Re: [EnergyPlus_Support] electric power (watts) of PTAC

On Mon, Nov 23, 2009 at 7:45 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

Hi, Richard and Hu Jia

I was just going to correct my observation on the Fan:On)ff object.

HVACTemplate-Always 1 is the availabilioty schedule. This is indicates that the the fan is always availale.

The other schedule Office HVAC was set to 1.0 in the IDF, and this is for the fan operating mode.
.
Jia wrote below that (it is AUTO FAN because I define 0 in the
field: Supply Fan Operating Mode Schedule Name.) The value in the schedule Office HVAC was set to 1.0.
=======
Schedule values of 0 denote cycling fan operation (fan cycles with cooling or heating coil).
Schedule values greater than 0 denote constant fan operation (fan runs continually regardless of coil operation).
The fan operating mode defaults to cycling fan operation if this field is left blank.
==============

Sorry for the confusion.

Dr. Li

> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: RRaustad@xxxxxxxxxxxx
> Date: Mon, 23 Nov 2009 16:58:44 -0500

> Subject: Re: [EnergyPlus_Support] electric power (watts) of PTAC
>
> From the PTAC Eng. Doc:
>
> The PTAC is able to model supply air fan operation in two modes: cycling
> fan ? cycling coil (i.e., AUTO fan) and continuous fan ? cycling coil
> (i.e., fan ON). Supply air fan operation is coordinated with the use of
> a supply air fan operating mode schedule. Schedule values of 0 denote
> cycling fan operation (AUTO fan). Schedule values other than 0 denote
> continuous fan operation (fan ON). Fan:OnOff must be used to model AUTO
> fan (i.e. if schedule values of 0 occur in the supply air fan operating
> mode schedule), while Fan:OnOff or Fan:ConstantVolume can be used to
> model fan ON (i.e. if schedule values of 0 do not occur in the supply
> air fan operating mode schedule).
>
>
> YuanLu Li wrote:
> >
> >
> > Hi, Hu Jia
> >
> > I point out the Schedule Always 4 to you, because in the error file,
> > it is in the ophan object warning. The Fan:OnOFF is always one. But
> > in your .xls you send earilier seemed to have the zero in the
> > schedule. Zero is constant flow, one is on/off auto. Therefore, the
> > two schedules are opposing each other.
> >
> > The ground temperature was also in your error file warning. I tried
> > changing it, and it added about one watt to the fan power. I know
> > that the efficiency value is included, because when I reduced the
> > efficiency from 0.7 to 0.5 the fan power increases.
> >
> > The other PTAC model in the example file is a 3Zone building in
> > Miami. The fan power for the 6m x 6m West Zone was sized to 90
> > watts. Those zones without any windows are a lot lower. In this
> > model, the template objects were not used. All the sizing objects
> > were present and no .expidf was generated. There were only one
> > warning on the weather file location data.
> >
> > I have a feeling that the 5Zone template was not correctly expanded
> > for sizing, and therefore generated those warnings. I have not solve
> > the problem yet.
> >
> > I do not have any EPlus project of my own and am doing this as my
> > hobby. So long you think my comments are useful, I shall pick up some
> > of your questions.
> >
> >
> > Dr. Li
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > From: hujia06@xxxxxxxxx
> > Date: Mon, 23 Nov 2009 15:11:35 -0500
> > Subject: Re: [EnergyPlus_Support] electric power (watts) of PTAC
> >
> >
> > I quite appreciate your help. I see the expidf and find the objects
> > you mentioned. At first, I did not use the template
> > model (PTAC) and used the schedule "Always 4". But when using the
> > template model, I did not delete this schedule because I think it will
> > not affect my the result.
> >
> > For the angle of the window blind, I define it deliberately to see the
> > effect. I will look at what will happen when changing the ground
> > temperate.
> >
> > From IO manual, the HVACTemplate-Always 4 is the Dual Thermostat of
> > HVAC. and HVAC Template-Always 1 is the schedule of fan on/off. For
> > my model, the fan is supposed to be on until the HVAC cooling or
> > heating coil stops working (it is AUTO FAN because I define 0 in the
> > field: Supply Fan Operating Mode Schedule Name).
> >
> > Jia
> >
> > On Mon, Nov 23, 2009 at 1:45 PM, YuanLu Li <yli006@xxxxxxxxxxx
> > <mailto:yli006@xxxxxxxxxxx>> wrote:
> >
> >
> >
