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BOILER MASS
The boiler mass setting allows the installer to adjust the control to the thermal mass of the type of heat sources used in the
application. There is a boiler mass setting for each boiler. The modulation of the boiler can become unstable if the incorrect Boiler
Mass setting is chosen. A key sign of the boiler modulation being unstable is the flame will continue to increase and then decrease
in short periods of time. By choosing a lower boiler mass setting, the boiler response will become more stable.
Lo (1)
The Lo setting is selected if the boiler that is used has a low thermal mass. This means that the boiler has a very small water
content and has very little metal in the heat exchanger. A boiler that has a low thermal mass comes up to temperature quite
rapidly when fired. This is typical of many copper fin-tube boilers.
The Lo mass setting provides a fast response to the heating system.
number into the Maximum Boiler Output setting.
For example, if a boiler has a maximum output of 100 MBH:
Maximum Boiler Output = 100,000 BTU/hr = 10 x 10,000 BTU/hr
10,000
MOTOR SPEED
The Motor Speed is the amount of time the boiler requires to go from 0%
modulation to 100% modulation. The control includes a Motor Speed
setting for each individual boiler.
Gas valve actuating motors have a design time from fully closed to fully
opened which can be found in the manufacturer’s manual. The Motor
Speed should be set to this time.
The Motor Speed setting for a Variable Frequency Drive (VFD) is the
amount of time required to go from a stopped position to 100% fan
speed. Since a VFD has a very quick response rate, it may be necessary
to increase the Motor Speed setting in order to increase the stability of
the boiler modulation.
Example 1:
A boiler’s input signal range is 2 to 9 V (dc). The 265 control has an output signal range of 2 to 10 V (dc). To make the two signal
ranges the same, the Maximum Modulation required is:
Maximum Modulation = 2 V – 9 V x 100% = 88%
2 V – 10 V
Example 2:
If the boiler’s input signal range is 6 to 19 mA the required Maximum Modulation is:
Maximum Modulation = 4 mA – 19 mA x 100% = 94%
4 mA – 20 mA
MINIMUM BOILER OUTPUT
In order to accommodate different boiler capacities in the same system, a minimum boiler output for each boiler can be set. This
allows the control to properly operate the boilers using either sequential or parallel modulation. The minimum boiler output range
is from 10,000 BTU / hour to 19,990,000 BTU / hour.
Each boiler typically has a rating plate that specifies the minimum output. This information is also available in the boiler manual. The
Minimum Boiler Output setting has units of 10,000 BTU / hour. Divide the minimum output rating by 10,000 and enter the number
as the Minimum Boiler Output setting.
For example, if a boiler has a minimum output of 20 MBH:
Minimum Boiler Output = 20,000 BTU/hr = 2 x 10,000 BTU/hr
10,000
MAXIMUM BOILER OUTPUT
In order to accommodate different boiler capacities in the same system, there is a maximum boiler output for each boiler. This
allows the control to properly operate the boilers using either sequential or parallel modulation. The maximum boiler output range
is from 10,000 BTU / hour to 19,990,000 BTU / hour.
Each boiler typically has a rating plate that specifies the maximum output. This information is also available in the boiler manual.
The Maximum Boiler Output setting has units of 10,000 BTU / hour. Divide the maximum output rating by 10,000 and enter the
