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How to fix the not met hours?

asked 2020-01-07 16:55:56 -0600

Amin's avatar

updated 2020-01-08 10:34:15 -0600

I am almost new to EnergyPlus, I tried to build a model by merging the geometry of the reference small office building and the ventilation system of a reference large office building. Furthermore, I selected the "autosize" option for determining the nominal capacity of the reheat coils in the terminal boxes, but I get "0" [W] capacities for all the reheat coils when I run the simulation on the whole weather file. Such a problem leads to a significant number of not met hours of heating periods. (I just joined the website and do not have enough credits to attach the model.)

The idf. text file:

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This is not enough information to identify the problem. Do you have thermostats in all controlled zones? Does the err file show any details that may help the diagnosis? What is the location? What is the zone temps in winter and summer (just one zone will suffice)?

rraustad's avatar rraustad  ( 2020-01-08 08:04:38 -0600 )edit

The original question has updated with a idf. text file of the model. The office building is located in Chicago with 5 zones equipped with "ThermostatSetpoint:DualSetpoints" follow the existing CLG and HTG setpoints. The temperature change of each zone has the following range: - CORE_ZN: 9.7 - 27 [C] - Perimeter_ZN: 7.0 - 27 [C]

Regarding the final errors, there is no fatal or sever errors. But the following errors are recorded: 1. Pump nominal power or motor efficiency is set to 0. 2. The condenser outlet temperature is outside the range of cond. outlet temp

Amin's avatar Amin  ( 2020-01-08 09:14:51 -0600 )edit

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answered 2020-01-08 10:58:39 -0600

updated 2020-01-08 11:06:50 -0600

You have your zone and system design heating SAT set to 40C. This means there is a 0C delta T across the zone reheat coil when it sizes. Lower the design heating SAT in the Sizing:System object and you should see reheat coil capacity > 0.

The Sizing:Zone object specifies the design requirements for zone equipment (e.g.. PTAC, fan coil, and coils in terminal units) and the coil entering air condition used to size zone coils is usually the zone temperature. The Sizing:System object specifies the design requirements for air loops and outdoor air systems (e.g., the SAT leaving the air loop and entering the zone (or zone equipment in the case of terminal units). For zone terminal units with reheat coils, the design entering coil air temperature is the temperature of the air leaving the air loop (i.e., Sizing:System design SAT).

Perimeter_ZN_4, !- Zone or ZoneList Name
40.0000, !- Zone Heating Design Supply Air Temperature {C}

AC_1_SDVAV, !- AirLoop Name
40.0, !- Central Heating Design Supply Air Temperature {C}
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That was very helpful and fixed the problem! Thanks a lot @rraustad!

Amin's avatar Amin  ( 2020-01-08 12:07:12 -0600 )edit

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Asked: 2020-01-07 16:55:56 -0600

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Last updated: Jan 08 '20