pumps that vary speed based on radiators open/closed?

R. Kalia

I know there are variable speed pumps governed by voltage levels from external controllers. What I'm wondering is if there are pumps that detect differential pressure changes due to radiator valves (e.g. TRVs) closing, and automatically slow down so as to avoid pushing the same flow through the remaining radiators. In other words, pumps that maintain a given differential pressure.

I know about pumps with flat(ter) curves, and also about differential pressure bypass valves, but it seems like a waste to have the pump working at full speed when not needed....

Incidentally this is a converted gravity system, so the differential pressures involved (and the changes due to opening/closing valves) would be small and the max flow rate needed would be large...

Mike T., Swampeast MO

http://www.grundfos.com/web/homecbs.nsf/Webopslag/BBD6F3516C71DF0FC1256C4C0075849F

Cost is likely prohibitive (even if they are available in 60-cycle) for residential applications.

Mike T., Swampeast MO

I should have said for \"US residential applications\"

That article seems to presuppose proportional control in the system.

Put such a circulator on a system zoned with valves and you better be certain that your zones are well balanced as the circulator is going to try for the MINIMUM.

Put such circulators on a system zoned with circulators and your equipment cost is going to go through the roof. Since pressure drop through the individual loops is already fixed, you're already two generations behind the state-of-the-art.

Proportional burner control seems to "mess" with some of the logic and it seems that even Viessmann (the Vitodens does have a variable speed circulator) is having a bit of a problem reconciling flow, delta-t and delta-p seamlessly. If they weren't they wouldn't require a low-loss header in converted gravity systems with TRVs (or at least I'm told this is a requirement).

There's a conflict--if your supply temp is just suited to the heat loss then your flow isn't going to change appreciably.

jwade55_3

You could use

A taco Variable speed/Variable voltage circulator with an external DP sensor. This will accomplish what you need. You will need to pick a point in the system to be your input, usually 2/3 the distance from the circulator.

J

http://www.veris.com/products/env/press/pw.html

http://www.taco-hvac.com/uploads/Product_PDF/261.pdf