Bryant 312AAV/JAV Altitude Derate Multiplier for U.S.A, Redundant Automatic Gas Control Valve

Table 11 – Altitude Derate Multiplier for U.S.A.

ALTITUDE	PERCENT	DERATE MULTIPLIER
FT. (M)	OF DERATE	FACTOR*
0–2000	0	1.00
(0--- 610)
2001–3000	8–12	0.90
(610--- 914)
3001–4000	12–16	0.86
(914--- 1219)
4001–5000	16–20	0.82
(1219--- 1524)
5001–6000	20–24	0.78
1524--- 1829)
6001–7000	24–28	0.74
(1829--- 2134)
7001–8000	28–32	0.70
(2134--- 2438)
8001–9000	32–36	0.66
(2438--- 2743)
9001–10,000	36–40	0.62
(2743--- 3048)

*Derate multiplier factors are based on midpoint altitude for altitude range.

Low NOx models in downflow or horizontal positions MUST use Table 16 (21,000 BTUH per burner). See input listed on rating plate.

a.Obtain average yearly gas heat value (at installed altitude) from local gas supplier.

b.Obtain average yearly gas specific gravity from local gas supplier.

c.Find installation altitude in Table 15 or 16.

d.Find closest natural gas heat value and specific gravity in Table 15 or 16.

e.Follow heat value and specific gravity lines to point of intersection to find orifice size and low-and high-heat manifold pressure settings for proper operation.

f.Check and verify burner orifice size in furnace. NEVER ASSUME ORIFICE SIZE. ALWAYS CHECK AND VERIFY.

g.Replace orifice with correct size, if required by Table 15 or 16. Use only factory-supplied orifices. See EXAMPLE 1.

EXAMPLE 1: (0-2000 ft. / 0-610 M altitude)

For 22,000 Btuh per burner application, use Table 15. Heating value = 1000 Btuh/cu ft.

Specific gravity = 0.62 Therefore: Orifice No. 43*

Manifold pressure: 3.7-In. W.C. for high-heat 1.6-In. W.C. for low-heat

*Furnace is shipped with No. 43 orifices. In this example all main burner orifices are the correct size and do not need to be changed to obtain proper input rate.

3.Adjust manifold pressure to obtain low fire input rate. (See Fig. 48.)

a.Turn gas valve ON/OFF switch to OFF.

b.Remove manifold pressure tap plug from gas valve.

c.Connect a water column manometer or similar device to manifold pressure tap.

d.Turn gas valve ON/OFF switch to ON.

312AAV

A06667

Fig. 48 - Redundant Automatic Gas Control Valve

e.Move setup switch LHT (SW-1) on furnace control to ON position to lock furnace in low-heat operation. (See Fig. 33 and Table 10.)

f.Manually close blower door switch.

g.Jumper R and W/W1 thermostat connections on control to start furnace. (See Fig. 33.)

h.Remove regulator adjustment cap from low-heat gas valve pressure regulators. (See Fig. 48.) Turn low-heat adjusting screw (3/16 in. (5 mm) or smaller flat tipped screwdriver) counterclockwise (out) to decrease input rate or clockwise (in) to increase input rate.

NOTE: DO NOT set low-heat manifold pressure less than 1.4-In. W.C. or more than 1.7-In. W.C. for natural gas. If manifold pressure is outside this range, change main burner orifices.

i.Install low-heat regulator adjustment cap.

j.Leave manometer or similar device connected and pro- ceed to Step 4.

NOTE: If orifice hole appears damaged or it is suspected to have been re-drilled, check orifice hole with a numbered drill bit of correct size. Never re-drill an orifice. A burr-free and squarely aligned orifice hole is essential for proper flame characteristics.

4. Verify natural gas low-heat input rate by clocking meter.

NOTE: Gas valve regulator adjustment caps must be in place for proper input to be clocked.

a.Turn off all other gas appliances and pilots served by the meter.

b.Run for 3 minutes in low-heat operation.

c.Measure time (in sec) for gas meter to complete 1 revolu- tion and note reading. The 2 or 5 cubic feet dial provides a more accurate measurement of gas flow.

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