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2. Max. Filling Time
Symptom(s) Diagnosed:
The fill valve has been
“on” for a longer time than is normally required for
non-zero current to flow between the electrodes or
for water level in the cylinder to reach the high
water sensor pin.
Probable Cause(s): Blocked drain due to blocked
cylinder strainer or blocked drain valve preventing
water from entering the cylinder. Drain valve
leaking due to dirt in seal or powered by defective
main PC board or powered by wiring error. High
water sensor circuit not responding due to sensor
plug not connected or defective high water sensor
PC board or wiring error or defective main PC
board. Water supply rate too low or zero due to
too low pressure or line restriction or clogged
built-in strainer. Too low supply water
conductivity. DI (de-ionized) or RO (reverse
osmosis) supply water has almost no conductivity.
Measure conductivity and report findings to factory
if suspected.
Response:
UNIT STATUS LAMPS REMOTE
INDICATION
(24 Vac to:)
UNIT
CONTACTOR
YELLOW GREEN 61-20
“YELLOW”
OFF ON OFF ON
NHB Explanation of Symptoms Without Automatic
Shutdown
4. No Current But High Water Sensor On
Symptom(s) Diagnosed:
High water level in the
steam cylinder is detected, yet no current is
detected in the steam cylinder.
Probable Cause(s):
Sensor plug connected to
wrong cylinder pin. High water sensor PC board
defective (activates with no water). Main PC
board defective (activates high water circuit
without sensor PC board). Monitored leg of three
phase power supply is dead. Main PC board
defective (does not sense current when current is
present in monitored leg).
5. Cylinder Spent
Symptom(s) Diagnosed:
The high water sensor
circuit is activated. Other criteria are used to
distinguish cylinder spent from normal startup and
diagnose the steam cylinder as spent, as
previously described.
Probable Cause(s):
As pure steam is produced
from tap water, most minerals are drained by the
auto-adaptive control system. However, it is
inevitable that minerals will buildup on the
electrodes and strainer inside the steam cylinder.
It is unavoidable and the cylinder is intended to be
disposable.
Unit Takes Self-Corrective Action:
The humidifier
continues to operate with gradually decreasing
capacity, giving the user notice by responding as
shown below.
Response :
UNIT STATUS LAMPS REMOTE
INDICATION
(24 Vac to:)
UNIT
CONTACTOR
YELLOW GREEN 61-20
“YELLOW”
ON ON ON ON
6. No Current But Humidistat Calling
Symptom(s) Diagnosed:
For a few minutes, no
current is detected in the steam cylinder, despite a
demand for humidity. (Current is not expected to
be zero when there is a demand for humidity.)
Probable Cause(s):
Drain valve is leaking, so
water never reaches the electrodes. Water supply
is obstructed. Contactor is not activated. Supply
water is “pure” without conductivity. Fill valve is
blocked. Fill valve is not being activated. Supply
water pressure is too low (less than 30 psig).
Wrong orifice in fill valve. High duct static
pressure blows back into the fill cup (via the steam
line and empty cylinder) diverting the fill water to
overflow. (Taking the steam hose off until some
water gets into the cylinder solves this.)
6. Output Too Low
Symptom(s) Diagnosed:
For a few minutes,
current does not increase in the steam cylinder,
despite the fill valve being activated. (Current is
expected to increase soon after the fill valve is
activated.)
Probable Cause(s):
Drain valve is partially open,
so fill rate maintains non-zero but non-increasing
current. Continual overflow because high water
sensor circuit did not respond to full cylinder.
Supply water insufficiently conductive. Fill valve is
partially restricted due to dirt, pinched supply line,
or wrong orifice. Steam supply line is obstructed
so back pressure causes continual overflow.
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