[Equest-users] Exhaust fans in appartment

[Julien Marrec]

David,

Your Solution N°2 is smart!
I have my space infiltration defined as being Air Changes per hour, so I
can compute the appropriate design day infiltration multiplier pretty
easily (using quadrature). I end up with some very high multipliers for
some of my spaces but it seems to do the job correctly as far as sizing
goes.

It's tedious if you have a lot of different rooms with zonal exhausts, but
I don't see anything else that would do the job in a better fashion anyways.

Thanks for the advice,
Julien



--
Julien Marrec, EBCP, BPI MFBA
Energy&Sustainability Engineer
T: +33 6 95 14 42 13

LinkedIn (en) : www.linkedin.com/in/julienmarrec
LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
<http://www.linkedin.com/in/julienmarrec>

2015-02-20 17:09 GMT+01:00 David Reddy <david at 360-analytics.com>:

>  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
> LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>
> 2015-02-20 16:33 GMT+01:00 Nathan Miller <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]
>> *Sent:* Friday, February 20, 2015 7:14 AM
>> *To:* David Reddy
>> *Cc:* Nathan Miller; 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 <%2B33%206%2095%2014%2042%2013>
>>
>> LinkedIn (en) : www.linkedin.com/in/julienmarrec
>> LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>>
>>
>>
>> 2015-02-20 13:04 GMT+01:00 Julien Marrec <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 <%2B33%206%2095%2014%2042%2013>
>>
>> LinkedIn (en) : www.linkedin.com/in/julienmarrec
>> LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>>
>>
>>
>> 2015-02-19 20:35 GMT+01:00 David Reddy <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>
>> 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
>> <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
>> *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 <%2B33%206%2095%2014%2042%2013>
>>
>> LinkedIn (en) : www.linkedin.com/in/julienmarrec
>> LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
>>
>>
>>
>>
>>
>
>
>
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