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Re: [EnergyPlus_Support] Space heating demand. HELP



Thanks again,

I thought exactly the same thing. 
You are right. The system is greatly oversized for most of the year and I think it is quite normal.
In order to study the effect that the different parameters can have on the heating sistem consumption and sizing, first I eliminated all heat gaings which could reduce the heating energy required during the operational time. However, I could't see any change. Then, I increased the temperature of the winter design day and I saw that its is the parameter which largely effects the final size of the heating sistem. However this "extreme condition" is not always present in reality, so this is the reason of this odd heating consumption.

Thanks again.
All the best,
Giusi


On Thursday, August 3, 2017 2:47 AM, "Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:


 
I was thinking about this further....
I think that if you observe the autosized heating coil's performance on the Design Day, you'll find that it is operating at full capacity (or close to it, also considering any Sizing Factor that you have applied). 

If that is the case, the coil is sized properly and the short peak you see during startup for non-design hours is exactly what will occur in a real system. This is because every properly sized system (for the design condition) is oversized for all other conditions. For most of the year it's GREATLY oversized (compared to the non-peak load).

On Wed, Aug 2, 2017 at 8:43 PM, Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
 
Dear Giusi,
I see that the peaks are very pronounced, which makes me agree with you about the system being oversized.

My next questions is "What is the purpose of your model?" It seems that total energy use will be accounted for reasonably in E+ even when the system is greatly oversized unless.....
..you have intentions of modeling a realistic, carefully selected heating system which has varying efficiency at partial load ... and the partial load efficiency is carefully defined with an appropriate curve.

Most systems with which I am familiar, however, are greatly oversized. The engineers want no complaints, even when the outdoor temperature falls to a very low temperature. I am not surprised to see 50-100% over-capacity in an operating building.

On Wed, Aug 2, 2017 at 3:17 PM, Giuseppina Buttitta giusybuttitta@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@ yahoogroups.com> wrote:
 
Thank you for your reply,

I guess it is normal for the heating system to have a peak upon startup, however I think that the peak is too large and the reason is that the heating system is not correctly dimensionated.
Please find attached the temperature schedules used in the design day and in the normal operational days. I also attached the resulting "meter file". 
I also tried to increse the setback smoothly for regular days, but it doesn't change the magnitude of the peak demand.

Thanks again for your help.

All the best,
Giusi



On Wednesday, August 2, 2017 7:12 PM, "Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxx m [EnergyPlus_Support]" <EnergyPlus_Support@yahoogroup s.com> wrote:


 
As I think about this....
Why is it a problem for the heating system to have a large peak upon startup? It seems that is exactly what occurs when the heating system starts and begins to transition the building from an unoccupied period with lower setpoint to an occupied period (and higher setpoint).

On Wed, Aug 2, 2017 at 6:43 AM, Giuseppina Buttitta giusybuttitta@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@yahoogroup s.com> wrote:
 
Thank you all for the reply,

I used your suggestions and I applied a schedule with a constant temperature as heating schedule of the design day. Peaks now are significantly reduced, however they are still there (see attached figure).
Do you have any idea about other possible causes? I also considered the heating sizing factor equal to 1.

Thanks again,
Giusi



On Tuesday, August 1, 2017 6:11 PM, "Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@ yahoogroups.com> wrote:


 
Your autosizing settings will determine how large the equipment is depending on how fast they have to bring the zone to the required setpoint after they are turned on. Either ramp the setpoint or increase the pulldown time in the autosizing options.

Am 31.07.2017 2:34 nachm. schrieb "Giuseppina Buttitta giusybuttitta@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@ yahoogroups.com>:
 
Hi all!
I have tried to model the energy consumption for heating of a dwelling heated by electric baseboards. All the installed electric baseboards are controlled by a thermostat.
However, the results I obtained look weird to me.
The heating energy request is not constant during the period but it has a really big peak when the heaters are turnud on and then the request is quite small during the rest of the day (see attached picture). It looks like the heaters are oversized for the dwellings.
I tried to check again my code several times but everything seems fine.
Do you have any idea what the problem could be?
I know it is a vague request, but probably it has already happened to some of you.

Thanks,
Giusi





--
James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, GR, MI 49504

(alphabet soup of efforts for excellence: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxx m

Website l  LinkedIn
Coffee conversation:
What spirit is so empty and blind, that it cannot recognize the fact that the foot is more noble than the shoe, and skin more beautiful than the garment with which it is clothed?







    

     


    
    








  
 
  



    

     


    
    













  
















-- 
James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, GR, MI 49504

(alphabet soup of efforts for excellence: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@buildingperformanceteam. com

Website l  LinkedIn
 
































Coffee conversation:
What spirit is so empty and blind, that it cannot recognize the fact that the foot is more noble than the shoe, and skin more beautiful than the garment with which it is clothed?







    

     



    
    













  
















-- 
James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, GR, MI 49504

(alphabet soup of efforts for excellence: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l  LinkedIn
 
































Coffee conversation:
What spirit is so empty and blind, that it cannot recognize the fact that the foot is more noble than the shoe, and skin more beautiful than the garment with which it is clothed?







    

     


    
    








  
 
  

















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         Posted by: Giuseppina Buttitta <giusybuttitta@xxxxxxxxx>         

    











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