79
• OutdoorSensor-TasseronTSA00AAOutdoorTemperatureSensor(1)
• OutdoorSensor-TasseronTSA00AAOutdoorTemperatureSensor(2)
• HeaderSensor-OptionalHoneywell32003971-003Sensor(1)
• HeaderSensor-OptionalHoneywell32003971-003Sensor(2)
• MODBUS-(A)
• MODBUS-(B)
• MODBUS-(-V)
With the exception of the alarm contacts, external power must not be applied to any of the low voltage terminals - doing so
may damage the boiler control. Also note the following:
a) External Limit-Theexternallimitterminalsareintendedforusewithaeldsuppliedsafetydevice,suchasamanual
reset high limit. When an external limit is used, the jumper between these two terminals must be removed. Failure to
remove this jumper will render the external safety devices ineffective.
b) Alarm Contacts - These contacts close when the boiler enters a “hard” lockout (lockout requiring manual reset). They
may be used as an input to a building alarm system. Contact rating is 24VAC, 0.63FLA. Do not use for line voltage ap-
plications.
c) EnviraCOM - Used to connect EnviraCOM thermostat or other EnviraCOM device approved by the boiler manufacturer
for use with this boiler. A Honeywell EnviraCOM connection is also located as labeled on the boiler control itself.
d) Outdoor Sensor - Use only the Tasseron TSA00AA outdoor sensor supplied with the boiler. When this sensor is con-
nected and enabled, the boiler will adjust the target supply water temperature downwards as the outdoor air temperature
increases. This sensor should be located on the outside of the structure in an area where it will sense the average air
temperature around the house. Avoid placing this sensor in areas where it may be covered with ice or snow. In general,
locations where the sensor will pick up direct radiation from the sun should also be avoided. Avoid placing the sensor
nearpotentialsourcesofelectricalnoisesuchastransformers,powerlines,anduorescentlighting.Wirethesensorto
the boiler using 22 gauge or larger wire. As with the sensor itself, the sensor wiring should be routed away from sources
of electrical noise. Where it is impossible to avoid such noise sources, wire the sensor using a 2 conductor, UL Type
CM, AWM Style 2092 shielded cable. Connect one end of the shielding on this cable to ground. See Section XII of this
manual for information on enabling the outdoor reset sensor.
e) Header Sensor - When this sensor is installed and enabled, the boiler will attempt to maintain the target water tempera-
tureintheheaderratherthaninthesupply.Wherethesystemowratevarieswidely,theuseofaheadersensoral-
lows the temperature of the water being sent to the radiation to be more accurately controlled. Use only the Honeywell
32003971-003 sensor listed above. Locate this sensor immediately downstream of the second primary-secondary Tee
(Figure 10.4). Installation of this sensor in a well, as opposed to on the surface of the header, is highly recommended.
The sensor wiring should be routed away from sources of electrical noise. Where it is impossible to avoid such noise
sources, wire the sensor using a 2 conductor, UL Type CM, AWM Style 2092, 300Volt 60°C shielded cable. Connect one
end of the shielding on this cable to ground. See Section XII for information on enabling the header sensor.
f) MODBUS - Boiler-To-Boiler communication network is used for multiple boiler (“Lead-Lag”) installations. See the
multiple boiler installation supplement for additional information.
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