> > Hi, Hu Jia
> >
> > I think you have two items in your IDF which can reduced the
> > cooling capacity requirement.
> >
> > 1) You did not have a Ground temperature below the building in the
> > IDF. The program used the default value of 18°C. If you raise
> > this value to 22°C, the cooling demand and fan power will
> > increase. The best value to use is to run the slab program. The
> > estimated value is two degrees below the indoor floor temperature.
> > (in IO Manual)
> >
> > 2) The other component that can reduce the heat load is the window
> > blind. You have the angles set to 65, 90, 90 degree. These may
> > still block some of the sun light.
> >
> > Because you are using the template model, the EPlus has added some
> > more objects in the .expidf for you. That is also why your Always
> > 4 schedule was not used. Another schedule: HVACTemplate-Always
> > 4 was generated and used.
> >
> > ZoneControl:Thermostat,
> > Rinker building office Thermostat, !- Thermostat Name
> > Rinker building office, !- Zone Name
> > HVACTemplate-Always 4, !- Control Type
> > Schedule Name
> > ThermostatSetpoint:DualSetpoint, !- Control Type
> > Rinker thermostat Dual SP Control; !- Control Type Name
> >
> > Fan:OnOff,
> > Rinker building office PTAC Supply Fan, !- Fan Name
> > HVACTemplate-Always 1, !-
> > Availability Schedule Name
> > 0.7, !- Fan
> > Efficiency
> > 75, !-
> > Delta Pressure {Pa}
> > autosize, !- Max
> > Flow Rate {m3/s}
> > 0.9, !-
> > Motor Efficiency
> > 1, !-
> > Motor in Airstream Fraction
> > Rinker building office PTAC Heating Coil Outlet, !- Fan
> > Inlet Node
> > Rinker building office PTAC Supply Inlet; !- Fan
> > Outlet Node Name
> >
> > I am not sure which one the program is using, when dealing with
> > the template model. That was the reason why I always display the
> > schedule value to verify in the .csv file.
> >
> >
> >
> > Dr. Li
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>
> > From: hujia06@xxxxxxxxx <mailto:hujia06@xxxxxxxxx>
> > Date: Mon, 23 Nov 2009 11:02:37 -0500
> >
> > Subject: Re: [EnergyPlus_Support] electric power (watts) of PTAC
> >
> >
> > Hello, Dr. Li, Thank you for your explanation. I understand now.
> > Thank you.Jia
> >
> > On Sun, Nov 22, 2009 at 2:08 PM, YuanLu Li <yli006@xxxxxxxxxxx
> > <mailto:yli006@xxxxxxxxxxx>> wrote:
> >
> >
> >
> > Hi, Hu Jia
> >
> >
> > RINKER BUILDING OFFICE PTAC SUPPLY FAN:Fan Electric
> > Power[W](Hourly:8-17) RINKER BUILDING OFFICE PTAC SUPPLY
> > FAN:Fan Delta Temp[C](Hourly:8-17) RINKER BUILDING OFFICE
> > PTAC SUPPLY FAN:On/Off Fan Runtime Fraction(Hourly:8-17)
> > 7.827441338 8.84E-02 1
> > 7.827441338 8.84E-02 1
> >
> >
> >
> > When the PLR is 1, the ran electric power is the fan power
> > consumption.
> >
> > This number includes the efficiency values 0.7 and 0.9
> > modification, entered in the IDF.
> >
> > I ran the 5Zone example IDF in the example folder, and it gave
> > the fan power ranging from 26 to 44 watts, with the zone area
> > from 60 to 140 m2 using Chicago weather file.
> >
> > I think your number of 7.82 watt for the fan size is reasonable.
> >
> > You have many DesignDay objects in the IDF. May be you should
> > reduce that to two worst case conditions and make sure that
> > the equipment is turned on for the required cooling and
> > heating temperature, by choosing the day type with the desired
> > correct set point schedule.
> >
> > Using the continuous fan mode, the fan power is displayed,
> > when the compressor is off. This can be verified with the
> > indicated power divide by the PLR, using the on off mode, or
> > at the few transition steps of the continuous mode.
> >
> > I try the 5Zone example with different DesignDay objects and
> > weather file run period, the sized fan size were different.
> > For the same zone, the range was from 32 watts to 44 watts.
> > The efficiency values are the same as in yours, 0.7 and
> > 0.9 for the fan.
> >
> > When I quoted the half HP window unit, the motor size of
> > quarter HP is used for both the condensing and evaporating
> > coils. The heat generated by the motor is not normally in the
> > cooling air path.
> >
> > A small table fan consumes about 50 watts, and this include
> > the power for turning or oscillating the fan direction. My
> > condo fan coil unit fan is 300 watt for 1000 sq.ft. with ducts
> > for four rooms. The little fan in the PC power supply is only
