Specifications

WATLOW IND. WATROD Duct Heater Installation & Maintenance Manual
I&M NUMBER: 316-42-6-1 Page: 9
Date:6/11/2008 Rev: 3.00
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WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE [phone] n FAX [phone]
The power circuit is required to include a branch circuit overcurrent protective device, a disconnect and a
secondary thermal cut-out with manual reset. The control circuit should include the temperature
controller, the primary thermal cut-out and an interlock with the fan motor. One method to do this is with
a pressure air flow switch. It will open the control circuit and de-energize the heater when any
circumstance prevents sufficient air flow through the heater.
The air handler should be set up to run on a time delay after the heater is de energized. The correct time
delay will depend on the blower rating, amount of duct insulation, and the total power output of
heaters(s). The time delay allows the elements to cool and prevents overheating the adjacent duct and
terminal areas.
Start Up
Before energizing the heater the following items should have been checked with the heater power
disconnected:
1. Electrical termination is tight and wiring is per wiring diagram supplied with heater
2. Proper disconnecting means and fusing have been installed
3. The voltage rating of the heater is the same as that being applied
4. Megohm is within acceptable limits
5. Proper temperature controls and safety limiting devices are in place
6. Heater is securely installed in duct
After applying power to the heater make sure that the system is being controlled properly before leaving
it to run unattended. Failure to do this could result in overheating resulting in personnel danger and fire.
Troubleshooting
PROBLEM Cause / Correction
No power available to heater Check disconnect switch to ensure it is in the "ON" position
and that fuses are not blown. Replace fuses if they are blown
Fuses blowing Check heater electrical rating. Applied voltage may be wrong
Check fuse rating. Fuses should be at least 25% more than full
load amperage.
Disconnect heater power source. Check the heater resistance
to ground. This should be no less than 1 Megohm. Refer to
Megohm checking.
Not enough power Check line voltage to ensure it is within specification
Check full line current if voltage is correct. If line current is lower,
the heater may be wired wrong or has open elements
Air not heating to desired Not enough Kw or incorrect voltage being applied
Temperature Too much heat loss, higher wattage heater may be required
High limit tripping / alarm Not enough fluid flow
Too much Kw
Line voltage higher than designed / allowable
Preventative Maintenance