Honeywell AQ25A Series Technical Reference Booklet page 70

AQ251 SERIES BOILER RESET CONTROL PANELS
Familiarize Yourself With the AQ251 Control
Panel Layout
Refer to Fig. 1. All AQ251 Control Panels consist of three
functional components:
1. AQ10X38 transformer (power supply module), which
connects to 120 Vac power and supplies 24 Vac power to
the Control Module and Zoning Modules
2. AQ15100B boiler/DHW Control Module, which controls
the boiler and domestic hot water (DHW) functions, as
well as coordinating the overall operation of the hydronic
system.
3. One of two different 4-zone Zoning Modules:
• AQ15740B (part of the AQ25144B Control Panel)
for zoning with 24 Vac zone valves with end
switches
• AQ15540B (part of the AQ25142B Control Panel)
for zoning with either line voltage circulators or 24
Vac zone valves without end switches.
TRANSFORMER
1 FOR THE AQ25142B TERMINALS CAN BE LINE VOLTAGE (IF USED WITH PUMPS) OR LOW VOLTAGE (IF USED WITH ZONE VALVES)
CONTACTS
SYMBOL
Fig. 2. Internal wiring for AQ2000 Series components line voltage relays.
69-1974—04
CONTROL MODULE
Fig. 1. AQ251 Control Panel layout (AQ25142B shown).
4
AQ251 Control Panels can control a maximum of 16 zones by
connecting additional Expansion Zoning Panels to the AQ251
Control Panel. Each Expansion Zoning Panel is configured
with its own bank of DIP switches, located in the left-most
section of each Zoning Module.
In general, the top terminals of the AQ2000 Series components
carry low voltage (24 Vac) power and the bottom terminals
carry line voltage (120 Vac) power. This is illustrated in Fig. 1.
The only exception to this is the AQ15540B Zoning Module
when used with low voltage zone valves (without end
switches). In this case, the bottom terminals of the Transformer
and Control Module carry line voltage (120 Vac), but the
bottom terminals of the Zoning Module will carry low voltage
(24 Vac) power.
The powered terminals on the bottom of the AQ2000 Series
Control Modules and Zoning Modules are connected internally,
as shown in Fig. 2. The voltage supplied to the N and L
terminals is also available at the adjacent terminal pairs when
the hot ( ) relays are switched.
ZONING MODULE
Menu
OK
Zone 1
Home
Menu
OK
Home
LOW
VOLTAGE
(24 V)
Zone 2 Zone 3 Zone 4
LINE
VOLTAGE
(120 V)
M27736A
Zone 1 Zone 2 Zone 3 Zone 4
M27737A
1