Grundfos Alpha circ

I was hoping

that this was (and maybe it is) a magnetic bearing motor. I saw a chiller by McQuay, 150 tons with two 75-ton compressors. The rotor/impeller was suspended by a magnetic field and took 2 amps of staring torque. No lube system, no "bearings" to wear. And when "off" the rotor parks itself. Magnetic bearings have been used for years on boomers (nuke subs) for their quiet running. And this chiller certainly was quiet.

So my hope was that this technology made it down to the lowly circulator. I will have to check these out. Available when, where and at what cost?

That was you, Weezbo?

I think I got there before you did. When I came back all of my circulator installations were red-tagged... trying to tell me something?

:^)>

Hot Rod Told us not to,.....

those pumps were working fine when i left

the management put special tags on mine from the highest eff rating the EU has for energy saving equipment.

i forget the DIN rating it's 2006 so it is kinda new.

i know that is what management put on your circs too. it was a different mechanical room

What's different...............

Having seen neither one, what's different between the Alpha and a VS Wilo?

Grundfoss at ISH in 05

Pics from the trade show floor at ISH - Germany

Side-by-side live demo showing energy usage.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Thanks for the pic *~/:)

that idea appeals to me so it may have to be incorperated somewherewhen... who makes those snazzy brass valves ?


You Sure about that Brad '.....'~/:) just thinking out loud

Yes, But I would at least like to see a curve for full output and minimum drive.

HB and Paul

I'm afraid it's going to be up to you and I to drag our customers out of the stone age, probably kicking and screaming as the go. This IS the flippin' US of A for cryin' out loud!! We're supposed to lead, not follow!!

Hang in there dude

The day is coming soon ($4.00 fuel) when customers will think efficiency first and foremost. Those that didn't take the best possible system will be cursing themselves.
Hind sight is ALWAYS 20/20!
Off season price here is now $2.30/gl.

I would tend to agree with you, J.

Of course the boiler might suffer with any turndown, bypass or not.

Now, if the same circulator could maintain a constant delta T, that would be something useful.

The danger if you will, of a flat pump curve

is that a very slight pressure difference, point to point, will yield a very wide flow difference. Grab the flattest pump curve that you can find and take a look.

Granted the most appropriate pump is the one that will do the specified duty with the least HP/Amps, but one still has to allow for "predicted" versus "actual/real life" installed conditions.

But this is why I would hope such a circulator would also allow taking into account temperature factors including differentials. Pressure differentials in a pump system are incidental and an indirect way to control a system. This is heating; it is all ultimately about temperature, whether in the pipes or, the objective, in the space.

I yield the floor

A good way to operate is to have a fixed flow rate in any branch whether other branches are open or not. For example, suppose there are two parallel radiators with open TRVs, say there is some appropriate flow rate. Then if one TRV closes, the pump should detect the change in head pressure and drop the flow rate to half, so that the open radiator has the same flow as before.

How can this be achieved using intelligence at the pump, given a complex and unknown system of mismatched radiators, some in series and some parallel? Beats me.

Hi Brad,

Why do you think that it has a low turndown? The power consumption can vary from 25 watts down to 6 watts.

Found the curves for full output for the 3 models in the manual. Similar max flow as a Grundfos 15-58 or a Taco 007. But a lot of other data seems to be lacking in the manual.

Of wide open gravity systems...

One point of information, Mike-

I can see your point if the gravity system you cite is direct return (that is, the first radiators both supply and return are closest to the circulator and the furthest are the furthest). You would be correct in that the first served would take more in proportion than the downstream ones, although the effect would be minimal with larger pipe sizes and especially if they are extended at larger sizes.

IOW: Say a 2-inch main carrying 5 gpm. Velocity is less than 0.5 FPS (yawn) and head loss is about 0.074 feet per 100 feet of pipe (double-yawn). Branch one drops off a gallon per minute. Your next segment carries 4 GPM at a velocity of less tha 0.4 FPS. Head loss drops by the square to 0.047 feet per 100 feet of pipe.... etc.

