estimating flow on 15-58FC circ based on amp reading

Dave_4

As restrictions increase the wattage will actually decrease. That might be the opposite to what you might be thinking.

If you took a pressure measurement right before the circ and right after, the difference in pressure (deltaP) would tell you exactly what you want to know. Unfortunately, that's not as easy as hooking up an ammeter.

Dave_4

flow on 15-58FC circ from amp reading

Does someone have an amp vs flow reference for the Grundfos SuperBrute 15-58FC circulator?

I took an amp reading between .78 and .79 on Speed 3 and I would like to have a rough idea where on the head/flow curve the pump is operating.

Dave_4

no pressure gage across circ

> As restrictions increase the wattage will

> actually decrease. That might be the opposite to

> what you might be thinking.

>

> If you took a

> pressure measurement right before the circ and

> right after, the difference in pressure (deltaP)

> would tell you exactly what you want to know.

> Unfortunately, that's not as easy as hooking up

> an ammeter.



You're correct, if I could measure the pressure change across the circ then I wouldn't even need to post the question here since the pump curve would tell exactly where it is operating.

I've been told the only other way of measuring flow is via an ammeter reading. Amperage would increase with flow. Its not as accurate and you need a cross reference. The Grundfos 3speed SuperBrute is such a popular model that I would think some wetheads here may have this info.

Dave_4

I actually tested this...

On a 15-58 connected to an ammeter, I started closing the flow with a ball valve. I stopped after the current dropped by 0.1 amp. I then tried it again... same deal.

Try it for yourself.

Darrell

If you have just a smidgeon of room...
I have a rig I built out of a pair of rubber universal 2-hole pump gaskets sandwiched and glued together with a probe like you'd use in a pete's plug or testing a circuit setter. One set on each side of the pump tightened down just enough to stop leakage but not crush the probes and then plumbed into ball valves and a guage. I even cut the bolt holes open so I don't have to un-bolt the pump completely. Works like crazy and it is fun to play with the pump speeds and do the math in a real system instead of just on paper.

I'd like to see Taco or Grundfos or one of the bronze flange manufactures make flanges with tappings in them for the smaller pumps...especially now that Taco and Grundfos both have integral check valves...it would help to burp the pumps.

Brad White

Amps, Schmamps....

Commercial type pump curves do have brake (net) HP curves superimposed over the flow/head curves we normally see for residential grade circulators.

A specific reading absent pressure will only tell you what the amp draw is. It could represent several combinations of flow and pressure. A low flow at high pressure may have the very same amp draw as a higher flow at lower pressure.