> > 2W, and its efficiency would be lower than a larger one.
> >
> > The HVAC power includes the compressor or heater and fan power
> > as drawn from the electricity supplier. The heat from the fan
> > is normally added into the air path, and a percentage value
> > can be set in the fan object. In your IDF I did not see this
> > object as a separate item, because this is special PTAC model.
> >
> > The dual band (type 4) thermostat is also not used (Schedule
> > Always 4). I have seen one occasion in the 5Zone example both
> > the heating and cooling were on at the same hourly period. I
> > need to verify that they are not in the same time step.
> >
> > The 5Zone model has 146 warnings, because the dry bulb
> > temperature was too low. This may be due to the fan power was
> > low. If I find any thing later after correcting the error
> > warning conditions, I will let you know.
> >
> >
> >
> > Dr. Li
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>
> > From: hujia06@xxxxxxxxx <mailto:hujia06@xxxxxxxxx>
> > Date: Sun, 22 Nov 2009 11:00:41 -0500
> >
> > Subject: Re: [EnergyPlus_Support] electric power (watts) of PTAC
> >
> >
> > Hello, Dr. Li, Thank you very much. I upload one idf. file and
> > weather file to clarify my question. You can see the range of
> > HVAC electric power (W) and fan power from the output file.
> >
> > The URL is
> > http://groups.yahoo.com/group/EnergyPlus_Support/files/_Problem_Submittals/input%20and%20weather%20file.zip
> > <http://groups.yahoo.com/group/EnergyPlus_Support/files/_Problem_Submittals/input%20and%20weather%20file.zip>
> >
> >
> > Jia Hu
> >
> >
> > On Sat, Nov 21, 2009 at 2:36 PM, YuanLu Li <yli006@xxxxxxxxxxx
> > <mailto:yli006@xxxxxxxxxxx>> wrote:
> >
> >
> >
> > Hi, Hu Jia
> >
> > I have not run the model you have quoted.
> >
> > In general, the PTAC has only one fan, therefore it is
> > used all the time for Winter and Summer. The split model
> > has two fans, one for the compressor and one for the
> > electric heater and coil unit (the fan coil unit) in the
> > zone.
> >
> > The size of the fan is related to the air flow rate. which
> > is calculated from the maximum cooling demand and the
> > minimum set point temperature. Once it is sized, the fan
> > size does not change for the Summer and Winter use. The
> > VAV models only varies the damper settings. The extra air
> > from the fan is by-passed back to the return air path.
> >
> > Therefore, the fan power or energy usage listed in the
> > simulation run is usually simply calculated form the PLR
> > and efficiency of the fan that you have entered.
> >
> > HVAC,Average,Fan Delta Temp [C]
> > HVAC,Sum,Fan Electric Consumption [J]
> > HVAC,Average,On/Off Fan Runtime Fraction []
> > HVAC,Average,DX Coil Total Cooling Rate [W]
> > HVAC,Average,DX Heating Coil Runtime Fraction []
> > HVAC,Average,Unitary Heat Pump Fan Part-Load Ratio []
> > HVAC,Average,Unitary Heat Pump Compressor Part-Load Ratio []
> >
> > These are from a heatpump model. I think, similar ones
> > should be available from your model as well.
> >
> > Although the DX bi-quard coefficients are given in the
> > object, it is set to unity, so that the efficiency does
> > not change with load. There are many fields you can set
> > in the model, therefore, it is difficult to tell without
> > looking at the IDF.
> >
> >
> >
> >
> > Dr. Li
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>
> > From: hujia06@xxxxxxxxx <mailto:hujia06@xxxxxxxxx>
> > Date: Fri, 20 Nov 2009 17:31:47 -0500
> >
> > Subject: Re: [EnergyPlus_Support] electric power (watts)
> > of PTAC
> >
> >
> > Hello, Dr. Li
> >
> > In my case, *the heating coil type is electric and cooling
> > coil type is SingleSpeedDX.*
> >
> > The power in the xls. is the total power of HVAC
> > (including electric consumption of HVAC
> > system) and not just the fan electric power. The maxmum
> > air flow is autosized by EP.
> >
> > I got the fan power through this formula: *Maximum of the
> > fan power = Max (for a timestep,Variable Fan Electric
> > Power / variable Packaged Terminal Air Conditioner Fan
> > Part-Load Ratio),* which is suggested by Richard. I think
> > the power of the fan may be small because the office is
> > small and EP regards the small fan is enough for the HVAC ?
> > **
> > For the electric consumption (W) of HVAC indicated in slx,
> > is it deviated from normal range?
> >
> > Jia*
> > *
> >
