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Ahmed,<br>
The fan mass balance probably failed because the input mass flow
rate to the fan was left unconnected. Type56 does not have an output
for the mass flow rate of ventilation air to my knowledge so while
you can (and should) pass the flow rate of air into Type56, you
can't pass it through Type56 and back to the Type112. In order to
avoid that warning, you can simple connect the flow rate output of
Type121 back to the fan.<br>
<br>
As far as the different results are concerned, there are a couple
of things to check. First, make sure that they system is actually
maintaining the set point temperatures in the zone. Type56's HEATING
and COOLING types are idealized and have infinite capacity. Type92
and Type121 have limited capacity and may therefore be limited in
the amount of energy that they can deliver to the zone. If they
aren't delivering enough, the zone temperature will fall away from
its setpoints. Second, make sure that you are looking at outputs of
energy transferred to the air stream, not energy (or fuel) consumed
by Type92 or Type121. Loads again are ideal and do not take into
account the efficiency (COP, EER, etc) of the system that is
delivering the energy. Third, Type56 is reporting sensible loads
only while Type92 (if you are correctly accounting for the
psychrometrics on the air stream by having a Type33 on the outlet
side of Type92 in case the Type92 set point is below the air's wet
bulb temperature) may be removing some latent energy as well.<br>
<br>
Kind regards,<br>
David<br>
<br>
<br>
On 12/28/2011 22:15, ahmed hamdi wrote:
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Hi,
<div><br>
</div>
<div>I designed an A/C system consists of Type 112b fan followed
by Type 92 auxiliary cooler followed by Type 121b heater. I
controlled this system using the Type 108 thermostat as
mentioned in the Restaurant Example. My problem is that after
running the simulation and comparing the loads with the loads
i got when i used Type 56 only without any additional fans,
coolers, or heaters, i found that the results are completely
different. </div>
<div><br>
</div>
<div>I noticed a warning stating that the fan mass balance
failed during 8760 time steps, which is the duration of my
simulation. I am not sure what is the problem, and will
appreciate your support.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Ahmed</div>
</div>
<br>
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