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45
Valves Maintenance
Fill and Drain system repair
GENERAL:
In the event of a “Drain Circuit P5” or a “No Inlet Water P4” indication on the display, perform the following steps to identify
and correct the fault.
DRAIN SYSTEM FAILURE:
Check for drain valve operation. With the unit on; press the manual drain button. You should hear the drain valve operate
with a sharp click. Repeatedly activate the manual drain button to determine if the valve is operating.
1. If the drain valve does not operate but the display reads manual drain, check for 24 VAC between the two leads on the
drain valve. After checking, TURN THE POWER OFF.
a. If 24 VAC was NOT found, check wiring continuity to the circuit board. Repair broken wires as necessary. If wires
are intact, call the factory for assistance.
b. If 24 VAC was found, measure the coil resistance of the drain valve with the leads disconnected. The coil resistance
should be 10 ohms; if it is not, replace the drain valve.
2. If the drain valves can be heard to operate but no water drains out, TURN THE POWER OFF, then:
a. Check for a plugged drain valve and/or plugged drain adaptor. It is often possible to see an accumulation of solids in
the inlet to the drain valve or in the neck of the steam generator. If this is the case, remove the generator and clean out
the drain valve and tank drain adaptor.
b. While the tank is out, look into the lower end of the tank. Make sure the drain screen is in place. Also check for
accumulations of lime at the bottom of the tank. Refer to “Steam Generator Disassembly” and “Cleaning Procedure”
sections to rectify these problems.
3. If the tank drains well when the water level is high but poorly or not at all when it is low, check the duct pressure where
the dispersion tube is mounted. A negative duct pressure can cause drainage problems. While this is relatively rare, it
has been known to happen.
4. If the water backs up into the drain pan inside the unit, check for a blocked drain cup under the pan. If the drain cup is
OK, check the drain piping for an accumulation of solids. Clean as required and increase the pitch of the drain piping if
necessary. If long runs of horizontal drain pipe cannot be avoided, it may be necessary to develop some kind of drain
flushing system. An air gap in between drain piping and drain hose from the EHU will allow “burping” of air from drain
piping.
Fill System Failure:
Make sure the drain valve is not leaking. A leaking drain valve may appear to the humidifier as a fill system failure. Check to
see that the fill valve is operating. While the fill light is on, disconnect one of the fill valve leads then momentarily touch the
lug to the coil terminal. You should be able to hear the valve operate.
1. If the valve is not operating, check for 24 VAC between the valve lead wires. After checking, TURN OFF THE POWER.
a. If 24 VAC WAS NOT found, check the continuity of the wires back to the circuit board. Repair broken wires as
necessary. If wires are intact, call the factory for assistance.
b. If 24 VAC WAS found, disconnect the fill valve leads and check the coil resistance. It should be 58-60 ohms. Replace
the coil if necessary.
2. If the fill valve is operating but the unit fills too slowly, check for either low water pressure (less than 25 psi) or a
partially plugged screen inside the inlet fitting. If the screen tends to plug too easily, it may well be removed and
replaced by a larger filter in the water line external to the unit.
3. If the valve makes humming or buzzing noises but fails to open:
a. Check for high water pressure (over 125 psi).
b. If a backflow preventer is used, crack open a fitting between the backflow preventer and the fill valve. If this causes
the fill valve to open, remove the backflow preventer from the system. Backflow preventers are not needed as the Series
EHU-800 incorporates a 1 inch air gap as an anti-syphon feature. For additional information on Armstrong Series EHU-
800 Humidifiers, contact your Armstrong Representative and request Bulletin No. 596.