> > On Fri, Nov 20, 2009 at 4:47 PM, YuanLu Li
> > <yli006@xxxxxxxxxxx <mailto:yli006@xxxxxxxxxxx>> wrote:
> >
> >
> >
> > Hi, Hu Jia
> >
> > I do not know how you get the fan power of 9W.
> >
> > In your xls, the HVAC power goes to zero, because it
> > is a on/off system. The power value has no real
> > meaning. PLR is varying and not the equipment power.
> >
> >
> > When the power reading averaged over an hour period,
> > it may be very low or zero. That was why I said your
> > numbers in the xls were reasonable. The maximum of
> > 992 watt is just over one HP, which is the average
> > size of a window unit.
> >
> > A typical window unit has a half horse power
> > compressor and a half horse power fan, or two
> > quarter HP fans in a split unit. I assume that the
> > wattage in the xls is not the fan power alone, and is
> > the total power of the HVAC equipment.
> >
> > A small window unit compressor is the same as the one
> > used in your refrigerator.
> > A quarter HP fan draws about 200 wats. This amount of
> > heat may be added to your cooling load, if the fan
> > motor is in the air flow path. The exact amount
> > depends on how you define it in the IDF.
> >
> >
> > Dr. Li
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>
> > From: hujia06@xxxxxxxxx <mailto:hujia06@xxxxxxxxx>
> > Date: Fri, 20 Nov 2009 14:41:42 -0500
> > Subject: Re: [EnergyPlus_Support] electric power
> > (watts) of PTAC
> >
> >
> > Thank you. And I will check the idf file.
> >
> > On Fri, Nov 20, 2009 at 12:50 PM, Richard Raustad
> > <RRaustad@xxxxxxxxxxxx <mailto:RRaustad@xxxxxxxxxxxx>>
> > wrote:
> >
> > 9 watts is too low.
> >
> > Hu,Jia wrote:
> > >
> > >
> > >
> > > Thank you for your specific explanation.
> > >
> > > HVAC I used is the templated PTAC provided by
> > EnergyPlus, that is, the
> > > heating is provided by electric power and
> > cooling is supplied by
> > > cooling coil.
> > >
> > > I calculate the fan electric power using the
> > first method you
> > > provided, and find the maximum of fan electric
> > power (W) is about 9W
> > > at the design day.
> > >
> > >
> > > On Fri, Nov 20, 2009 at 10:49 AM, Richard Raustad
> > > <RRaustad@xxxxxxxxxxxx
> > <mailto:RRaustad@xxxxxxxxxxxx>
> > <mailto:RRaustad@xxxxxxxxxxxx
> > <mailto:RRaustad@xxxxxxxxxxxx>>> wrote:
> > >
> > >
> > >
> > > You need to identify the maximum power draw
> > of your fan and
> > > compare that
> > > to your design intent.
> > >
> > > Report these 2 report variables:
> > >
> > > Output:Variable,*,Fan Electric Power,timestep;
> > > Output:Variable,*,Packaged Terminal Air
> > Conditioner Fan Part-Load
> > > Ratio,timestep;
> > >
> > > and, if you are using an On/Off Fan object:
> > > Output:Variable,*,On/Off Fan Runtime
> > Fraction,timestep;
> > >
> > > Maximum fan power is then roughly equal to
> > Fan Electric Power /
> > > Packaged
> > > Terminal Air Conditioner Fan Part-Load Ratio
> > or is equal to Fan
> > > Electric
> > > Power / On/Off Fan Runtime Fraction.
> > >
> > > Another method is to either look for a time
> > during the simulation
> > > when
> > > the PTAC is operating at full load or force
> > the PTAC to operate at
> > > full
> > > load and then look at the reported fan power
> > for that time period.
> > >
> > > You will then need to determine if this
> > maximum fan power is
> > > representative of your system.
> > > Fan power of 900 W sounds high for a PTAC
> > (unless it is very
> > > large), my
> > > AC system at 3 tons (10.5 kW) gives an
> > estimated fan power of 0.018 W
> > > per W of rated capacity.
> > >
> > >
> > >
> > > Hu,Jia wrote:
> > > >
> > > > Thank you, Richard.
> > > >
> > > > It is realistic then to have the HVAC
> > consumption of 200 W per hour
> > > > (let's say on average) or in the range of
> > 200-900 W per hour
> > > > depending on a day, time, that is,
> > external weather conditions.
> > > >
> > > --
> > > 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
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> > <http://www.fsec.ucf.edu/>>
> > >
> > > UCF - From Promise to Prominence:
> > Celebrating 40 Years
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> > >
> > >
> >
> > --
> > 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
> > <http://www.fsec.ucf.edu/>
> >
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> 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
>
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