Understanding Eplus output variables to report total ventilation load

asked 2024-05-28 10:45:58 -0600

Arhaan
3 ●1

updated 2024-05-28 10:49:04 -0600

14155 ●83 ●24 http://bigladdersoftware.com/

Hi, I have a Parkade below ground with an electric heating coil supplying ventilation air 4 hours/day, LA temp is 10C, No cooling included. There is no other system in the picture. Parkade: Heating coil energy use 30,934 kWh (10C LA), Output variables : Zone Mechanical Ventilation No Load Heat Addition Energy (J) = 2,160 kWh(annual) and Zone Mechanical Ventilation No Load Heat Removal Energy=59,020 kWh(annual). Hoping someone can help answer the following questions:

I am trying to understand how I can use the Eplus Zone mechanical ventilation output variables to arrive at total ventilation heating energy. Which in this case is clearly heating coil heating annual energy use 30,934 kWh. However the Eplus output variable Zone Mechanical Ventilation No Load Heat Removal Energy=59,020 kWh on its own is higher than the heating coil energy use. The zone setpoint temperature is also 10C so why would this value be so different?!
To calculate total ventilation load can the output variables listed below be used reliably? Are there any exceptions?

Here are the output variables

HVAC,Sum,Zone Mechanical Ventilation No Load Heat Removal [J]
HVAC,Sum,Zone Mechanical Ventilation Cooling Load Increase [J]
HVAC,Sum,Zone Mech Ventilation Cooling Load Increase: OverHeating [J]
HVAC,Sum,Zone Mechanical Ventilation Cooling Load Decrease [J]
HVAC,Sum,Zone Mechanical Ventilation No Load Heat Addition [J]
HVAC,Sum,Zone Mechanical Ventilation Heating Load Increase [J]
HVAC,Sum,Zone Mech Ventilation Heating Load Increase: OverCooling [J]
HVAC,Sum,Zone Mechanical Ventilation Heating Load Decrease [J]

Thanks

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answered 2024-05-29 14:18:38 -0600

Craig Simmons
523 ●11 ●7

updated 2024-05-29 14:31:32 -0600

The zone ventilation loads may not line up exactly with the coil load. Your best bet would be to review the output descriptions in the Input-Output Reference, but also just report them out and inspect to see what combination is closest.

The underlying issue is that the zone ventilation loads are summing all differences in temperature between the ventilation air and the zone temperature no matter how negligible. The heating coil only engages when there is a call for heating. Depending on the climate there are potentially lots of times when the ventilation air could be providing "heating" or "cooling" even if only a degree or 2 different than the zone temp.

Hope that helps.