[Equest-users] How intermittent fan operation works

Fri Apr 5 06:39:50 PDT 2019

Mayank,

The attached NYSERDA tech tip describes how to model several common
multifamily ventilation strategies in eQUEST. It’s based on 90.1 2010 App G
and eQUEST v3.65 build 7173 (pre-VRF/DOAS version) so may require some
adjustments if you use the latest version. See also EPA Energy Star
Multifamily Highrise Program Guidelines
<https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/mfhr/ENERGY_STAR_MFHR_Simulation_Guidelines_AppG2016.pdf?56fa-56ac>
 Examples 6-9 & 6-10 and Sections 6.5.12.1 (a) & 6.5.12.3(c).

Maria

*From:* Equest-users <equest-users-bounces at lists.onebuilding.org> *On
Behalf Of *Mayank Bhatnagar via Equest-users
*Sent:* Friday, April 05, 2019 8:39 AM
*To:* Nathan Miller <nathanm at rushingco.com>
*Cc:* equest-users at onebuilding.org
*Subject:* Re: [Equest-users] How intermittent fan operation works

Dear Nathan,

Thank you for quick response.

The project is a residential building and the ventilation is through the
system. To meet the ventilation requirement with *intermittent* operation
mentioned in *ASHRAE 62.2-2010,* the system need to run atleast 30 minutes
in each hour. From this the question is come for sub-hourly operation.

I am thinking of an approximation which I want to put for expert opinion:

A PVVT system can be modelled with minimum air flow ratio to 50% with
continuous fan to approximate cycling and minimum operation time for
ventilation.  The reduction of low speed based on cooling/ heating load can
be similar to intermittent operation where the system is running for
fractions of an hour (similar pattern as in intermittent operation in my
earlier mail).

Please let me know your thoughts and/ or other work around.

Thank you.

Regards,

Mayank Bhatnagar

On Thu, Apr 4, 2019, 7:29 PM Nathan Miller <nathanm at rushingco.com> wrote:

Assuming you have another system/method responsible for providing
ventilation  to the units, I’d model it more or less the way you have, but
I’m not clear from your description that you have all the settings correct
for a cycle-on-demand system. In the climate zones I usually model in there
would be hours where the fan does not run at all, but that’s obviously
highly depending on T-stat settins and ambient conditions.

   1. Coolin fan schedule should be something that is all-zeros (meaning
   the system never HAS to run). This essentially means the unit thinks it is
   in “night/unoccupied” mode all the time.
   2. Select Cycling fan control, and intermittent operation (looks like
   you did that)
   3. Night Cycle Control should be “Cycle On Any”. Since you already told
   the system it is ALWAYS in night-mode (meaning it’s not forced to run),
   then fan will remain off until temps in the space drift out of dead-band
   mode, and then system will turn on fans and condition the space until temps
   are satisfied, and then shut off agin. With settings above, partial hour
   fan operation is allowed.

You said you want to know if you can “create schedule to restrict cycle off
on sub-hourly”. I’m not clear what you mean. If you want the fan to be
prevented from only running for partial hour you can use Continuous instead
of Intermittent Indoor Fan Mode.

*Nathan Miller, PE, LEED AP BD+C** – **Mechanical Engineer/Senior Energy
Analyst*

*RUSHING* | *O* 206-285-7100 | *C* 207-650-3942

*www.rushingco.com <http://www.rushingco.com/>*

*From:* Equest-users <equest-users-bounces at lists.onebuilding.org> *On
Behalf Of *Mayank Bhatnagar via Equest-users
*Sent:* Thursday, April 4, 2019 9:31 AM
*To:* equest-users at lists.onebuilding.org
*Subject:* [Equest-users] How intermittent fan operation works

Dear all,

I am working on a residential project in which the indoor units fan is
cycling with load. For this, I have modelled as PSZ HP (as designed) and
changed indoor fan mode from continuous to intermittent operation. My first
question is whether it is correct to model intermittent for system with
cycling or should I model different system.

Additionally, as per definition of intermittent operation : The indoor fan
operates as in CONTINUOUS, but only for  that fraction of the hour required
for space heating or cooling. I want to check how many hours it is cycling
as I assumed that the eQUEST is working on hourly timestep. By extracting
hourly report of fan cycle ON for continuous and intermittent operation,
the hourly profiles are:

>From the figure, it appears that fan is running maximum 60% of an hour in
intermittent operation whereas 100% in continuous. As it is providing
results in sub-hourly basis, is it possible to create schedule to restrict
cycle off on sub-hourly?

Thank you.

Regards,

Mayank Bhatnagar
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