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P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
Situation
Suggested procedure
Unable to change the # of Boilers
in the BOILERS menu.
In H-Net method, the control auto-detects the boilers in the system and adjusts the number of boilers
❑
accordingly.
Using H-NET, if the number of boilers is not being detected properly as the actual number of boilers in the
❑
system, check each boiler. There can only be (1) master boiler, but there can be up to 15 member boilers.
Make sure only the master boiler has a Header Sensor (SYSTEM HEADER) connected.
❑
Verify that each boiler’s HeatNet cable is in place.
❑
Verify that each boiler has a unique address assigned (ADVANCED SETUP | DISTRIBUTED CTRL |
❑
H-NET ADDRESS).
The BOILERS menu only indicates
one boiler, but there are member
boilers connected. The amber
light blinks on all of the boilers’
communications jacks.
Verify that the latest version of firmware is installed on all boilers.
❑
All boilers in a system must have the same firmware revision (version).
❑
Verify the proper termination is set on the Master and the last Member boiler.
❑
H-Net boilers are detected but
then lost and then detected again.
The H-Net communications cable may be receiving interference from the blower, ignition, or other form
❑
of radiated electrical noise. The communications cable must be run separate from other wires.
Termination of the jumpers may not be correct or there is more than one master.
❑
Ensure that the termination dip switches are set on the MASTER boiler and only the LAST MEM-
a.
BER boiler. All of the other member boilers should have their termination dip switches OFF.
There may be two or more MASTER boilers. Ensure that only one header sensor is present and con-
b.
nected to the SYSTEM HEADER input. There should be no wires or sensors connected to the SYS-
TEM HEADER input if the boiler is operating as a member.
Verify that the HNet cables are of a shielded or twisted pair type. Shielding of the cable is required.
c.
Minimize possible electrical interference by routing the communications cables away from electrical
d.
noise sources, such as motors, ignition controls, contactors, etc.
Only the MASTER boiler Fires, but
the system has many boilers and is
using H-Net.
In order for the MASTER boiler to act as a MASTER, the header sensor must be set to TYPEZ, and there
❑
must be a header sensor present.
At power-up, the header sensor is auto detected. If the temperature of the header sensor at power-up is
❑
greater than –25 °F and less than 240 °F it is considered a valid sensor. The boiler will default to the MEM-
BER mode if the temperature is not in this range, and can only be run locally or by external inputs.
If the LOAD FACTORY DEFAULTS has been used to restore all the default settings, the header sensor
❑
has been set to NONE. This needs to be set as stated above (TYPEZ). The header sensor will need to be
replaced or the temperature brought into a valid range. Power cycle the boiler and the HeatNet control will
detect the sensor (if temperature is in the range listed above).
The HNet needs a communications cable daisy-chained between boilers. Ensure that a good connection
❑
is made on the communications board and that the lights on the dual RJ45 jacks flash (roughly twice a
second). The MASTER is the only one that should flash with no communications cables plugged in.
You get the error message –
WATER FLOW SWITCH or WAITING
FOR FLOW.
If the control does not sense a closed circuit at input connection, FLOW SWITCH, check to make sure
❑
the circuit for the circulator pump is correct, that the pump is being energized, and that the flow prove
switch is working properly.
If there is no flow prove switch, check to make sure that a jumper wire has been connected across J11B,
❑
WTR FLW interlock.
Troubleshooting
(continued)
9
Table 12
Troubleshooting suggestions
(continued)
