A
If a flexible liner is to be used, it must be made of the proper materials:
•For most residential applications, an aluminum liner should be acceptable.
•If the combustion air supplied to the furnace will be contaminated with compounds containing chlorine or fluorine, a liner of AL294C stainless steel should be used. Common sources of chlorine and fluorine com- pounds include indoor swimming pools and chlorine bleaches, paint strippers, adhesives, paints, varnishes, sealers, waxes (which are not yet dried) and solvents used during construction and remodeling. Various commercial and industrial processes may also be sources of chlorine/fluorine compounds.
•Heavier gauge 300 and 400 series stainless steel liners were developed for use with oil or solid fuel appliances. They are not suitable for use with
For sizing of flexible liners, see Note 22 and the tables in the National Fuel Gas Code, NFPA 54/ANSI Z223.1 - latest edition and in the National Standard of Canada, CAN/CGA B149.1 and CAN/CGA B149.2 - latest editions and amendments.
To install the liner, read and follow the liner manufacturer’s instructions and your local codes. Excess liner length should be pulled out of the chimney and cut off. Use caution when doing this, as the cut edges of flexible liners may be sharp. Do not spiral excess liner inside of the chimney. Support the liner as recommended by the liner manufac- turer.
Some manufacturers of flexible liners offer an insulation sleeve designed to be added to the liner before it is installed in the chimney. (Poured insulation, either vermiculite or other materials, is no longer recommended.) Insulation will need to be added to the flexible liner if:
•It is required by the liner manufacturer’s instructions.
•The previous liner was properly sized and installed, and suffered from condensation damage.
•It is required by your local building codes.
Even if none of those three conditions exist which require additional liner insulation, the installer may wish to con- sider it if:
•The local climate is very cold
•The chimney is very tall
•The vent connectors used are very long or have a large number of elbows
•Local experience indicates that flexible liners installed without insulation are likely to have condensation problems.
Insulation must be selected and installed in accordance with the liner manufacturer’s instructions.
Finally, cap the chimney and terminate the liner in accor- dance with the liner manufacturer’s instructions.
VI. Gas Piping
The rating plate is stamped with the model number, type of gas and gas input rating. Make sure the furnace is equipped to operate on the type of gas available.
| Inlet Gas Pressure |
Natural | Min. 5.0" W.C., Max. 10.0" W.C. |
Propane | Min. 11.0" W.C., Max. 14.0" W.C. |
Inlet gas pressure must not exceed the maximum value shown in table above.
NOTE: Adjusting the minimum supply pressure below the limits in the above table could lead to unreliable ignition.
Gas input to the burners must not exceed the rated input shown on the rating plate. Overfiring of the furnace could result in premature heat exchanger failure. Gas pressures in excess of 14 inches water column could result in perma- nent damage to the gas valve.
IMPORTANT NOTE: The furnace will naturally derate itself with altitude. Do not attempt to increase the firing rate by changing orifices or increasing the manifold pressure. This can cause poor combustion and equipment failure.
At all altitudes, the manifold pressure must be within 0.3 inches WC of that listed on the “Specification Sheet” for the fuel used. At all altitudes and with either fuel, the air temperature rise must be within the range listed on the furnace nameplate.
GAS PIPING
IMPORTANT NOTE: To avoid possible unsatisfactory op- eration or equipment damage due to underfiring of equip- ment, do not undersize the natural/propane gas piping from the meter/tank to the furnace. Include all appliances which may be operated simultaneously when sizing a trunk line.
The gas pipe supplying the furnace must be properly sized based on gas flow required, specific gravity of the gas and length of the run. The gas line installation must comply with local codes, or in the absence of local codes, with the latest edition of the National Fuel Gas Code ANSI Z223.1.
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (CFH)
Length of |
| Nominal Black Pipe Size |
| ||
Pipe in Feet | 1/2" | 3/4" | 1" | 1 1/4" | 1 1/2" |
10 | 132 | 278 | 520 | 1050 | 1600 |
20 | 92 | 190 | 350 | 730 | 1100 |
30 | 73 | 152 | 285 | 590 | 980 |
40 | 63 | 130 | 245 | 500 | 760 |
50 | 56 | 115 | 215 | 440 | 670 |
60 | 50 | 105 | 195 | 400 | 610 |
70 | 46 | 96 | 180 | 370 | 560 |
80 | 43 | 90 | 170 | 350 | 530 |
90 | 40 | 84 | 160 | 320 | 490 |
100 | 38 | 79 | 150 | 305 | 460 |
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on 0.60 Specific Gravity Gas)
CFH = BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
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