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Re: [EnergyPlus_Support] Re: Warmest Function Increases Boiler Natural Gas Usage?
Noel,
Please upload your input. Most likely you have conflicting
setpoint managers.
Fred
noelcrrl wrote:
> Mike-
>
> To answer your question...yes I do have a central heating coil. I
> paid special attention to the setpoint managers as you suggested. I
> have three set point managers, as follows:
>
> 1)I have a mixed air set point manager that controls the mixed air
> outlet and the cooling coil outlet.
>
> 2)I have set point manager at the heating coil setting it 55F.
>
> 3)I have the warmest setpoint manager controlling the supply fan
> outlet between 55F and 65F.
>
> It seems that the heating coil continues to ignore the 55F setpoint
> and heats the air to a higher temperature.
>
> Please advise? Thanks in advance for your help.
>
> Noel
>
>
>
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
> <mjwitte@...> wrote:
>
>> Rich addressed the fan power, chiller, and tower energy use.
>>
>> The increase in gas use is not right. Is there a central heating
>>
> coil in this
>
>> VAV system? Is it picking up it's setopint from the air loop
>>
> outlet node? If
>
>> so, it may be warming cool mixed air to that some VAV damper
>>
> somewhere can stay
>
>> fully open at low cooling loads.
>>
>> Be sure the heating coil setpoint is not linked in any way to what
>>
> the warmest
>
>> set point manager is doing for cooling. No two setpoint managers
>>
> should be
>
>> setting a temperature setpoint on the same node.
>>
>> Mike
>>
>>
>> On 22 May 2007 at 0:22, noelcrrl wrote:
>>
>>
>>> All-
>>>
>>> I am modeling the warmest function in a Hospital building. The
>>>
> model
>
>>> is equipped with a VAV system (pre-heat coil, cooling coil, a
>>>
> central
>
>>> heating coil, & reheat coils). I have the warmest setpoint node
>>>
> set
>
>>> at the supply fan outlet. The warmest function is set up to
>>>
> deliver
>
>>> supply air between 55F and 60F. Also, the chilled water is
>>>
> delivered
>
>>> to the cooling coils between 44F and 52F, depending on outside
>>>
> air
>
>>> temperature.
>>>
>>> When I increase the upper limit of the warmest function from 60F
>>>
> to
>
>>> 65F and the chilled water upper limit from 52F to 54F, the
>>>
> natural
>
>>> gas consumption of the boiler increases by 7%. In addition, the
>>> supply fan energy usage increases by 6%. The energy saving
>>>
> benefit
>
>>> of the chiller and the cooling tower, 2% and 3%, respectively, is
>>>
> not
>
>>> enough to overcome the boiler and fan energy usage increases.
>>>
> The
>
>>> overall energy usage (total facility) increases by 2%.
>>>
>>> I am confused to why this is happening? How can increasing the
>>>
> reset
>
>>> temperatures increase overall energy consumption instead of
>>> decreasing it? Why is the heating energy usage increasing in
>>>
> this
>
>>> manner?
>>>
>>> Thanks in advance for your help.
>>>
>>> Noel
>>>
>>>
>>>
>>>
>>> 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.
>>>
>>> EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf
>>>
> under the
>
>>> Documentation link and press the "search" button.
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>> ========================================================
>> Michael J. Witte, GARD Analytics, Inc.
>> EnergyPlus Testing and Support
>> EnergyPlus-Support@...
>>
>>
>
>
>
>
> 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.
>
> EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
>
> Yahoo! Groups Links
>
>
>
>
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