HVAC Questions? Ask an HVAC Expert for Answers ASAP
My name is XXXXX XXXXX I will glad to offer assistance today.
First - the furnace should be vented out a sidewall and not the chimney. As your friend mentioned the only way this would work is if you ran the pvc vent pipes all the way to top out chimney.
BUT, then where do you vent the water heater?
They will need to run intake and exhaust for new furnace out a side wall. Then they must run a chimney liner down the chimney for the water heater. Then the water heater will attach to this liner with 4" galvanized.
Also make sure they use BOTH the intake pipe and vent pipe for the furnace. That way you are not sucking in house air for the burner. It will come from outside..through the burners...out the furnace and to the outside via the vent pipe.
DO NOT vent into chimney. Please let me know if you have any concerns at all. I carry a code book with me.
The water heater is vented through the chimney just like the furnace.
I assume if they run a liner in the chimney then both the water heater and the chimney could continue to be vented through the chimney correct?
The furnace is located in the center of the house with no easy access to the outside wall in this rancher. The side wall piece venting is not essential right? The roof is just as good?
Is it against code to run this high efficiency furnace just into the chimney?
It is not against code to go through roof. The chimney is ok IF the pvc ran all the way up and out...
But I do not see how you will be able to fit a chimney liner and 2 pvc pipes through chimney.
If you have the model number I can supply the install directions to you
Billy, it's the Carrier 59TPA Data you sent me this three days when I had other questions. Can you check that if the HVAC guy just replaces the 6 in with a 4 inch pipe and just connect it into into the chimney if that is a code violation?
Connecting to chimney with any pipe = code violation.
The ONLY acceptable way is if they run a 1 pipe system up and out the top. But you still have the water heater concern needing a liner.
The days of venting in an unlined chimney are gone. And 90%+ furnaces cannot be vented into the chimney.
Here is the installation guide
I can tell you with 100% certainty that the chimney cannot be used as it is to vent either the furnace OR water heater.
Feel free to ask anything you need
Let me know if this makes sense. I am guessing 43 years ago when the system was put in that this was not a violation of code. I am guessing that just because I am getting a new furnace that I am not required to go back and vent the water heater differently. What do you think, maybe I should just have a chimney inspection and see if 43 years of a hot water heater being vented that way has done damage to the chimney liner, no?
Once you touch this the system must be brought to code. It was no big deal before because you had so much heat going out chimney. Now that we milk the heat out we have a warm vapor going out. This would rot your chimney out.
Also we have a big chimney with just the water heater left...not enough heat to keep dry..so it is code to install chimney liner (flexible metal liner) in the chimney whenever changing furnace or water heater.
None of this will be grandfathered. And actually it is just for the good of your property and safety.
By code you will have to vent the furnace properly (not into chimney) and run a liner for the water heater.
Last question and I will pay...if the HVAC guy adds the flexible metal liner to the chimney can they then run both the water heater and the furnace through the chimney like is currently being done. Thanks for all your help.
no, the furnace is power vented with a blower...if it were added to the water heater then this could happen:
Chimney gets plugged..tile falls, nest etc...the furnace would then pump the carbon monoxide back through the water heater and into your home.
This furnace must be piped individually until it exits the home.
Billy, when I look on my roof, beside the chimney which (has been) the exhaust output. Are you saying when they install the new system tomorrow there should definitely be a new pipe from the outside for the intake? Currently, intake would just be your return registers no? Thanks again.
So the guys just got here (there's a team because new furnace and new a/c) and I got good news and questionable news. I was told we will be running two new pipes through your roof for intake and outtake for the new system but we are not doing anything with your hot water heater that currently vents into the chimney. Is there any code that I can show them? Thanks, Andy
Billy, I just spoke to the guy and he said because the chimney is an interior chimney, right through the center of the house that it does not need a metal liner but that the current clay liner is sufficient. Does that sound right to you? Thanks.
See note 3
WHEN TO LINE: The National Fuel Gas Code is clear when liners are needed. 1 If an 80% furnace is alone in any chimney. 2 If an 80% furnace and water heater are using a chimney with 1 or more sides exposed to outdoors below the roofline. 3 If the installation doesn’t meet the “7 times” rule on sizing. That rule says “the flow area of the chimney cannot be more than 7 times the area of the smallest draft hood outlet. “ Since most water heater draft hoods are 3” diameter (7 sq inches times 7 = 49 sq inches) and most chimneys have interior areas larger than 49 sq. inches, most fail to pass this test. Note: the rule looks at the outlet of the draft hood, not the size of the flue pipe used. Few water heater draft hood outlets are larger than 3” even if 4” flue pipe is used. This test applies when a water heater shares an inside chimney with an 80% furnace or if the water heater is alone in a chimney.
The chimney runs through about 3 1/2 feet of unheated attic space. Does that change the equation?
Ok Billy maybe I'm a little slow today ...for a liner...point 1 and 2 don't apply that leaves us with point 3...and I don't understand point 3 well enough to understand whether a gas water heater alone can vent without a metal liner through an interior chimney. Sorry.
Ok,what is the size of the inside of the chimney?I amnot trying to drag this out....this is a basic thing for a contractor and is practiced by all.I do not see why they are hesitant.Tell me the inside diameter aprox of chimney.
Ok...I just went and took some measurements, let me get the soot off my fingers... here's my best estimates...it's a one story house, center chimney, 8 foot walls, 14 feet high chimney. At the base, and for the first say 6 feet the chimney opening is like 3 1/2 feet by 1 1/2 feet and then like at 6 feet to 9 feet it narrows to the point where at like 9 feet to 14 feet there is that clay liner and it's 1 1/4 feet to 1 1/4 feet.
net/net...we need the liner because the area, the space is just too big for the water/condensation to properly vent leading to possible erosion of the chimney?
Thank you. You can close out this line of questioning. Great job! Your help has been outstanding!
My bad, one last question, calculation. I don't realize that my chimney had a double output, like two chimney's in one. The measurement of smaller "exhaust" chimney is 6.5 inches by 12 inches. Can they just use that?