Carrier 48MA/50ME016-040 specifications Pressure Adjustment Natural GAS, Mgv

		LEGEND
GV	Ð Gas Valve (Zone Module)
MB	Ð Main Burner
MGV	Ð	Main Manual Gas Valve
PB	Ð	Pilot Burner

NOTE: Unit is equipped with a forced-draft blower and the following safety de-

vices: forced-draft air¯ow switch, ¯ame roll-out protection switch, combustion chamber access door switch, heating limit switches, and spark-ignited auto- matic pilots. All of these switches are located in the heating section and must be in safe condition before the main burners can ignite.

Fig. 32 Ð Gas Piping Schematic (10-Zone 48MA Unit Shown Ð 8- and 12-Zone Units Similar)

3.Turn system switch to ON position. Set each zone ther- mostat at setting to call for heat. Pilot will ignite.

NOTE: A time-delay relay will shut unit down in 180 sec- onds if main manual gas valve is not open.

4.Remove burner access panel.

5.Remove screw-cap cover on zone gas valve to expose pi- lot adjusting screw. With a small screwdriver, turn ad- justing screw until ¯ame is correct height. Replace screw- cap cover on gas valve.

6.Turn system switch to OFF position.

7.Reconnect main gas valve wires to W1 on pilot switches.

8.Set system switch at ON position, and set zone thermo- stats as desired.

9.Replace burner access panel.

PRESSURE ADJUSTMENT (NATURAL GAS)

1.Turn control circuit service switch to OFF position, and set thermostat at lowest setting.

2.Remove the 2 heating control access panels and the burner access panel.

3.Remove plug from zone manifold pressure tap. Connect suitable gage. Route gage line through pilot switch grom- met so that burner access panel may be closed.

4.Close burner access panel.

5.Turn control circuit service switch to ON position. Set zone thermostat to call for heat. After pilot is proven, burner will operate.

NOTE: A time-delay relay will shut unit down in 180 seconds if main manual gas valve is not open.

6.Remove screw cap from zone module gas valve pres- sure regulator to expose pressure adjustment screw.

7.Turn pressure adjustment screw with a small screw- driver until 3.5 in. wg is achieved.

8.Replace screw cap.

9.Turn control circuit service switch to OFF position and set zone thermostat at lowest position.

10.Remove burner access panel. Disconnect gage line con- nection on zone manifold. Replace plug in manifold pres- sure tap.

11.Repeat steps 3-10 for each heating module.

12.Replace all unit panels. Turn control circuit service switch to ON position, and set zone thermostat as desired.

Main Burner Adjustment (48MA) Ð Flame should appear clear blue (almost transparent) in color with a well- de®ned inner cone. If there is insufficient primary air, ¯ame will be yellow tipped. If there is too much primary air, ¯ame will be well de®ned but have a tendency to lift or dance off ports. Allow unit to operate for at least 15 minutes before making ®nal primary air adjustment.

ORIFICE ALIGNMENT Ð The most likely cause of burner ¯ame ¯ashback is misalignment of the burner ori®ce. Be sure that ori®ce points straight down the burner.

PRIMARY AIR ADJUSTMENT Ð Observe ¯ame charac- teristics through view ports in main burner access panel. Turn off main manual gas valves in burner control compartment. Then remove main burner access panel.

If Flame Is Yellow (Insufficient Primary Air) Ð Turn spoiler screw counterclockwise about 4 turns for each 1¤4 in. of change in spoiler length. See Fig. 33 for spoiler screw location.

If Flame Lifted Off Ports (Too Much Primary Air) Ð Turn spoiler screw clockwise about 4 turns for each 1¤4 in. of change in spoiler length. See Fig. 33 for spoiler screw location.

Replace main burner access panel and turn on main manual gas valves. Observe ¯ame characteristics. Repeat these pro- cedures as required until correct ¯ame characteristics are achieved.

Outdoor-Air Thermostat Adjustment (50ME with Electric Heat) Ð The outdoor-air thermostat (OAT) is located in upper right-hand area of zone control board (Fig. 34 and 35), is factory set at 40 F, and is adjustable be- tween −10 F and 55 F.

36