tekmar 664 Snow Detector & Melting Control Installation - Manual (Page 5)

5 of 36 © 2009 D 664 - 07/09
Section B1: General Snow Melting
SLAB PROTECTION ( ΔT MAX)
The control can limit the rate at which heat is applied to the currently operating zone through
the ΔT Max setting. The ΔT (delta T) is the temperature difference between the snow melting
supply temperature and the snow melting return temperature. By limiting this temperature
difference, the rate at which heat is applied to the currently operating zone can be controlled
and thermal stresses in the slab can be minimized. When the control is operating at the
ΔT MAX, the Maximum pointer can be seen when viewing the ΔT item in the VIEW menu.
The control provides slab protection differently based on boiler sensor placement.
Note: The ΔT MAX function is only available if the PRIORITY item is set to COND or FULL.
VISCOSITY COMPENSATION (EXCEEDING ΔT MAX)
At low temperatures, the glycol solutions used in snow melting systems become very viscous and difficult to pump. In order to
overcome this condition during a cold start of a snow melting system, the 664 is allowed to exceed the ΔT Max setting for a period of
time in order to warm the glycol solution. This allows the control to compensate for the high viscosity of the glycol solution and is used
when the mixing return temperature is below 30°F (-1°C). When the control exceeds the ΔT Max setting, the Maximum pointer will
fl ash when viewing the ΔT item in the VIEW menu.
Note: This operation only occurs if the PRIORITY item is set to COND or FULL.
MIXING TARGET (MIX TRG)
The mixing target temperature is the supply fluid temperature calculated by the control. The control will operate the snow melt
system so that the mix supply temperature reaches the mixing target except while providing boiler return protection for the boiler.
MIXING MAXIMUM (MIX MAX)
The Mix Max sets the highest fluid temperature that the control is allowed to calculate as the mixing target temperature. If the control
does target the Mix Max setting, and the mix supply temperature is near the MIX MAX, the Maximum pointer is displayed in the LCD
while the MIX SUP temperature is being viewed.
Section B: Snow Melting
Section B1
General
Snow Melting
tensile stresses
BOILER PROTECTION (Boil MIN)
The 664 is capable of providing boiler protection from cold mixing system
return fl uid temperatures. If the boiler sensor temperature is cooler than
the Boil Min setting while the boiler(s) is fi ring, the 664 reduces the output
from the mixing device. This limits the amount of cool return water to the
boiler(s) and allows the boiler temperature to recover. This feature can
only be used if the Boil Sens item is set to Sup or Ret. The 664 can not
provide boiler protection if the Boil Sens item is set to None.
EXERCISING (EXERCISE)
The 664 has a built in pump and valve exercising function. The exercising period is adjustable and is factory set at 70 hours. If a
pump or valve output has not been operated at least once during every exercising period, the control turns on the output for 10
seconds. This minimizes the possibility of a pump or valve seizing during a long period of inactivity. In the case where a mixing valve is
being used as the mixing device, the 664 ensures that the valve operates over its entire range at least once each exercising period.
Note: The exercising function does not work if power to the control, valves or pumps is disconnected.
Boiler Supply
Sensor
Mixing
Sensor
Boiler Return
Sensor
OR