Manual
27
A gas detecting warning system is the only reliable way to detect a
propane gas leak. Rust can reduce the level of odorant in propane
gas. Do not rely on your sense of smell. Contact a local propane
gas supplier about installing a gas detecting warning system. If
the presence of gas is suspected, follow the instructions on Page
4 of this manual.
All propane gas equipment must conform to the safety standards
of the National Board of Fire Underwriters, NBFU Manual 58.
For satisfactory operation, propane gas pressure must be 11 inch
w.c. at the furnace manifold with all gas appliances in operation.
Maintaining proper gas pressure depends on three main factors:
1. Vaporization rate, depending on temperature of the liquid,
and “wetted surface” area of the container or containers.
2. Proper pressure regulation. (Two-stage regulation is
recommended for both cost and efficiency).
3. Pressure drop in lines between regulators, and between
second stage regulator and the appliance. Pipe size will
depend on length of pipe run and total load of all appliances.
Complete information regarding tank sizing for vaporization, rec-
ommended regulator settings, and pipe sizing is available from
most regulator manufacturers and propane gas suppliers.
Since propane gas will quickly dissolve white lead and most stan-
dard commercial compounds, special pipe dope must be used.
Shellac-based compounds resistant to the actions of liquefied pe-
troleum gases such as Gasolac
®
, Stalactic
®
, Clyde’s
®
or John
Crane
®
are satisfactory.
Refer to the following illustration for typical propane gas installa-
tions.
200 PSIG
Maximum
5 to 15 PSIG
(20 PSIG Max.)
Continuous
11" W.C.
Second Stage
Regulator
First Stage
Regulator
Propane Gas Installation (Typ.)
Sizing Between First and Second Stage Regulator*
Maximum Propane Capacities listed are based on 2 psig pressure drop at 10 psig setting.
Capacities in 1,000 BTU/hour.
Pipe or Nominal Pipe Size
Tubing Tubing Size, O.D. Type L Schedule 40
Length, 3/8" 1/2" 5/8" 3/4" 7/8" 1/2" 3/4"
Feet
10 730 1,700 3,200 5,300 8,300 3,200 7,500
20 500 1,100 2,200 3,700 5,800 2,200 4,200
30 400 920 2,000 2,900 4,700 1,800 4,000
40 370 850 1,700 2,700 4,100 1,600 3,700
50 330 770 1,500 2,400 3,700 1,500 3,400
60 300 700 1,300 2,200 3,300 1,300 3,100
80 260 610 1,200 1,900 2,900 1,200 2,600
100 220 540 1,000 1,700 2,600 1,000 2,300
125 200 490 900 1,400 2,300 900 2,100
150 190 430 830 1,300 2,100 830 1,900
175 170 400 780 1,200 1,900 770 1,700
200 160 380 730 1,100 1,800 720 1,500
To convert to capacities at 15 psig settings - multiply by 1.130
To convert to capacities at 5 psig settings - multiply by 0.879
Propane Gas Piping Chart I
Sizing Between Single or Second Stage Regulator and Appliance*
Maximum Propane Capacities Listed are Based on 1/2" W.C. pressure drop at 11" W.C. setting.
Capacities in 1,000 BTU/hour.
Pipe or Nominal Pipe Size
Tubing Tubing Size, O.D. Type L Schedule 40
Length, 3/8" 1/2" 5/8" 3/4" 7/8" 1-1/8" 1/2" 3/4" 1" 1-1/4" 1-1/2"
Feet
10 39 92 199 329 501 935 275 567 1,071 2,205 3,307
20 26 62 131 216 346 630 189 393 732 1,496 2,299
30 21 50 107 181 277 500 152 315 590 1,212 1,858
40 19 41 90 145 233 427 129 267 504 1,039 1,559
50 18 37 79 131 198 376 114 237 448 913 1,417
60 16 35 72 121 187 340 103 217 409 834 1,275
80 13 29 62 104 155 289 89 185 346 724 1,066
100 11 26 55 90 138 255 78 162 307 630 976
125 10 24 48 81 122 224 69 146 275 567 866
150 9 21 43 72 109 202 63 132 252 511 787
200 8 19 39 66 100 187 54 112 209 439 665
250 8 17 36 60 93 172 48 100 185 390 590
*Data in accordance with NFPA pamphlet NO. 54
Propane Gas Piping Chart II
XIII. CIRCULATING AIR & FILTERS
DUCTWORK - AIR F LOW
Duct systems and register sizes must be properly designed for the
CFM and external static pressure rating of the furnace. Design the
ductwork in accordance with the recommended methods of “Air
Conditioning Contractors of America” Manual D.
Install the duct system in accordance with Standards of the Na-
tional Board of Fire Underwriters for the Installation of Air Condi-
tioning, Warm Air Heating and Ventilating Systems. Pamphlets No.
90A and 90B.
A closed return duct system must be used, with the return duct
connected to the furnace. NOTE:
Ductwork must never be attached
to the back of the furnace. Flexible joints may be used for supply
and return connections to reduce noise transmission. To prevent
the blower from interfering with combustion air or draft when a
central return is used, a connecting duct must be installed be-
tween the unit and the utility room wall. Never use a room, closet,
or alcove as a return air chamber.
NOTE: Two side openings or a side opening and bottom opening
are required for airflow delivery of 1800 CFM and greater.
CHECKING DUCT S TATIC
Refer to your furnace rating plate for the maximum ESP (external
duct static) rating.
Total external static refers to everything external to the furnace cabi-
net. Cooling coils, filters, ducts, grilles, registers must all be con-
sidered when reading your total external static pressure. The sup-
ply duct pressure must be read between the furnace and the cool-
ing coil. This reading is usually taken by removing the “A” shaped
block off plate from the end on the coil; drilling a test hole in it and
reinstalling the block off plate. Take a duct static reading at the test
hole. Tape up the test hole after your test is complete. The negative
pressure must be read between the filter and the furnace blower.
Too much external static pressure will result in insufficient air that
can cause excessive temperature rise. This can cause limit switch
tripping and heat exchanger failure.
To determine total external duct static pressure, proceed as fol-
lows;
1. With clean filters in the furnace, use a draft gauge (inclined
manometer) to measure the static pressure of the return duct
at the inlet of the furnace. (Negative Pressure)
2. Measure the static pressure of the supply duct. (Positive Pres-
sure)
3. The difference between the two numbers is .4” w.c.