RE: [EnergyPlus_Support] Extremely high user design load for heating for HVAC system 3

[YuanLu Li <yli006@xxxxxxxxxxx>]

When I was replying to you, I was not yet sure how the expandIDF would handle your case.

After looking at the expIDF, I found that the thermostat was expended to Type 4, the zone unit was ADU uncontrolled.  These are the correct settings.

A split unit can have a fan coil unit in the zone.  That was why I was not sure without checking the expIDF file.

The expandIDF is actually making use of the information in the object I highlight below and changed your IDF.   Always On means no seasonal control, and therefore use Type 4 thermostat.
=====================
Templates in general requires in the zone Thermostat and a zone equipment.  The Zone:unitary is for this.  It has an OA mixer and a zone heater.  It is not the same as the system:unitary.

I am not sure why it is called unitary.  By observation, unitary version need not have any plant equipment.   The template model was previously called  compact model.  In the older model, the OA mixer is not automatically included.

The system:unitary is a complete air loop system. It can be used as an AHU to feed multiple zones.  When only feeding one zone, I guest, the expendIDF down sized this to fit the zone requirement and modified the zone:unitary to an zone:ADU.

The combination together however did not match your real system, because the coil curve, coolent type, double fan or compressor speed, etc are not taken into account.

===============
The following are for the other two emals.:

You need not delete the Zone:unitary, if you are continue to use the templates.

The second DesignDay object for Summer may be deleted.  Only one is needed for sizing.

Because the expandIDF is inserting its own thermostat schedule some of your entries were commented out.
===============
One HVAC for one zone can have the packaged model, PTAC, PTHP, etc.  These are the window units, some with cooling only.

If you do not use the template model, you can add your own objects.  That is where you can have customed coil, fan, compressors.  What you do is to take the whole section of objects for one zone in the current expIDF and study it carefully.  For the DX cooling coil, you can look up the other versions in the I/O manual, and learn how to modify the curves to match you real equipment.  The theory is in the Engineering Manual.  There are some coolent data in the data set directory.

Specifying the fan speed and the maximum capacity do not modify the DX coil properties.
========================
The economizer is a more complex application.  You have only filled in one temperature for maximum temperature.  You can shut it off with low temperature limit in Winter or at night as well.  I am still behind in the application of EPlus as the later versions has added many features.

 It looks like I need to have both Zone and System Unitary in HVAC template. There are two additional pieces of roof because I have one room with two piece of roof in unconditioned statute. Could you tell me the difference between Zone Unitary and System Unitary? What should I have if I have one HVAC unit for one zone? Thank you.

