[Equest-users] VFD Pumping

Sharad Kumar sharadcapricious at gmail.com
Fri Jun 19 03:43:48 PDT 2015


Hi Michael,

Kindly find my responses in blue.

I’ve performing an energy model to compare VFD Chiller pumping and Constant
Volume Chiller pumping for a multi-story office building using eQUEST v
3.65. Although I expect to save pump energy utilizing VFD pumping I’m not
seeing a savings and I believe this is due to my “Pump Properties Inputs”.

For both the VFD and constant volume pump scenarios I’ve input the
scheduled pump flow (1,300 gpm) and head (200 ft) and the other pump inputs
are default values. The energy difference between the two pumping scenarios
is negligible,

[SK] As i think that over defining the inputs may be not perfect, as there
is default flow based head and power defining curve which are also in
eQUEST. So may be over defining the inputs may over-ride or lessen the
effect of these curves.

.............................................................................................................
If there is no input in the pumps then the default value of the pumps will
be as per the design flow of the loop.

These design loop flow may be calculated as per loop design delta T, which
is normally 10-12 degrees Fahrenheit.
So as per me the default values may also be right if the specification
value are not perfectly calculated.
.............................................................................................................
Sometime in past i have felt that by inputting all the technical
specification values, may cause simulation error, if they mismatch with the
default pump properties.

So the eQUEST pump values calculation stream is like this, Delta T in
circulation loop< Loop design flow<pump design flow<Other properties like
head and power of the pump.

however, if I set the pump gpm to a default, which inputs a 1.00 Flow
Ratio, the energy savings is significant in the VFD pumping model.

Am I over defining the pumps by inputting the scheduled pump gpm? Should
the pump gpm always be set to default?

[SK] The default pump curves and input values may be conflicting so i get
dependent on the default properties of pumps as per my experience.
eQUEST can guide you by default values.
Hope this is helpful. Other related posts are also helpful.


Thanks,

*Michael*

Thanks,
Sharad.Kumar
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