Building Controls VI: When to Use Each Response

Gain

Amount of response changes when gain decreases

When a derivative is added

A cost is incurred.

Slow Responding Systems

Best fit for a Proportional Response

How much offset is resonable

Depends on the needs.

Fast response system

Floating Control is the best choice.

Proportional Response has

Good Stability, Reasonable Offset

Higher Strength Loads Require

Proportional System tuning that pushes back harder

Stabilization with too much offset

Requires more work to satisfy requirements

Slow responses are expected when we are controlling the

Temperature and Humidity

Gain is not concerned with setpoint, but with

a constant value reached.

A system is tuned to

best respond to a certain load condition

Setpoint Adjustments are a reason to have

derivatives

Duct temperature and humidity changes are

felt more quickly.

If a system is below setpoint, gain added is

negative

Duct pressure and flow changes

occur even faster.

If a system is above setpoint, gain added is

positive

Integral component gets added to the system the longer

that the system is away from setpoint.

When the gain is changed,

the step for what is up and down changes for every given temperature change

Gain encourages stability

to be more easily reached.

PI gives the ability

to decrease the gain for stability.