Product Overview
© 2012 A 274 - 01/12 4 of 8
Electrical
Application A 274-4
System Description: The Boiler Control 274 controls two, 2 stage boilers to provide DHW and outdoor reset for the
space heating zones.
The tN4 Gateway 483 allows for remote monitoring of the 274 and access to the tN4 system
through a web browser. The 274 receives a boiler demand over the tN4 boiler bus from the tN4 thermostats. A 161
Setpoint control is used to create a DHW demand over the tN4 network. This allows for both DHW production and the
use of the pump sequencer function.
Mechanical
Concept Drawing: This is only a concept drawing, not an engineered drawing. It is not intended to describe a complete system, nor any particular system. It is up to the
system designer to determine the necessary components for and configuration of the particular system being designed, including additional equipment, isolation relays
(for loads greater than the control’s specified output ratings), and any safety devices which in the judgement of the designer are appropriate, in order to properly size,
configure and design that system and to ensure compliance with building and safety code requirements.
S1 = Outdoor Sensor 070
S2 = Boiler Supply Sensor 082
S3 = DHW Sensor
A1 = High Limit Aquastat
S2
Z1 Z2 Z3
S1
120 V (ac)
483
335
P3
S3
274
F1
P2
P1
A1
24 V (ac)
Class 2
Transformer
161
P5
P4
Boiler 1
Lo Stage
Boiler 1
Hi Stage
Boiler 2
Lo Stage
Boiler 2
Hi Stage
N
115 V (ac)
L
S2S1
483
L
1
Power
N
2
7
tN4
6
C0
0
P2
To 335
Zone Manager
P1
6
DHW
5
4
Sup
3
+
2
-
1
Do not apply power
274
N
720
Power
L
8
tN4 Com Out Boil Com BRet/ Relay
1
910
Relay
2
11 12
Relay
3
13 14
Relay
4
15 16
C.A./
Alert
21 22
Boiler
Demand
23 24
DHW
/Setp
Com
Dem
25
Pr.
Dem
19
Prim
P1
18
DHW
/P2
17
S3
No Power
161
5
4321
tN4 C R Com S1
7
6
Rh R1
R1
7
8
1
2
6
5
4
3
C
24V(ac)
R
Class 2
Transformer
P3
A1
P1 = Primary Pump
P2 = DHW Pump
Z1,...,Z3 = Zone Valves
Demands
Setback
Off
EMS
Rotate
Fixed Last
Pump Sequencer
Exercise
Off
Fixed Lead
First On / Last Off
First On / First Off
274 Switch Settings:Essential Control Settings:
Mode = 3