tekmar 423 Universal Reset Module - Manual (Page 23)

23 of 36 © 2007 D 423 - 08/07
Boiler Motor Speed
The Boiler Motor Speed is the amount of time the boiler
requires to go from 0% modulation to 100% modulation.
Gas valve actuating motors have a design time from fully closed
to fully open which can be found in the manufacturer’s manual.
The Boiler Motor Speed should be set to this time.
The Boiler 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.
•
• Locate the Boiler Motor Speed setting in the Adjust
Menu.
Minimum Modulation
The minimum modulation defines the minimum output
signal from the control to the boiler burner. It is based on
a percentage of the control’s output signal range.
The Minimum Modulation default setting is 0%.
For boilers with electronic operators, the boiler’s input signal
range may not match the output signal range of the 423
control. The Minimum Modulation setting limits the control
output range in order to match the boiler’s input range.
•
• Locate the Boiler Minimum Modulation setting in the
Adjust Menu.
To calculate the Minimum Modulation, use the following
formula:
For 0-10 V (dc):
Minimum Modulation =
0 V (dc) – Boiler’s Minimum Input Signal x 100%
0-10 V (dc)
Example:
A boiler requires a 1.8 V (dc) signal to fire the boiler at
low fire. The boiler can be modulated to 10 V (dc) where
it reaches high fire.
This means the boiler’s input signal range is 1.8 to
10 V (dc). The 423 control has an output signal range of
0-10 V (dc).
To make the two signal ranges the same, the Minimum
Modulation required is:
Minimum Modulation =
0 V-1.8 V x 100% = 18%
0 V-10 V
1.8 V (dc)
10 V (dc)
Control Rang
e
Boiler Rang
e
0 Vdc
18%
tekmar Stager Operation Section D
In some cases, multiple boilers may be required. In these
cases, the 423 allows for a connection to a tekmar Boiler
Control 264, 265, or 268. The 423 uses the Mod1 (dc)
modulating output to provide a 0-10 V (dc) signal to the
external input terminals on the Boiler Control. The 423
controls the Boiler Control target temperature by changing
the voltage signal. The Boiler Control responds to the boiler
target by staging the multiple boilers. The following table
can be used to convert a 0-10 V (dc) signal to a boiler
target temperature: To use the tekmar Staging operation, the following DIP
switch settings are required:
1. Set the 423 Off / tekmar Stager DIP switch to tekmar
Stager.
2. Set the 423 Boil Sup / Ret DIP switch to Sup.
3. Set the 423 Boil On-Off / Mod DIP switch to Mod.
The 423 boiler sensor must be located on the supply pipe
leading from the boilers. On the Boiler Control 264, 265,
or 268, the External Input / Stand Alone DIP switch must
be set to External Input. Any domestic hot water (DHW)
demands or Setpoint Demands in the system must connect
to the 423 in order to allow for DHW or setpoint priority.
Voltage (dc) 0 1 2 3 4 5 6 7 8 9 10
Boiler Target Off 50°F (10°C) 68°F (20°C) 86°F (30°C) 103°F (40°C) 121°F (50°C) 139°F (60°C) 157°F (70°C) 174°F (80°C) 192°F (90°C) 210°F (99°C)