In HVAC
design “Purchased” Air is a novel term, unless you refer to buying an air
system from an air-conditioning contractor. Does it mean total Supply airflow,
or what does it mean? Should a term other than “Purchased” be used?
Najad Tuffaha, PE, CEM
PEPCO ENERGY SERVICES
Office 703
253-1774
Mobile 202 309-0553
Fax
703 253-1799
-----Original
Message-----
From: Michael J. Witte
[mailto:mjwitte@xxxxxxxx]
Sent: Wednesday, November 20, 2002
12:02 PM
To:
EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support]
i cannot get the heating and cooling load
Yes, Purchased Air is modeled as an ideal system. I have not
tested
various supply temperatures to confirm that it does not impact the
reported load, but it should work within limits. Obviously, the
heating supply temperature must be greater than the heating setpoint
in the zone. Likewise, the cooling supply must be below the cooling
setpoint. Setback recovery is an important consideration when using
Purchased Air. Purchased Air will provide enough heating/cooling to
recover from setback in a single timestep. This is why sizing
calculations should be done without setback.
Mike
On 20 Nov 2002, at 14:59, Adriana Angelotti wrote:
> About Ian's question a and Mike's answer on heating/cooling load :
>
> If Purchased Air is a system you add only to compute heating and
> cooling load, the simulation results should be independent from the
> parameters you must input such as: - heating/cooling supply air
> temperature - heating/cooling supply air humidity ratio
>
> Moreover, the thermostatic control should be ideal, that is able to
> respond immediately to temperature changes.
>
> Are my ideas correct? Is Purchased Air an ideal system in every sense?
> Thanks
>
> Adriana Angelotti
>
> ----------
> Adriana Angelotti
> PhD student
> eErg end-use Efficiency Research Group
> Politecnico di Milano, Dipartimento di Energetica
> Piazza Leonardo da Vinci 32
> 20133 Milano
> Italy
> ph +39.02.2399.3859
> fax +39.02.2399.3940
>
>
> ----------
> At 09.09 19/11/02 -0600, you wrote:
> >Ian:
> >
> >You do not need a complete HVAC system to compute the heating and
> >cooling loads, but you do need to add a "Purchased Air"
system. You
> >can read about this option in the Input Output Reference starting
on
> >page 393. For an example of the objects required to describe
this,
> >see EnergyPlus\ExampleFiles\PurchAir.idf
> >
> >Mike
> >
> >
> >On 18 Nov 2002, at 22:15, Ian Yiheng Wang wrote:
> >
> > > Hi there,
> > >
> > > i am using the program for buildings' heating and cooling
systems
> > > designing. First of all i need the result of heating and
cooling
> > > load because what i need now is the heating and cooling load
alone
> > > before i move on to other apects of the design. i have
already put
> > > in the nscessary data for the heating and cooling load as
such,
> > > the geometry of buildings, the weather date, people,
> > > equipment,etc. the problem i have got is that i cannot view
my
> > > result for the heating and cooling load. do i have to
complete the
> > > whole processs such as the Nodes, air distribution,
water loops,
> > > etc. to get the heating and cooling load. i believe that the
loads
> > > are independent of heating and cooling system itself. kindly
give
> > > me your advise on how to go about it.
> > >
> > > regards,
> > >
> > >
> > > Ian YH Wang
> > >
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