[Equest-users] Exhaust fans in appartment

[David Reddy]

Hi Julien,
Forgot to mention this, I've noticed this too... We've looked a number 
of work-arounds but unfortunately I am also under a deadline and don't 
have time to go track down what we have been doing lately...

Here are a a few work-arounds that I recall looking at.

 1. Use larger HEAT-SIZING-RATIs to get capacities up
 2. Specify equivalent infiltration at the Space, but set the
    infiltration schedule to 0 on all days/hours other than the design
    days.  This requires some coordination with the design day windspeed
    if you are modeling the wind-speed proportional infiltration that I
    mentioned, otherwise, pretty straight-forward if you are using the
    constant infiltration input.

Will try to dig up more definitive information later today when I have time.

David

PS: That info on the HRV modeling is also included in the help for 
EXHAUST-SOURCE = BALANCED-INFIL.  This approach seems like a reasonable 
work-around for unit-by-unit HRV/ERVs.


On 2/20/2015 7:45 AM, Julien Marrec wrote:
> Nathan,
>
> Thanks for the answer. Your baseboard workaround is interesting, I'm 
> curious whether it produces differences or not.
>
> I'm not using baseboards. I have both UVT systems (gas furnace) for my 
> heated-only spaces as well as PTAC (hot water coil / DX cooling coil) 
> for the apartments, and both are behaving the same way.
>
> I've played around a little bit, switching between Zonal Exhaust and 
> Outside Air Flow. It's not taking the airflow into account when it's 
> set as Zonal Exhaust, see attached pictures (Tenant Storage is a UVT 
> with 400 CFM exhaust, 2Sys is a PTAC with 41.6 CFM exhaust)
>
> I don't know what to do...
> Aside from running the model with it as Outside Air Flow, writing down 
> the sizing, going back to the model to put it back as zonal exhaust 
> and manually setting the sizing... I'd do that if I had only a couple 
> of zones... But I don't, so it seems highly unpractical.
>
> Anyone has ideas?
>
> Thanks,
> Julien
>
> --
> Julien Marrec, EBCP, BPI MFBA
> Energy&Sustainability Engineer
> T: +33 6 95 14 42 13
>
> LinkedIn (en) : www.linkedin.com/in/julienmarrec 
> <http://www.linkedin.com/in/julienmarrec>
> LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr 
> <http://www.linkedin.com/in/julienmarrec/fr>
>
> 2015-02-20 16:33 GMT+01:00 Nathan Miller <nathanm at rushingco.com 
> <mailto:nathanm at rushingco.com>>:
>
>     Julien,
>
>     I don’t have time to dig into your questions at this moment
>     (deadlines!), but just a quick check for you, are you modeling
>     electric resistance heat via the system-> baseboards entries? If
>     so, I don’t believe eQUEST ever autosizes baseboard heat, you
>     always have to manually input (or use a formula based on space
>     square footage…).
>
>     To get around this I often use the PTAC system, zero-out the
>     fanpower, and then select electric resistance heat as the primary
>     system level heat source. eQUEST should autosize that for you, and
>     it would seem to be a thermodynamically similar system to
>     inputting via-base-board (though I’m sure somebody can point out
>     why it is better to use baseboards).
>
>     **
>
>     *Nathan Miller, PE, LEED AP BD+C**– */Mechanical Engineer/Senior
>     Energy Analyst/**
>
>     *RUSHING*| *D*206-788-4577 |*O*206-285-7100
>
>     *www.rushingco.com <http://www.rushingco.com/>***
>
>     *From:*Julien Marrec [mailto:julien.marrec at gmail.com
>     <mailto:julien.marrec at gmail.com>]
>     *Sent:* Friday, February 20, 2015 7:14 AM
>     *To:* David Reddy
>     *Cc:* Nathan Miller; equest-users at lists.onebuilding.org
>     <mailto:equest-users at lists.onebuilding.org>
>     *Subject:* Re: [Equest-users] Exhaust fans in appartment
>
>     Hi again,
>
>     After implementing zonal exhaust, I'm still in a bit of a pickle.
>     For those familiar with it, I'm actually modeling a building per
>     the ENERGY STAR MultiFamily High-Rise Simulation Guidelines,
>     slightly modified because it may go for NYSERDA Multifamily
>     Performance Program (MPP). MPP New Construction, in its v6
>     version, has a different calculator that the MFHR one for
>     infiltration, and you have to model infiltration and local exhaust
>     separately.
>
>     Anyway, the calculator is telling me to put:
>     - 0.08 ACH in the space with hourly fraction at 0.5 (so 0.04
>     ACH...): it's doing some kind of calculation to come up with 0.04
>     CFM/sqft of exterior above grade surfaces (roof + ext walls)) that
>     leads to the 0.08 ACH figure.
>     - Model the exhaust as about 40 CFM per apartment with a fraction
