[Equest-users] Exhaust fans in appartment
David Reddy
david at 360-analytics.com
Mon Feb 23 09:59:28 PST 2015
Julien,
Glad to hear you got it working. I looked back over some of our past
projects, and wanted to follow-up on a few key inputs that I'd recommend
reviewing and adjusting to see how they impact your model:
ZONE:SIZING-OPTION: In my opinion, ADJUST-LOADS is the correct setting.
The eQ Wizard sets this to ADJUST-LOADS, but if you have restored BDL
defaults, the DOE-2 default is FROM-LOADS, so you'll want to create a
user default to change this.
ZONE:DESIGN-HEAT-T and ZONE:DESIGN-COOL-T: These are important inputs
for sizing zone air flows, and then subsequently the size of
heating/cooling coils. Make sure they are properly coordinated with the
system deisgn supply air temperatures.
In addition to the space infiltration option I mentioned, you could
follow a similar approach by setting a zone OA rate (OUTSIDE-AIR-FLOW,
OA-FLOW/AREA, etc) equal to the design exhaust rate, and using the
SYSTEM:MIN-AIR-SCH to set the system OA to 1 on design days, but 0 on
all other days. However, one thing to keep in mind is that if you
specify OA at the zone, the zone system fans will run continuously even
if SYSTEM:FAN-CONTROL = CYCLING. I think setting the FAN-SCHEDULE to a
schedule of 0s and NIGHT-CYCLE-CTRL = CYCLE-ON-ANY, is another way to
make the system operate only on calls for heat/cool, but I'd recommend
testing it to confirm. In any case, a continuously running fan is not
really an issue if the fan power is 0, so if you've set up your model
that way, this other approach might be OK and easier to implement.
David
On 2/23/2015 5:32 AM, Julien Marrec wrote:
> 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
> <http://www.linkedin.com/in/julienmarrec>
> LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
> <http://www.linkedin.com/in/julienmarrec/fr>
>
> 2015-02-20 17:09 GMT+01:00 David Reddy <david at 360-analytics.com
> <mailto: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 <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 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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