Radiator (5)
A radiator terminal unit has a large heated surface that is exposed to the room. A radiator
provides heat to the room through radiant heat transfer and natural convection.
Default values: BOIL DSGN = 160°F (71°C), BOIL MIN = 140°F (60°C)
Baseboard (6)
A baseboard terminal unit is similar to a radiator, but has a low profile and is installed at
the base of the wall. The proportion of heat transferred by radiation from a baseboard
is greater than that from a fin-tube convector.
Default values: BOIL DSGN = 150°F (66°C), BOIL MIN = 140°F (60°C)
Section B3: Advanced
BOILER INDOOR (BOIL INDR)
The BOIL INDR is the room temperature used in the original heat loss calculations for the building. This setting establishes the beginning
of the
Characterized Heating Curve
for the boiler zones.
BOILER DESIGN (BOIL DSGN)
The BOIL DSGN temperature is the supply water temperature required to heat the boiler zones when the outdoor air temperature is
as cold as the OUTDR DSGN setting.
BOILER MAXIMUM
The boiler maximum is the highest water temperature that the control
is allowed to calculate as the BOIL TARGET temperature. The boiler
maximum is the BOIL DSGN plus 10°F (5°C), but limited to 225°F
(107°C). If the control does target the boiler maximum, and the BOIL
temperature is near the boiler maximum temperature, the MAX segment
will be displayed in the LCD while either the BOIL TARGET temperature
or the BOIL temperature is being viewed. At no time does the control
operate the boiler above 248°F (120°C).
BOILER MINIMUM (BOIL MIN)
The BOIL MIN is the lowest water temperature that the control is allowed
to use as the BOIL TARGET temperature. During mild conditions, if the
256 calculates a BOIL TARGET temperature that is below the BOIL MIN
setting, the BOIL TARGET temperature is adjusted to at least the BOIL
MIN setting. During this condition, if the boiler is operating, the MIN seg-
ment turns on in the LCD while the BOIL TARGET or BOIL temperature
is being viewed. If the installed boiler is designed for low temperature
operation, set the BOIL MIN adjustment to OFF.
© 2019 tekmar 256_D - 09/19
7 of 20
70
(21)
90
(32)
110
(43)
130
(54)
150
(66)
170
(77)
190
(88)
Outdoor Air Temperature
Supply W
ater
Temperature
210°F
(99°C)
-20
(-29)
0
(-18)
20
(-7)
40
(5)
60
(16)
80 °F
(27°C)
BOI L DSGN
BOI L MAX
BOIL MIN
WWSD UNOCC
BOI L INDR
OUTDR DSGN
Boiler Characterized
Heating Curve
50
(10)
ROOM UNOCC
WWSD OCC
ROOM OCC
