Energy Tech Laboratories Modular Direct Fired Heaters manual Main Burner Adjustment

Maxitrol MR212 Low

Fire Bypass Screw

Maxitrol M511 and M611 Low Fire Bypass Screw

Firing Mode

Low Fire

Modulation

High Fire

Volts DC

0 to 5 VDC

5 to 15 VDC

15 to 20 VDC

Mod Valve Voltage Summary

Main Burner Adjustment

1. Once the pilot has been properly established, the manifold gas pressure or temperature rise should be adjusted to jobsite conditions. The gas pressure regulator (integral to the combination gas control on size

1-3 heaters and located in the modulating valve on size 4-5 heaters) is adjusted at the factory for average gas

conditions. It is important that the gas be supplied to the burner in accordance with the input rating on the rating plate.

2. Create a high fire call for heat. This should be done with the blower on and all gas controls on. High fire can be achieved by removing the wire at terminal #4 (remove wires #2 and #4 for Maxitrol 44 systems) from the Maxitrol 14 amplifier.

3. The manifold pressure should be checked			Average Manifold Pressure vs. Firing Rate/Ft. of Burner
at the pressure tap downstream of the
		6.00
modulating valve. The graph to the right
indicates the proper manifold pressure for		5.00
the desired amount of BTUs per foot of	(in. w.c.)		Natural Gas	Propane Gas
burner. For natural gas systems, the high		4.00
fire manifold pressure should not exceed 5		3.00
in. w.c. For propane gas, the high fire	Pressure
manifold pressure should not exceed 2.5		2.00
in. w.c. Another method of checking high	Manifold
fire is to measure the temperature rise of		1.00
the unit. The temperature rise should be
set to design conditions and typically is		0.00
minimum 70°F.
4. Remove the cap from the combination gas		-1.00
		0	100000	200000	300000	400000	500000	600000
valve regulator adjustment (size 1-3) or			Firing Rate (BTU/Hr/Ft. of Burner)

the cap from the MR212 valve (size 4-5).

Using the regulator pressure adjusting screw, adjust the high fire manifold pressure to 5 in. w.c. maximum for natural gas and 2.5 in. w.c. maximum for propane gas. High fire should be set to generate the desired temperature rise. If the high fire screw is at the end of its adjustment and more pressure is needed, then adjust the main building gas pressure regulator spring (located external to the unit) to achieve the proper manifold pressure. Turning the regulator screw clockwise will increase pressure and counter-clockwise will decrease pressure. Remember -

The high fire DC voltage should read 12 VDC minimum and should typically be 15 VDC on the Flame Safety Controller test jacks.

5.Reconnect the wire on the Maxitrol 14 amplifier at terminal #4 (wires #2 and #4 for Maxitrol 44).

6.The low fire manifold pressure must now be set. Low fire can be achieved

by removing the wire at terminal #5 from the Maxitrol 14 amplifier (remove #8 for Maxitrol 44). Check the low fire flame signal to ensure that the DC voltage is 12 VDC minimum on the Flame Safety Controller test jacks.

7.Using the bypass screw (located on the side of the M511 and M611 valves, and under the cap of the MR212 valve), adjust low the low fire manifold pressure until there is a very thin flame along the entire length of the burner. No dark spots should be seen in the burner. The burner may be observed through the view-port located on the external wall of the heater. Replace the cap to the Maxitrol valve and restore all of the original wiring on the

Maxitrol amplifier and gas components.

8. A final gas leak check shall be performed to verify the gas-tightness of the heater’s components and piping under normal operating conditions. This can be done by measuring the gas pressure at the ¼” gas plug just downstream of the modulating valve.

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