Pump to Maintain a fixed delta T

Garritt

Taco makes a varible speed pump based on delta t.

Unknown

scratching my head

How do you run a variable speed pump to maintain attempt a fixed temperature differential between two sensors, AND run only if one is larger than the other.

say sensor A is on system return, sensor B is reading the outlet of a solar tank, and you shoot for a ten degree optimal differential. As long as A is less than B, the pump runs (powered up by a heat demand, or constant circ, your choice), ramping up in speed as the differential grows to full power at your specified differential.

I know there must be something out there that will translate a temperature differential to a variable power output....

Andrew Hagen_2

Why?

You want a control that turns on at a specified differential and then increases pump speed to a set higher differential? ie 40Hz at 5°F differential and 60Hz at 30°F differential? Then if the differential drops below 5°F it shuts off? I'm not sure I follow why one would do this? Why is the differential important?

Could you use a differential setpoint control to kick on the circ and then use a Wilo Stratos on dT control? I haven't used a Stratos, so I'm not completely sure on all of the control options included.

Mark Hunt_6

Wilo Stratos

The Stratos can accomplish this via a 0-10 vdc signal and our 0-10vdc module.

Honeywell makes a control that will modulate the signal based on DT and this will ramp the pump up and down accordingly. I am sure there are other control companies that make similar devices and I do not mean to leave anyone out.

Feel free to contact me if you have further questions.

Mark H

Mike C._4

Maybe

Resol has a line of solar controllers that use a differential to run a variable speed pump. Not sure if they are available in the US. I use the fixed relay version. Here's one link:

http://www.acmegreen.com/page4/assets/Resol_Solar_Controller.pdf

S Ebels_2

Rob

What flow rates are you looking for. Are we talking a OO series Taco variable speed or something larger?

Unknown

doing a solar contribution tie in with a differential control reading the outlet temp of a solar coil, and the return temp of a heating system.

if outlet is higher than heating, transfer.

Problem is, when you transfer on full speed, the sensor temperature plummets, and it kills transfer pretty fast. I am suspecting that a delta-T control pump might prevent that "see saw" and instead allow for a more consistent draw from the solar tank. Worst case, another option for the problem is that the tank "flips" when we draw a lot of heat out very fast, and a delta-T control might fix that too...

Unknown

very low flows desired. Negligable frictional loss and low, perhaps even fractional GPMs at times.

Unknown

Thanks for the help mark and pexrunner!

S Ebels_2

I'd look at the OO Taco VS first although I don't know how low it will go. Wilo would be high on the list also.

Unknown

thanks! we're checking it out: seems like it might be a decent fit.