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Re: [EnergyPlus_Support] Re: Heating:Electricity
VAV min flow fraction is determined by several critieria including minimum OA
requirements to the zone, and minimum circulation requirements to prevent the
zone from feely "stuffy". I usually see values in the range of 0.2 to 0.3, but
you will need to determine that for yourself.
The reheat coils and the boiler hot water supply loop all have schedules
available to disable them if you desire. But doing so may result in cold
zones. Better is to use SET POINT MANAGER:OUTSIDE AIR or SET POINT
MANAGER:WARMEST to reset the VAV supply air temperature set point to be warmer
when the weather is mild.
The sizing warnings are because you have a ZONE SIZING object for these
uncontrolled zones. Delete the ZONE SIZING object for these zones, because it
is not needed.
Maximum iteration errors are usually related to mass flow or temperature
problems around the loop. This occurs when the air loop side is doing
something contrary to the zone equipment. Examples of situations which may
cause this include: sum of peak terminal unit airflows does not equal the peak
supply fan air flow, node connection errors, bad control nodes, incorrect use
of active and passive branches, inconsistent equipment schedules, and
inconsistent control setpoints. Loose controller convergence tolerances can
also cause max iteration errors. Changing to smaller values for tolerances can
sometimes eliminate the problem. If you are unable to find the problem, please
submit your input file.
Mike
On 5 Oct 2004, at 16:37, beyangj wrote:
>
>
> Dear Mike,
>
> Thank you very much for your help. Yes, my input file is 2e3102 as
> you mentioned before. I don't know which is the exact value of the
> peak design cooling load, and I want to know which is the reasonable
> value for the VAV "Zone Minimum Air Flow Fraction" fields, could
> you tell me? How can I set the the schedules for the reheat coils
> and boiler and let them work properly?
>
> Moreovr, I have some problems about the SimAirLoops: Maximum
> iterations exceeded for VAV SYS 1. I just downloaded the newest
> version of EnergyPlus (1.2.1) today and installed it. I run my input
> file(2e3102) and the ERR output file gave warnings as follow:
> ** Warning ** Version in IDF="1.2.0" not the same as
> expected="1.2.1"
> ** Warning ** Requested Sizing for Zone="CORE", Zone is not found
> in the Controlled Zones List
> ** Warning ** Requested Sizing for Zone="RFCORE", Zone is not
> found in the Controlled Zones List
> ** Severe ** Deprecated Object -- Coil:Water:SimpleCooling.
> Please use Coil:Water:Cooling.
> In my model, the zones of CORE and RFCORE aren't served by the
> systems, but it gave the warnings for requesting sizing for these
> two zones, and is it necessary?
> I changed the version for 1.2.1,and I substituted Coil:Water:Cooling
> for Coil:Water:SimpleCooling, and the input file was run again, the
> ERR output file gave warnings as follow:
>
> ** Warning ** SimAirLoops: Maximum iterations exceeded for VAV
> SYS 1, at HONG KONG CHN IWEC DATA WMO#=450070, 01/10 08:17 - 08:18
> ** Warning ** SimAirLoops: Maximum iterations exceeded for VAV
> SYS 1, at HONG KONG CHN IWEC DATA WMO#=450070, 01/10 08:18 - 08:19
> ** Warning ** SimAirLoops: Maximum iterations exceeded for VAV
> SYS 1, at HONG KONG CHN IWEC DATA WMO#=450070, 01/10 09:34 - 09:36
>
> <snip>
> ** Warning ** SimHVAC: Maximum iterations exceeded for all HVAC
> loops, at HONG KONG CHN IWEC DATA WMO#=450070, 12/20 18:00 - 18:15
> ** Warning ** SimAirLoops: Exceeding max iterations
> continues...2500
> ** Warning ** SimAirLoops: Exceeding max iterations
> continues...2550
>
> I don't know why this happened. Could you kindly help me?
>
> Best Regards,
>
> Stewart
>
>
>
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
> <mjwitte@g...> wrote:
> > I am assuming this is the same input file that we were looking at
> last month
> > (2e3102.imf). This mode is a VAV system serving 16 zones with hot
> water reheat
> > coils served by an electric boiler. The VAV "Zone Minimum Air
> Flow Fraction"
> > fields are all set to either 0.3 or 0.5, and the reheat coils and
> boiler are
> > scheduled to be on at all times the fan system operates. So,
> whenever a zone
> > sees a cooling load below 30% (or 50%) of the peak design cooling
> load, the
> > reheat coil will come on to prevent overcooling.
> >
> > Mike
> >
> >
> > On 3 Oct 2004, at 5:57, beyangj wrote:
> >
> > >
> > >
> > > Dear,
> > >
> > > The building in my IDF file is located in Hong Kong, but the
> > > simulation results showed that the Heating:Electricity was
> needed
> > > all the year round.Especially, the amount of Heating:Electricity
> in
> > > January was 1.08E+11 J, but that in July was 1.55E+10 J. In
> summer,
> > > the temperature in Hong Kong is very high, so there should be no
> > > need for heating. I don't know why this happened. Could you
> kindly
> > > help me?
> > >
> > > Best,
> > >
> > > Stewart
> > >
> > >
> > >
> > >
> > >
> > >
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov
> > >
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> > >
> > > Attachments are not allowed -- please post any files to the
> appropriate folder
> > > in the Files area of the Support Web Site.
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support
> > EnergyPlus-Support@g...
>
>
>
>
>
>
> The primary EnergyPlus web site is found at:
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>
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>
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>
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