Janfire NH Installation And Servicing Instructions page 7

The regulator works with three factors:
P – Proportional power to temperature difference
I – Integrating power over time due to temperature difference
D – Differential power, due to rapid changes in temperature
For P and I factors, the difference between actual temperature and target temperature is used to calculate the
power output. If the actual temperature is 140°F (60°C) and the target temperature is 163°F (73°C), the
difference is calculated as 23°F (13°C).
The D-factor compares the actual temperature to the temperature at the last control position. If there is any
difference, this will be multiplied with the D-factor and the burner power will change thereafter.
The result from the above values will be added together to calculate the new required power output level for the
burner.
Example:
Nominal power, start up power: 20 MBTU
Regulation interval: 1:00 min
Power level min: 20 MBTU
Power level max: 51 MBTU
P-factor: 10000%
I-Factor: 500%
D-factor : 0%
Boiler temperature: 140°F (60°C)
Target temperature: 163°F (73°C)
Temperature difference = 73 – 60 = 13
P = 10000% x 13 = 1300
I = 500% x 13 = 65
D = 0% x 0 = 0
Sum of P + I + D = 1365.
This added to nominal, start up, power 600 (6kW, 20 MBTU) 1365 + 600 = 1965. The output is in units of 10 W
so 1965 will be (19.6 kW) 67 MBTU. Since the maximum power level is set to (15kW) 51MBTU, the power will
be limited to that. The integrating (I-value) memory starts with nominal power, and will get the new value of 665.
If the boiler temperature is higher than target, the P- and I-factor will decrease power output.
The PID regulator will come in balance when actual and target temperatures are equal. The P factor will then be
0 and the integrating memory will hold the power level.
The P factor determines how much power the burner will provide due to a temperature difference.
The I factor specifies how fast the burner will increase / decrease power over time.
The D factor is often used in fast processes to stop controller from over shooting. It is not very usable in this
slow process.
The control interval determines how often calculations and changes in burner output settings are made.
Power modulation
In order to modulate burner output, a PT-100 sensor measuring the boiler water temperature must be
connected. PID Control must be activated, "service menu 66".
Janfire NH Burner Service Installation Manual 4.16.09 - Technical specifications are subject to change without prior
notice.
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