Instruction manual

21
P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
Wiring (continued)
6
DHW wiring
To operate the boiler for domestic water heating with a •
storage tank, install and pipe the tank according to the tank
manufacturer’s instructions and the recommended piping
diagrams in the Boiler Installation & Operating Instructions
manual
. Consult the factory for applications not covered.
Read the options and explanations given on • page 16
through page 19 to determine the best conguration for the
system.
External interlocks
If used, wire external limits and ow switch, as shown in 1. Fig-
ure 5, page 24.
If wiring to and from a motorized combustion air damper 2.
(or dampers), follow the guidelines given in Figure 5,
page 24. Connect only to the master boiler. Make sure the
AUX FUNCTION options are set correctly.
If any of the member boilers is to operate in
override mode, and the system is equipped with
a single, master combustion air damper, you
must provide special wiring in order to ensure
the damper opens and proves when the boiler
res. is must be done without compromising
the wiring between the master boiler and the
damper.
Overrides — Control priorities
e HeatNet control can provide override operation for 1.
any or all boilers in a HeatNet network. is requires the
boilers be piped with appropriate isolation piping and con-
trols as needed for isolation.
Do not wire boilers for override operation unless
the piping design provides automatic isolation of
the overriding boilers. e master boiler would
be unable to properly control system water
temperature if member boilers were to input heat
to the system without control from the master.
DHW operation, in particular, would raise the
supply temperature from overriding boilers to
the DHW Setpoint.
Override operation control setup — MEMBER boilers must be set
up with operating parameters necessary during their override (local)
operation.
A HeatNet boiler will respond to overrides in the following order. e modes 2.
listed will override any other activation function listed below it.
Boiler input prioritiesFigure 2
MASTER BOILER MEMBER BOILER
Priority 1
AA terminals
ON/OFF operation
Master boiler operates in ON/OFF
and res all member boilers ON/OFF
together based on system seings.
See Figure 8, page 27 for wiring con-
nections.
Priority 1
AA terminals
ON/OFF operation
Member boiler switches to local control
in ON/OFF operation, using the
boiler’s seings.
See Figure 8, page 27 for wiring con-
nections.
Priority 2
HEAT DEMAND
Master boiler operates in full modula-
tion and res/modulates member
boilers based on system seings.
Priority 2
HEAT DEMAND
Member boiler switches to local control,
using the boiler’s seings for operation
and modulation.
Priority 3
HeatNet input
Member boiler receives operating com-
mands om the master boiler through
the cable or shielded wires between
HeatNet boilers.
Priority 3
4-20mA/0-10VDC input
Requires closure across the 4-20mA
ENABLE terminals.
Master boiler operates and controls
member boilers based on 4-20mA
signal received at master.
Priority 4
4-20mA/0-10VDC input
Requires closure across the 4-20mA
ENABLE terminals.
Member boiler operates on local con-
trol based on 4-20mA signal received
at member.
Seing the 4-20mA parameter to HIGHEST in the ADVANCED
SETUP menu will cause 4-20mA ENABLE to move to priority 1.
Priority 4
T1/T2 stage control
Master boiler operates based on closure
of T1 and T2 terminals on master, r-
ing member boilers at the same rate.
See Figure 8, page 27 for wiring con-
nections.
Priority 4
T1/T2 stage control
Member boiler operates on local con-
trol based on closure of T1 and T2 on
member boiler.
See Figure 8, page 27 for wiring con-
nections.