[Equest-users] Default Performance Curves

[James Hansen]

Someone will be able to explain this better than me, but eQuest curves
are not intuitive.  I wish they were, but they aren't.

 

As an example:  when you enter a chiller EIR curve as a function of PLR,
you would think this would be really easy, right?  0.1, 0.2, 0.3 etc as
the PLR, and then the corresponding EIR (KW consumed vs current
tonnage).  But that's not the case....you end up basically having to
square the EIR to get proper outputs.  Perhaps the same thing needs to
be done here? 

 

Again, someone will chime in with the real reasoning for this, as I've
seen it discussed before.

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

www.ghtltd.com <http://www.ghtltd.com/> 

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Clifford McDonald
Sent: Wednesday, October 13, 2010 4:29 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Default Performance Curves

 

Hello,

 

I'm fairly new to eQuest, but I was looking at the default performance
curves for VSDs on fans and pumps (EIR as a function of PLR), and with
the exception of the cooling tower fan (htrej-Fan-Pwr-fSpeed) which is a
cubic equation, they are all quadratic equations.  Why would this be
when, in theory, energy use should vary with the cube of motor speed
with a VSD?  Why would it be quadratic for supply fans and chilled water
pumps but cubic for cooling tower fans?  Is there anywhere I can go to
get more information on these default values?

 

Thanks for the help...


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