Re: [EnergyPlus_Support] Re: Unmet load hours due to increased fan pressure rise

Wow. That is a simple question for probably one of the trickiest bits of using energy plus. Fortunately and at the same time unfortunately e+ allows for a wide variation on control stradegies and systems. How and which setpointmanager objects are used is highly specific both to system and control stradegy. The simplist form of control is setting a wished constant temperature on a node of the system (for example the exit node of a heating coil) using setpointmanager:schedule. I believe the program utilizes the next componant object emmidiately upstream of the node in question (or possibly group of componants, depending on the setpoint manager type used) to get the air conditions as close to the wished for conditions as the(se) componants can manage as per their own limmits.

Describe your system a bit to us.

Also, another place to look is the sizing of the equipment. A quick check to see if the sizing was done properly is to use the sizing:parameter object to put an oversizing factor of say 1.5 on the heating and cooling equipment.

Also, report over extream weather periods to try and see when exactly the loads are not being met.

Hope that gets you on the solution path.

Jean

Sent from my iPhone

On 25.01.2013, at 07:38, "JFCS" <jamo0312see@xxxxxxxxx> wrote:

Still can't figure this out, how do you properly manage your setpoint?

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, jeannieboef wrote:
>
> Fan Pressure should have zero bearing on unmet loads. Its only
> function is to calculate electricity consumption. even though the
> motor heat will enter the airstream if it is designated as being in
> the airstream, I doubt this is your problem.
>
> That being said, your method for baseline fan power sizing by
> adjustment of the pressure rise looks right.
>
> You are allowed 300 hours unmet load, as long as the design case also
> has 250 or more but less than 300 (deviation of 50), though proper
> setpoint management should keep you under 50 for a good model.
>
> Sent from my iPhone
>
> On 17.01.2013, at 10:15, "JFCS" wrote:
>
> > My model gains unmet load hours or time set point not met during
> > cooling operations, when even i increased fan pressure rise of my
> > fans.
> >
> > First I autosized a working model with complete hvac system for my
> > Baseline case as per "G3.1.2.8 Design Airflow Rates". Then I need to
> > adjust my VAV's fan power as "G3.1.2.9 System Fan Power" therefore I
> > need to increase the pressure rise of my fans. Thought i got the
> > correct fan power but the unmet load hours is below 300hours...
> >
> > Any suggestions?
> >
> >
>

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