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Re: [EnergyPlus_Support] Re: Minimum ventilation ACH in summary report tables

I learnt a hard lesson. night in night manager has no meaning. If you want it only to work at night, then you must schedule it that way.

Sent from my iPhone (excuse the brevity)
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Jean Marais
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On 13.07.2013, at 19:15, "adam.barker67" <abarker@xxxxxxxx> wrote:


Thanks for your response James, much appreciated!

I am pretty certain my problem is explained by your first note below, however I am also debugging the night cycle manager, so thanks again.


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jim Dirkes <jim@...> wrote:
> Dear Adam,
> As it happens, I got the exact same question recently, posted a question to the Help Desk and was ably assisted by three different people. Here's my condensed experience:
> * The OA Summary uses actual air density, so there can be slight fluctuations in the ventilation air change rate due to air temperature variations.
> * E+ always determines occupancy as the number of People > 0. If you have ANY people in the zone when the fan / air loop is OFF, the A Summary Report will show zero ventilation as the minimum value for that zone (because the fan is OFF while people are present) That means you need to line up your fan and people schedules carefully or be ready to explain why zero ventilation is OK :).
> * I think that there may be an issue with the AvailabilityManager:NightCycle that I am still pursuing. In short:
> o I had a 24/7 fan schedule for a hotel guest room zone and also used a Night Cycle Manager that was always ON and referring to the 24/7 fan schedule
> o Apparently the Night Cycle Manager was turning the fan off for one timestep every day, causing the minimum ventilation rate to be zero (people present, fan OFF)
> o I may have missed something, but it seems to me that the fan should have never shut off. I disabled the Night Cycle Manager and the problem went away.
> * Even after making the above corrections, there are still small differences in most zones and a few that I'm still trying to figure out why they differ more than a little....
> James V Dirkes II, PE, BEMP, LEED AP
> www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of adam.barker67
> Sent: Friday, July 12, 2013 4:51 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Minimum ventilation ACH in summary report tables
> I've had a LEED reviewer ask that I clarify the minimum amount of OA is the same in my proposed and reference files.
> After changing some discrepancies I believe I have corrected this, however I note that when comparing the minimum outdoor air HTML tables, under mechanical ventilation there are still discrepancies between my two models. This is in the range of 0.1-0.01 ACH.
> Considering the models have different HVAC layouts (in this case it is a VAV system as designed, and single zone CV units in the baseline), would the differences in delivery of OA between the system types be a possible explanation. I.e., does the OA report take this into consideration, or should these values really be the same down to the 0.001 ACH?
> Thank you.
> Adam


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