tekmar 667 Snow Detector & Melting Control - Manual (Page 7)

7 of 28 © 2002 D 667 - 09/02
BOILER SENSOR ON THE SUPPLY (Boil SENS = SUP)
When operating a boiler that is dedicated to a snow melting system, the 667 is designed
to operate the boiler as efficiently as possible. The boiler is cycled based on the mixing
supply fluid temperature. This is to provide longer and more efficient boiler cycles. This
mode of operation only works if the Boil SENS item is set to SUP.
Section C: Boiler Operation
Section C1
Boiler Supply
Sensor
Section C3
No Boiler
Sensor
Section C2
Boiler Return
Sensor
Section C1: Boiler Supply Sensor
BOILER MINIMUM (Boil MIN)
The Boil MIN is the lowest water temperature that the control is allowed to use as a boiler target temperature. If the boiler is oper-
ating, and the boiler supply temperature is near the Boil MIN setting, the Minimum pointer turns on in the LCD while the Boil SUP
temperature is being viewed. If the installed boiler is designed for condensing or low temperature operation, set the Boil MIN adjust-
ment to OFF.
FIRE DELAY (FIRE DLY)
The FIRE DLY is the delay time that may occur between the time that
the 667 closes the Boiler contact and when the burner fires. This delay
is usually the result of burner pre-purge or other forms of time delay
built into the burner’s safety circuits.
Boiler T
em
per
ature
Minimum
On Time
Minimum
On Time
Minimum
Off Time
Boiler Contact Closes
Boiler Fires
Fire
Delay
Fire
Delay
Time
BOILER MASS (Boil MASS)
The Boil MASS setting allows the 667 to adjust to different types of heat sources depending on their thermal mass.
Light (LITE)
The LITE setting is selected if the boiler that is used has a low thermal mass. This means that the boiler has a very small water
content and has very little metal in the heat exchanger. A boiler that has a low thermal mass comes up to temperature quite rap-
idly when fired. This is typical of many copper fin-tube boilers.
Medium (MED)
The MED setting is selected if the boiler that is used has a medium thermal mass. This means that the boiler either has a large
water content and a low metal content or a low water content and a high metal content. This is typical of many modern residential
cast iron boilers or steel tube boilers.
Heavy (HEVY)
The HEVY setting is selected if the boiler that is used has a high thermal mass. This means that the boiler has both a large water
content and a large metal content. A boiler that has a high thermal mass is relatively slow in coming up to temperature. This is
typical of many commercial cast iron and steel tube boilers.
DIFFERENTIAL (DIFF)
An on / off heat source such as a boiler must be operated with a differential in order to prevent short cycling. With the 667, either a
fixed or an automatic differential may be selected.
Fixed Differential
The differential is centered around the target temperature. If the temperature drops 1/2 the differential below the target
temperature, the 667 closes the boiler contact to fire the boiler. If the temperature rises 1/2 of the differential above the target
temperature, the 667 opens the boiler contact to turn off the boiler.