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3.3.3 High Voltage (TB2) Terminal Block
HOT L1 – Connect the hot lead of the 120VAC, single phase, 60Hz
electrical service to the TB2-1 terminal.
NEUTRAL – Connect the neutral lead of the 120VAC, single phase,
60Hz electrical service to the TB2-3 terminal.
GROUND G1 – Connect the ground lead from the electrical service
to the TB2-4 terminal.
Start Interlock #2 – The Start Interlock #2 TB2-5 & TB2-6 terminals
are in series with Start Interlock #1 and provide additional connection
points for auxiliary safety devices. This circuit is energized with
120VAC, so the contacts on any auxiliary safety devices must be
rated for minimum 120VAC.
Start Interlock #1 – The Start Interlock #1 TB2-7 & TB2-8 terminals
can be used for auxiliary safety devices such as damper limit
switches, control valve limit switches, emergency stop buttons, and
low water cutoff devices. This circuit is energized with 120VAC, so
the contacts on any auxiliary safety devices must be rated for a
minimum of 120VAC.
The boiler ships with a factory-installed jumper across Start
Interlock #1 and Start Interlock #2 terminals. Remove the
jumper(s) if using any auxiliary safety devices.
Both the Start Interlock #1 and Start Interlock #2 circuits must
close within 5 minutes of a call for heat. Failure to close the Start
Interlock circuit will cause the boiler to lockout on alarm.
Auxiliary Input #2 – The TB2-9 & TB2-10 terminals are reserved for
future use. This circuit is energized with
Auxiliary Input #1 – The TB2-11 & TB2-12 terminals are reserved
for future use. This circuit is energized with
Air Damper Interlock – The Air Damper Interlock TB2-13 & TB2-14 terminals allow for proof of open
end limit switch on a motorized air damper. This circuit is energized with 120VAC, so the contacts on
the end limit switch must be rated for minimum 120VAC.
The boiler ships with a factory-installed jumper across the Air Damper Interlock terminals. Remove
the jumper if connecting a motorized air damper with end limit switch.
Ground – Grounding connection for auxiliary safety/limit devices on terminal TB2-15.
This ground terminal is connected to the TB2 sheet metal and is not common with the boiler's
Revised: January 3, 2020
Released: January 3, 2020
NOTE
NOTE
.
120VAC
.
120VAC
NOTE
NOTE
electrical service ground.
Patterson-Kelley 2020
All Rights Reserved.
®
P-K MACH
Technical Service 1.877.728.5351
Be sure to check the
nameplate on the boiler
before connecting the
electrical supply.
N
!
OTICE
A dedicated earth ground
(green wire) is required to
avoid nuisance shutdowns.
Do not ground through the
conduit!
The high voltage (TB2)
terminal block on the
MACH
CM300-CM399-CM500
and C750-C900-C1050 boilers
with NURO controls contains
one hot lead (HOT L1), a
neutral lead (NEUTRAL) and a
ground lead (GROUND) for
110 - 120 VAC, single phase
60Hz electrical supply. This
terminal block (TB2) also
contains dry-contact relays
with a maximum voltage
rating of 240VAC and 1/2 Amp
maximum current capacity.
Incorrect wiring can result in
equipment damage, injury, or
death.
1004905980 P-K MACH CM300-CM500&C750-C1050
Installation and Owners Manual (Rev F Jan-2020).docx
Gas Fired Boiler
P-K
Page 18
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