[EnergyPlus_Support] Re: ASHRAE Compliant Fans and Pumps

["jeannieboef" <jeannieboef@xxxxxxxxx>]

Dear Mr. Dirkes,

I'm modelling a building with ventilation purely for ASHRAE 90.1 code compliance as it is in reallity 100% Naturally ventilated with just heating (radiant floor). As you know the mechanical system takes the shape of the baseline model which I gave as design supply air flow rates as per the minimum rates outdoor air rates of ASHRAE 62.1. These air flow rates obviously don't also meet the heating and cooling loads when all the heating and cooling loads are met with the AHU systems, meaning that e+ has sized the needed air flows and fan flow rates larger than the fan flow rates that I have thus far used in the fan power calculation as per ASHRAE G3.1.2.5 & G3.1.2.8.

I'm busy assigning deltaP to achieve the desired fan powers given in by the ASHRAE fan power calcualtion in e+, and wanted to ask your oppinion if this methodology is correct. Because the input in the fan power calculation uses the air flow purely for minimum outdoor air rates and not also to meet the heating cooling load.

 I've not found anything in Appendix G that would make me think that I couldn't make the design air flow rate for the fan power calculation ZERO. E+ would still calcualte the larger rate to meet heating and cooling loads, but I could leave all my fan deltaPs at zero.

What is the best approach here? What should I use for design Air Flow Rates for the baseline building (as the naturally ventilated proposed design  building doesn't have any requirement)?

Regards,

Jean.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "James V Dirkes II, PE" <jvd2pe@...> wrote:
>
> Dear Vinay,
> 
>  
> 
> While .6 fan efficiency is within normal range, the goal is to define a
> combination of fan efficiency and pressure rise which results in the
> acceptable fan power.  You start with known air flow, make a reasonable
> estimate of fan efficiency and then derive the pressure rise.
> 
>  
> 
> For a "Proposed" system, the derivation is not needed; you use the actual
> fan and motor efficiencies, actual airflow and actual pressure rise.
> 
>  
> 
> For your information (just in case it's helpful), the derivation of fan
> power is shown below in IP units.
> 
>  
> 
> 
> 
>  
> 
>  
> 
>  
> 
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Vinay Devanathan
> Sent: Wednesday, July 07, 2010 9:32 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] ASHRAE Compliant Fans and Pumps
> 
>  
> 
>   
> 
> Mr. Dirkes,
> 
>  
> 
> Thanks for your reply. So, is 0.6 Fan Efficiency (including motor
> efficiency) acceptable? or does it depend on any other variable? I am
> assuming there are no set specifics for Fan Efficiency value. So, with this
> procedure, we can calculate Fan Power from Appendix G formula and adjust
> Pressure difference. Am I right on this?
> 
> 
> Thank you.
> 
> Regards,
> 
> Vinay
> 
>  
> 
> On Wed, Jul 7, 2010 at 9:25 PM, James V Dirkes II, PE <jvd2pe@...>
> wrote:
> 
>   
> 
> Dear Vinay,
> 
>  
> 
> ASHRAE 90.1-2007 specifies Baseline system fan power in Table G3.1.2.9.  For
> VAV systems, also use Table G3.1.3.15 for part load performance.  A sample
> object for the VAV fan is shown below.
> 
>  
> 
> For all baseline fans, I made a spreadsheet which, based on anticipated
> motor and fan efficiency, calculates the pressure rise which will result in
> the correct ASHRAE 90.1 fan power.  Remember that E+, when asking for "fan
> efficiency", really wants (Fan mechanical efficiency x Motor efficiency).
> For example, if the fan mechanical efficiency  = .60 and motor efficiency =
> .90, the E+ "fan efficiency" = .54.
> 
>  
> 
> 
>  
> 
> Fan:VariableVolume
> 
> 
> Name
> 
> SFan_MainBldg
> 
> 
> Availability Schedule Name
> 
> SchCpct_FanOpern
> 
> 
> Fan Efficiency (incl. motor)
> 
> 0.6
> 
> 
> Pressure Rise (Pa)
> 
> 498
> 
> 
> Maximum Flow Rate
> 
> Autosize
> 
> 
> Minimum Flow Rate
> 
> 0
> 
> 
> Motor Efficiency
> 
> MT
> 
> 
> Motor In Airstream Fraction
> 
> 1
> 
> 
> Fan Coefficient 1
> 
> 0.0013
> 
> 
> Fan Coefficient 2
> 
> 0.147
> 
> 
> Fan Coefficient 3
> 
> 0.9506
> 
> 
> Fan Coefficient 4
> 
> -0.0988
> 
> 
> Fan Coefficient 5
> 
> 0
> 
> 
> Air Inlet Node Name
> 
> NodeOut_ClgCoilAir_MainBldg
> 
> 
> Air Outlet Node Name
> 
> NodeOut_SFan_MainBldg
> 
> 
> End-Use Subcategory
> 
> 	
> 
>  
> 
>  
> 
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Vinay Devanathan
> Sent: Wednesday, July 07, 2010 5:53 PM
> 
> 
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> Subject: Re: [EnergyPlus_Support] ASHRAE Compliant Fans and Pumps
> 
>  
> 
>   
> 
> Alan,
> 
> In regards to your reply,
> 
> Does ASHRAE specify any efficiency value for the fans? If yes, could you
> please direct me to the same.
> 
> Thank you.
> 
> Regards,
> Vinay
> 
> On Tue, Jun 29, 2010 at 11:33 AM, Jackson, Alan <ajackson@...>
> wrote:
> 
>   
> 
> You're going to want to adjust your Static Pressure DeltaP. Once you
> have your Watts for the Baseline from auto sizing the flow you can use
> DeltaP[Pa] = Power[W]*Eff/Flow[m3/s]
> 
> Since ASHRAE is telling you Flow and Power you have to solve for static.
> 
> Alan Jackson, LEED AP
> KlingStubbins
> 
> 
> 
> -----Original Message-----
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> 
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> ] On Behalf Of eddiecorwin
> Sent: Tuesday, June 29, 2010 11:13 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> 
> Subject: [EnergyPlus_Support] ASHRAE Compliant Fans and Pumps
> 
> I am curious as to how people have gone about modeling ASHRAE compliant
> pumps and fans. 
> 
> The pumps seem relatively strait forward, run the model, see what the
> flow is, then enter in a wattage that equates to 22W/GPM. The fans,
> however, do not have an input for the rated wattage. The only option I
> see is to alter the fan's Motor Efficiency until you get close to the
> correct W/CFM. 
> 
> Are these the same methods people have applied in the past, or is there
> a better way to the the correct W/GPM and W/CFM?
> 
> ------------------------------------
> 
> 
> 
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