What is oversizing, really? The goal must be to keep occupant discomfort levels to an acceptable level. There are different measures of discomfort and different levels of acceptabillity based on our current knowledge and gathered statistics (see ASHRAE 55).
What is zone load? Zone load is the energy input required to keep the air at the air temperature setpoint that you define. You also define the amount of time over which this must be injected into the zone (sizing:parametric).
Agree a set of performance parameters with the building owner. E.g.
Roomlist indicating room function, peak occupant count, lighting levels and lighting power density, persons dissatisfied percent PPD% comfort level, allowable annual discomfort hours relative to PPD, room heating setpoint (both air and operative), room lower relative humidity level, room cooling setpoint (both air and operative), room highest humidity level, outdoor air rate, etc.
Reference the standard or norm that you use to quantify each entry.
Agree schedules for each relavant entry.
Setup and simulate with a sizing factor of 1 and check your discomfort hours. Also check your hours load not met to make sure that your equipment is working properly.
Depending on what kind of systems you will use, the controls thereof must be carefully considered. Even the performance expectation may be different. For example, a radiant system take longer to heat room air than an air heating system. The room air temperature setpoint for heating can be dropped because of the higher mean radiant temperature. Thermostat setback temeratures don't deviate by more than a few degrees, etc, etc.
- "calculated" was what the zone required at peak on the sizing day
- "user" is either a fixed value entered by the user not left to autosize, or the "calculated" value multiplied with the sizing factor.
- the capacity of your equipment is defined by the "user" column.
Mit freundlichen Grü�en- Sent from my iPhone (excuse the brevity)
i. A.
Jean Marais
b.i.g. bechtold
Tel. +49 30 6706662-23
On 30.07.2014, at 22:12, "benjamin_khuong@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Ok so the HVAC summary only gives peak demands which will lead to over sizing an HVAC system.
If this is the case, is there a rule of thumb that I should follow?I have a bunch of questions that you don't have to answer. Learning E+ / Open Studio on my own has been really frustrating but you have already been a big help!What is the difference between Calculated design loads / user design loads?Also, after finding the heating / cooling energy demand in Watts, how do I relate that to HVAC components in order to determine their size? Would that just be the units cooling/heating capacity?We're planning on using a solar thermal system for domestic hot water and an absorption chiller or radiant system for air conditioning. I have a simple understanding of how these systems work theoretically from school, but I have no real life experience on putting a system together / calculating loads and what not.Again,BIG thanks Jean.
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