Tekmar 261 Boiler Control Manual de usuario descargar pdf (Pagina 8)

FIRE DELAY (

Fire Delay

)

The Fire Delay is the delay time that may occur between the time that

the 261 closes a stage contact, and the burner fires for that stage. This

delay is usually the result of burner pre-purge, or other forms of time

delay built into the burner’s safety circuits.

BOILER DIFFERENTIAL (BOIL DIFF)

An on / off heat source such as a boiler must be operated with a differential in order to prevent short cycling. With the 261, either a fixed

or an auto differential may be selected.

Fixed Differential

The boiler differential is divided around the BOIL TARGET temperature.

The contact will close when the supply water temperature is 1/2 of

the differential setting below the BOIL TARGET temperature, and will

open when the supply water temperature is 1/2 of the differential setting

above the BOIL TARGET temperature.

Auto Differential (Ad)

If the Auto Differential is selected, the 261 automatically determines

the best differential as the load changes. This setting is recommended

as it reduces potential short cycling during light loads.

WARM WEATHER SHUT DOWN (WWSD) OCC & UNOCC

When the outdoor air temperature rises above the WWSD setting, the 261 turns on the WWSD segment in the display. When the

control is in Warm Weather Shut Down, the

Boiler Demand

pointer is displayed, if there is a demand. However, the control does not

operate the heating system to satisfy this demand. The control does respond to a setpoint demand and operates as described in

section C.

Section C: Setpoint

SETPOINT DEMAND

A setpoint demand is required in order for the 261 to provide heat to the setpoint load. The

261 registers a setpoint demand when a voltage between 24 and 240 V (ac) is applied

across the

Setpoint Demand

terminals (3 and 4). Once voltage is applied, the

Setpoint

Demand

pointer turns on in the LCD. The control operates the boiler(s) to maintain at least

the

Setpoint

setting. The setpoint demand does not turn on the boiler pump. If a setpoint

load is used, the installer must make sure that the setpoint device provides its own flow

through the boiler(s).

BOILER TARGET DURING SETPOINT (BOIL TARGET)

The BOIL TARGET during a setpoint demand is increased to at least the

Setpoint

setting. This temperature is maintained as long as

the 261 has a setpoint demand.

Desired temperature

this example

160°F(71°C)

Cooler

Temperature

Warmer

Time

Differential

this example

10°F(5°C)

165°F(74°C)

155°F(68°C)

BOILER

OFF ON

Boiler Temperature

Time

Fire

Delay

Fire

Delay

Boiler Contact Closes

Boiler Fires

Minimum

Off Time

Minimum On Time

Minim

Setpoint

Demand

24 to 240 V (ac)

Off

Time

Heating Load

Differential

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 19 20

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Tekmar 261 Boiler Control Manual de usuario Pagina 8

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