Hello everyone. I have a query regarding HVAC outputs we get from simulation. What’s the difference between zone peak and component sizes?. Incase if we want to get a tonnage for a zone which output we can consider?

Hi @Asisnath,

I believe you are using PTAC. Please look for Design Size Gross Rated Total Cooling Capacity in the component sizing summary in .htm report.

Hey @devang. Thanks for your input. Just to be more precise, with a residential case I am trying to work out the tonnage, with “Residential AC with no heat”

After reading a good amount of posts I am using the data from “component values” denoting “gross rated cooling coil capacity.” Will it be correct?

@devang 's answer is correct and that output you have found is correct for Window AC if the question that you are trying to answer is “what size/power rating of an air conditioner do I need to buy to cool this room?” Or if the question is “do I need to buy two air conditioning units to cool the room, given that the ACs are only sold in units of X power?”

To clarify the difference between the zone peaks and the component sizes, the two have a direct relationship with one another. The zone peak is the maximum cooling/heating demand that the room experiences in the design day of the EnergyPlus sizing simulation. You will see that it aligns with the plot of cooling demand that you get by parsing the ZSZ csv:

In order to turn this into a power rating for a piece of HVAC equipment, EnergyPlus performs two operations:

- The peak cooling load gets multiplied by a safety factor. The default factors are 1.15 for cooling and 1.25 for heating, which I believe come from one of the ASHRAE standards (I don’t remember which one). However, different engineers may use different safety factors and you can always change the factors that EnergyPlus uses with the “HB Sizing Parameter” component like so:

- EnergyPlus will model the dynamics of the given HVAC template to determine the size of each piece of equipment. This can account for things like losses through pipe or duct conduction, etc. All of the equipment gets sized to meet the peak demand * the sizing factor.

I hope that clarifies things.