alpha 2 pumps

mike12 · November 26

System: boiler 60 ft from house. 1" insulated underground line to pumps and manifolds. 60 ft 1' insulated pipe back to boiler.

Three zones. Two 4 loop manifolds each with 300' runs per loop. One 2 loop manifold with 300' runs per loop. Grundfos Alpha 2 15-58 for each manifold. Mixing valve 3.5 cv for each manifold. Flow through the manifolds (they have the little flow meter on top) will show 0.4 gallons/min per loop when in high speed and delta T of 20 degrees. The two loop manifold will have 0.6 gallons/min. All other settings little to no flow. Auto adapt little to no flow as measured by the return water not changing temperature. If only one zone is activated the flow does not change appreciably. Is there too much head for the pumps? Should I have a return pump to decrease the resistance? If I take the boiler out of the picture and drain the return water just before the boiler the flow will increase to .7 gallons/min.

Second question. Fourth zone is two circuits of 1' pipe to heat exchanger in the air handlers which have a capacity of 18 gallons/min each. One unit is on ground level, the other is 22ft above ground level. Same 60' foot run to house and 60 ft to boiler. No mixing valves. Pump is Grundfos Alpha 26-99. Can not determine the flow since every time the pump turns on it either blows the GFI or the 20 amp breaker so I disconnected it. If the pump did work would it be able to supply water to the second floor heat exchanger? It seems that it should from the graph. Comments/suggestions

hot_rod · November 26

We need to see how it is piped. Does the 1" pex form a primary loop somehow? Or just manifold to all the zone pumps? How are you taking the boiler out of the loop? How many total btu/hr. are you trying to move from the boiler to the building?

Knowing or measuring flow rate is a better way to troubleshoot. That delta will be wide when the system is cold, and close down as rooms come up to temperature. It could take hours to reach thermal equilibrium. At that point measure the ∆ and calculate btus delivered.

Do you have a design that calls out how many gpm the loops need to cover the load? .5 gpm is common for a 300' loop.-

hot_rod · November 26

About 8 gpm is what you could expect through that 120' with a few fittings added. That puts you at the maximum velocity for the pex tube. 10' of head at that 8 gpm flow rate, in the loop.

If you have other fittings, valves, 3 ways, that needs to be in the calculation.

Screenshot 2024-11-25 at 7.51.46 PM.png

mike12 · November 26

The primary loop is around the boiler. The 1' pex branches off the 1 1/4 inch primary loop to supply the manifold and return from the manifold. There is a cutoff to the return water at the boiler (which holds 700 gallons of water at 15-20 psi) with a place to connect a hose if the boiler needs to be drained. by turning the cutoff and opening the spigot the return water just drains to the ground and the flow increases. I do not have the original calculations for btu's per hour but remember that I was supposed to have 0.8 gallons/min thru each loop.

So my 1" pex runs from the boiler should be 1 1/4? Or does it depend on the pressure?

hot_rod · November 26

https://forum.heatinghelp.com/discussion/comment/1822670#Comment_1822670

everything sizes to the job you are trying to get done. So the btu/hr load is what the pipe and pumps need to size to. Realistically about 8-9 gpm, so 80,000 btu/hr is what that 1” loop will do for you. Is that adequate to do the job?

10 loops total on that 1” run? That is probably workable. 10x.7 gpm = 7 gpm

hot_rod · November 26

the mixing valves, do they have check valves and screens in the H and C ports? If so you can remove them and check flow

mike12 · November 26

Those three zones do heat the house. I was just wondering if something was wrong since the pumps have to work at their highest setting in order to have adequate flow. Right now the flow is 0.4 gallons/min in the loops and the house is warm. I will have to check with the plumber if there are screens in the mixing valves. It seems the only thing that can be changed is adding a return pump to decrease the head pressure and make the other pumps not work as hard. Is that necessary?

hot_rod · November 26

there is no issue with the pumps running on their highest setting, they are designed to run this way.

Check for any flow restrictions.

There is no need I can see to split the load between two pumps if you are getting the heat you need with one?

Jamie Hall · November 26

Adding a return pump is a remarkably poor idea. Two pumps in series (which they would be) is problematic enough when the pumps are identical… If you need more flow (and you may not) you need a pump with a higher flow rate at the pressure differential you are looking at.

mike12 · November 27

Ok no return pump. Next issue. I am replacing the Alpha 26-99 which has never worked. That pump triggers the GFI and breaker when it turns on. This was placed to supply the air handler heat exchanger on the second floor which is 20' above the pump. What should I replace this pump with. I assume I need a pump that can handle a minimum 30' of head and that the radiant pumps must be off when that pump is on? All the fittings are copper and the width between the flanges is 6.5 inches. Any suggestions?

hot_rod · November 27

that Alpha may have run dry and seized, unless it is mis-wired it should not trip the GFI. An expensive lesson if you fried that circulator?

The circ sizes by the flow required and the pressure drop of the circuit. The height has nothing to do with the size in a closed loop system

mike12 · November 27

I did not plumb it and I did not wire it. When I disconnected the wires from the pump they appeared to be wired correctly. Black to black, white to white and green to green. It definitely was tripping the gfi for whatever reason.

So the 26-99 should have been able to pump 8 gallons/min (max flow through the 120ft 1" pex to and from boiler with the other manifolds off) since there is likely 12 ft of head (prior 120 ft run of 1" and another 80' of 1" to/from heat exchanger). The graph states that it should at that head. The heat exchanger is rated at 18 gallons/min. Should I get the same type of pump to replace it or should I get a more powerful pump like the UPS 26-150

GroundUp · November 27

The 26-99 is more than enough circ to move that loop. There is either a wiring issue or the motor is seized- that circ only draws 1 amp when running wide open. The exchanger rating has nothing to do with the circ- just that it's capable of (x) BTU with 18 GPM at (z) inlet temp. There is no 26-150 in ECM (unless you go to a Magna) so if the customer doesn't care about power draw, a standard 26-99 is more than enough circ for that loop and would flow about 8 GPM

mike12 · November 28

Thanks all for your help

alpha 2 pumps

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