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Advice Needed re: Chimney Liner for Oil Furnace

11K views 3 replies 2 participants last post by  #CARRIERMAN 
#1 ·
Hi, Our home has an oil furnace and oil hot water heater. They both used to vent through the same 8" square masonry chimney, but the chimney cleaner found some large gaps between the flue tiles and recommended a chimney liner. We had the work done, but I'm worried that the liner they installed is too small. Both the furnace and the water heater had 6" round vent pipes. In order to connect them to the liner, they made a "Y" connection between the appliances into one 6" round pipe, then reduced that to 5" and connected it to the liner. So we've gone from two 6" stacks to one 5" stack. It seems to be drawing fine, but I'm worried about the possibility of backdrafts, carbon monoxide, etc. The heater is 120,000 BTU max but has a .85 gallon/hour nozzle, and the water heater is a 30 gallon unit with a smaller oil burner. (I don't know the BTUs for the water heater.) The chimney is approximately 30 feet high.
If anyone can advise us whether this is a safe installation, I'd appreciate it.

Thanks,
Mike
 
#2 ·
Hi Mike R

You need to have them come back and put in an 8" flue. You are never supposed to go smaller on the flue than the appliances they are connected to. The ratio we use for gas appliances is add 1" for the secondary appliance which is usually the water heater. But for oil or wood you add 2" for the secondary appliance. You didn't say what type of pipe they installed, but if it is exposed it has to be the high temp stainless. A standard type B pipe will melt under the heat. Hope this helps.

Good luck
Rusty
 
#3 ·
Thanks, and an answer

Hi Rusty,

Thanks for your helpful response. The chimney liner is never exposed, but runs up through the existing masonry chimney. Hopefully it is the high temperature steel, but I will definitely ask them to install a larger liner.

Thanks,
Mike
 
#4 ·
Hi Mike R

I will be able to sleep better knowing you are adressing this. Just make sure they use the high temp stainless liner for wood, pellet, and oil. Outside of that you should be good to go for years.

Good luck
Rusty
 
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