Application Brochure

3 of 4 © 2009 A 257 - 03/09
Mechanical
P1 = DHW Recirculation Pump
P2 = Boiler Pump 1
P3 = Boiler Pump 2
S1 = DHW Sensor 082
Electrical
S1 = DHW Sensor 082
DIP Switch Settings
Rotate = On
Application A 257-3
System Description:
The 257 stages 2 single-stage boilers in order to maintain the DHW Target temperature as measured by the DHW Sensor.
Two DHW tanks are piped in parallel providing equal flow through each tank. The boiler pumps operate off the boiler
ignition control. The DHW recirculation pump is operated with an on /off switch or timer.
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.
120 V (ac)
24 V (ac)
Class 2
Transformer
S1
Potable
Supply
P1
P2 P3
DHW
Tan k
DHW
Tan k
257
Boiler 1 Boiler 2
24 V (ac)
N
R
C
120 V (ac)
Class 2
Transformer
L
S1
Rotate
On
Off
78
No Power
257
132
Heat 1Power
4 5
Heat 2 Com DHW
6
Sen SenRC