Point being, each segment has minor head loss to begin with as you often pointed out. When the pipe size is extended as a trunk as often is the case, the losses drop exponentially. Sort of a regain situation (as recent reminded lessons in Bernoulli's Principles have demonstrated). Even if the pipe size is reduced, the losses are pretty teensy. (Scientific term, smaller than a mole.)

So I think there is room to turn down even direct-return piped systems.

Now, if the system is piped "reverse return" (first radiator served starts the return run) then all piping differentials are essentially equal anywhere in the system (assuming of course that the radiators or terminal units have equal pressure drops). Then I would respectfully submit that a gentle ramping up and down of the circulator would be rather beneficial and not default to a high speed especially.

Random thoughts...

Brad

Rise and restriction

I would submit that rise and restriction cancel each other out, Mike. Minute or not they compensate for one another.
That was the intent, to thwart the upstairs from over-heating and to make it all quite even.

That said, the motive force at whatever level should have a proportional result, that being even heating or at least even distribution of what is in the pipe. My "main" focus (pun partially intended) was just to illustrate the effect on the piping least effected by thermal bouyancy.

The best systems I have seen have been reverse-return. Self balancing under power or under gravity influence. This included a 1910 mansion near me in Chestnut Hill, MA, fired by an H.B. Smith boiler. Indirect CI pin radiators with outside air to the nursery, big CI radiators (to which I applied TRV's). I do not recall if it was top-down, but I think it was. 6-inch piping and the returns collected around the perimeter and followed the basement walls (warming it thank you) for a final cooling effect to increase flow contrast. Very elegant.

Sorry to break this too you, Mike...

Static pressure does nothing for the dynamic side of things by definition. All static pressure does in a closed system is get the water to the top with sufficient surplus pressure to force the air out. It fills once, then is closed off.

After that it is only the circulator and/or gravity forces that induces water to move. In forced systems we do our best to prohibit ghost flows with flow-check valves and in gravity systems we do our best to facilitate that effect.

Static is just that, a body at rest. You are right about the circulator just moving the water (creating a dynamic force known as differential pressure) such that the water in the closed system acts like a ferris wheel.

We do both agree that this differential pressure gradient will be very small, hence my leaning toward a temperature based control; speeding up or slowing down the circulator to maintain a constant delta-T for example. This would have the effect that upon reaching warm-up, the circulator would slow down and dribble in boiler water much like an injection loop circulator would. Not the same but as close an analogy as I could come up with in the moment.

Let's see....

I guess I would say the only effect that static pressure has on the dynamic side, Mike, is that it cancels out any effect static lift might have if it were a truly open system, meaning one where the water actually had to be lifted against gravity as part of it's circuit. An open cooling tower would fall into this category.

JUST occurred to me: When you use the term open gravity system, I took it to mean that it was "open" in terms of having little pressure drop. Is that what you meant?

That aside, the principle is the same: So long as the system fill volume completes a circuit over the high point and down to the returns, the net "ferris wheel" effect is the same.

"Ghost Flow" indeed is attributable to unwanted gravity flow in a forced system and when the circulator is off, correct.

Lowering or raising the speed (flow) will not effect the balance in and of itself in any system.

When a system is balanced (such as with fixed dampers in an air system or valves in a water system), the flow is "X" at a given head or inches of water in an air system. When you change the flow, the gradient changes across the system by the square of the flow. But the net effect is the same on any one branch because all started from the same point. If flow is reduced by half at the pump (or fan) and all other things remain equal, each branch will deliver half the original flow (or whatever proportion of the original it carried relative to the new sum total of the system).

In a system with TRV's (or VAV boxes in an air system by analogy) there is a different dynamic afoot: Pressure. The system pressure differential changes, supply to return (or supply to atmosphere, again in an air system). The pump or fan then raises or lowers it's speed in response to the pressure change, to maintain it as a constant. Some more sophisticated systems we design actually RESET that starting pressure so as to not maintain an artificially high pressure differential. How's that?

Hope this helps, Mike- As always I enjoy the discussion!

Brad