Product Overview

5 of 8 © 2012 A 274 - 01/12
Electrical
Application A 274-5
System Description: The Boiler Control 274 controls one 3 stage boiler and a pump to provide outdoor reset for the
space heating zones. The boiler is piped in primary secondary and the 274 controls the boiler pump to allow post purging
of excess heat from the boiler to the system. The zone valve end switches provide a 24V(ac) powered demand to the 274
control in order to create a call for heat. The 274 also controls a DHW pump. This system can provide DHW priority over
space heating to provide faster DHW tank recovery.
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.
A1
S2
Z1 Z2 Z3
S1
P1
P2
120 V (ac)
P3
S3
274
S1 = Outdoor Sensor 070
S2 = Boiler Supply Sensor 082
S3 = DHW Sensor 082
A1 = High Limit Aquastat
P1 = Boiler Pump
P2 = Primary Pump
P3 = DHW Pump
Z1... Z3 = Zone Valves
N
115 V (ac)
L
S2
Boiler
Stage 1
S1 S3
Boiler
Stage 2
P3
P2
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
Boiler
Stage 3
P1
C
24V(ac)
R
Class 2
Transformer
A1
Z1...Z3
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 = 5