tekmar 546 Thermostat Installation - Manual (Page 28)

© 2008 D 546 - 07/08 28 of 44
Heating Operation Section F
One-Stage PWM Heating
W
a
rmer
Set
Heat
Cycle Length
Heat
Reset Water
Temperature
100%
On Time
85%
On Time
90%
On Time
Two-Stage PWM Heating
W
a
rmer
Set
Heat
Cycle Length
Heat 2
Heat 1
Indoor Temperature Feedback
Indoor feedback applies when the thermostat is connected to
a tN4 network with a tN4 System Control. Indoor temperature
feedback fine tunes the water temperature of the system
based on the requirements of the thermostats.
Each thermostat tells the tN4 System Control the water
temperature that it requires to heat its zone.
•
• If the zone is becoming too cool, the thermostat asks
for a higher water temperature.
• • If the zone is becoming too warm, the thermostat asks
for a cooler water temperature.
The tN4 System Control provides the highest water
temperature required by all of the thermostats.
•
• The thermostat with the highest water temperature
requirement stays on 100% of its cycle.
• • The remaining thermostats stay on for a percentage of
their cycles.
One Stage Heating
Room Sensor Only
When operating with only an room sensor, the on time for
the Heat 1 relay is calculated to satisfy the requirements
of the room sensor.
Floor Sensor Only
When operation with only a floor sensor, the on time for
the Heat 1 relay is calculated to satisfy the requirements
of the floor sensor. The floor temperature varies between
the floor minimum and the floor maximum settings.
Note: Operation with only a floor sensor can lead to either
overheating or underheating of the space.
Room and Floor Sensor
When operating with both a room and floor sensor, the
thermostat calculates an on time for the Heat 1 relay to
satisfy the floor sensor and an on time to satisfy the room
sensor. The Heat 1 relay operates for the longer of these
two on times.
During light heating loads, overheating can occur due to
the minimum floor temperature setting.
During heavy heating loads, the maximum floor temperature
setting limits the on time of the Heat 1 relay. In this situation,
underheating can occur.
Two Stage Heating
The temperature in a two stage zone is controlled by varying
the on time of the Heat 1 and Heat 2 relays during a cycle.
Under light loads, the Heat 1 relay is cycled on and off. As
the load increases, the Heat 1 relay on time is increased
until it reaches the maximum of the cycle length or, if a
floor sensor is used, the slab temperature reaches the floor
maximum setting. The Heat 2 relay is then cycled and its
on time is increased as the load increases.
When the heating load decreases, the on time of the
Heat 2 relay is reduced until the Heat 2 relay is turned off
completely. The thermostat then reduces the on time of
the Heat 1 relay.
Note: When using a floor sensor, the Heat 2 relay may be
on while the Heat 1 relay is off if the floor temperature has
reached the floor maximum setting.
Room Sensor Only
When operating with only an air sensor, the on times for
the Heat 1 and Heat 2 relays are calculated to satisfy the
requirements of the room sensor.
Floor Sensor Only
When operating with only a floor sensor, the on times for
the Heat 1 and Heat 2 relays are calculated to satisfy the
requirements of the floor sensor. The thermostat operates
to maintain the floor at the minimum floor temperature
setting.
Note: Operating with only a floor sensor can lead to either
overheating or underheating of the space.