>     of always 1.
>
>     I don't know why, but this seems fairly low to me (0.38 ACH would
>     seems about right for a fairly tight building when you consider
>     that building-wide, but here I'm only entering it for the
>     apartments right now).
>     What do you think?
>
>
>     Ultimately, I have one major problem: the heating consumption
>     reported is abnormally low. I've been banging my head since
>     yesterday trying to figure out why. I think I've ruled out pretty
>     much everything (but I'm confident that missing something is
>     possible) aside from this ventilation thing.
>
>     If I add (or increase) Zonal exhaust to a zone:
>     - The attached system sizing doesn't seem to change
>     - but suddenly I'm getting unmet heating hours...
>     - And I do have *some* more consumption
>     *This make me think eQuest somehow doesn't really take zonal
>     exhaust into account when autosizing *(but does for consumption)*.
>     Do you have the same experience with it? Any workaround to avoid
>     this problem?*
>
>     Finally, I think I'm in dire need of a pair of experienced yet
>     fresh eyes... I'd be extremely grateful if someone was willing to
>     take a look at my model. Ping me and I'll send you the file, and
>     hopefully return the favor soon.
>
>     Thanks a bunch,
>
>     Julien
>
>
>     --
>     Julien Marrec, EBCP, BPI MFBA
>     Energy&Sustainability Engineer
>     T: +33 6 95 14 42 13 <tel:%2B33%206%2095%2014%2042%2013>
>
>     LinkedIn (en) : www.linkedin.com/in/julienmarrec
>     <http://www.linkedin.com/in/julienmarrec>
>     LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>     <http://www.linkedin.com/in/julienmarrec/fr>
>
>     2015-02-20 13:04 GMT+01:00 Julien Marrec <julien.marrec at gmail.com
>     <mailto:julien.marrec at gmail.com>>:
>
>         Thanks to both of you for your answers!
>
>         David,
>
>         You say its combined in quadrature. Is there documentation
>         somewhere about this?
>
>         Also, I'm confused about how it's more flexible to add HRVs
>         when using zonal exhaust. I thought the core principle of
>         Zonal Exhaust was that it was directly exhausted to outside,
>         which means not going to the central system and thus
>         completely bypassing any Heat recovery.
>         From the help file: "The SYSTEMS program simulates heat
>         recovery from central exhaust only, not from zone exhaust. If
>         heat is to be recovered, zone exhaust should not be entered
>         but rather allowed to default to the central system."
>
>         Am I missing something?
>
>         Thanks,
>
>         Julien
>
>
>         --
>         Julien Marrec, EBCP, BPI MFBA
>         Energy&Sustainability Engineer
>         T: +33 6 95 14 42 13 <tel:%2B33%206%2095%2014%2042%2013>
>
>         LinkedIn (en) : www.linkedin.com/in/julienmarrec
>         <http://www.linkedin.com/in/julienmarrec>
>         LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>         <http://www.linkedin.com/in/julienmarrec/fr>
>
>         2015-02-19 20:35 GMT+01:00 David Reddy
>         <david at 360-analytics.com <mailto:david at 360-analytics.com>>:
>
>             I agree with Nathan's recommendation; that is also how
>             we have also settled on modeling whole house exhaust
>             ventilation.  With regards to infiltration, we do model a
>             nominal amount that is calculated using PNNLs infiltration
>             modeling guidelines and is input at the space as the
>             component adjusted with wind speed. The EXHAUST-SOURCE =
>             infiltration will automatically combine the space and zone
>             exhaust in quadrature, which we believe is appropriate, at
>             least with respect to what is readily available in
>             Doe-2. The space component is assumed the same in
>             proposed/baseline unless the intent of the analysis is to
>             illustrate the impacts of reducing uncontrolled air leakage.
>
>             In addition to other noted flexibility, it is also easier
>             to incorporate modeling of variable flow and even HRVs.
>
>             -David
>
>
>
>             On Thursday, February 19, 2015, Nathan Miller
>             <nathanm at rushingco.com <mailto:nathanm at rushingco.com>> wrote:
>
>                 We model that type of system all the time, and prefer
>                 to model the outside air as zonal-exhaust (infiltration).
>
>                 The primary reason is that it ensures the space
>                 conditioning system sees the same vent load regardless
>                 of if you switch systems types (or have different
