Understanding 007e curve

mjstraw

I think I have an understanding of the application of conventional circ performance curves.  But the curve for the 007e has me confused.

At 10 feet of head, it shows 0-8.5gpm flow.  How does the circ determine exact flow at 10ft?

Jamie Hall

It doesn't, really. Rather, if it is used as a constant head device, it will automatically vary its speed so that it delivers the requested head -- in this case, 10 feet. Varying the speed varies the flow, which in turn varies the head lost in the system. The maximum flow it can produce at that head is the 8.5 gpm.

mjstraw

Still confused.  If it's going to bump head up to 10ft by ramping up speed, why does the curve show flow values for lower head?

Jamie Hall

If I recall correctly, if you are using it as a constant head device you can set it for any head you want -- up to its cutoff head, of course -- or, if used as a constant flow device for any flow up to the maximum it can deliver.

Keep in mind that for any given pump, the combination of head and flow which it will deliver is based on the rpm of the pump. The exact combination of head and flow which the pump will produce in a given system is determined by the head loss characteristics of the system as related to the head gain characteristic of the pump. The former is -- in most cases -- fixed. More flow, more head loss. The latter is also fixed for any particular rpm. More flow, less head added. At some point the characteristic curve of the system will intersect with the characteristic curve of the pump, and that's what the system will operate at.

The 007e is a variable speed pump. It can be controlled to run at any speed from zero up to its maximum speed. With a suitable controller, you can set it to run at any combination of head and flow you want, provided only that it is within the maximum curve. In the case in which you are interested -- varying flow at a lower fixed head -- it's mostly for convenience. From the engineer's standpoint, it might be more helpful, I suppose, to have curves showing the pump rpm or, better, the pump efficiency at various constant heads, or the same information at various constant flows. But the resulting graphs are going to get pretty complicated...

mattmia2

Looking at the manual it is constant head only, so it will produce whatever flow the resistance of the system supports at 10 ft of head, if the resistance of the system is too low for it to produce 10 ft of head at maximum speed, it produces more flow at less pressure.

Dave H_2

The circulator doesn't determine the flow, the system does.

We need to know what the system curve is and then plot that with the circ performance curve and where the two curves intersect it the actual flow and head that is occurring.

We go into details on how to get those numbers with this webinar

Enjoy

jumper

Good explanations. I'd add that those little circs can be made with various characteristics. Before variable speed Taco catalogue offered pumps whose flow was finite even at zero head and others with ever increasing flow as resistance decreased. Chosen correctly one could then design intelligent circuits with simplistic on/off control. Now with variable speed one must decide how she wants each circ to behave.

mattmia2

Most of the small ECM circulators have the control circuit built in and you can choose the behavior(although the 007e does not, something like the Grunfos Alpha 2 does)

Joe Mattiello

that's a great question, is the decimal that's throwing you off? I would agree, net flow is dictated by system curve, and there is small precentage of error; it will be close.

mjstraw

Thanks Dave H_2 (can't get @ to work with your ID)

I watched that webinar and the one on ECM circs.  The latter was the more helpful of the two.

@mattmia2 had it right earlier.  The 007e runs in constant pressure aka constant head aka zone valve mode.  Can't be changed to any other mode. Curious that it's also advertised as a zone circ while the ECM webinar recommended a fixed speed circ for that purpose.
  

mjstraw

Correction - After 7 days of continuous circulation it switches to proportional pressure mode.  But there is nothing you can do to force a mode change.