Attention pump manufacturers... (ME)

Mark Eatherton1

Times, they are a changin'. Was a time when one could generate a single curve for a given pump with a given impellar size and everyone was happy. Nowadays, with the advent of variable frequency drive controllers, and the ability to use variable speed controls, I find it necessary to ask all you manufacturers for information you probably never thought you'd have to supply, and that is performance curves for your pumps at different RPM's.

Obviously, the number of curves would be infinite, as the number of potential RPM settings can be varied between 1 and 1750 for example. That's not what I'm asking for. I think what we need are performance curves for the pumps showing the minimum recommended RPM's, and curves for 10 different points between the minimum and the maximum RPM's. This would give us the ability to fine tune the VFD controllers for any given pump manufacturers performance curves.

Additionally, at this point in time, its a guessing game as to how to program these devices. The control manufacturers don't have a clue, and neither do the pump manufacturers. As an example, I had a 5 HP base mount TACO pump. It was so strong, that even with a manual bypass wide open (1-1/4" on a 3" main) it was STILL blowing by the zone valves nearest the pump. I looked at the manufacturers curve, and chose a spot nearest the knee cap on the curve, and used this as the controllers set point. It seems to work great, but I think I just got lucky... Time will tell. The zone valves are no longer bypassing, and there have been no complaints of no heat, but it hasn't gotten that cold yet either.

Recommendations and comments welcome. Taco, Grundfos, Bell and Gossett, step up to the microphone...

ME



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Carl PE_2

B&G

You can generate pump curves for any rpm you want on B&G's web site. http://www.bellgossett.com/selectpumps.stm

Jerry Boulanger_2

This spreadsheet

will plot a variable speed curve for any pump. Enter information from the full speed pump curve in the highlighted cells on the second page. I condensed this from one that I built to plot similar curves for multiple pumps in parallel.

You will note that it plots for 85%, 70%, 55% and 30%, which is the minimum speed recommended. You can modify it, however, to plot at as many speed intervals as you want. You can also add another plot to the chart for the system curve. Some small pumps that run from electronic speed control rather than variable speed drives, e.g. Tekmar, will not go down to 30%.

I agree with you about the art of controlling variable speed pumps. I see many that do not achieve significant reductions in speed regardless of load. It's too complex to discuss here, but I'd be happy to answer any specific questions you might have.

Mark Hunt

Carl PE and Jerry


You missed Mark's point.

The data you mention is old hat. He is suggesting a change.

Re-read his post. It might help if you checked out his credentials as well.

Click on his "Find A Professional" link at the bottom of his post.

Not your average heating tech guys.

Mark H

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jerry scharf_2

running constant delta P

Mark,

What if you took a delta P transducer, ran it into a simple PID controller that runs the VFD to keep the pressure differential constant? Then you're not sweating if you got the right spot.

Many pumps sold in Europe have the pressure sensors and controls built in, and some are very energy efficient as well (Wilo Stratos, Grundfos Magna.) Just that no one imports them into the US because the industry wisdom is that they won't sell enough to make it worth the certification, support, etc. What I want is for someone to sell some of these in the US, or at least for someone to sell a low maintenance residential sized pump that can take a 56C motor mounting. I can hang the 3 phase motor and VFD from there.

You're right, current building control products don't have a clue about this. You end up having to roll your own for each case. I pick up used delta P tranducers on ebay and I can probably spare one if you want to take a go at it.

As for pump information, it would also be great if they told us the AC power curves at each speed. That's probably asking way too much.

jerry

Mark Eatherton1

Thanks guys...

It's ALL good information.

ME

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Mark Eatherton1

The problem is...

in this particular case, there is no record of the piping system configuration. It's a distric heating system, and all distribution piping is underground. Determing where the "sweet spot" really is is a challenge unto itself. This is a common problem in my estimation. I've seen engineers calculations where they CYA (theirs, not mine) and the pumps are GROSSLY oversized to the point that no one will ever complain about a lack of heat, but at what cost to the detriment of the system piping, parasitic operating costs and controls? If you chose to control based on delta T, and the system is configured direct return, you'll probably short the far end of the system for flow. The same goes for guessing at delta P.

I guess the only good way to figure it out would be to keep lowering your delta P requirements until the people on the far end of the system complain, then turn it back up a few notches, eh..

Open to suggestions.

Thanks for your input Jerry.

ME

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jerry scharf_2

I hear you

Mark,

It's tough when you don't know what's going on, and you're in that boat any way you run the pump. The scary part about those oversized pumps is that it's quite possibly they are hiding undersized piping, and you won't know until there's an unusually cold winter stretch.

