Lp Conversion; Adjusting Or Checking Furnace Input - McQuay Maverick I MPS006AG Series Installation And Maintenance Manual

IMPORTANT: Check the rating plate to make certain the unit is
equipped to burn the type of gas supplied. Care should be taken
after installation of this equipment that the gas control valve not
be subjected to high gas supply line pressure.
In making gas connections, avoid strains as they may cause
noise and damage the controls. A backup wrench is required to
be used on the valve to avoid damage.
Table 2: Gas Pipe Capacity Table (Cu. Ft./Hr.)
Nominal
Equivalent Length of Pipe, Feet
Iron Pipe
Size,
10 20
Inches
1 ⁄ 132 92
2
⁄ 278 190 152
3
4
1 520 350 285
1 1 ⁄ 1,050 730 590
4
1 1 ⁄ 1,600 1,100 890
2
The capacities of gas pipe of different diameters and lengths in
cu. ft. per hr. with pressure drop of 0.3 in. and specific gravity
of 0.60 (natural gas) are shown in Table 2.
After determining the pipe length, select the pipe size which
will provide the minimum cubic feet per hour required for the
gas input rating of the furnace. By formula:
Cu. Ft. Per Hr. Required =
The gas input of the furnace is marked on the furnace rating
plate. The heating value of the gas (BTU/FT
determined by consulting the local natural gas utility or the
L.P. gas supplier.

LP Conversion

▲ ▲
!
This unit is equipped at the factory for use on natural gas
only. Conversion to LP gas requires a special kit supplied by
the distributor or manufacturer. Mailing addresses are listed
on the furnace rating plate, parts list and warranty. Failure to
use the proper conversion kit can cause fire, carbon
monoxide poisoning, explosion, personal injury, property
damage or death.
Convert the valve to use liquefied petroleum (LP) gas by
replacing the pressure regulator spring with the conversion kit
spring. This LP kit spring allows the regulator to maintain the
proper manifold pressure for LP gas. The correct burner LP
orifices are included in the kit. See Figure 13.
IMPORTANT: To remove the gas valve, remove the four screws
securing the manifold pipe to the burner tray. Remove the manifold
pipe with gas valve attached. See Figure 14.
NOTE: Order the correct LP conversion kit from the furnace
manufacturer. See Conversion Kit Index shipped with unit for
proper LP kit number. Furnace conversion to LP gas must
be performed by a qualified technician.
12
30 40 50 60 70
73 63 56 50 46
130 115 105 96
245 215 195 180
500 440 400 370
760 670 610 560
Gas Input of Furnace
(BTU/HR)
Heating Value of Gas
3
(BTU/FT )
3
) may be
DANGER
Table 3: LP Gas Pipe Capacity Table (Cu. Ft./Hr.)
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied
petroleum gases (at 11 inches water column inlet pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
Nominal
Iron Pipe
Size, Inches 10 20
1/2 275 189
3/4 567 393
1 1,071 732
1-1/4 2,205 1,496 1,212 1,039
1-1/2 3,307 2,299 1,858 1,559 1,417 1,275 1,181 1,086 1,023
2 6,221 4,331 3,465 2,992 2,646 2,394 2,205 2,047 1,921 1,811 1,606 1,496
80
Example (LP): Input BTU requirement of unit, 150,000
43
Equivalent length of pipe, 60 ft. = 3/4 IPS required.
90
170
350

Adjusting or Checking Furnace Input

530
– Natural Gas Line Pressure 5 - 10.5 W.C.
– LP Gas Line Pressure 11 - 13 W.C.
– Natural Gas Manifold Pressure 3.5 W.C
– LP Gas Manifold Pressure - 10 W.C.
Supply and manifold pressure taps are located on the gas valve
body 1/8 N.P.T. and on the manifold.
Use a properly calibrated manometer gauge for accurate gas
pressure readings.
Only small variations in the gas flow should be made by
means of the pressure regulator adjustment. Furnaces
functioning on LP gas must be set by means of the tank or
branch supply regulators. The furnace manifold pressure
should be set at 10 W.C. at the gas control valve.
To adjust the pressure regulator, remove the regulator cap and
turn the adjustment screw clockwise to increase pressure or
counterclockwise to decrease pressure. Then replace the
regulator cap securely.
Any necessary major changes in the gas flow rate should be
made by changing the size of the burner orifices. To change
orifice spuds, shut off the manual main gas valve and remove
the gas manifold.
For elevations up to 2,000 feet, rating plate input ratings
apply. For high altitudes (elevations over 2,000 ft.), see
conversion kit index 92-21519-XX for derating and orifice
spud sizes.
Check of input is important to prevent over-firing of the
furnace beyond its design-rated input. NEVER SET
INPUT ABOVE THAT SHOWN ON THE RATING
PLATE. Use the following table or formula to determine
input rate.
Cu. Ft. Per Hr. Required =
Start the furnace and measure the time required to burn one
cubic foot of gas. Prior to checking the furnace input, make
certain that all other gas units are shut off, with the exception
of pilot burners. Time the meter with only the furnace in
operation.
Length of Pipe, Feet
30 40 50 60 70 80 90
152 129 114 103 96 89 83
315 267 237 217 196 182 173
590 504 448 409 378 346 322
913 834 771 724 677
Heating Value of Gas
(BTU/Cu. Ft.) x 3600
Time in Seconds
(for 1 Cu. Ft.) of Gas
100 125 150
78 69 63
162 146 132
307 275 252
630 567 511
976 866 787
IM 861