VFD for WSHP 2

[dewall]

I've seen high savings information for Variable Freq Drives for WSHP. Is this realistic? It's my understanding that the main loops which need the large pumps are kept at a constant flow rate. Thus less need for ramping and that the individual pumps usually already have ramping? Does it come into play with the heat source and cooling source or am I just misunderstanding the system?

 

[dewall]

I found the answer to my own question. The key lies in zoning valves that shuts down the loops that aren't needed. Then you can use a vfv system and a variable freq drive to achieve upto 70% electricty savings on the pumps.

 

[ilan7]

Dewall
Main idea to use VFD for saving energy is to open the pump control valve all the way and control the pump flow with the VFD.
This way you save the energy (which was wasted on the valve) minus the efficency of the VFD. I had the chance to add two VFD's for a system last December. They cost about 18,000 $ each and saving about 50 KW. Electricity is about 0.08$ for KW/Hr so every month the saving is 2,500$ and in a year the VFD paied for itself and for the installation cost.