Install Instructions

© 2019 tekmar 671
_
D - 08/19 29 of 36
671
tekmarNet
Snow Melt
Zone 1
Snow Melt
Zone 2
671
Snow Melt Zones and Priority
Dividing a system into a number of snow melting zones and
prioritizing the zone operation reduces the size requirements
of the hydronic heating plant or the amperage of the electrical
service panel. This results in lower initial capital cost of the
snow melting system. The trade off is that some snow melt
zones may not be able to melt as soon as the snow fall begins
and the user must tolerate snow accumulation on the slab.
The snow melt system using Snow Melting Control 654,
670 and 671 may have up to 12 snow melt zones. Zone 1
has the highest priority and zone 12 has the lowest. The
priority setting in the tekmarNet
®
menu allows the installer
to select the level of zone priority for the entire snow melt
system. Changing the priority setting on one control will
update on all other snow melt controls at the same time.
The zone priority has 3 setting levels. There is some risk
that lower priority zones may ice up when they are shut off
by the higher priority zone. For example, if a high priority
zone should finish melting and allow a lower priority zone
to start melting, and then a new snow fall occurs, the high
priority zone will shut off the lower priority zones. This may
potentially allow the lower priority zones to ice over. The
limitations of zoning and using priority must be carefully
considered and discussed with the building owners and
occupants when designing the snow melting system.
Priority does not apply when the application mode is set to
Boiler. In this mode, the boiler is dedicated to a single snow
melting zone so priority is no longer applicable.
Slab Temperature Control
Controlling the slab temperature is critical to minimizing the
cost of snow melting. This requires that either a Snow/Ice
Sensor 090 or 094 or a Slab Sensor 072 or 073 is installed.
The Snow/Ice Sensor contains a built-in slab temperature
sensor. While the control can operate without a slab sensor
installed, operating costs are much higher.
The slab is operated using slab outdoor reset. As the outdoor
temperature gets colder, the heat loss of the slab increases.
In order to keep the slab surface at a constant temperature
while operating, the inner core of the slab must be heated
above the melt, idle or storm temperature setting. The amount
that the slab inner core temperature is above the melt, idle
or storm setting is proportional to the outdoor temperature.
Since the slab sensor is installed below the surface of the
slab, it is not measuring the true slab surface temperature but
rather the inner core temperature. The control automatically
compensates for this temperature difference. The Slab item in
the Status menu displays the actual measured temperature,
so it is normal to view slab temperatures that exceed the melt,
idle, or storm temperature settings.
Sur
face temperature = 35ϒF
Decreasing Air Temperature
Increasing Slab Core Temperature
Slab Surface Temperature is Constant
Slab Outdoor ResetSlab Outdoor Reset
Core (sensor)
is warmer