tekmar 161 Setpoint Control Installation - Manual (Page 6)

© 2007 D 161 - 08/07 6 of 36
Mode 4 Floor
Relay 1 Pulse Width Modulation
(PWM) Operation
PWM operates by centering the throttling
range around the target setpoint temperature.
PWM is best suited for large heating loads
that do not change rapidly in temperature
such as radiant floors.
Heating Operation
When the temperature is at the setpoint,
Relay 1 is on for 50% of a cycle and off
for 50% of a cycle. When the temperature
is 1/2 of the throttling range below the
setpoint, Relay 1 is on for 100% of a
cycle. When the temperature is 1/2 of the
throttling range above the setpoint, Relay
1 is off for 100% of a cycle. For ranges
within the throttling range, Relay 1’s on
time increases linearly as temperature
falls. The throttling range is fixed at 3°F
(1.5°C).
The cycle length is either the same as
the tN4 system control, or when a tN4
system control is not present, the cycle
length is fixed at 15 minutes.
Mode 3 DHW Tank
Relay 1 On / Off Differential
Operation
The On / Off Differential operates by
centering a differential range around
the target setpoint temperature. On / Off
differentials are best suited to heating loads
that quickly change temperature.
Heating Operation
When heating, the setpoint control turns
on Relay 1 when the temperature falls to
1/2 of the differential below the setpoint
and turns off Relay 1 once the temperature
reaches 1/2 of the differential above the
setpoint.
Target + ½ Differential
Target – ½ Differential
Target Differential
Heating On / Off Differential
Relay 1
On
Relay 1
On
Heating PWM Operation
Wa
rm
er
Set Heat
Cycle Length
Heat
Relay 1
On
Relay 1
On
Relay 1
On
Setpoint
Applications: Pulse Width Modulation