Gas Furnace Flue Pipe Sizing

Clearance installations must provide the proper clearances to combustible materials as specified in the appropriate underwriters laboratories inc.

Gas furnace flue pipe sizing. The different types of venting. To make it simple if you have a gas water heater with a 3 draft hood and a furnace with a 4 flue collar connected to the same chimney flue you d calculate that chimney flue size based on the 3 draft hood the smaller of two. Reduce furnace flue vent connector size below furnace outlet size. 6 flue 28 27 square inches 8 flue 50 27 square inches total 78 54 square inches.

Higher btuh furnaces produce higher flue gas temperatures. So let s calculate or why don t we skip those calculations and i ll give you the answers. The size would depend on your furnace s flue pipe connection. Proper furnace water heater venting is an extremely important issue which depends on the performance of the house chimney chimney flue or other exhaust assemblies.

I have a single 2650 sq ft home that was once subdivided one side had a 133 000 btu oil boiler and i have a 115 000 gas boiler. I want to purchase a new boiler to heat both sides which i have zoned. In contrast modern high efficiency condensing furnaces exhaust much cooler gasses and need only plastic pipe materials such as pvc cpvc or abs for their exhaust vents some high efficiency furnaces also include a plastic pipe for intake area and all types. Illustrations of proper gas fired water heater venting using type b double wall vent pipe through a roof above or through a chimney below include details for the flue vent connector such as the requirement of a minimum vent connector upwards slope of 1 4 per foot of horizontal run.

Oct 13 2012 brent said. Flue gas temperature flue gas temperature affects vent operation because the hotter the gases are the lighter they are. You would core a hole 1 4 to 1 2 inch bigger than the outer diameter of the pipe. The pipe then slips into the hole and is sealed with a high temperature silicone caulk.

The conditions explained in this post also apply to the wood burning appliances. To determine the main flue size refer to figure 3 and locate the square inch area of each individual flue size. Let s say you have a job where you combine a furnace or boiler 8 flue with a water heater 6 flue. Consequences of improperly assembled vent pipes problematic chimney flue deteriorating chimney walls can be sometimes fatal fire and carbon.

When we are talking about gas furnace vent pipe code we need to talk about the different types of the vents first after all you want to keep your family safe from harm. The design btuh british thermal units per hour capacity of the vent plus the furnace input and efficiency are factors affecting the temperature of the flue gases. Flue gas temperatures that do not exceed 400 degress fahrenheit above ambient for category i appliances.