tekmar 667 Snow Detector & Melting Control - Manual (Page 8)

© 2002 D 667 - 09/02 8 of 28
Section D1
Snow Melting
Enable
Section D2
Snow Melting
Disable
The snow melting system can be enabled manually or automatically. A melting enable signal applied to the control places the system
into the melting mode. If a melting enable signal is applied once the system is already in the melting mode, the control responds to
the last command received.
MANUAL MELTING ENABLE
A manual melting enable signal requires the user to manually start the snow melting system and can be provided from the Start
button on the control, Remote Start / Stop Module 039, Remote Display Module 040, or an external melt demand.
Auto Differential (AUTO)
If the AUTO differential is selected, the 667 automatically adjusts
the differential setting under the current load conditions to avoid
short cycling.
Section C2: Boiler Return Sensor
Section C3: No Boiler Sensor
BOILER SENSOR ON THE RETURN (Boil SENS = RET)
The boiler sensor should be located on the boiler return if the 667 is one of many controls
that can call for boiler operation. When in the return mode, the 667 provides a boiler enable
through the Boiler contact. The 667 no longer tries to control the boiler supply water tem-
p erature directly, but allows the boiler to op erate at its op erating aquastat setting when
required. If this mode of operation is selected, the boiler pump should either operate contin-
uously, or be operated in parallel with the system pump contact (Sys P1). When the mixing
device begins to ramp up, the Boiler contact closes on the 667. The Boiler contact remains
closed until the mixing device no longer requires heat. With the sensor on the boiler return,
the 667 is still capable of providing boiler protection as described in section A.
Sno
wmelt Load
Time
Differential On
Off
NO BOILER SENSOR (Boil SENS = NONE)
The 667 is capable of operating without a boiler sensor if desired. Without a boiler sensor,
the 667 is unable to provide boiler protection. In this mode of operation, the Boiler contact
is used to provide a boiler enable. When the mixing device begins to ramp up, the Boiler
contact on the 667 closes. The Boiler contact remains closed until the mixing device no
longer requires heat. This type of application is typical if the 667 is drawing heat from a
source that already incorporates some form of boiler protection.
Section D: Melting Enable / Disable
Section D1: Snow Melting Enable