Armstrong World Industries EHU-704 User Manual

1)   Remove 24 metal clips by pushing gently on top of

each clip with a screwdriver while cupping the clip with 
the other hand.

2)   Clean the inside of the steam generator thoroughly

unsing a scraper, stiff bristle brush and/or water spray 
and rinse with clear water.

3)   High voltage units are supplied with a barrier/drain screen

assembly in the lower tank half to increase tank life. 
Inspect the barrier/drain screen assembly and replace if 
necessary.

4)   Place a flat washer and O-ring on each ¼" electrode 

stud and push the studs through the holes in the upper     

tank half (Figure 35-2).

5)   The mounting hole on each electrode is attached to the 

tank top with a slotted self-tapping screw.

6)   From the outside, install a flat washer and ¼" hex nut on

each electrode stud. Tighten these with a 7/16" wrench
so they are just snug (Figure 35-2).

FILL AND DRAIN SYSTEM REPAIR
General:
In the event of a "drain system failure" (C05) or a "fill system failure" (C06) indication on the three digit
numerical 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 tank on/off button, turning off the tank con-
tactor (tank off light illuminated). Press the manual drain button. The drain light should go on and 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 drain light is on, check for 24 VAC between the two 

leads on the drain valve (Figure 28-1, 28-2). 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. 
See tank removal section on Page 33.

34

Barrier

Barrier Retainer

Drain Screen

Hex Nut

Washer

Washer

'O' Ring