tekmar 262 Boiler Control Installation User Manual

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Sequence, Section A

Light (LITE)

The LITE setting is selected if the boiler(s) that is used has a low thermal mass. This means that the boiler(s) 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 rapidly
when fired. This is typical of many copper fin-tube boilers. The minimum inter-stage delay for the LITE setting is two minutes.

Medium (MED)

The Medium setting is selected if the boiler(s) that is used has a medium thermal mass. This means that the boiler(s) 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. The minimum inter-stage delay for the MED setting is four minutes.

Heavy (HEVY)

The Heavy setting is selected if the boiler(s) that is used has a high thermal mass. This means that the boiler(s) 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. The minimum inter-stage delay setting for the HEVY setting is six minutes.

BOILER DIFFERENTIAL (BOIL DIFF)

An on / off heat source must be operated with a differential in order to prevent short cycling. With the 262, either a fixed or an auto
differential maybe selected.

Fixed Differential

The boiler differential is divided around the Boil TRG temperature. The
first stage contact will close when the supply water temperature is 1/2 of
the differential setting below the Boil TRG temperature, and will open
when the supply water temperature is 1/2 of the differential setting above
the Boil TRG temperature. The second stage operates if the first stage
cannot bring the water temperature up to the Boil TRG temperature.

Auto Differential (AUTO)

If the Auto Differential is selected, the 262 automatically determines the
best differential as the load changes. This reduces potential short
cycling during light loads.

STAGE 1&2 (STAGE)

The stage 1 and 2 setting may be selected to AUTO or OFF. When AUTO
is selected, the stage is activated and the control operates the appropriate
boiler. When OFF is selected, the control does not fire the stage.

ROTATION (ROTATE)

The ROTATE item is an adjustable setting that is factory set at 48 hours.
The firing order of the boilers changes whenever one stage’s accumulated
running time exceeds the other stage’s accumulated running time by more
than the ROTATE setting. After each rotation, the stage with the least
running hours is the first to fire and the stage with the most running hours
is the last to fire. This function ensures that both stages receive equal
amounts of use. When this item is set to the OFF setting, Stage 1 is always
the first stage to fire.

BOILER PURGE (PURGE)

After the boiler demand is satisfied, the 262 continues to operate the boiler
pump (

Boil P1, terminal 8) for a period of time. The length of time that the

boiler pump continues to run is adjustable (PURGE). This setting allows
purging of any excess heat out of the boiler after the burner is shut off. This
also helps to prevent the water in the boiler from flashing into steam after
the boiler is shut off. The boiler pump continues to run either until the
purging time has elapsed or the boiler supply (Boil SUP) temperature
drops more than a differential below the boiler minimum (Boil MIN) setting.

SETBACK (UNOCCUPIED)

To provide greater energy savings, the 262 has setback capability. With setback, the supply water temperature in the system is reduced
when the building is not used (AWAY) or when the building is UnOccupied. By reducing water temperature, air temperature in the space
can be reduced even when thermostat(s) are not turned down. This feature is enabled by setting the

Setback / None DIP switch to the

Setback position, and providing either an external signal or an internal override.

Note: AWAY does not require the DIP switch = Setback.

Off

Time

Heating Load

Differential

720 hours

672 hours

720 hours