10
Step Six
Essential control settings
To obtain the best operation from a reset control, it is important to measure the system supply temperature as accurately
as possible. Whenever the control receives a heat demand signal, the system pump must be operated to maintain
continuous water flow past the supply temperature sensor.
For specific application details refer to Application Brochure A 258.
A more detailed technical description of the effect of control settings on overall system operation is described in the tekmar Essay, E 002.
Reset operation
Stpnt — Reset switch
When the boilers are used in a heating system and the supply temperature is to be
controlled on an outdoor reset schedule (Heating Curve), this switch must be set
to "Reset".
Programming the control for Occupied/Unoccupied room temperatures and setback
schedules will be covered in the "Programming" section starting on page 15.
Heat Demand switch
When the heating system uses zone valve end switches or some other means of
delivering an external heat demand signal to terminals
Heat Dem (5 and 6), set this
selector switch to "External Demand" and the control will be enabled when it receives
a 24Vac signal from the heat demand circuit. If an external heat demand signal is not
used, set the switch to "Permanent Demand".
Auto
Stage
1 2 3 4 5 6 7 8
Perm.
Demand
Ext. timer
Fixed last
Int. timer
Lo-Hi fire
Fixed lead
Rotate
Off
1
2
3
4
5
6
7
8
9
External
Demand
Off
1
2
3
4
5
6
Stpnt
Reset
Heating Curve
As outdoor temperatures drop, heat losses from a building become greater and the
heating system supply water temperature must be raised to maintain a constant room
temperature. The heating curve value describes how many degrees the supply water
temperature is raised for a one degree drop in outdoor temperature. The supply
temperature starts to increase when the outdoor temperature falls below the WWSD
point. To calculate the correct setting for the Heating Curve, use the following
formula.
Outdoor air temperature
Supply water temperature
50
(10)
30
(-1)
10
(-12)
-10
°
F
(-23)
°
C
110
(43)
70
(21)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
3.6 3.0 2.4 2.0
1.6
0.8
0.4
1.0
0.6
90
(32)
50
°
F
(10)
°
C
Heating
Curve
WWSD
Point
1.2
For more information regarding the Heating Curve, refer to page 2 of this brochure.
If the actual design supply water temperature for a system is unknown, a trial setting
can be calculated using these typical supply temperatures:
• Fan coils …180
°
to 210
°
F (82
°
to 99
°
C) • Baseboards …160
°
to 190
°
F (71
°
to 88
°
C)
• Radiant floors …100
°
to 130
°
F (38
°
to 54
°
C).
160
°
F - 70
°
F
70
°
F - 5
°
F
90
°
F
65
°
F
design supply temperature – room temperature
room temperature – design outdoor temperature
Heating Curve =
For example:
• design outdoor temperature = 5
°
F (-15
°
C)
• room temperature = 70
°
F (21
°
C)
• design supply temperature = 160
°
F (71
°
C)
Heating Curve =
=
= 1.4
Setpoint operation
Stpnt — Reset switch
When the boilers are used to maintain the supply temperature at a setpoint, set this
switch to "Stpnt".
Programming the control for Occupied/Unoccupied setpoint temperatures and set-
back schedules will be covered in the "Programming" section starting on page 15.
Setpoint Demand switch
End switches, aquastats or some other means of delivering an external setpoint
demand signal can be used to bring 24Volts to terminals
Heat Dem (5 and 6) when
the control is used as a setpoint control. This selector switch should be set to "External
Demand" and the control will be enabled when it receives the 24Vac signal. If an
external setpoint demand signal is not used, set to "Permanent Demand".
Auto
Stage
1 2 3 4 5 6 7 8
Perm.
Demand
Ext. timer
Fixed last
Int. timer
Lo-Hi fire
Fixed lead
Rotate
Off
1
2
3
4
5
6
7
8
9
External
Demand
Off
1
2
3
4
5
6
Stpnt
Reset
Auto
Stage
1 2 3 4 5 6 7 8
Perm.
Demand
Ext. timer
Fixed last
Int. timer
Lo-Hi fire
Fixed lead
Rotate
Off
1
2
3
4
5
6
7
8
9
External
Demand
Off
1
2
3
4
5
6
Stpnt
Reset
Auto
Stage
1 2 3 4 5 6 7 8
Perm.
Demand
Ext. timer
Fixed last
Int. timer
Lo-Hi fire
Fixed lead
Rotate
Off
1
2
3
4
5
6
7
8
9
External
Demand
Off
1
2
3
4
5
6
Stpnt
Reset
0.4
2.0
3.6
Heating Curve
Settings
