[EnergyPlus_Support] Re: Manually sizing baseboards and plant loops

["avdbree" <avdbree@xxxxxxxxx>]

I changed the flow rate of the Pump:Constantspeed for the HW loop also
from autosize to a manual value.  And now the occuring flow rate in the
HW loop indeed followed this manual value. I can even change the maximum
loop flow rate from the Plant:Loop back to autosize without any problem.
So, case solved. Thank you for your support.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "James V Dirkes II, PE"
<jvd2pe@...> wrote:
>
> If you have defined a single pump for the hot water loop, then the
pump
> affects the boiler AND the rest of the loop.  If you have a
> primary-secondary loop, then the primary pump affects (mostly) the
supply
> side (boiler) and the secondary pump affects the demand loop.
>
>
>
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
>
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of avdbree
> Sent: Monday, August 30, 2010 4:47 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Manually sizing baseboards and plant
loops
>
>
>
>
>
> An object Pump:ConstantSpeed (Flow Rate: autosize) is used for the HW
> loop. The object Boiler:HotWater has a variable flow mode. I am not
sure
> if this variable flow inflicts the HW loop or is just an internal
aspect
> of the boiler.
>
> The model is run in E+ v.4.0.0.024.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> , Richard Raustad
> RRaustad@ wrote:
> >
> > Are you using a variable-speed or constant-speed pump?
> >
> > avdbree wrote:
> > >
> > > I am investigating an existing building. The idea is to add
> insulation
> > > and keep the existing baseboards. So, the (new) heating can work
> with
> > > a lower supply temperature.
> > >
> > > When I autosize maximum (water) flow rates and/or UA-factors in
the
> > > objects ZoneHVAC:Baseboard:Convective:Water, Boiler:HotWater and
> > > PlantLoop, I get a Delta T of the HW-loop up to 15 °K (which is
> fine).
> > >
> > > Then I set myself maximum water flow rates for the baseboards
(based
> > > on the maximum heating rates from a simulation), while keeping the
> > > flows of Boiler:HotWater and PlantLoop autosized. Delta T of the
> > > HW-loop dropped to about 3 °K (which is to small). The results
> for the
> > > Zone Mean Air Temperatures and Baseboard Heating Rates are still
> fine
> > > (and similar to the autosized situation). Apparently, the flow in
> the
> > > HW-loop is quite big now and most of the flow during most of the
> time
> > > is going through the bypass on the demand-side of the HW-loop.
This
> > > increases the return temperature and decreases Delta T. A small
> Delta
> > > T is not economic.
> > >
> > > The occuring maximum loop flow in the HW-loop is exactly the sum
of
> > > all maximum water flows of all the baseboards (as specified in the
> > > object ZoneHVAC:Baseboard:Convective:Water). So, I tried to set
> myself
> > > a lower Maximum Loop Flow Rate of the Plant:Loop (in order to
lower
> > > the bypassed flow and thus increasing Delta T). I choose the
maximum
> > > sum of all the baseboards water flows AT ANY GIVEN MOMENT. This
> > > maximum is -- in my case-- less then half of the sum of all
> > > (non-simultaneously) maximum water flows. And, by the way, about
> twice
> > > as much as for the completely autosized situation.
> > >
> > > But even when I manually set the Maximum Loop Flow Rate of the
> > > Plant:Loop, the occuring flow in the HW-loop is still the (much
> > > higher) sum of all (non-simultaneously) maximum flows of all
> baseboards.
> > >
> > > Did I forgot to change another object too or is this a bug?
> > >
> > > PS. I tried to attach the idf-file but could not find the way to
do
> this.
> > >
> > >
> >
> > --
> > Richard A. Raustad
> > Senior Research Engineer
> > Florida Solar Energy Center
> > University of Central Florida
> > 1679 Clearlake Road
> > Cocoa, FL 32922-5703
> > Phone: (321) 638-1454
> > Fax: (321) 638-1439 or 1010
> > Visit our web site at: http://www.fsec.ucf.edu
> >
> > UCF - From Promise to Prominence: Celebrating 40 Years
> >
>




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