anyone use a Variable speed drive to control heating pump motor?

elfie

was considering using a VSD to control the speed of the hot water heating pump which runs 24/7.  in periods of reduced demand it makes sense to reduce water flow.



I am interested in learning from anyone on their knowledge about functionality of a VSD connected to a pump motor (and pictures of installed device if you have one)





thanks

SWEI

heating pumps

What is the function of the pump?  If it's on the distribution side, slowing it down will increase delta-T, which will decrease the average temp, lowering the transfer rate of the connected radiation.  Unless you simultaneously close off zone valves and/or lower the firing rate of the boiler(s) the savings will be relatively small unless the pump was oversized to begin with.

elfie

pump is likely oversized

the pump is on the distribution side, use to circulate heating hot water to a facility with a mixing valve that automatically adjusts the temp of water circulating to facility based on outside temp changes.



the strong belief is that motor driving the pump is oversized.



the facility is complex (2 bldgs, one controlled better than other and newer and heating water is shared), and both bldgs are controlled by multiple zone valves thru out.



the motor runs at a constant rate for 6 months 24/7



on warmer days when demand is less, reducing water flow would likely not be a problem.



and if we find that motor is oversized, pump may be able to fulfill facility needs at a much lower rpm rate; adding to this equation is a substantially oversized hot water boiler - 75% excess capacity on coldest of days (pump/motor appears to have been sized with the assumption that boiler would be operating at high much higher capacity level)



ideally, i would envision a VSD with a pressure sensor that would control the motor speed automatically (ie. when lots of zone valves are closed, less water flow/pressure is needed)