Step Five
Testing the wiring
Caution
• These tests are to be performed using standard testing practices and
procedures and should only be carried out by a properly trained and
experienced technician.
• Before applying power to the control for testing, each terminal plug must be
unplugged from its header on the control. Pull straight down to unplug.
• A good quality electrical test meter, capable of reading from at least
0 — 200 Volts AC, and at least 0 — 1,000,000 Ohms, is essential to properly
test this control.
Test the sensors
• These tests must be made
before turning on the power supply, and with the
terminals unplugged.
• The sensors are to be tested according to the instructions in Brochure D 001.
6
Terminal plug disconnected
from its header on the control
OR
type 252
Do not apply
power here!
Maximum 24 Volts
10A
Safety Divider
9
10
24
Vac
120
or
240
Vac
External
24Vac
60Hz class II
transformer
Heat Demand
Apply 24Vac signal
when heat requested
from system
System Pump
Relay
closes to turn on
System Pump
OR
2K RTU or
Zone Control
240 (optional)
Outdoor
Sensor
070
Supply
Sensor
071
6
7
8
5
C
R Pmp Pmp
1
2
3
4
Dem Dem
Dem Dem
12
13
14
11
1
Safety Divider
Boiler Relays
close to
turn on boilers
Pmp Pmp
1
2
2
Stage
Unoccupied
Switch
(optional)
DHW Pump
Relay / valve
closes to turn on
pump / valve
Heat
System
15
16
17
18
19
UnO
Sw
10K
Sen
2K
RTU
Com
Sen
20
Sup
Sen
21
Out
Sen
Com
Sen
22
Stage
DHW
DHW
Sensor
(optional)
071
DHW
Sen
DHW
10K Indoor
Sensor 074 or
Zone Control
(optional)
10A
10A
10A
DHW Demand
When DHW
requested and there
is no DHW sensor
Power
Electrical connections to the terminal plugs of the 252 control. Control relays are shown in "power down" condition.
For a detailed wiring schematic of your specific application, refer to
the Application Brochure A 252.
15 16 17
19
18
20 21 22
2K
RTU
DHW
Sen
Com
Sen
UnO
Sw
Sup
Sen
Out
Sen
10K
Sen
Com
Sen
Out
Sen
22
15
2K
RTU
18
UnO
Sw
21
Sup
Sen
16
DHW
Sen
17
Com
Sen
19
10K
Sen
20
Com
Sen
Option: DHW Sensor 071 input:
Install the DHW sensor in a well in the lower half of the DHW storage tank. Connect the two wires
from a Sensor 071 to terminals
DHW Sen — Com Sen (16 and 17).
Option: Indoor temperature feedback sensor: (Choose one option only)
(1) Connect the two wires from an Indoor Sensor 074 or a tekmar 10K Zone Control
to terminals
10K Sen — Com Sen (19 and 20).
OR
(2) Connect the two wires from a tekmar 2K RTU, (305, 307, 308, or 310) or a tekmar 240 Zone
Control to terminals
2K RTU — Com Sen (15 and 17).
Option: Occupied/Unoccupied switch input:
Connect the two wires from the Occupied/Unoccupied dry contact switch (timer, relay, etc.) to
terminals
Com Sen — UnO Sw (17 and 18).
18
UnO
Sw
16
DHW
Sen
21
Sup
Sen
19
10K
Sen
20
Com
Sen
Out
Sen
22
15
2K
RTU
17
Com
Sen
16
DHW
Sen
Out
Sen
22
21
Sup
Sen
20
Com
Sen
19
10K
Sen
15
2K
RTU
17
Com
Sen
18
UnO
Sw
Out
Sen
22
19
10K
Sen
15
2K
RTU
18
UnO
Sw
21
Sup
Sen
20
Com
Sen
16
DHW
Sen
17
Com
Sen