mine for a really good price, about half of what I've seen them going for.

[RSI]

The PL36 only draw that much at real low head and high flow. With long small pipe it will be running at a much higher head pressure and drawing less current.

[schoppy]

That's good to know.

I will admit my experience with HVAC is in servicing much more than installation but it is satisfying to me when I finish a project and it works good and looks good too. I will be trying various pump configurations before I add any chemicals.