Aprilaire 800 Installation & Maintenance Instructions Manual page 21

CHeCkInG SySTeM oPeRaTIon & TRoUbleSHooTInG
Table 5 – Troubleshooting Guide
Problem Possible Cause
General operating Field-wired terminal
problems . Humidifier connections .
will not turn on or
turn off .
Internal connections .
No power to humidifier .
Humidifier not turned on .
No power to 24 volt control
circuit .
Steam Light does not Call for humidity not being
turn on . received .
Water is leaking from Loose plumbing
humidifier . connections .
Hoses are blocked .
Drain hose is blocked .
Water constantly runs Malfunctioning drain valve .
down drain .
Debris in drain valve
preventing it from closing .
O-ring in drain valve is not
properly seated in groove .
Water is flowing from fill
cup overflow port .
High static pressure in duct
is causing back pressure in
canister .
Humidifier is filling Internal wiring connections .
and water is flowing
down drain but drain
High static pressure in
light is not on .
steam line is causing back
pressure in canister .
action
Check L1, N/L2 and Ground connections .
Check HUMIDISTAT and FAN PACK Terminal connections .
HUMIDISTAT terminals must be connected to an on/off device . Control circuit board will be damaged
if If 24 volts are connected to HUMIDISTAT terminals .
Check wiring connections and settings on Accessory items such as high limit switch and airflow
proving switch .
Check electrode and high water probe connections on the top of the canister .
Make sure blue/white wire jumpers (2) connecting Control PCB and Current Sensing PCB are secure
and properly oriented . See Wiring diagram figure 10, 11 or 12 .
Make sure ribbon cable from membrane switch is securely plugged into control circuit board .
Check that terminals from internal components are securely attached to proper tabs on circuit boards .
Make sure one of the electrode wires extends through toroid ring on current sensing circuit board .
Make sure Black/white wire from L1 is attached to terminal that matches input voltage .
Check main power supply and switch .
Ensure breaker is sized appropriately for the amperage draw .
Check for proper voltage across L1 and N/L2 terminals .
Make sure front cover is attached to engage safety interlock switch . Press On/Off button .
Make sure ribbon cable from membrane switch is not damaged and is securely plugged into the
control circuit board .
Check reset switch on transformer .
With humidifier energized, check for 24± 6 volts AC across J2 & J5 terminals . If okay, check for 5
Volts DC across +5V and GND test points on control circuit board . If okay, replace membrane switch .
If not, replace control circuit board .
If 5 volts DC are not present between +5V and GND test points, remove blue/white wire jumpers and
check DC voltage across +5V and GRD points . If 5 Volts DC are present, replace current sensing circuit
board . If 5 volts DC are not present, replace control circuit board .
Check ADHC wiring and setting . (Do not leave ADHC in TEST mode .)
Check wiring and settings of high RH limit switch and airflow proving switch .
Check water supply connection at fill valve inlet . Tighten as needed .
Check internal hose clamp connections . Reposition clamps and tighten as needed .
Check steam hose connection on top of canister . Tighten clamp as needed .
Check internal hoses and eliminate kinks or blockage .
Make sure drain hose has constant downward slope and is not blocked .
Check valve function using Test Mode .
Remove canister and clean debris from drain valve .
Remove canister and reposition O-ring .
Check internal hoses and eliminate kinks or blockage .
Disassemble brass fitting in feed line between inlet valve and fill cup . Make sure small rubber flow
orifice is in place in brass fitting .
Make sure dispersion tube is not discharging into duct with greater than 2 .0 in .wg static pressure .
Make sure dispersion tube tubelets are pointed up .
Make sure blue/white wire jumpers (2) connecting Control PCB and Current Sensing PCB are secure and
properly oriented . See Wiring diagram figure 10, 11 or 12 .
Install a tee and drain trap in any low points in the steam line . See figure 4 .
(ConTInUeD)
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