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Re: [EnergyPlus_Support] Pump datasheet info vs EnergyPlus input
Jean and Jim,
Thanks for your feedback. The advertised motor efficiency of 90.1% is at full (motor) capacity so, 7.5kW. Yet the motor efficiency from the pump performance curve is .684/.744 = 91.9% at full (pump) capacity. That's slightly puzzling me too. But you're right, these are questions for Grundfos.
Regards,
Patrick
On 25 February 2014 20:58, Jim Dirkes <<mailto:jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> It seems that something is not quite adding up properly. I expect that:
> Pump efficiency * Motor efficiency = (Pump + Motor) efficiency
> .744 * .904 = .673 (which is not the same as .684)
>
> This is not a big difference, but it might be worth asking the Grundfos technical people about.
> Regarding the motor power, it is common to use a motor somewhat larger than is needed by the load, since motors are available only in specific power increments. In this case, I?m guessing that the ISO power rating of 5.5kW has something to do with selecting a 7.5kW motor. Otherwise a 5kW motor could be used.
>
> p.s., I am not familiar with European norms for technical data, so some of this is conjecture.
>
>
> James V Dirkes II, PE, BEMP, LEED AP
> <http://www.buildingperformanceteam.com/>> www.buildingperformanceteam.com
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
>
> From: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of <mailto:jeannieboef@xxxxxxxxx>jeannieboef@xxxxxxxxx
> Sent: Tuesday, February 25, 2014 2:21 AM
> To: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
> Cc: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] Pump datasheet info vs EnergyPlus input
>
>
> If I had to guess...it looks like the rated power excludes the efficiencies. Or it's given like this for the electrical engineer, who has do cover a wider range of power draw (during start for example).
>
> Your calcs seem right. P=Vdot x dP / eff.
> Mit freundlichen Grüßen- Sent from my iPhone (excuse the brevity)
>
> i. A.
> Jean Marais
> b.i.g. bechtold
> Tel. +49 30 6706662-23
>
> On 25.02.2014, at 05:13, Patrick Bivona <<mailto:patrick.bivona@xxxxxxxxx>patrick.bivona@xxxxxxxxx> wrote:
>>
>> Hi,
>>
>> I'm trying to make sense of the attached pump datasheet and see how the information there relates to input fields for the Pump:ConstantSpeed object.
>>
>> The Pump:ConstantSpeed object needs:
>> * rated power consumption (W)
* rated flow rate (m3/s)
* rated head (Pa)
* motor efficiency
Here's information available in the datasheet that seems relevant (there's more in there):
>> * motor rated power P2: 7.5 kW
* flow rate: 946.9 L/min (0.0158 m3/s)
* head: 20 mAq (196200 Pa)
* pump+motor efficiency at full load: 68.4%
* pump efficiency at full load: 74.4%
* motor efficiency at full load: 90.4% (which is also 68.4% / 74.4%)
Now, here are my observations and questions. From the engineering reference, EnergyPlus calculates the total efficiency from the following formula:
>>
>> total efficiency = flow * head / rated power consumption
>>
>> So I guess, I should calculate the rated power consumption in reverse from the available datasheet info:
>>
>> rated power consumption = flow * head / total efficiency = 0.0158 * 196200 / 0.684 = 4532 W
>>
>> Does that seem correct?
>> What troubles me is the much higher figure for the motor rated power: 7.5 kW
>>
>> How does that all tie in together?
>>
>> Thanks in advance for your help,
>> Patrick
>>
>> <PC1-B502.pdf>
>
>
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