tekmar 654 Snow Melting Control Installation - Manual (Page 34)

© 2013 654_D - 06/13 34 of 44
Single Stage On/Off Boiler (1STG) --------------- ---------------
The control turns on or off the heat relay to fire the boiler in order
to maintain the Boiler Target temperature. The boiler supply
temperature operates on a differential that is half above and
half below the boiler target. The status of the boiler is shown
by the Boil Relay item in the View menu.
Modulating Boiler (MOD) ------------------------ ------------------------
The control can operate a single hot-water modulating boiler
using the Mod output and the Heat contact. The control
operates the boiler by first switching the heat contact to allow
the modulating boiler to go through the ignition sequence
(the heat contact may not be required on all modulating
boilers). A 0-10 V (dc) or 4-20 mA analog signal is then used
to modulate the boiler firing rate starting at 50% (5 V (dc) or
12 mA signal) for 30 seconds. After the 30 second delay has
elapsed, the control will then allow the boiler to modulate down
to the Minimum Modulation setting and hold it there for the
Modulation Delay time setting. After the modulation delay has
elapsed, the control uses PID logic to change the boiler firing
rate signal in order to satisfy the boiler target temperature.
When the firing rate signal is reduced down to the minimum
modulating setting and the boiler supply temperature exceeds
the boiler target by 1/2 of the differential, the control will shut
off the boiler burner. The modulating signal output is shown
by the Boil Rate item in the View menu.
The Modulation Delay setting is determined by the boiler
manufacturer. It is the amount of time that the burner must
operate before the internal boiler control allows an external
signal to operate the burner.
The Motor Speed sets the rate at which the modulating electrical
signal can change. For most modulating boilers with a ECM
fan, the motor speed can be set to 30 seconds. For commercial
boilers with a mod motor, set the motor speed according to
the time required by the mod motor to travel from the closed
to open position.
EMS1 -------------------------------------------- --------------------------------------------
The EMS1 signal is a method for the snow melting control to
send the boiler target temperature to a tekmar Boiler Control
268. The control provides a 0-10 V (dc) signal proportional
to the boiler target and turns on the heat relay to operate the
boiler to maintain the Boiler Target temperature.
EMS1 Conversion Table
0-10 V (dc) Boiler Target
0 – – – (OFF)
1 50°F (10°C)
2 68°F (20°C)
3 86°F (30°C)
4 103°F (39°C)
5 121°F (49°C)
6 139°F (59°C)
7 157°F (69°C)
8 174°F (79°C)
9 192°F (89°C)
10 210°F (99°C)
EMS2 -------------------------------------------- --------------------------------------------
The EMS2 signal is a method for the snow melting control to
send the boiler target to a Viessmann boiler that supports the
OpenTherm temperature targeting. Typical boilers include the
Viessmann Vitodens 100-W and 200-W. The boiler may require
an OpenTherm Input Module 0-10V. Contact Viessmann for
details. The control provides a 0-10 V (dc) signal proportional
to the boiler target and turns on the heat relay to operate the
boiler to maintain the Boiler Target temperature.
Control (CTRL) ---------------------------------- ----------------------------------
When the Application Mode is set to Mix or to PWM, the
snow melting control can send a call for heat message using
tekmarNet
® communication to the tN4 System Control. The
call for heat is received on the water temperature bus that
the snow melting control is communicating on. When wired
to a boiler bus, the snow melting control calls for heat on the
boiler bus. The same logic applies to the mixing and tank bus
available on the tN4 System Control. In most cases, the Boiler
Type is set to Control when the snow melting system has a
non-dedicated boiler plant.
A tN4 System Control is defined as a control that operates a
boiler or mixing system. At the time of this writing the available
controls are:
Boiler Control 274, 275, 284
House Control 400, 401, 402, 403, 406
Reset Modules 420, 421, 422, 423
Enable (ENBL) ----------------------------------- -----------------------------------
When the Application Mode is set to Mix, the snow melting
system may have a non-dedicated boiler plant. When not using
tekmarNet
® communication, the heat relay closes whenever
the mixing device is increasing and reaches a position or
speed of 10%. The heat relay opens when the mixing device
is decreasing and reaches a position or speed of 5%.
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