P-K MACH
®
Gas Fired Boiler
Technical Service 1.877.728.5351
Revised: January 3, 2020
Released: January 3, 2020
Patterson-Kelley 2020
All Rights Reserved.
1004905981 P-K MACH C1500H-C4000 Installation and
Owners Manual (Rev F Jan-2020).docx
Page 23
3.3.5 High Voltage (TB2) Terminal Block
Start Interlock #1
– The Start Interlock #1 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.
Start Interlock #2
– The Start Interlock #2 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.
Auxiliary Input #1
– These terminals are reserved for future
use. This circuit is energized with 120VAC.
Auxiliary Input #2
– These terminals are reserved for future
use. This circuit is energized with 120VAC.
Air Damper Interlock
– The Air Damper Interlock provides
dedicated terminals 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.
Relay A
– User-configurable relay output #1. The normally-
open contacts on this relay have a maximum voltage rating of
240VAC and maximum current capacity of 1/2 Amp.
Relay B
– User-configurable relay output #2. The normally-
open contacts on this relay have a maximum voltage rating of
240VAC and maximum current capacity of 1/2 Amp.
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
P-K MACH
C-1500H, C-
2000H, and C-2500 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.
The high voltage (TB2) terminal
block on the MACH C-3000 & C-
4000 with NURO controls 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.
NOTE:
Refer to
wiring and configuration of the
electrical connections.
Relays A through D can be user-
configured through the NURO
touch screen interface to control
devices such the Comfort Heat
(CH) Pump, Domestic Hot Water
(DHW) Pump, Air Damper, System
Pump, etc.
NOTE
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.
NOTE
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.
NOTE
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.
