RE: [EnergyPlus_Support] Warning meassage in Exercise 2C of "Getting Started..."

[YuanLu Li <yli006@xxxxxxxxxxx>]

Hi, Alvero

Because you are using templates, some sizing parameters are set by the program.

When the outdoor temperature and the Zone controlled  temperature are very close  (21°C), the cooling system is over sized.  Therefore, you get the warning that the DX coil is less then 2°C, which is close to  compressor freezing condition.

You can raise the zone thermostat temperature or the coil temperature limit in the Sizing:zone object to a higher value to avoid this warning.

When you are not using template or autosizing, these limit values can be set by you in the IDF.

 Dr. Li  

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: alvarofialho@xxxxxxxxx
Date: Thu, 5 May 2011 14:20:42 +0200
Subject: [EnergyPlus_Support] Warning meassage in Exercise 2C of "Getting Started..."

 

Hello all,

I was playing a bit with the sample Exercises provided in the "Getting
started with EnergyPlus" document. And Exercise 2C (the most "complete"
one) outputs a warning message (and some consequent error messages) that
I don't know what to do. As a "learning exercise", could you please help
me into solving this? It is important to let you know that I'm a
computer scientist, with no experience at all (for the moment) with the
design of HVAC systems :-) Thanks!

Here goes the warning message:

** Warning ** Coil:Cooling:DX:SingleSpeed "NORTH ZONE UNITARY
COOLING COIL" - Full load outlet air dry-bulb temperature < 2C. This
indicates the possibility of coil frost/freeze. Outlet temperature = 1.29 C.
** ~~~ ** ...Occurrence info = Chicago Ohare Intl Ap IL USA
TMY3 WMO#=725300, 04/25 14:00 - 14:15
** ~~~ ** ... Possible reasons for low outlet air dry-bulb
temperatures are: This DX coil
** ~~~ ** 1) may have a low inlet air dry-bulb temperature.
Inlet air temperature = 21.146 C.
** ~~~ ** 2) may have a low air flow rate per watt of cooling
capacity. Check inputs.
** ~~~ ** 3) is used as part of a HX assisted cooling coil
which uses a high sensible effectiveness. Check inputs.

And the consequent error message:

************* ===== Recurring Error Summary =====
************* The following recurring error messages occurred.
*************
************* ** Warning ** Coil:Cooling:DX:SingleSpeed "NORTH ZONE
UNITARY COOLING COIL" - Full load outlet temperature indicates a
possibility of frost/freeze error continues. Outlet air temperature
statistics follow:
************* ** ~~~ ** This error occurred 46 total times;
************* ** ~~~ ** during Warmup 0 times;
************* ** ~~~ ** during Sizing 0 times.
************* ** ~~~ ** Max=1.986818 Min=0.362192

Thanks lot!
Álvaro.

ps: I'm sending the IDF attached, although you might all have it in the
Examples/BasicsFiles folder of your E+ installation.

__._,_.___

Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.

Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe

__,_._,___