[Equest-users] Fan usage - PTHP vs PSZ
David Reddy
david at 360-analytics.com
Mon Mar 16 08:07:06 PDT 2015
Hi Harshul,
If you specify some small of outside air at the zone, say
ZONE=OUTSIDE-AIR-FLOW = 0.001 cfm, the system (TYPE = PTAC, right?) fans
should run 24/7 if your SYSTEM:FAN-SCHEDULE is set to 1 for all hours.
As for the modeling the system as TYPE= PSZ, it sounds like you made
sure that SYSTEM:INDOOR-FAN-MODE = Continuous, which is correct if you
want the fan to run continuous regardless of heating/cooling demand.
- David
On 3/16/2015 7:19 AM, Singhal, Harshul wrote:
>
> Hello forum,
>
> Our team received a note from our LEED reviewers that our equivalent
> full load hours (EFLH) in our baseline model were less than 8760,
> despite the ASHRAE 90.1 requirements that fans be run at constant
> speed 24 hours per day for multifamily occupancy type. Our baseline
> system type is PTHP. When we plot hourly fan energy usage for the
> building, usage varies hourly and loosely follows the profile of the
> outside air temperature. The EFLH is approximately 7517 hours (88%).
> When we switch the system to ‘packaged single-zone heat pump’ from
> ‘packaged terminal heat pump’ EFLH becomes 8760. This seems to
> indicate that the lower EFLH of our baseline model is somehow
> associated with the system type, however our team can’t seem to figure
> out what characteristic of a PTHP causes fan energy to change hourly
> despite the ‘constant speed’ designation. Does anyone have any insight
> as to why PTHP EFLH would be below 8760 while packaged single-zone
> heat pump would not be? Thanks for any insight you might have.
>
> Cheers,
>
> cid:image002.jpg at 01D05CF2.73106640
>
> *Harshul Singhal, LEED AP BD+C*
> Project Consultant
> Thornton Tomasetti
> 386 Fore Street, Suite 401
> Portland, ME 04101
> *T* +1.207.245.6060 *F* +1.207.245.6061
> *D* +1.207.245.6074
> HSinghal at ThorntonTomasetti.com
> www.ThorntonTomasetti.com
>
>
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