[EnergyPlus_Support] Re: Cooling coil overcools

["JV Dirkes II" <jvd2pe@xxxxxxx>]

Dear Brent,

Thank you SO much!  After several trials, your guidance resulted in a
successful run which has no sub-cooling.

As I was going through the process of trying to make this work
properly (both before and after your input), it occurred to me that
controlling mixed air and coils in a real air handler is far simpler
than it seems to be in E+.  At least it's far more intuitive.  Is
there a white paper or other discussion somewhere which explains how
the various controllers and set point nodes "think" in E+?  That would
be exceptionally valuable.
In fact, if someone were willing to spend a bit of time on the
telephone with me explaining it, I'd be happy to write the paper
(assuming that none exists).

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Griffith, Brent"
<brent_griffith@...> wrote:
>
> 
> The coils won't fight each if they each have their own set points
(at their outlet nodes) rather than all referencing the same fan
outlet node.  You can use a node list in the Set Point Manager: Mixed
Air (or multiple manager objects) to put the mixed air set point on
the outlet of the oa mixer, cooling coil, and heating coil.    Then
change the control nodes in the heating coil and cooling coil
controller to be the coil outlets. 
> 
> -----Original Message-----
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx on behalf of JV Dirkes II
> Sent: Fri 4/18/2008 6:49 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Cooling coil overcools
>  
> Dear EPlus forum,
> 
> I've got a simple air loop with, in direction of airflow, an outdoor
> air mixer, chilled water cooling coil, gas heating coil and fan.  The
> report variables reveal that the air temperature leaving the fan is a
> constant 12.8C, which is my intention and the setpoint of a set point
> manager.  However, other variables reveal that the mixed air gets
> cooled too much, then the heating coil warms it, and the fan heat
> warms it further.
> As an example:
> Tma   Tcc  Thc   Tfan
> 19.2  9.2  10.4  12.8
> 
> I have another model set up identically except that the heating coil
> is a hot water coil.  It works just fine;  Tcc = 10.4
> 
> This is a big problem because there is a LOT of excess energy used by
> the sub-cooling.  Will someone please look at the file to determine
> the cause of the sub-cooling?
> 
> Thanks!  (File uploaded very shortly)
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>



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