Armstrong World Industries EHU-704 Let the unit continue to fill and allow the water to boil

If the stat demand display is greater than 35% and the unit does not begin filling, press the mode select button three times and the diagnostic mode indicator will light. Note the diagnostic message and refer to the diagnostics information in the troubleshooting section of this manual (page 20).

c)If the stat demand is less than 35%, force a 100% humidity demand by setting humidistat dial to 95% RH. Alternately, a 100% demand can be simulated by setting BJ4 jumper to position 3-4 (on/off), set BJ5 to position 1+2 (5 VDC) and installing a jumper between terminals 17+1 of the low voltage terminal block inside humidifier.

7)Let the unit continue to fill and allow the water to boil.

a)If the water level reaches within 4" of the Steam Generator Tank top, the High Water Float Switch will block the fill and illuminate the High Water light momentarily. This is normal on relatively pure water. Pressing the mode button to check the diagnostic display will result in an indication of C01. To complete the start-up testing in this instance, push the Drain switch to drain 1/2 of the tank. Next, turn off power at the breaker or safety switch and add one pinch (1/2 teaspoon) of Epsom salts to the Fill Cup (See Part #25 on Page 28). This should allow the water to boil by increasing the water's conductivity. (See "Water Quality and Treatment for EHU Humidifiers" in the troubleshooting section on page 23.) Reapply power to energize the humidifier.

8)On typical beginning fill, after the fill stops, press the mode button until percentage of maximum power is indicated. The numerical display should read a few points above 40%.

9)Press the Drain switch. Verify that the unit is draining freely.

10)Inspect the steam outlet piping. Verify that there are no un-trapped low spots. Also verify that the piping is insulated and properly sloped (See Step 8 on Page 7).

11)If the Dispersion Tube is equipped with a drain fitting, verify that is working.

12)Verify operation of high limit humidistat and or air proving switch, if used.

a)If high limit is used, turn dial to minimum setting, 10%. Display of unit should read CO4 and unit should stop steam production. Turn humidistat dial to maximum of 90% and unit should return to normal operation.

b)If pressure switch is being used, verify airflow condition in duct or air handler.

- If air flow is present, unit should be in normal operation. Disconnect wire from terminal

15 at humidifier. Display should show CO3, and unit will stop operation. Reconnect wire to terminal 15, and unit should return to normal operation.

- If Air Flow is not present in Duct or Air Handler, unit should be sitting IDLE and Display should be showing CO3. Turn fan on and verify duct or Air handler now has airflow present. Unit should return to normal operation.

13)While humidification is being demanded, turn humidistat dial down to near zero. The following should happen:

a)The stat demand reading will decrease to zero.

b)The unit will shut down, lighting the Tank Off light.

14)Turn humidistat dial to the desired value.

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