Odyssey
│
Installation and Operation Instructions - Field Wiring
CT80-250
32
Inferring Heat Load (“Automatic Means” of Adjusting Boiler Temperature)
The HydroStat control incorporates two (2) options for Inferring Heat Load:
1) Thermal Targeting Method – default method
2) Outdoor Reset Method – method used when outdoor sensor is connected to OR and C
1) Thermal Targeting Method:
Default method for satisfying central heat demands.
For the duration of a central heat demand, the target temperature is boosted by 10ºF every Boost Interval.
For each new central heat demand, the control reduces the target temperature established in the previous cycle
by 5ºF.
For every 30 minutes of no central heat demand, the control will reduce the target temperature by 5ºF.
The Subtractive Differential establishes how much the boiler temperature must drop below the target
temperature, before the burner will fire for a central heat demand.
The Economy Feature setting determines the Boost Interval and Subtractive Differential values; see Table 9-4.
Thermal Targeting is overridden when Economy Feature is set to OFF, i.e. central heat demands operate to the
HI TEMP setting.
A central heat demand is activated by a T-T demand or ZC-ZR demand when the Zone
/
Indirect switch is set to
"Z".
With an Outdoor Sensor connected to WWSD and C, the control will perform Warm Weather Shutdown and
Thermal Targeting.
With an Outdoor Sensor connected to OR and C, the control will override Thermal Targeting and instead
function as an Outdoor Reset control with Warm Weather Shutdown – see 2) Outdoor Reset Method below.
Table 9-4 Economy Feature Setting (for Thermal Targeting)
Setting
1
Subtractive
Differential
Boost
Interval
Recommended Settings and Applications
OFF
10
o
F
N/A
Disables Thermal Targeting. Applications where a boiler must fire to the High
Limit (HI TEMP setting)
LO
20
o
F
10 min
Lowest level of fuel savings. Use only if other settings can’t meet the demand load.
1
20
o
F
15 min
1 zone heating system.
2
20
o
F
20 min
2 zone heating system.
3
20
o
F
25 min
3 zone heating system.
4
20
o
F
30 min
4 zone heating system.
5
20
o
F
35 min
5 zone heating system.
HI
20
o
F
40 min
Maximum efficiency. Highest level of fuel savings.
Notes:
1 - Do not include Indirect Water Heaters in the number of heating zones.
