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RE: [EnergyPlus_Support] Model demostic hot water energy use

 
Zhen Tian,
 
I'm assuming the example file you are talking about is DHWPurchHeating.idf which features the DOMESTIC HOT WATER object.  To model hot water usage with this object, it is coupled as a component in the plant loop simulation.  The plant loop supply-side equipment (usually a water heater or boiler) provides the heating and determines the loop hot water temperature.  The DOMESTIC HOT WATER object sets the flow rate of water that is used and lost down the drain.  The object also sets the return water temperature (presumably from the water mains), or if blank, the WATER MAINS TEMPERATURES object set the temperature.  
 
If you are looking for something similar to the "DHW-" keywords under the PLANT-ASSIGNMENT command in DOE-2, I suggest using the WATER HEATER:MIXED object in "stand-alone" mode--that means with no plant loop connections.  See the example file WaterHeaterStandAlone.idf.  In "stand-alone" mode, the water heater will accept a water use flow rate schedule that will allow you to set the DHW demand.  See the documentation for more on this object.  With the WATER HEATER:MIXED object you should find capabilities equivalent to DOE-2 and beyond.  
 
For those on the list who recall the energy balance bug that was recently identified with WATER HEATER:MIXED, I just want to note that the object _does_ work_correctly_ when in stand-alone mode.  The energy balance bug only occurs when the water heater is coupled to a plant loop.  
 
Let me know if you have further questions.
 
Peter Ellis
National Renewable Energy Laboratory
 
 
-----Original Message-----
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]On Behalf Of Zhen Tian
Sent: Monday, September 25, 2006 3:09 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Model demostic hot water energy use



Dear All,

I try to model annual demostic hot water energy use in EnergyPlus. Is there any method to model this in detail. I have looked over the examples of EnergyPlus. It seems that one example has a very simple example which simulate enegy use based on hot water flow rate and water temperature.

Could somebody tell me weather I can simulate demostic hot water enegy use similar to that in DOE-2? Thanks for all suggestions. If somebody has an example, could you let me know.

Thanks a lot.

Regards,

Zhen Tian


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