Pressure Adjustment (Natural Gas); Main Burner Adjustment (48Ma); Outdoor-Air Thermostat Adjustment; (50Me With Electric Heat) - Carrier 48MA/50ME016-040 Installation, Start-Up And Service Instructions Manual

LEGEND
GV — Gas Valve (Zone Module)
MB — Main Burner
MGV — Main Manual Gas Valve
PB — Pilot Burner
Fig. 32 — Gas Piping Schematic (10-Zone 48MA Unit Shown — 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 flame 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.
NOTE: Unit is equipped with a forced-draft blower and the following safety de-
vices: forced-draft airflow switch, flame 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.
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) —
appear clear blue (almost transparent) in color with a well-
defined inner cone. If there is insufficient primary air, flame
will be yellow tipped. If there is too much primary air, flame
will be well defined but have a tendency to lift or dance off
ports. Allow unit to operate for at least 15 minutes before
making final primary air adjustment.
ORIFICE ALIGNMENT — The most likely cause of burner
flame flashback is misalignment of the burner orifice. Be sure
that orifice points straight down the burner.
PRIMARY AIR ADJUSTMENT — Observe flame 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) — Turn spoiler
screw counterclockwise about 4 turns for each
in spoiler length. See Fig. 33 for spoiler screw location.
If Flame Lifted Off Ports (Too Much Primary Air) — Turn
spoiler screw clockwise about 4 turns for each
in spoiler length. See Fig. 33 for spoiler screw location.
Replace main burner access panel and turn on main manual
gas valves. Observe flame characteristics. Repeat these pro-
cedures as required until correct flame characteristics are
achieved.
Outdoor-Air Thermostat Adjustment (50ME with
Electric Heat) —
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
Flame should
⁄ in. of change
1
4
⁄ in. of change
1
4
The outdoor-air thermostat (OAT) is