© 2018 OJ Electronics A/S
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INSTRUCTIONS Commissioning guide for AHC-3000
20.1 Temperature control loop settings
• If the control of the supply air oscillates, it may be necessary to
change the parameter settings in the temperature control loop.
• The available parameters are the P-band and I-time.
• Normal these parameters are OK from the factory.
• If a control sequence such as “Constant supply” or “Constant supply/
extract diff.” is selected, the P-band and I-time in the “Supply” section
will be active and may be changed if the temperature oscillates more
than is acceptable.
• If a control sequence such as “Constant extract” or “Constant room is
selected, the P-band and I-time in the “Extract” section are active and
may be changed if the temperature oscillates more than is acceptable.
Flow down function
• If the temperature cannot be reached even though the heat exchanger
AND the heating are 100% open, the air flow will be reduced to 50%
of the air flow setpoint
Basics on the temperature control sequence:
Fault on the sensor = Output will take half of the fault on the P-band as a ”here-and-now-reaction”.
The velocity of the second half of the P-band will be cut in or cut out using the I-time. The calculation
and recalculation of the fault are on-going calculations.
If the temperature oscillates more than is
acceptable, the first thing to change is the
P-band and/or the I-time.
A higher P-band and I-time will give a slower
reaction on the output, and a slower reaction
on the output will increase the stability of the
temperature control.
Not all oscillations can be resolved by changing
the P-band and I-time.
For instance, in a water-based heating system, the differential pressure over the valve is important.
P-band and I-time cannot save the world??.
If the differential pressure over the valve is very high (
more than 0.1 bar or 1.0 mH2O
) it may not be
possible to create a stable temperature control only adjusting the P-band and/or the I-time.
If differential pressure over the valve is higher than mentioned AND it is not possible to a stable
temperature control via adjusting the P-band and I-time, you must lower the differential pressure over
the valve.
