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[EnergyPlus_Support] Re: Small School - Modelling Simple Heating and Ventilation Equipment
I´m reposting my two previous posts hoping to get any help I can get.
I'm really desperate for some help here!
Thanks in advance
Nuno Brandão
-------------------------------------------------------
> Dear Group Supporters,
>
> I´m simulating a small school, with 4 controlled zones. All the zones
> are equipped with radiators. Two unit ventilators equiped with heating
> coils, supply air, each one supplying air to a group of two zones. The
> system is suppose to maintain the 4 controlled zones to a setpoint of
> 20ºC, so outside air is preheated to 20ºC by the ventilator's heating
> coil, and injected at that temperature into the zones. The radiators
> are responsible for the final heating requirement adjustments,
> although they have priority. The building has no cooling requirements.
>
> The system is only functioning during occupancy hours with a 20ºC
> setpoint. It turns on when the temperature is below 20ºC and turns off
> if the temperature is above that value. Uses 100% outside air and it
> is not recirculated.
>
> I've introduced the system in order to get the autosizing results, but
> I´m having hard time to figure out the excessive boiler autosized
> capacity obtained from the "Report:Table".
>
> I´m expecting for an anual simulation:
>
> - Boiler capacity - 30 KW
> - HVAC EnergyConsumption - 23626 KWh
> - Miscellaneous Equipment Energy Consumption(including lights,
> gas and electric equipment) - 51027 kWh
>
> However, I´m obtaining exaggerated high values. I suspect the problem
> is related to "System Control" and "Zone Sizing" issues, which I still
> don´t quite understand. My questions are as follow:
>
> 1. In the system sizing objects, what does the field "preheat design
> temperature" stands for? The I/O reference definition says that it is
> "The design air temperature exiting the preheat coil(if any)".
> In my specific case, to obtain the heating coil capacity is it enough
> to specify an exit temperature in this field, or do I still have to
> define a COIl:WATER:SIMPLEHEATING object? If it refers to another
> preheat coil, do I still have to specify a temperature even if the
> coil does not exist?
>
> 2. As described above, the system uses 100% outside air with no
> recirculation. Do I still have to specify a "CONTROLLER:OUTSIDE AIR"?
>
> 3. How do I guarantee, that the system uses only 100% outside air?
>
> 4. Air is exhausted from the building by exhaust fans located in 3
> zones. I need to account for the fan´s and kitchen gas equipment
> energy consumption, in the total building energy consumption internal
> gains from both equipments are ignored since I do not need to estimate
> zone loads or equipment size). Do I have to define a FAN object for
> each ventilator, or is it enough to use the "ELECTRIC EQUIPMENT" and
> "GAS EQUIPMENT" objects with an "ALWAYS OFF" schedule in order to
> ignore heat gains?
>
> 5.If the inlet/outlet boiler temperatures are 85/70, and the sizing is
> done by using the design day "Maximum Dry-Bulb Temperature" which
> temperatures do I need to specify at the "Set point at outside
> low/high" and "Outside low/high" fields from the "SET POINT
> MANGER:OUTSIDE AIR"? In I/O reference, the supply air set point
> temperature at outside high(SATOH) for example, is described as an
> outside air temperature, can it be a water supply loop temperature?
>
> 6. If the inlet air at the "MIXED AIR BOX" is only outside air with no
> zone recirculated air, do I need a "SET POINT MANAGER:OUTSIDE AIR"? I
> use a "SET POINT MAANGER:OUTSIDE AIR" to control the hot water loop
> flow and a "SET POINT MANAGER:SCHEDULED" to control the both air loops
> air outlet temperatures, is this procedure correct? If not, how do I
> control the heating coil flow in order to meet the heat demand?
>
> 7. I´m using one controller for each AIR LOOP, and one for each
> HEATING COIL, this assures the air control and the water control, is
> this right?
>
> I´m having hard time to understand how and what do I need to specify,
> to model system control procedures in EnergyPlus.
> I would appreciate any help I can get. I´m uploading my idf file so
> that you can have a look at it if necessary.
>
> Thank you for your patience.
> Nuno Brandão
>
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