Tekmar Mixing Control 354 Data Brochure page 9

Heat Demand switch
When the heating system uses zone valve end switches or some other means of delivering an
external heat demand signal to terminals Heat Dem — Heat Dem (1 and 2), set this switch to
"External (1 & 2)" and the control will only be able to operate the mixing valve when it receives a
24Vac signal from the heat demand circuit.
If an external heat demand signal is not used, set the switch to "Permanent" and the control will be
enabled all the time.
Maximum Supply temperature
This setting determines the maximum allowable supply temperature to be delivered to the system.
When the supply temperature gets too hot, the mixing valve closes until the temperature is stabilized
at the maximum. To get the fastest system heat up times, this setting should be set as high as
allowable. Refer to page 4 for more details on maximum supply operation and requirements.
Minimum Boiler Return temperature
When a Return Sensor 071 is connected to the control, and the dial is turned up from "Off", this
setting determines the minimum allowable boiler return temperature. When the return temperature
becomes too cold, the mixing valve is closed until the temperature is stabilized at the minimum. To
get the fastest system heat up times, this setting should be set as low as allowable. Refer to page
4 for more details on minimum boiler return operation and requirements.
Boiler Enable switch
The position of this switch determines at which valve position the control will fire the boiler under
normal conditions. If there is a Return Sensor 071 installed and the boiler return temperature is too
cold, the control will override this setting in order to raise the water temperature more quickly.
• At the "10% open" position, the control will not fire the boiler until the valve has opened at least
10%, and will turn the boiler off when the valve closes to 0% open. This setting would normally be
chosen for high mass boilers (cast iron, steel fire tube, etc.), or systems with a large thermal mass
in the loop between the boiler and the mixing valve.
• At the "25% open" position, the control will not fire the boiler until the valve has opened at least 25%, and will turn the boiler off
when the valve closes to 15% open. This setting would normally be chosen for low mass boilers (copper fin tube, low mass
cast iron, etc.), and systems with low thermal mass in the loop between the boiler and the mixing valve.
Note:
Some heating systems combine high input, low mass boilers with very little thermal mass in the loop between the boiler
and mixing valve. In some extreme cases, erratic boiler action (short cycling and tripping of high limits) may result from
this type of system even at the "25% open" position. To prevent this type of operation it may be necessary to add thermal
mass to the system by installing a storage tank or making the loop larger.
Motor Speed
The control determines the position of the mixing valve by timing the actuating motor, and comparing
the elapsed time of open signal against the elapsed time of close signal. Selecting the correct Motor
Speed setting is essential for proper valve and boiler operation. The tekmar Actuating Motor 010
takes 210 seconds to move from the fully closed to the fully open position and the Motor Speed dial
on the control is labeled with a mark indicating the correct position.
If you are using a different make of actuating motor and you know its opening time, set the Motor
Speed dial to match. If you are unsure of the exact opening time, complete the following procedure:
(1) Set the Motor Speed dial to the longest (fully clockwise) position.
(2) Power up the control and let it run the actuating motor/mixing valve to the fully closed position.
(3) When the test light turns off, push the test button.
(4) Observe the motor as it is driven open by the test routine. When the motor reaches its fully open position by stopping against
its end switch, turn the Motor Speed dial down just until the control cycles through to the next step in the test routine.
(5) The Motor speed dial is now calibrated to the motor. Let the control cycle through to the end of the test routine.
Testing the Control Functions
Test button
With the settings made and the terminal plugs firmly seated, power up the control. The control will
do the last step of the following test routine. It is adviseable to re-check the power supply voltage
while the control is powered and operating.
The control can be made to cycle through the test routine whenever the Test button is pushed. The
test can be halted at certain times during the test by pushing the button a second time. For details
of the test routine, refer to the test routine description starting on the next page.
9
Zone Control
External
(1 & 2)
25% open
Heat Demand Boiler enabled
Permanent 10% open
Indoor Sensor
150°F
190
100 Off
Max. Supply
100°F
60
Off 150
Minimum
Boiler Return
Zone Control
External
(1 & 2)
25% open
Heat Demand Boiler enabled
Permanent 10% open
Indoor Sensor
140 sec.
tekmar
motor
30 250
Motor
Speed
T est