Thomas & Betts RZ-NA 441-OMS Air Pressure, Circuit Indicator Board check lights

S4. Air Pressure

Profile plate sensing tubes should be checked quarterly and cleaned no less than semiannually. If the sensing tubes become even partially blocked, false pressure readings may be relayed. To clean, remove the screened end caps. Clean the screens and the tubes, if necessary. Re- place the cleaned end caps. Check the pressure differential across the profile plate using a slope gauge. Air pressure differential should be between -.5" and -.7" w.c.

To attach the slope gauge, open the control compartment door panel. Just below the junction box, locate the tubing connections. Remove the cap at each connection and attach the slope gauge using two field- supplied 1/4" x 1/8" female NPT barbed tubing connections. For in- structions on measuring air pressure, see Service Section, Paragraph 9.

R5. Circuit Indicator Board (check lights)

The circuit indicator board is located in the control compartment elec- trical box (See Figure 7). Check operation of all indicator lights by switching lights that are not lit with one that is currently lit. Replace all burned out indicator bulbs (P/N 125189).

Figure 4 - Circuit	Row of Bulbs
Indicator Board,
P/N 151263
Check bulbs not
lit with other
bulbs; replace
any burned out
bulbs

S6. Main Burner and Pilot Assembly

For the most part, the burner and pilot are self cleaning. However, if the application is extremely dirty or dusty, cleaning of the burner and pilot may be necessary. Inspect the burner annually. Follow these instruc- tions. If it is necessary to replace any parts, use only factory-autho- rized replacements.

1)Turn off the gas and power supply to the system.

2)Remove the door panels in the burner/control cabinet (four or six depending on whether or not the system has return air). Locate the pilot.

3)Disconnect the two ignition wires (male and female quick connec- tions) and disconnect the flame sensor lead at the burner. Remove the set screw located in the ignitor tube (set screw holds the brass bushing in place). Carefully remove the brass bushing and the igni- tor.

Check the hot surface ignitor for cracks or unusual deterioration. Check the flame rod for integrity. Replace the flame rod (P/N 131188) and/or the hot surface ignitor (P/N 121865) if not in good condition.

4)Clean the burner and pilot by back-flushing, using high pressure air (40-80 lbs). Continue until dust particles are completely expelled from both the upstream and downstream sides of the burner.

CAUTION: Wear eye protection while pressure cleaning and drilling.

Figure 5 - Burner

End Plate showing

Hot Surface Ignitor

Burner End Plate

Flame Sensor

Ignitor

If air pressure does not unplug burner orifices or pilot tube, drill burner orifices with a Size #50 drill and/or pilot tube with a Size #55 drill.

WARNING: Do not enlarge burner ports or performance may be drastically affected.

Inspect the upstream and downstream sides of the mixing plates. Remove any accumulation of scale or foreign material with a wire brush. If any mixing plate fasteners are loose or missing, tighten or replace. Always use zinc plated or stainless fasteners.

If any cracks are present, replace that mixing plate. Because of the effect of flame temperature on the metal, fasteners may be difficult to remove. Be careful not to damage the gaskets that go between the mixing plates and the burner body. The gaskets are designed to overlap approximately 1/16" for tight air seal.

5)Follow Steps in reverse order to re-install the pilot assembly. Close all panels and check for proper operation.

Figure 6 - Illustration of the first Burner Section

Mixing

Plate

Full length of the burner is made up of a series of 6" or 12" burner sections in a linear or oval configuration

Burner

WARNING: Burner profile plates are factory set to match CFM requirements.

Do not adjust profile plates without contacting your Sales Representative for technical assistance.

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