tekmar 268 Boiler Control - Manual (Page 8)

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BOILER MASS
The BOIL MASS setting allows the installer to adjust the control to the thermal mass of the type of heat sources used in the
application. The BOIL MASS setting also adjusts the minimum inter-stage delay time when operating with an automatic differential.
Lo (1)
The Lo 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 Lo MASS setting provides the quickest staging on of boilers.
Med (2)
The Med 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 Med MASS setting stages on additional boilers at a slower rate than the
Lo MASS setting.
Hi (3)
The Hi 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 HI MASS setting stages on additional boilers at the slowest rate.
DIFFERENTIAL
An on / off heat source must be operated with a differential in order to prevent short cycling. With the control, either a fixed or an
auto differential may be selected. The boiler differential is divided around the boiler target temperature. The first stage contact
closes when the supply water temperature is ½ of the differential setting below the boiler target temperature. Additional stages
operate if the first stage is unable to bring the supply water temperature up to the boiler target temperature at a reasonable rate. As
the supply temperature reaches ½ of the differential above the boiler target temperature, stages are staged off.
Section C1
Pump
Operation
PRIMARY PUMP OPERATION
The primary pump operates under the following conditions:
• The control receives a boiler demand and is not in warm weather shut down (WWSD).
• The control receives a DHW demand when DHW MODE is set to 3 or 4.
• The control receives a setpoint demand and setpoint MODE is set to 3.
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Te
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Cooler T
emperature W
armer
Time
Desired temperature
160°F (71°C)
Differential
10°F (6°C) Boiler Off
Boiler On
155°F (68°C)
165°F (74°C)
Heating Load
On
Differential
Off
Time
Auto Differential
If the Auto Differential is selected, the control automatically
determines the best differential as the load changes. This
reduces potential short cycling during light load conditions.
Section C: Pump Operation
Section C1: Pump Operation
Fixed Differential
If the user desires to have a fixed differential, this is set
using the BOIL DIFF setting in the ADJUST menu.