I don 39 t know what temperature your furnace flue pipe should run but an 80 efficiency furnace is not very efficient so i would expect that the flue pipe would run quite hot.
Furnace exhaust pipe temperature.
With a conventional gas furnace you should be at about 140 f 170 f at the supply plenum.
Exhaust temperature o f o c chemical oxidation.
These highly efficient furnaces have a heat exchanger and a condensing chamber that help maintain a considerably low temperature on the pipes.
Gas fired heating appliance no draft hood.
Natural gas fired heating appliance with draft hood.
To make it simple the typical combustion gas temperature for a 90 efficient furnace should be in the 100 to 130 degree f range.
This usually equates to a median pipe material temperature value of 86 to 100 degree f.
When this temperature starts to exceed 130 degree f it is usually an indication that there is a problem.
Also known as the induced draft fan this one has a fan that is located on the end of the pipe.
This is another affordable option for the heating solution.
Some building inspectors discourage taping up furnace clothes dryer and water heater flue joints so check your local building codes before using this tape especially when selling your home.
Liquefied petroleum gas fired heating appliance with draft hood.
You would have what is called a mid efficiency furnace basically a regular non efficient furnace that has a flue damper and sometimes a power exhaust added to reduce.
Sidewall venting when your new high efficiency condensing furnace is installed your contractor should take extra precautions to make sure all ventilation systems are properly placed and working correctly.
This temperature is an indication that your furnace is not running at maximum efficiency and you are losing heat up the chimney.
The low temperature residual flue gases vent outside through special plastic pipes.
However the temperature at the outlet of the furnace is dependent on the temperature of the incoming air.
Heat will seal the tape to the metal pipe as the temperature climbs.
Good up to 600 degrees f.
These different plastics have different maximum heat service temperatures.
When applied to a cooled down pipe.
A high efficiency furnace will be lower around 110 f 140 f.
Pvc has the lowest rating at 140 degrees fahrenheit cpvc has the highest at 194 degrees and abs falls in between at a maximum service temperature of 160 degrees.
It will draw in air for the combustion and then expel the fume outside.