tekmar 664 Snow Detector & Melting Control Installation - Manual (Page 13)

13 of 36 © 2009 D 664 - 07/09
ADDITIONAL MELTING TIME (ADD MELT)
In cases where areas of the snow melting system haven’t completely
melted after the Melting mode has fi nished and the 090 is dry, the 664 has
a function in which additional time can be added to melt the zone(s). This
is an adjustable time through the ADD MELT item in the ADJUST menu of
the control. The ADD MELT time is calculated into a running time and is
displayed in the STATUS item of the appropriate zone while in the VIEW
menu. Once the 090 becomes dry and the currently operating zone(s)
slab temperature is at least its slab target temperature, the running time
starts counting down.
Note: This function is only available if the Snow / Ice Sensor 090 is used
in zone 1.
PRIORITY OPERATION
In a multiple zone system where the zones have different heat
requirements, or the total combined heat requirement of the snow melting
system exceeds that of the heat source, the 664 has a function which
can provide priority of zone 1 over zone 2. The 664 allows for full priority,
conditional priority or no priority. This is a selectable item through the
PRIORITY item in the ADJUST menu.
Note: If either Full Priority or Conditional Priority is selected, there is the
potential for the non-priority zone to freeze over.
Full Priority (PRIORITY = FULL)
It can be selected that zone 1 has full priority over zone 2. Zone 1 begins melting first when the Melting mode is initiated. While
zone 1 is melting, the control keeps track of how long zone 1 operates at its melting temperature. Once zone 1 fi nishes melting, the
control turns off zone 1 and starts melting zone 2. Zone 2 then operates at its melting temperature for the same amount of melting
time as zone 1. If at any time while zone 2 is melting and the system is restarted either manually or automatically, the control turns
off zone 2 and begins melting zone 1. If the slab temperature of zone 2 is warm enough when the system is restarted, the control
provides any extra heat to zone 2 that zone 1 is not using. If the slab temperature of zone 2 is not warm enough when the system
is restarted, the control only provides heat to zone 1. Zone 2 then only receives heat when zone 1 fi nishes melting.
Conditional Priority (PRIORITY = COND)
It can be selected that zone 1 has conditional priority over zone 2. Zone 1 begins melting first when the Melting mode is initiated.
While zone 1 is melting and up to temperature, the control provides any extra heat to zone 2 that zone 1 is not using. While zone 1
is melting, the control keeps track of how long zone 1 operates at its melting temperature. Once zone 1 fi nishes melting, the control
turns off zone 1 and provides all available heat to zone 2. Zone 2 then operates at its melting temperature for the same amount of
melting time as zone 1. If at any time while zone 2 is melting and the system is restarted either automatically or manually, the control
turns off zone 2 and begins melting zone 1 again. The control then operates zone 1 and zone 2 as described above.
NON-PRIORITY OPERATION (PRIORITY = NONE)
If the PRIORITY item is set to NONE, zone 1 and zone 2 begin melting
simultaneously when the Melting mode is initiated. The 664 operates
based on the mixing fl uid temperature requirement of each zone. The
mixing target temperature is calculated for the zone with the highest heat
requirement, and that zone output runs continuously. The zone output
with the lower heat requirement is cycled using Pulse Width Modulation
(PWM) with a 20 minute cycle length.
Dry
Snow Ice Sensor
Zone 2
Zone 1 melts
before Zone 2
Zone 1
Zone 2
Zone 1 and
Zone 2 melt
simultaneously
Zone 1