On Mon, Jul 11, 2011 at 8:41 AM, Qianmin Zhang <<mailto:zqianmin@xxxxxxxxx>zqianmin@xxxxxxxxx> wrote:
> Thank you for all of your reply. I'm going to delete "HVAC Templete:Zone: Unitary". Why the 2nd example on GettingStarted has both Zone and System Unitary if they are repeated? Or they are not repeated?
> To modify my idf, I will delete Sizing:DesignDay, AlwaysOn, and Zone:Unitary, use default"office min OA schedule".
> Do I need to have a economizer low temperature limit? There is only a temperature of economizer high-limit shutoff on Appendix G3.1.2.6B. 
> I will give it a try after this modification.  Thanks a lot.
> Qianmin
> 
> On Sat, Jul 9, 2011 at 7:31 PM, YuanLu Li <<mailto:yli006@xxxxxxxxxxx>yli006@xxxxxxxxxxx> wrote:
>>  
>> 
>> For direct-expansion cooling, packaged and split system simulations: HVACTemplate:Thermostat
>> HVACTemplate:Zone:Unitary
>> HVACTemplate:System:Unitary
>>  
>> I think this grouping provide  both cooling and heating in the system:Unitary.  The Zone Unitary can provide additional heating.  Therefore the use of availability schedules must be very carefully considered.
>>  
>> In the IDF,  the cooling is always ON.  Then what happens, when heat is required?
>> The expIDF did provide type 4 thermostat for you.
>> I am  surprised that the use of Weekdays twice in the following schedule did not produce a warning.  The schedule should be split into Summer and Winter seasons.
>>  
>> Schedule:Compact,
>> Minimum Outside Air, !- Name
>> Fraction, !- Schedule Type Limits Name
>> Through: 12/31, !- Field 1
>> For: Weekdays SummerDesignDay, !- Field 2
>> Until: 24:00, 1, !- Field 4
>> For: Weekends WinterDesignDay Holidays AllOtherDays, !- Field 5
>> Until: 24:00, 0; !- Field 7
>> 
>> Because the expIDF used the template schedule, I think the above was not used.  I think the expandIDF knows the preferred conditions and corrects them.================
>> HVACTemplate:System:Unitary,
>> UnitarySystem4, !- Name
>> School HVAC, !- System Availability Schedule Name
>> Zone 4, !- Control Zone or Thermostat Location Name
>> 0.708, !- Supply Fan Maximum Flow Rate {m3/s}
>> continuous, !- Supply Fan Operating Mode Schedule Name
>> 0.6, !- Supply Fan Total Efficiency
>> 250, !- Supply Fan Delta Pressure {Pa}
>> 0.9, !- Supply Fan Motor Efficiency
>> 1, !- Supply Fan Motor in Air Stream Fraction
>> SingleSpeedDX, !- Cooling Coil Type
>> Always_On, !- Cooling Coil Availability Schedule Name
>> 13130, !- Cooling Coil Capacity {W}
>> autosize, !- Cooling Coil Rated Sensible Heat Ratio
>> 3.6635, !- Cooling Coil Rated COP {W/W}
>> Gas, !- Heating Coil Type
>> , !- Heating Coil Availability Schedule Name
>> 16120, !- Heating Coil Capacity {W}
>> 0.8, !- Gas Heating Coil Efficiency
>> , !- Gas Heating Coil Parasitic Electric Load {W}
>> autosize, !- Maximum Outdoor Air Flow Rate {m3/s}
>> 0.22656, !- Minimum Outdoor Air Flow Rate {m3/s}
>> Minimum Outside Air, !- Minimum Outdoor Air Schedule Name
>> DifferentialDryBulb, !- Economizer Type
>> NoLockout, !- Economizer Lockout
>> 25, !- Economizer Upper Temperature Limit {C}
>> , !- Economizer Lower Temperature Limit {C}
>> , !- Economizer Upper Enthalpy Limit {J/kg}
>> , !- Supply Plenum Name
>> , !- Return Plenum Name
>> BlowThrough, !- Supply Fan Placement
>> StayOff, !- Night Cycle Control
>> , !- Night Cycle Control Zone Name
>> None, !- Heat Recovery Type
>> 0.7, !- Sensible Heat Recovery Effectiveness
>> 0.65, !- Latent Heat Recovery Effectiveness
>> , !- Dehumidification Control Type
>> , !- Dehumidification Control Zone Name
>> , !- Dehumidification Setpoint {percent}
>> , !- Humidifier Type
>> , !- Humidifier Availability Schedule Name
>> , !- Humidifier Rated Capacity {m3/s}
>> , !- Humidifier Rated Electric Power {W}
>> , !- Humidifier Control Zone Name
>> ; !- Humidifier Setpoint {percent}
>> ============================
>>  
>> Some of the numbers are modified by the template expension.  I have not look into the expanded version yet.
>> Because you are using multiple origines for the zones geometry, I have not b een able to associate the zone names with the room location yet.  There are 6 zones, but the roof is divided into 8 parts.
>> 
>> The modified air flowrate by the template schedules may have changed your design values. 

Dr. Li  
>>  
>> To: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
>> From: <mailto:zqianmin@xxxxxxxxx>zqianmin@xxxxxxxxx
>> Date: Fri, 8 Jul 2011 12:54:43 -0700
>> Subject: Re: [EnergyPlus_Support] Extremely high user design load for heating for HVAC system 3
>> 
>>  
 yea, I found out the user design value are closed to my input. 
>> Like what I said, it is a finished design project, so I will assume they selected the correct equipment based on their calculation. But from energyplus hvac summary report, the calculated design air flow is about 400cfm, which is too small compared to the equipment of 1800cfm for a 800ft^2 class room. Above is for zone cooling. For zone heating, the calculated design air flow are less than 70cfm for each classroom zone.
>> 
>> On Fri, Jul 8, 2011 at 12:14 PM, Jason Kirkpatrick <<mailto:jason.alan.kirkpatrick@xxxxxxxxx>jason.alan.kirkpatrick@xxxxxxxxx> wrote:
>>>  
 The user design airflow is the calculated design airflow x the sizing factor
>>> 
>>> 
>>> 
>>> On Fri, Jul 8, 2011 at 2:15 PM, Qianmin Zhang <<mailto:zqianmin@xxxxxxxxx>zqianmin@xxxxxxxxx> wrote:
>>>>  
>>>> Hello All,
>>>> First I want some help to better understand the result. Under HVAC Summary, for both heating, cooling, and airflow rate, there are two objects, one is calculated design, one is user design. I'm not that understand the difference between these two. Is there any relation between these two? Which document should I read to get know these things?
>>>> From the report summary, user design load for heating is much too high from my simulation. I used HVAC template, and I don't think I make any special change in my.idf file regarding the system. The weather data I used is Sacramento, CA. I found "zone/sys sensible heating rate" is really large. Could you take a look at my .idf and tell me the problem? It's a simply model. Thanks a lot.
>>>> Qianmin
>>> 
>>> 
>>> 
>> 
>> 
>> 
> 





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