Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a venting system commonly run with separate gas ap- pliances, the venting system is likely to be too large to properly vent the remaining attached appliances.
Conduct the following test while each appliance is operat- ing and the other appliances (which are not operating) re- main connected to the common venting system. If the venting system has been installed improperly, you must correct the system as indicated in the general venting re- quirements section.
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each appliance connected to the venting system being placed into operation could result in carbon mon- oxide poisoning or death.
The following steps shall be followed for each ap- pliance connected to the venting system being placed into operation, while all other appliances connected to the venting system are not in operation:
1 − Seal any unused openings in the common venting sys- tem.
2 − Inspect the venting system for proper size and horizontal pitch. Determine that there is no blockage, restriction, leakage, corrosion, or other deficiencies which could cause an unsafe condition.
3 − Close all building doors and windows and all doors be- tween the space in which the appliances remaining connected to the common venting system are located and other spaces of the building. Turn on clothes dry- ers and any appliances not connected to the common venting system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will oper- ate at maximum speed. Do not operate a summer ex- haust fan. Close fireplace dampers.
4 − Follow the lighting instructions. Turn on the appliance that is being inspected. Adjust the thermostat so that the appliance operates continuously.
5 − After the main burner has operated for 5 minutes, test for leaks of flue gases at the draft hood relief opening. Use the flame of a match or candle, or smoke from a cigarette, cigar, or pipe.
6 − After determining that each appliance connected to the common venting system is venting properly, (step 3) return all doors, widows, exhaust fans, fireplace damp- ers, and any other gas−burning appliances to their pre- vious mode of operation.
7 − If a venting problem is found during any of the preced- ing tests, the common venting system must be modi- fied to correct the problem.
Resize the common venting system to the minimum vent pipe size determined by using the appropriate tables in Appendix G. (These are in the current stan- dards of the National Fuel Gas Code ANSI Z223.1.
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