How It Works - Honeywell TrueSTEAM Series Reference Manual

III. Optional Add-On Air Proving
What is it?
air proving can be defined two ways – proving the fan has power to move air, or proving physical air movement in the duct. Proving the fan
has power has been integrated into truesteaM's Fan enforcement feature. this integrated air proving through fan G-terminal enforcement
makes wiring easy, while safeguarding the home by positively confirming the fan has power to move air before allowing truesteaM to
humidify. Follow the Fan enforcement steps applicable to the home during the installation, as illustrated in the previous section of this guide.
In nearly all applications, enforcing the fan G-terminal (G wiring and power monitoring) will provide the necessary safeguards against humidity
production without airflow.
an optional add-on accessory is available, at extra cost, for proving physical air movement in the duct. this optional accessory is above and
beyond fan G-terminal enforcement. By adding this air proving switch and setting dIPs accordingly, truesteaM will verify fan operation – first
via G-terminal enforcement, then by looking for air movement via the switch making contact. think of the system fan G-energization as the
primary safeguard feature, and the air proving device as a supplementary option.

How it works

• Air proving via integrated fan G-enforcement
— see previous section
• Air proving via an additional air proving option
— Wiring an air proving device requires breaking a wiring contact between truesteaM and the hVaC system.
• Break TrueSTEAM C and HVAC system C contact with the air proving device.
• On TrueSTEAM, flip DIP-5 UP. This configures TrueSTEAM to monitor physical air movement prior to steam production.
• Once wired in this way with DIP 5 up, TrueSTEAM will check for air movement in the duct when the tank's water temperature reaches 170°F,
just prior to humidity production.
— this check is switch-based and depends on what air proving device is employed (i.e., pressure switches check for a desired +/-
pressure in the duct to prove air, while a sail switch waits for the 'sail' to flip over from air movement). each actuation will complete
the C contact between truesteaM and the hVaC system C, allowing for truesteaM to prove air movement in the duct.
— If airflow is not present, truesteaM will shut down prior to humidity production.
What are my options and when would I use one over the other?
In nearly all applications, enforcing the fan G-terminal provides the necessary safeguards against humidity production without airflow. either
truesteaM or the thermostat will force the fan on prior to humidity entering the duct.
some contractors may want to include the optional air proving in homes where the occupants are gone for extended periods of time, such as
vacation homes. this ensures the home is safeguarded against excessively dry conditions, while simultaneously ensuring humidity production
is shutdown if the system fan is physically not moving air. an example would be where the system G has been energized, but the fan belt is
broken so air is not moving.
the optional air proving device is not critical in homes where there are daily occupants. If the fan has power but air is physically not moving the
occupant will notice temperature discomfort and take action (service call) well before truesteaM could affect the ductwork.
24