C
17 18
Sen
10K
0.4
2.0
3.6
Heating Curve
22
°
F
2
42
Dem
R
1
2
5
6
7
8
Pmp
Two Stage Boiler & DHW Control 252
Dem
Heat
System
Pmp
11 12
19
Com
Sw
UnO
20 21
Sen
Sup
140
°
F
80
200
DHW
120
°
F
Off
170
Minimum
Supply
Boiler
Differential
80
Power Supply: 24V 60Hz 3VA
Relay capacities: 24V 10A
Test
No power here
Maximum 24 volts
Dem
3
4
Dem
Stage
Sen
Occupied
35
(2)
105
(41)
70
°
F
(21
°
C)
Unoccupied
35
(2)
105
(41)
70
°
F
(21
°
C)
H1072
Date
S/N
1492
1234567
1
1
13 14
Stage
2
2
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
1
2
3
4
5
6
7
8
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
9 10
Pmp
DHW
Pmp
DHW
15 16
Sen
DHW
22
Out
Sen
Com
Sen
RTU
2K
DHW valve
DHW pump
DHW
pump
System
pump
Power
- Data Brochure
Two Stage Boiler & DHW Control 252
The tekmar Two Stage Boiler & DHW Control 252 is a microprocessor-based control
which regulates the supply water temperature from one or two boilers by turning them
on or off. The supply temperature is based on the outdoor, and optionally, the indoor
air temperatures. When Domestic Hot Water (DHW) is required, the control will operate
the boiler(s) to regulate the supply water temperature in order to satisfy the DHW
requirements.
D 252
Operating Mode
selector switches
Terminal Plugs:
Power and out-
put connections
Terminal Plug:
Sensor and
timer inputs
Outdoor Reset Strategy . . pg. 2
Testing . . . . . . . . . . . . pg. 10
Sequence of Operation . . pg. 3
Error Messages . . . . . pg. 11
Installation . . . . . . . . . . . . pg. 4
Technical Data . . . . . . pg. 12
Settings . . . . . . . . . . . . . . . pg. 7
Limited Warranty . . . . pg. 12
10/92
Heating
is required
24Vac power
supply is on
System is in
Warm Weather
Shut Down
System is
switched to
Unoccupied
Control is
maintaining
Minimum Supply
DHW
pump or valve
is on
DHW
is required
System Pump
is on
Occupied
temperature
setting
Heating Curve
setting
DHW
temperature
setting
Boiler
Differential
setting
Minimum
Supply setting
Test button &
LED to test
main control
functions
Stage 2 is on
Stage 1 is on
Unoccupied
temperature
setting
Input: 2K RTU
Optional
Input:
Indoor Sensor
074
Optional
Input:
Unoccupied
signal.
Optional
Input: DHW Sensor
071
Optional
Output: Turn
on stage #1
Output: Turn
on stage #2
Output: Turn on
System Pump
Output: Turn on
DHW Pump / Valve
24Vac power supply
Note: Wiring
is detailed in
Application
Brochure
A 252
Input: Outdoor
Sensor 070
Included
Input: Universal
Sensor 071.
Included
Input:
Heat Demand
signal.
Optional
Input: DHW Demand
signal.
Optional
Two Stage Boiler & DHW Control 252
Power
Heat
Demand
WWSD
UnOcc.
Minimum
Stage 1
Occupied
35
(2)
105
(41)
70
°
F
(21
°
C)
Unoccupied
35
(2)
105
(41)
70
°
F
(21
°
C)
Stage 2
System
Pump
DHW
Demand
DHW
Pump