>                 systems in a baseline vs. proposed case for example).
>                 On jobs where I input it as OA on systems, I was never
>                 able to get the ventilation load energy use to line up
>                 when I compared, for example, electric resistance heat
>                 to PTACs, probably due to the slightly different
>                 algorithms employed for each system type.
>
>                 The other nice thing is that it allows you to model
>                 the space conditioning fans as cycling to meet the
>                 load (schedule = 0 all the time, night-cycle-control
>                 allowed, fan operation = intermittent). If you
>                 introduce the outside air through the system inputs,
>                 often it will force the mechanical system fans to
>                 operate all the time to provide ventilation, but in
>                 your case, you already have the whole-house-fan to do
>                 that.
>
>                 I believe any infiltration air assigned at the zone
>                 gets tacked on to infiltration air assigned at the
>                 space. If you want greater control of the net
>                 infiltration air, you’d probably have to do some math
>                 and decide when those values should stack, and when
>                 they would be “double counting” infiltration.
>
>                 **
>
>                 *Nathan Miller, PE, LEED AP BD+C**– */Mechanical
>                 Engineer/Senior Energy Analyst/
>
>                 *RUSHING*| *D*206-788-4577 |*O*206-285-7100
>
>                 *www.rushingco.com <http://www.rushingco.com/>*
>
>                 *From:*Equest-users
>                 [mailto:equest-users-bounces at lists.onebuilding.org]
>                 *On Behalf Of *Julien Marrec
>                 *Sent:* Thursday, February 19, 2015 11:44 AM
>                 *To:* equest-users at lists.onebuilding.org
>                 <mailto:equest-users at lists.onebuilding.org>
>                 *Subject:* [Equest-users] Exhaust fans in appartment
>
>                 Hi,
>
>                 I'm modeling an apartment building that has toilet and
>                 bathroom exhaust, and mechanical supply. Make-up air
>                 comes from trickle vents.
>                 (Side note: the corridor has mechanical supply, much
>                 higher than 62.2 at 0.6 CFM/ft²,  and no exhaust
>                 whatsoever, so I expect /some /makeup air would come
>                 from there too, but I'm prohibited to capture this
>                 effect...)
>
>                 I have been thinking about the best way to do this:
>                 whether I should assign this to a zonal exhaust fan
>                 (EXHAUST-FLOW) or whether I should specify the CFM
>                 exhausted as an outdoor air flow (OUTSIDE-AIR-FLOW).
>
>                 I think the OUTSIDE-AIR-FLOW would be the least
>                 problematic if I only had to deal with the baseline,
>                 but in my proposed building I only have baseboards for
>                 heating, so this wouldn't work.
>
>                 First, Am I correct in the above statements?
>
>                 Second, if I do specify an exhaust fan in the
>                 following way:
>                 FAN-CONTROL = CONSTANT-VOLUME
>                 EXHAUST-FLOW = 50
>                 EXHAUST-FAN-SCH = "Fraction Always 1 Yr"
>                 EXHAUST-SOURCE = INFILTRATION
>
>                 (I'm also defining exhaust systems like this for
>                 mechanical rooms in my basement)
>
>                 Will eQuest actually take into account that it (he?)
>                 should add 50 CFM of outside air (through
>                 infiltration) as a load? Will eQuest also take that
>                 into account for the sizing of my zonal equipment?
>
>                 Finally, will it interact in any way with the
>                 infiltration defined under Internal Loads for the Space?
>
>                 Thanks for any clarifications you can offer.
>
>                 Best,
>                 Julien
>
>                 --
>                 Julien Marrec, EBCP, BPI MFBA
>                 Energy&Sustainability Engineer
>                 T: +33 6 95 14 42 13 <tel:%2B33%206%2095%2014%2042%2013>
>
>                 LinkedIn (en) : www.linkedin.com/in/julienmarrec
>                 <http://www.linkedin.com/in/julienmarrec>
>                 LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>                 <http://www.linkedin.com/in/julienmarrec/fr>
>
>

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