Fireman's Switch Connection/Remote Control Connections; Mastertemp 125 Heater Terminal Board/Control And Connection Wiring Diagram - Pentair MT125 Installation And User Manual

USE THE PROVIDED WATERPROOF WIRE NUTS WHEN CONNECTING THE POWER SUPPLY.
A time clock controlling the filter pump should have a low-voltage Fireman's Switch that switches off the heater at
least 15 minutes before shutting off the pump.
1. - Remove the factory installed jumper from the Fireman's Switch terminals.
- Connect wires between the Fireman's Switch terminals on the heater and the relay. Connect wires from the
controller or timer to the Fireman's Switch. Controller, timer or relay should be sized to handle 24VAC at 0.5
Amp (because it will be completing the 24VAC control board circuit on the heater as shown in Figure 31 and
Figure 37 (page 40). DO NOT apply line voltage to the Fireman's Switch terminals. Use 18 gauge wire with a
minimum 1.2 mm (3/64 in.) thick insulation rated for a temperature rise of at least 105° C.
- Knock-outs are provided to route the wires through the bottom of the control box and past the junction box.
2. To connect a 3-Wire Control:
- Connect wires between the control board terminals on the heater and the external relays, as shown in Figure 37,
on page 40. Use at least 2 relays per heater, to allow for an "OFF setting" on each heater mode. Select relays
that can handle logic level switching. DO NOT apply line voltage to control board terminals.
- Move jumper (as show on page 40) to enable external control and to disable the heater membrane pad's "Pool
POOL/SPA buttons (the HEATER (ON/OFF button control panel remains functional).
- Knock-outs are provided to route the wires through the bottom and the top of the control box and past the
junction box.
3. Close control box cover.
4. Re-install the access door panels.
460906 Rev. D 8/2020
TRANS
OPERATING CONTROL
BK O
MEMBRANE PAD
CONNECTION
ENABLE TOGGLE
DISABLE TOGGLE
TERMINAL BOARD
F
I
R
E
L1
M
A
N
F1 S
L1
GND
24VAC
MASTERTEMP 125 Pool and Spa Heater Installation and User's Guide
Section 1. Installation Instructions
BK
O
Y
Y
Y Y
24 VAC
J6
W
W
TRAN S
S
W
W
I
L2
FL
T
C
H
R
BM
R
L2
Time Clock or Remote
(Purchase Separately –
Supplies Power to
Circulator Pump)
Fireman's Switch
Completes the heater
24 Volt AC Control
Board Circuit.
DO NOT connect this
circuit to Line Voltage!
Figure 31.
35