Camus Hydronics ADVANTUS AVH 1000, Installation, Operation And Service Manual

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5.2 VARIABLE FREQUENCY DRIVE (AV800-4000)
This appliance uses a VFD which provides power to the combustion fan. The fan motor operates on 230VAC 3 phase power. This three
phase voltage is generated by the VFD and supplied directly to the fan motor. The VFD receives a 4-20mA modulating signal from the
SOLA to vary the frequency of the voltage supplied to the fan motor. This varies the output of the combustion air fan from 4% up to 100%
of capacity corresponding to the same variation in burner input. Once the
‘self-checks’ are completed by the SOLA, the VFD is provided
with a signal to operate at soft start level for initial burner ignition. After main burner ignition is established, the modulating signal is
generated by the VFD to vary fan speed based on desired water temperature set point.
CAUTION
The voltage output from the variable frequency drive to the combustion air fan is 230VAC, 3 Phase. AVOID contact with high
voltage wiring.
5.3 LOW AIR DIFFERENTIAL PRESSURE SWITCH
Models 500 & 600 use a normally open differential air pressure switch to prove air flow. A pressure transducer coupled with an electronic
controller is used to prove operation of the combustion air fan on the AV800-4000. The pressure switch sensing points are installed at
the fan outlet housing for models 500 & 600 and they are installed at the fan intake for models 800 - 4000. One point measures total
pressure (+air) and is connected to a pitot tube facing the flow. The other point measures static pressure. Differential pressure at the
switch will be affected by blockages in the intake pipe or at the flue discharge. A minimum differential pressure across the sensing points
of the pressure switch proves operation of the combustion air fan. The diagnostics display will exhibit a status of an open Interrupted Air
Switch (LCI OFF) when the differential pressure switch detects a sustained low air condition. This condition could be caused by a number
of factors including:

Sensing line broken or loose fitting

Dirty filter or blocked vent

Steady high wind condition

Incorrectly set switch
Figure 24: Low Air Proving Switch (AV500 & 600)
The staging relay utilizes 4 individual relays. Relay 1 operates the high end gas valve and the air inlet damper. Relay 2 and 3
activate/deactivate the hot surface igniter during the gas valve transition sequence. Relay 4 is dedicated to low air switch operation and
ensures that if a low air condition occurs the control will enter into an automatic reset error.
Figure 25: Electronic Low Air Switch (AV800
– 4000)
- Large red numbers indicate
actual real-time differential
air pressure reading
- Small green numbers
indicate differential air
pressure setting
-
“1” indicates air switch is
open.