[Equest-users] Throttling Range and Pipe Insulation

B. Fountain bfountain at greensim.com
Thu Jan 21 08:09:02 PST 2010

Throttling range is defined as the number of degrees F the zone
temperature needs to be away from setpoint for the VAV box to be fully
open or the heating or cooling coil valve to be fully opened.  So, if you
have a VAV system and are setting the throttling range to 0, those boxes
are going to be modelled as fully opened whenever the space is not
completely satisfied.  (Rereading your message -- that is probably not
what you meant by 0).  Depending on your system -- 2 to 4 degrees F is
probably reasonable.

The BEPS is telling you that there are hours outside the throttling range
(underheated or undercooled hours -- see SS-R report or air side summary
for all systems in eQUEST interface to find which zones have problems;
SS-O helps tell when underheated/undercooled hours are happening) but that
plant has sufficient capacity in all hours.
> 1)       What is the definition of "throttling range"?  I have always
> had 0 until my last project which is a Police Station.  We do mostly
> energy retrofits and the existing boiler, 37 years old, has an input of
> 450 MBH.  The total HVAC load is 222.651 MBH per eQUEST.  For the first
> time Report BEPU shows my base case model to be 34.1% outside of the
> throttling range.  What does this mean?  The % of hours any plant load
> is not satisfied is 0.

In the heating circulation loop, there is a tab for "losses" where you can
put in a UA value for the uninsulated piping as well as defining where
that heat loss goes.  You can then decrease the UA in a parametric run to
model the pipe insulation.  Have not done this too much though but in

> 2)       I have a church to model, starting this morning, which has no
> insulation on the steam piping and we want to determine the savings by
> putting 1" of              fiberglass on the pipes.  Usually we would
> determine the savings in e-plus but is there any way to model this in
> eQUEST?  There are other measures and it would be convenient to have
> everything in one report.
> Walt Henry
> Energy Specialist
> RISE Engineering
> 1341 Elmwood Ave.
> Cranston, RI 02910
> U.S.A.
> Phone:  401-784-3700 Ext. 119
> Fax:      401-784-3710
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