Service Manual

ManualsBrandsTekmar ManualsHeating SuppliesSnow Melting Control - BAS, Boiler and Mixing

Idle Operation

When the snow melting system starts from a cold temperature,

there may be a long time delay before the slab is warm enough

to melt snow. This time delay allows snow to accumulate on

the slab which is not acceptable in some commercial and

institutional applications. To decrease the start-up time, the slab

can be pre-heated to maintain a minimum temperature. This

is known as the Idle temperature. Idling requires large energy

consumption and is generally recommended for institutional

and/or commercial installations where safety concerns are

paramount. The display shows "System is Idling" when the

control is in idle operation.

When designing a snow melting system, an engineer may

specify the amount of allowed snow accumulation as the

Snow-Free Area Ratio. There are three different levels. A

Snow-Free Area Ratio of 1 is defined as a system that melts

all snow as it falls with no allowed accumulation. This requires

that the Idle temperature be set just below freezing. Examples

of these types of applications include:

• Hospital emergency areas

• Helicopter landing pads

• Parking garage ramps

A Snow-Free Area Ratio of 0.5 is defined as a system with

partial snow accumulation on the slab but not in all areas.

These types of systems may also use Idling but usually set

at a temperature several degrees below freezing to reduce

energy consumption. Applications may include:

• Steep residential driveways

• Commercial sidewalks

• Loading docks

A Snow-Free Area Ratio of 0 is defined as a system that

allows snow accumulation. These systems operate the snow

melting system from a cold start resulting in the lowest energy

consumption costs and the longest times to start melting snow.

In this case set the Idle to off. This is recommended for most

residential applications such as:

• Flat residential driveways

• Patios

• Residential sidewalks

Some systems are designed for keeping a slab surface free of

ice rather than free of snow. The most common applications

include:

• Car wash bays and aprons

• Aircraft hanger aprons

• Turf conditioning on golf course greens

These systems require the use of Idling at or near freezing through-

out the winter and may result in high energy consumption.

Storm Operation

For many applications it is too costly to Idle the snow melt system

all winter. The Storm operation combines the benefits of a fast

response time together with lower operating costs. The Storm

operation does this by allowing the user to manually pre-heat

the slab temporarily in preparation of a snowfall warning. In

the event that snow falls and is detected by a Snow/Ice Sensor

or a Snow Sensor or the system is manually started, the snow

melt system heats the slab up to the melting temperature

and completes a melting cycle. Should no snow fall during

the storm time period, the control exits Storm operation and

returns to Off.

The Storm operation is set up by setting the Storm temperature

and the Storm Run Time in the Setpoints menu. The Storm

operation is activated by the Storm/Stop Request parameter

in the BACnet or Modbus communication protocol.

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 T

emperature

Slab Surface Temperature is Constant

Slab Outdoor ResetSlab Outdoor Reset

Core (sensor)

is warmer