All installations and services must be performed by qualified service personnel.
temperature stability. If the chimney is on the homes exterior and condensing occurs, the chimney may be insulated around its exterior to help the flue hold its temperature. Also, check to see if the chimney is too large for the flue gases to heat, if so reduce to proper size by lining. Be sure to use stainless steel liners such as types 430, 304 or for the toughest corrosion resistant type 316. If the chimney is the correct size for the unit and condensing still occurs then further insulating of the chimney must occur or the efficiency of the furnace may have to be reduced to raise the chimney temperature.
More detailed information may be obtained from the current ASHRAE Equipment Handbook.
G. REPLACING AN EXISTING FURNACE FROM A COMMON VENT
When an existing furnace is removed from a common vent serving other appliances, the vent system is likely too large to safely vent the remaining attached appliances. If only two appliances remain on the venting system, then the system may be sized with the venting tables in the NFGC of this manual. If more than two appliances remain, then the following steps shall be followed with each appliance remaining connected to the common venting system placed in operation, while the other appliances remaining connected to the common venting system are not in operation.
a. Seal off any unused opening(s) in the common venting system.
b. Visually inspect the venting system for proper size and horizontal pitch and determine there is no blockage or restriction, leakage, corrosion and other deficiencies which could cause an unsafe condition.
c. Insofar as is practical, close all building doors and windows and all doors between the space in which the appliances remaining connected to the common venting system are located and other spaces of the building. Turn on clothes dryers and any appliance not connected to the common venting system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will operate at maximum speed. Do not operate a summer exhaust fan. Close fireplace dampers.
d. Follow the lighting instructions. Place the appliance being inspected in operation. Adjust thermostat so appliance will operate continuously.
e. Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use the flame of a match or candle or smoke from a cigarette, cigar or pipe.
f. After it has been determined that each appliance remaining connected to the common venting system properly vents when tested as outlined above, return doors, windows, exhaust fans, fireplace dampers and any other gas- burning appliance to their previous conditions of use.
g. If the improper venting is observed on any of the appliances during the above testing, the common vent system must be corrected. Follow the steps outlined in the National Fuel Gas Code, NFPA 54/ANSI
H. GENERAL GAS PIPING
WARNING: Because of the potential of odorant fade, a gas leak may not be detected by smell. If this furnace is installed below grade, contact your gas supplier for a gas detector.
All gas piping and testing must be performed by a qualified installer or service person. The installation must comply with local codes, these instructions and The National Fuel Gas Code NFPA54/ANSI
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