[Bldg-sim] How to model CAV system with VFD in E+

Nicholas Caton Nicholas.Caton at schneider-electric.com
Thu May 10 08:56:49 PDT 2018


Hi Javed,

It’s a relatively common thing in modeling existing facilities / systems to encounter VFD’s installed as “expensive motor starters,” which do not actively vary the speed of the associated pump/fan motor.  At times it can be observed the motor is operating at a steady, unvarying speed (i.e. 50.2 Hz) on the VFD display, which may suggest the installation/commissioning agent used the VFD to “tune” the water or airflow to match something scheduled.

Is this specifically what you’re trying to simulate?

If by contrast you mean to describe a constant volume system which has undergone a VAV conversion at the main supply fan, there is some nuance in system type selection over in doe2/eQuest world depending on exactly how that is controlled, but ultimately many system types have the option of switching from constant speed fan motors to variable speed.  I know you’re asking specifically about E+ but it’s my impression these platforms have more in common in terms of functionality than not – are you able to take a template for a CV system and assign a curve to establish how the motor power input varies as the fan is made to operate at less than 100% of it’s rated airflow capacity?  For visual reference, here are some of the options visualized from our doe-2 curve library (visual specifically is sourced from the reference manual, Volume 2: Dictionary > HVAC Components > SYSTEM > Air Flow and Fans > Supply Fan > SUPPLY-KW/FLOW) :
[cid:image003.png at 01D3E84D.9364D0E0]

[cid:image001.png at 01D3E84B.8D8F8220]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

D  913.564.6361
M  785.410.3317
F  913.564.6380
E  nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

[cid:image002.png at 01D3E84B.8D8F8220]



From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Javed Iqbal via Bldg-sim
Sent: Thursday, May 10, 2018 7:17 AM
To: Bldg-sim <bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] How to model CAV system with VFD in E+

Dear All,

I am trying to model CAV system which is serving a large volume of space and equipped with VFD control. As far as I know, we can't model this setup directly in the E+. However there could be an alternative approach for this. What do folks use for such system in E+ models.

Thanks for any pointers,


--

Javed Iqbal, LEED AP, CEA
Sr. Energy Analyst



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