Carrier 48XL installation instructions d. Make sure model plug is installed

a.129secto. complete one revolution

b. 3600/129 = 27.9

c. 27.9 x 2 = 55.8 ft3 of gas flow/hr. d. 55.8 x 1050 = 58,590 Btuh input.

In this example, the nonfinal input rate for low stage is 58,500 Btu/hr, so the low stage manifold pressure is correctly set.

If the measured low stage rate is too low, increase the manifold pressure to increase rate. If the measured low stage rate is too high, decrease the manifold pressure to decrease rate.

NOTE: Double-check that UI is running on low stage gas heat while clocking the low stage firing rate.

4.Verify proper low stage gas heat temperature rise.

a.Furnace must operate within rise range listed on rating plate.

b.Select "COMFORT" or "EFFICIENCY" mode on UI.

"COMFORT" mode will provide a warmer supply air

temperature, while "EFFICIENCY" will provide lower gas consumption.

c.Make sure access panel is re-installed on the unit.

d. Measure supply and return temperatures as close to the

unit as possible. Subtract the return temperature from

the supply temperature to deternfine rise. Rise should fall within the range specified on the rating plate.

5.Adjust manifold pressure to obtain high stage input rate (See Fig. 19).

a.Set unit to run for 20 minutes in high-stage gas heat

operation using the "INSTALLER CHECKOUT" menu on the UI.

b.Remove regulator adjustment cap from high stage gas valve pressure regulator (See Fig. 19) and turn

high-stage adjusting screw (3/16 or smaller flat-tipped

screwdriver) counterclockwise (out) to decrease rate and clockwise (in) to increase input rate.

NOTE: DO NOT set high stage manifold pressure less than 3.2 IN.W.C. or more than 3.8 IN. W.C. for natural gas. If manifold pressure is outside this range, change main burner orifices.

c. Re-install high stage regulator adjustment cap.

d. Leave manometer connected.

6.Verify natural gas high stage input rate.

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

b.If unit is not running, set unit to run for 20 minutes in high stage gas heat operation using the "INSTALLER

CHECKOUT" menu on the UI.

c.Record number of seconds for gas meter to complete 1 revolution.

d.

Divide

number

of

seconds

in

step c. into

3600

(number

of seconds in 1 hour).

e.

Multiply

result

of

step

d. by

the number

of

cubic

feet

shown for one revolution of test dial to obtain cubic feet

of gas flow per hour.

f.

Multiply

result

of

step

f. by

Btu heating

value

of

the

gas

to obtain total measured input shown in Table 4.

(Consult

the

local

gas

supplier

if the

heating value of

gas is not known).

EXAMPLE:

Assume

a

90,000

high

stage

input

unit

is being

installed.

Assume

that

the

size

of the dial is 2 cubic

ft.,

one

revolution

takes

84

sec.,

and

the

heating

value

of

the

gas

is

1050

Btu/ft3. Proceed

as

follows:

a.

84 sec.

to

complete

one

revolution

b.

3600/84

= 42.9

c.

42.9

x

2 = 85.8

ft3

of

gas

flow/hr.

d.

85.8

x

1050

= 90,090

Btuh

input.

In this example, the nonfinal input rate for high stage is 90,000 Btu/hr, so the high stage manifold pressure is correctly set.

If the measured high stage rate is too low, increase the manifold pressure to increase rate. If the measured high stage rate is too high, decrease the manifold pressure to decrease rate.

NOTE: Double-check that User Interface is running on high stage gas heat while clocking the low stage firing rate.

7.Verify proper high stage gas heat temperature rise.

a.Furnace must operate within rise range listed on rating plate.

b.Make sure access panel is re-installed on the unit.

c.Measure supply and return temperatures as close to the unit as possible. Subtract the return temperature from the supply temperature to deternfine rise. Rise should fall within the range specified on the rating plate.

NOTE: If the temperature rise is outside the rating plate range, first check:

a. Gas input for low and high stage gas heat operation. b. Derate for altitude, if applicable.

c. Return and supply ducts for excessive restrictions causing static pressures in excess of .5 IN. W.C.

d. Make sure model plug is installed.

8.Final Check

a.Turn off gas to unit

b. Remove manometer from pressure tap.

c.Replace pipe plug on manifold (See Fig. 20). d. Turn on gas to unit.

e.Check for leaks.

CHECK GAS INPUT (PROPANE GAS)

Refer to propane kit installation instructions for properly checking gas input.

NOTE: For installations below 2,000 ft (610 m), refer to the unit rating plate for proper propane conversion kit. For installations

above 2,000 ft (610 m), contact your distributor for proper propane conversion kit.

CHECK BURNER FLAME

With burner access panel removed, observe the unit heating

operation. Watch the burner flames to see if they are light blue and

soft in appearance, and that the flames are approximately the same

for each burner. Propane will have blue flame (See Fig. 21). Refer

to the Maintenance section for information on burner removal.

MANIFOLD PIPE PLUG

099019

Fig. 20 - Burner Assembly

24