Hi All,
How can i model DCV for a laboratory building with 100%
fresh air ie no recirculation.
Since there is no return air path here so HVAC consultant says that
CO2 sensors will be placed in the occupied zones between 3 to 6ft, and
fresh air ie supply air will be modulated based on CO2 ppm
differential of outside and zone air.
But if when i tried to do it by making OA control method as DCV zone
sensors in OA and economizer tab in Air size system HVAC i am getting
75% reduction in my cooling energy which is unimaginable.
I look forward for any response.
Thanks
Sambhav.
Sambhav,
If the lab is served with 100% OA there will little to no difference
between the OA CO2 and the space CO2 sensor readings - likley only
sensor error.
CO2 sensing is not the way to modulate the amount of OA serving lab
space. If you wish to modulate the amount of OA delivered to the Lab I
would recommend consulting an Industrial Hygienist who can best
determine air-change rates etc. appropriate MUA and exhaust systems.
Best Regards, Fred
Frederick Doherty, PE, CEM, LEED-AP
I wanted to build upon the other reply - DCV in this case probably takes another form, such as reducing minimum airflow when labs are unoccupied or reduced fume hood exhaust when no users are present.
These you'll have to arrange by making customized schedules rather than using the CO2-based DCV module built in to eQUEST.
Your HVAC consultant will have to explain the proposed sequence of operation for the AHUs in a little more detail. CO2 is often used as a surrogate for other contaminants related to the building occupants.
In your case for a laboratory building the contaminants from the occupants may not be a chief concern, so it doesn't seem likely that eQUEST's built-in DCV is what you should be using.
Could the system operate more along the lines of this perhaps: http://www.i2sl.org/elibrary/documents/sharp.pdf
David
Hi David,
I agree with you , using equest DCV module should not be
correct way of DCV in this case but customizing min OA schedule at
system level proportional to Occupancy variation schedule should be
method to claim savings from DCV.
By doing it that way i am getting 9% overall saving what is correct also.
Thanks
Sambhav