stepper motors for valve control

[pybyr]

between my figurings about how to do a reasonably well considered overall system given both initial build cost and long-term operating efficiency (combustion + electrical), plus reading others' comments about motorized valves and their pros and cons.... versus using circulators for zoning....

why the ____heck___ isn't there an existing product using a "stepper motor" to control a ball valve, and/or a three or four way mix & or flow-reversing valve?

existing zone valves seem to generally have dinky flow openings compared to the pipes they are fitted to, and sorta dinky/flimsy operating motors, which also require constant power consumption for the full time they're " open " -- resulting in losses in all the fluid/ thermal/ operating electric load aspects of things.

stepper motors, on the other hand, are a very well-established, moderate-cost technology (they're all over the place in things like copiers and printers), have a lot of available torque, can _very, very_ precisely control exact proportional/ partial motion, don't consume a lot of power to operate, and can be run and then left for long periods in a given stationary position with NO power needed to "leave them there" in a static mode.

I got to thinking earlier this evening about how I could maybe use a single stepper motor, with appropriate (and not too exotic) controls to operate two "ganged" 4 way valves, all joined with toothed belts and pulleys, to maintain counterflow conditions on both sides of a plate heat exchanger when both charging and drawing from unpressurized storage.

With the collective practical experience and mental horsepower here on Hearth, this- use of steppers for better and more efficient valve control- is a topic that deserves exploring, so I hereby launch it

 

[Nofossil]

As with so many things in life, there are lots of tradeoffs. I too dislike the fact that the typical zone valve consumes power the whole time that it's open. However, it's a very clever piece of engineering that satisfies several system criteria. In the case of the Honeywell valve:

1) Fails to a safe and predictable state - no power, it's closed.
2) Can be manually opened if necessary.
3) If manually opened, reverts to automatic operation on next activation.
4) Requires no electronics of any sort - just simple 24vac to activate. Any thermostat and a 24vac control transformer and you're in business.
5) Provides an 'open' signal in the form of a contact closure.
6) Bare minimum of things that can fail. In 150 valve-years of experience, I've had two failures: a limit switch and a gear train.

All in all, not a bad piece of engineering. I do like the Taco EBV for its clever solution to eliminate power draw while open.

If you're building something with a microprocessor and a circuit board (like a copier) then it's not a lot of extra cost to include a stepper motor controller. As more heating systems begin to have onboard computers your valve may become an affordable reality - it's certainly technically feasible. However, including the required electronics as part of the valve would make it pretty expensive, in part because a hydronic system valve is a more hostile environment for electronics than a copier.

All that aside, I want one too

 

[leaddog]

http://cgi.ebay.com/HONEYWELL-V5013...ryZ42932QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

On ebay there is sometimes available 3 and 4 way valves in sizes up to 2in made by honeywell, semiens, johnson,and others that have actuators that modulate. I have acouple that my son and my self are going to install for boiler control. You have to do your homework on what will work on what valves but retail they would cost upwards of $1000 to $1500 but on ebay they can be had for under $200 if you by the parts seperate and take your time. They are controled with 0-10vdc and are available in open or closed, springloaded or not.