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SallySensation 03-04-2013 05:00 PM

Furnace and Water Heater Venting
I have a 1000 SF single floor home (actually a 2 story duplex) with a natural gas forced air furnace and water heater located in a small (~7'x10') enclosed room in the basement.

The furnace is a Rheem Criterion 85% efficient RGDG-100AUER. It's in decent condition and heats the house reliably with no problem. Gas bill is quite reasonable considering the age and draftiness of the house. It is sidewall vented using some type of hard plastic 3" piping that is not PVC or CPVC. The vent is only about 5' long and has a relatively steep slope. It is transitioned to type B vent where is exists the house through the perimeter joist. This was the setup that existed when I bought the house 10 years ago and the inspector had no problem with it. It appears to be venting well, except that I recently noticed a crack in the pipe where it connects to the furnace blower. I realize this is a problem and I also discovered that this is not the proper way to vent this type of furnace (there is no additional exhaust fan installed).

The water heater is a 3 year old lochinvar 50gal tank. It vents using a 3" single walled steel duct with good slope, about 3 feet to the brick chimney. The chimney has a 4x8 tube block liner (sorry for my poor terminology). There is no proper liner. And it runs about 25' to the top where it has a new chimney cap designed to prevent downdraft. It is the only appliance venting into the chimney, and the chimney is clear or obstructions. The only problem is that in the winter if I have the door to the furnace room shut, I have on a couple of occasions noticed that the plastic covers on the top of the tank, around the inlet and outlet water pipes, have become slightly melted. I assume this is due to a slight backdraft where hot exhaust gasses as being pulled back in and the area around the exhaust hood is getting too hot. I could be wrong.

I have tried to test for negative pressure in the furnace room due to the furnace running but it doesn't seem very significant. There are no returns in the furnace room. I can't imagine it's a very air tight house. But there is no fresh air intake for either appliance.

So my questions. What would be the best and least expensive way to repair what needs repairing? I would like to do the minimum amount of work to make the house safe. I have a CO sensor in the furnace room, and it has never gone off, but I assume that doesn't necessarily mean that it's a healthy or safe condition. Does anyone have any thoughts about that? Do I need to install a chimney liner? Would it be unwise to simply replace the cracked furnace vent pipe and leave it venting through the sidewall? I appreciate any advice or suggestions.


beenthere 03-04-2013 05:59 PM

Post pics of the vent pipes for both the water heater and the furnace.

If your furnace is connected to HTVP, that pipe has been against code for 15 plus years.

SallySensation 03-05-2013 07:56 AM

5 Attachment(s)
I don't have a pic of the water heater vent, but i'm certain that one meets code, at least up to the chimney. I have attached pics of the furnace and vent. I would not mind replacing the vent piping if necessary. But if I can no longer sidewall vent this, then I'm going to run into trouble. It would be very difficult and expensive to route it up to the roof. Or if I run it through the chimney, I would need a liner probably, if I don't already need that. That would be difficult because there is no a clear access to the chimney in the basement, due to the installation of a finished bathroom. Given the age of the furnace I'd like to hold out as long as possible until I can get a high efficiency furnace that I know I can sidewall vent. Thoughts?

beenthere 03-05-2013 04:06 PM

That stuff is not allowed. You can get a power ventor and still side wall vent. You'll need to run metal pipe from the furnace to the power venter.

If you have the same stuff on your water heater, its not allowed.

old_squid 03-05-2013 05:19 PM

There was a industry wide recall on that type of venting material in the 90's. You need to have it replaced asap.

yuri 03-05-2013 05:53 PM

that's a pretty old furnace/19 yrs (1994 in serial #). not worth spending a lot of $$ repairing or re-venting it IMO. most of those units the exhaust fan/bakelite splits and the whole fan needs replacing, plus the circuit board is getting older.

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