I've learned alot looking on the Grundfos UK site for how their European variable speed pumps are controlled. They have flat deltaP and they have a second strategy where the pump pressure rises slowly as flow increases. This helps overcome the greater head as flow increases. This may be what you are looking for. You'll need to find some compromise between the pressures near the pump and near the end of the runs or run pressure reducers on the close by stations.. Do you even know where the ends of the runs are?

jerry

Kal Row

the teckmar people recomend...

that you add a regulating valve so that the vai-speed takes place in the 65-90% range for longest pump life,

S Davis

Grundfos

Grundfos does have two pumps out the UP15-42FVS and the
UP26-96FVS that will work the way you describe and are available in the states (they are fun to get because most of the parts houses don't know they exist) I am installing a job using the UP26-96FVS with a Veris Indistries wet to wet pressure transducer in a radiant floor application, See attachment below.

Mark Eatherton1

COOL!!

Funny thing, this is not the same as their European model. This looks like a tekmar controller on a Grundfos american pump. Whatever it takes. Glad to see them finally bringing sometiing out. I've only been bugging them (Grundfos, Taco and tekmar) for the last 6 or 7 years..

Now, if the sensor technology will settle down, we can REALLY start cooking with these devices.

Thanks Steve

ME

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Kal Row

mark - what you really need is delt/p/t sensor pairs...

that can be used to drive the whole show, couple that, with “Permanent Magnet BRuShLesS DC VariableFrequencyDrive motors - that are just as home at 5rpm as 5000rpm, with centrifugal controlled pump impellor angles, and a camera type iris in the eye of the pump and now you have a sweet system - till you check the pocketbook, then it aint so sweet

though – the PM BRSLS DC VFD motors will soon be a reality for us – they are getting cheaper every day – (Appliance magazine), and their starting and low rpm torque is simply amazing and lend itself to slow flow like injection or radiant etc – and they need very little motor cooling since the electronics switches and ramps the coils so perfectly as to all but eliminate the elector-magnetic losses which cause a lot of the heat in the windings to begin with - not to mention the noise, look at the hard disk in you computer, it uses one of those, and evens it’s rpm and balances itself with instantaneous acceleration/deceleration live, like someone adjusting the speed control on a nanosecond basis many times per revolution – simply amazing – it doesn’t take that much to ramp up the size of the motor to our needs – ao-smith and emerson electric – and maxon, are on it, just to name a few –

maybe – such pumps can be powered off batteries charged from thermopiles in the flue gasses…. Not!!! hey, a guy can dream…

Mike T., Swampeast MO

That IS Cool

There's got to be a reason that the Vitodens varies its pump speed as a simple function of outdoor temperature.

Surely there's a suitable (and probably inexpensive) 0-10v temperature controller that can be adjusted appropriately.

Mark Eatherton1

We used..

a KELE sensor on the job we did with the 5 HP Taco pump, and the controller came with a BIG warning letting the installers know that if it wasn't properly commisioned that the sensor would be DESTROYED. This scared the installers to the point that they wouldn't hook it up without my being responsible for commissioning it. I accepted responsibility. There's a very delicate diaphragm that can't be allowed to see major pressure differentials, or it will burst, thereby rendering it useless, hence the warning.

http://www.kele.com/cgi-bin/navigate.cgi?cat=Model BVA-5&amp;js=setuser
http://www.kele.com/cgi-bin/prodsrch.cgi


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Mark Eatherton1

The tekmar people...

are making an incorrect assumption that SOMEONE did a proper job of sizing the pump in the first place...

Whatever fits between the flanges:-)

ME

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Kal Row

fyi: taco makes these also + more

http://www.taco-hvac.com/News.130/current_category.366/news_detail.html

hr

Mark, talk to

Rich Corcoran at Grundfos. He had some larger sized delta P pumps brought in for a job that fell through. I think They might be up for grabs for a guru like you

They have some cool stuff at the KC lab.

hot rod

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jerry scharf_2

I think they built it

Except for the battery part. Check out the Wilo Stratos (www.wilo.de,) it's a wet rotor pump with an ECM motor on the back. It's a spendy beast, but it should do all that you talked about. I talked to Wilo about getting one of these, but it was too dear for my system.

jerry

Joe Mattiello

Variable speed 00's

There is no minimum flow rate when varying the flow using a variable drive circulator. The rpms are controlled by wave chopping, and not a VFD.
Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com