Hi, I am installing an 80% eff. forced air furnace and I need to put a liner in the chimney. What is a good product to use? Are there any tricks to installing one? Can you vent both a 4 inch furnace and a 3 inch water heater in the same liner? Thanks, Dave
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Replies
I'm not sure what you mean by what is a good product to use, you use a chimney liner. You can run both a furnace and water heater through one, but you have to size it correctly. When you pick up your liner you will need to know the length of the chimney, the BTU's of each unit and how they are vented(gravity or fan assisted). Also you must be very careful installing it down the chimney. First remove the liner from the box and stretch it out. Then tie a rope to one end of it. run the rope down the chimney. You will need two people, one down and one up. the guy at the bottom will more guide the liner than pull it. the guy on top will also guide the liner and keep it from getting caught on anything. Becareful not to rip the liner or it will be useless.
Edited 10/18/2004 9:43 pm ET by MSA1
Art when you are installing a liner and you have a friend sticking his hand through a thimble, maybe holding a mirror or flashlight to see, make sure you do not drop the liner. It will be like a guillotine and cut your friends hand off. Heard of it happening. If your liner is very light weight it may not be a problem. Better safe than captain hooks ex friend.
Edited 10/18/2004 10:19 pm ET by catfish25
Edited 10/19/2004 6:49 am ET by catfish25
Can you? Local codes may vary, but that is common and accepted in my area.
Be sure to use a Y, not a T.
In theory, an 80+ isn't supposed to pressurize the flue, just control the flow of air thru the heat exchanger, but I have seen them blow furnace flue gases out the water heater bonnet.
And be sure both vent properly after installation. Close all doors and windows, fire each independently and together, run house fans, all the while measuring the draft in each flue - each should be at least 0.01 water column inches, and no more that .03 - .04.
You can follow the GRI/GAMA venting tables, but be aware that they don't guarantee the tables will actually work:
"The user should realize that no safety factors have been included in the VENT - II calculation routines for vent capacities. The results will be reasonably accurate for new, well defined vent configurations under transient-cycling or steady - state conditions. However, the field performance of vent systems can be adversely affected by installation peculiarities, outside wind conditions, house tightness, leaky vents, other exhausting appliance, partial blockage of vent pipe, or other conditions. There fore, appliance vent designer should use good engineering judgment in making allowances for the various perturbations which may occur in the field.
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