tekmar 284 Boiler Control - Manual (Page 4)

© 2014 284_D - 08/14 4 of 60 A Watts Water Technologies Company
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.
Minimum Modulation = 1.8 V x 100% = 18%
10 V
Control’s
Output
Signal
Range
Boiler’s
Input
Signal
Range
100% 10 V (dc) 10 V (dc)
0 V (dc)
88%
Boiler’s
Minimum
Input
Signal Minimum
Modulation
0%
1.8 V (dc)
18%
Maximum Modulation ----------------------------------------------- -----------------------------------------------
The Maximum Modulation is the highest signal the control
can send to modulate the boiler. For boilers with electronic
operators, the boiler’s input signal range may not match the
output signal range of the 284. Use the MAX MOD setting in
the Source (#) Menu to select an appropriate boiler maximum
modulation.
For 0 to 10 V (dc):
Maximum Modulation =
Boiler’s Maximum Input Signal x 100%
10 V (dc)
For 4 to 20 mA:
Maximum Modulation =
Boiler’s Maximum Input Signal - 4mA x 100%
16 mA
Example:
A boiler’s input signal range is 0 to 9 V (dc). The 284 control
has an output signal range of 0 to 10 V (dc).
Maximum Modulation = 9 V x 100% = 90%
10 V
Control’s
Output
Signal
Range
Boiler’s
Input
Signal
Range
100% 10 V (dc)
9 V (dc)
0 V (dc) 0 V (dc)
90%
Boiler’s
Maximum
Input
Signal Maximum
Modulation
0%
Maximum Boiler Outlet --------------------------- ---------------------------
The control has the capability for each boiler outlet temperature
to be monitored & limited. The MAX OUT setting sets the
maximum boiler outlet temperature. For modulating boilers,
as the boiler outlet temperature approaches the boiler outlet
maximum temperature, the control will reduce the firing rate.
Once the boiler outlet temperature reaches the boiler outlet
maximum temperature less 15°F (8.0°C), firing rate reduction
will begin. Once the boiler outlet temperature reaches the boiler
outlet maximum temperature less 5°F (2.5°C), the firing rate
will be reduced to minimum modulation. If the boiler outlet
temperature reaches the boiler outlet maximum, the boiler is
turned off. In order for the boiler to be able to be turned back
on again, the boiler outlet temperature must drop 5°F (2.5°C)
below the boiler outlet maximum.
If MAX OUT is set to OFF, the control only monitors the boiler
outlet temperature.
Boiler Pump / Valve Post Purge ----------------------------- -----------------------------
This setting sets the amount of time the control operates the
boiler pump / valve after the boiler is turned off. This will purge
heat out of the boiler, reducing stand-by losses, & also aid in
reducing “kettling”. The amount of time for the boiler pump post
purge is adjustable between 10 seconds & 20:00 minutes. Auto
is also available in which the control automatically determines
the amount of time based on the boiler mass.