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P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
External 4-20ma control
4
Follow the Boiler manual
— Install the boilers according to the
Boiler
Installation & Operating Instructions
manual before attempting to set up
the control system.
If using a 0-10 VDC signal multiply any references to current in the
manual by 0.5. Example: 5ma / 0.5 = 2.5 VDC.
Option 1:
Modulation using HeatNet control
Set up the boilers following the instructions for a HeatNet modulated system, be-
1.
ginning on page 8.
See
2.
Figure 7, page 26 for wiring from the 4-20mA external controller. The con-
troller must provide the 4-20mA signal and a contact for each boiler to enable its
operation by closing across the Remote Enable contact.
Set parameters as for the HeatNet modulated system.
3.
Closing the 4-20mA enable contact will cause the master boiler to modulate all
4.
boilers at a level proportional to the 4-20mA signal.
Make sure to set the 4-20mA parameters for compatible boiler start current.
5.
Electrical shock hazard —
Disconnect all electrical power
sources to the boiler before making any electrical connections.
Label all wires prior to disconnection when servicing controls.
Wiring errors can cause improper and dangerous operation!
Verify proper operation after servicing.
Failure to comply with the above could result in severe personal
injury, death or substantial property damage.
The electrical connections to this boiler must be made in
accordance with all applicable local codes and the latest revision
of the National Electrical Code, ANSI /NFPA-70. Installation
should also conform to CSA C22.1 Canadian Electrical Code
Part I if installed in Canada. Install power supplies to the
boiler as indicated on the boiler wiring diagram, making sure
to provide the correct voltage, phase and amperage capacity
specified. A properly rated shut-off switch should be located at
the boiler. The boiler must be grounded in accordance with the
authority having jurisdiction, or if none, the latest revision of
the National Electrical Code, ANSI/NFPA-70.
Line voltage field wiring of any controls or other devices must
use copper conductors with a minimum size of #14 awg. Use
appropriate wiring materials for units installed outdoors.
Option 2:
Direct modulation, up to 5 boilers
Set up parameters as for a stand-alone boiler, beginning on
1.
page 6.
The 4-20mA input is daisy-chained (connected in series)
2.
from boiler to boiler. Connect the 4-20mA input signal
with its “+” input on boiler 1, and its “-” input on the last
boiler. Then connect the 4-20mA input terminals from
boiler to boiler in series; i.e., the - from boiler 1 goes to + on
boiler 2, etc.
Close the external gas valve on every boiler.
3.
Wire all boilers following the guidelines in this manual.
4.
DO NOT install a system header sensor or DHW sensor
5.
on any of the boilers.
Disconnect the wires to the boilers’ Remote Enable termi-
6.
nals (and any override wiring to Heat Demand or DHW
Demand terminals) to ensure there will be no call for heat
while proceeding.
Set the boilers’ control parameters using their display/key-
7.
pads.
Follow the instructions in the Boiler manual to start up each
8.
boiler before proceeding further.
Finish by reconnecting call-for-heat wiring, then operating
9.
the complete system to verify operation in all modes.
Option 3:
Remote setpoint operation
A HeatNet system or an individual boiler can be operated
1.
using remote setpoint by providing a 4-20mA input and en-
able. Set the 4-20mA parameters for compatible boiler start
current and correct temperature range.
See
2.
Figure 7, page 26 for wiring from the 4-20mA control-
ler.
Wiring
See
1.
page 20 for wiring information and wiring diagrams.
Note that the boilers can be wired for override operation.
2.
The wiring section provides information on override priori-
ties.
