Valid Coil Process - The coil process line
resulting from your data crosses the saturation curve. The process is
possible. It may or may not be appropriate for your application.
Invalid
Coil Process - The coil process line resulting from your data does not
cross the saturation curve. The process is impossible. This is
probably due to a very high latent load. This does not imply you cannot
achieve your desired leaving air conditions. However, you will need to
revise your system design to do so.
Impractical Coil Process - Either the ADP is lower than 48 oF or the bypass factor is less than 5%. An ADP of 48 oF is considered by many to be the lowest economical ADP for comfort cooling conditions. The 5% lower limit on bypass factor is arbitrary, but is generally obtainable only with a deep coil. Consult your manufacturer's specifications to determine what is available. For all practical purposes, a bypass factor of 0% may be considered impossible.
Leaving Air Conditions Modified - This
message can only occur when a fan heat calculation is desired and you've
specified a draw through supply fan.
Regardless of whether or not you include fan heat in your calculations, the
entering conditions represent those air conditions leaving the return fan and
entering a blow through supply fan (if your fan is blow thru). Likewise,
the leaving conditions are those conditions leaving the a draw through supply
fan (if your fan is draw thru) and being supplied to the
distribution duct work, not to the space. (Did you remember to account
for duct heat gains?) When you ask for fan heat to be included and your fan is a
draw through fan, the program calculates a temperature change across
the fan and subtracts that from your desired leaving air condition resulting
in an off-coil condition necessary to achieve your desired supply condition
after the fan. If your desired condition has a very high dew point,
then it is mathematically possible for the dry bulb to be numerically less
than the dew point coming off the coil. Obviously, this is cannot happen.
Under this condition, the off-coil dry bulb temperature is raised
to equal the dew point of your specified leaving air condition and the air
temperature leaving the fan is recalculated. This also results in the
aforementioned message in the ADP Message Box of 'Impractical
Coil Process' since the bypass factor required to do this is 0%.
Entering
conditions are outside the scope of ANSI/ASHRAE 41.6-1994 - Although
based on the papers of Goff and Gratch and of Hyland and Wexler, this standard
does simplify the complex psychrometric formulas defined by these
researchers. Since the formulas are simplified, there may be
some error in extreme conditions. Thus limits are provided
within the standard. These limits are incorporated into this
program. This message indicates your input data will not
provide reliable output when calculation via this standard.
Given normal comfort cooling conditions as well as an arbitrary
limit imposed on the input data, it is unlikely you will ever see
this message.
Results
are within the scope of ANSI/ASHRAE 41.6-1994 - This message indicates
your input data yielded results that fell within the parameters of this
standard as briefly explained above. This message should not be
construed as a validation of your design.
Entering/Leaving Wet bulb is to low for stated
dry bulb - if you look at a psychrometric chart, you will see that at
any dry bulb temperature with 0% relative humidity, there is a corresponding
wet bulb temperature. Since the air is devoid of water at 0% relative
humidity, this wet bulb is the lowest possible condition attained. This
message means you have entered a wet bulb below this value. Mathematically, this would result in a negative value of relative humidity.
The following messages are related to faulty input and are self explanatory.
Entering/Leaving Wet bulb cannot exceed dry bulb
Entering/Leaving Dew point cannot exceed dry bulb
Entering/Leaving Relative humidity must be between 0% and 100% inclusive
Disclaimer and Copyright Information
Program Release History