Furnace/water heater venting

On Thu, Oct 8, 2009 at 7:53 AM, David Huss <dave@customrefrigeration.com> wrote:

I currently have 80,000 btuh (output) 80% sealed combustion furnace and a 40 gallon natural vent water heater. My old chimney vent is 5 or 6" not sure (I’m not at home).
My furnace is vented as per instructions with PVC pipe with proper pitch and termination fitting outside (20’ away from furnace) and the water heater is vented up the old stack.
Due to recent home addition I would like to move my furnace vent to the old stack with the water heater. My plan is to leave the air intake where it is but move the exhaust.
The water heater is about 7’ away from the old stack and the furnace is within 3’.
If the suggestion involves joining the two vents how do I transition from PVC to vent pipe??
Any ideas would be helpful.

Thanks, Dave

This won’t help you much but I don’t believe that a 80% furnace uses a PVC vent piping, as the temperatures of the exhaust gases are too high. The 90%+ furnaces can use it though.
As to the your original question one of the more advanced HVAC type guys may chime in to help out.

If your furnace has PVC flues and a combustion air intake, it is a 90% high efficiency furnace.

These type of funraces cannot be vented to a chimney. The exhaust gasses have a high moisture content and this will seriously degrade the interior of the chimney.

If an older furnace, vented in tandem with a conventional water heater, is replaced with a high efficiency furnace, the remaining water heater should have a chimney liner installed. If not, the water heater will backdraft.

In my opinion, the least espensive solution would be to but a newer, forced draft water heater which is vented out the side of the house, just like the furnace. Then you could move both of them pretty much anywhere you need.

Hope this helps;

hi im looking for a manufacture date of a furnace made by international heater company model # gt-150b can you help me