Honeywell W8735ER Installation Instructions Manual page 5

(design temperature) is the point at which the boiler should be
set to its high limit setting. Setting the boiler temperature too
low during the coldest periods will result in the inability to keep
up with heat demand. This is the critical setting in avoiding
call-backs.
High Outdoor Temperature: This is the outdoor temperature
for which the Low Boiler Temperature is set. This is the
parameter that most impacts energy savings. Setting the High
Outdoor Temperature too high results in less energy savings
as the boiler may run at a higher temperature during warmer
weather than necessary to maintain comfort in the space.
Setting this parameter too low will result in too narrow a range
for the control to be adjusting boiler temperature. In most
cases the default of 40 °F (4.4 °C) is fine.
NOTE: In many cases these parameters will not need to
be adjusted as their default values are designed
to accommodate mid-Atlantic and lower New
England areas.
CAUTION
Possible Equipment Damage
When enabling the Outdoor Reset function, be sure to
refer to the boiler OEM's instructions for the lowest
return water setting to avoid condensation in the heat
exchanger, which can result in equipment damage.
Table 1. Outdoor Reset Curve Settings and Defaults.
Aquastat
Minimum
Parameter value
High Limit
Minimum Outdoor
Temperature (-40 °C)
Minimum Boiler
temperature
Maximum Outdoor
Temperature
IBC
Minimum
Parameter value
High Limit
Minimum Outdoor
Temperature (-40 °C)
Minimum Boiler
temperature
Maximum Outdoor
Temperature (12.7 °C)
1
Minimum values, Maximum values and Default High Limit
settings shown are for the L7224U and the S9361 IBC. Val-
ues may change for other Aquastats and IBCs. Check the
specific Aquastat and/or IBC Installation Instruction manual
for more information on default settings.
Maximum
value Default
130 °F 240 °F
(54 °C) (116 °C)
-40 °F 40 °F
(4.4 °C)
80 °F 180 °F
(27 °C) (82 °C)
30 °F 70 °F
(-1 °C) (21 °C)
Maximum
value Default
130 °F 220 °F
(54 °C) (104 °C)
-40 °F 40 °F
(4.4 °C)
130 °F 150 °F
(54 °C) (56 °C)
40°F 70 °F
(21 °C)
W8735ER WIRELESS OUTDOOR RESET MODULE
Boost
If heat demand is not met within a certain time period while
the boiler is in setback mode (following the Outdoor Reset
curve), a Boost Period is invoked where the boiler set point is
increased by a value called the Boost Step. Each time the
Boost Period elapses and heat demand is not satisfied, the
boiler set-point is again increased by the Boost Step, up to the
maximum setting provided by the High Limit setting (see Table
2 and Fig. 5). Boost is reset when the heat demand is satisfied
(local or remote call for heating has ended). Simply reaching
the boiler set-point does not reset the Boost. Continuous
Boost calls may be an indication of a poorly set Outdoor Reset
Curve for the environment or faulty equipment. For the
Aquastat, a Boost warning will be indicated on the 3-digit
Aquastat display if Boost is required on 60 consecutive cycles.
See Table 5.
For the Aquastat, the Boost Period can be set from OFF to a
range of 5 minutes to 30 minutes, adjustable in 1 minute
increments. The default setting is 10 minutes. The Boost Step
can be set from Off to a range of 5 F (-15 C) to 20 F (-7 C).
For the IBC, the Boost Period is fixed at 30 minutes and the
Boost Step is fixed at 5 °F. See Table 2.
Table 2. Boost Settings and Defaults.
Aquastat
1
Parameter name
Boost Period
Boost Step
180 °F
(82 °C)
IBC
0 °F
Parameter name
(-18 °C)
Boost Period
130 °F
Boost Step
(54 °C)
40 °F
1
For the IBC, both the Boost Period and Boost Step are fixed
(4.4 °C)
parameters and can not be adjusted.
Warm Weather Shutdown - Aquastat
The Warm Weather Shutdown feature causes a "Warm Start"
boiler to shut down when the outdoor temperature exceeds a
specified value. Warm Start boilers maintain a minimum
180 °F
temperature by setting the Low Limit on the Aquastat. If
(82 °C)
enabled this features cancels the Low Limit setting when the
0 °F
outdoor temperature exceeds a specified value.
(-18 °C)
140 °F
CAUTION
(60 °C)
Zone Panel Settings
40°F
In applications with zoning panels having a priority
(12.7°C)
zone for domestic hot water: Disable the warm
weather shutdown feature on the Aquastat.
The Warm Weather Shutdown feature can be set from OFF to
a range of 40 °F (4.4°C) to 70 °F (21 °C), adjustable in 10
degree increments. The default setting is OFF. See Table 3.
5
Minimum Maximum
value Value
5 minutes 30 minutes
(or Off)
5 F (or Off) 20 F
1
Value
30 minutes
5 F (or Off)
Default
10 minutes
10 F
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