Grundfos Maga3 - any advice on that one?

[EnergyProfessional]

I have a small pump replacement and came across the new Grundfos Magan3 pumps and got pricing on them and also got pricing on the regular Grundfos TP along ith external VFD.

the current pumps have no VFD. So i either want to install "nrmal" pumps and a separate VFD. Or these Magna3 pumps. thsoe have a built-in adaptive controller to control flow etc. and have ECM motor. Cost probably is lower than using normal pumps with VFDs.

Does anyone have experience with them? They make them sound more efficient than regular pumps. but i wonder if an external dP sensor and VFD woudl work better since they have the dP sensor further in the system (the Magan3 has it in the pump).

Most of our pumps have VFDs. The mechanic for this building wants to try this one out, and so do I. We use quite some Grundfos pumps, especially the small UP with variable speed option. So I generally have faith in what they produce.

Do you guy have any experience or comment?

I could imagine in distribution systems they could work fine. I may be concerned in equipment loops where we need specific flows (heatpumps, chiller etc.).

This application is a secondary boiler loop with lead/lag pumps. 34 gpm,/ 40 ftH2O.

 

[MTES93]

Check w/ a vendor, but I believe the magna three works off power consumption, speed and a system curve based on input from design. You give it design head and flow and minimum control head and it generates a system curve in the software and then uses 'its' pump curves to match up to it. It doesn't use differential pressure to modulate speed, rather it checks its speed & power and checks where it should be on the system curve and speeds up/slows down to hit it. Very simplistic explanation here, but with out diving into them again it is the best I can do...

Other pumps do this now.... Taco Viridan, Armstrong has one too.

They look pretty promising, looking a putting a couple in our office as a replacement and trying them out on ourselves first.

 

[EnergyProfessional]

11241: thanks for your thoughts. for thsi project i actually went ahead and ordered regular Grundfos TP pumps with VFDs. Teh cost of TP pups including VFDs and Lon cards inc. VFD installation and commissioning actually is the same as for the Magna3 with the Lon card option. In addition Loncard only is available in 1-phase (I have 3-phase on site).

I'm not sure how the pump can know all the system details. It can measure tourque and derive pressure and flow from that. Correct. but how does it know I don't need more flow?

What I do with above pump-VFD setup is:

- install dP sensor in system (at largest coil, or 3/4 of main pipe)
- the VFD maintains a certain dP
- based on valve position I implement static pressure reset and static setpoint is in between a range (i.e. 3 psi - 5 psi). when more than 3 (adjs.) valves are 100% open, pressure setpoint gradually is increased. whne all but 1 valves (adjs.) are less than 100% open, I gradually decrease dP setpoint. Very similar to AHU static pressure esetpoint.

I don't know how the Magna3 can know all that, like valve position. In addition when a valve is stuck open, it will happily provide even more flow.

I also use pressure-independent control valves, not sure if thsi makes a difference for the logic.

I also had talked that over with our mechanic, who is open to try something out. but my concern also is repairability. Right now if a pump fails, we can easily determine the problem and replace the cheaper pump. Same for VFD. but with these "all in one" pumps trouble-shooting may be harder, and you may be forced to replace the entire expensive unit.

 

[z00b]

The MAGNA pump measures three inputs. The temperature of the liquid via an internal temperature sensor, the RPMs of the motor, and the amp draw of the motor. Knowing the RPM and amp draw allows the algorithm to calculate the power curve and the flow. From this information the performance of the pump is determined.
The only input that can be inputted into the MAGNA pump is a 0-10 VDC input that will control the output to a specific value. Anywhere between 0 to 0.5 VDC the pump operates at the 30% of maximum flow. At a 10 VDC signal the pump goes to maximum flow. If the signal is between the 0.5 VDC and 10 VDC the pump operates linearly between 30% and 100%, respectively.
Hope this helps.