Venting Furnace Intake Outdoors

[JSA]

Hi All,

I am in the process of making plans to finish my basement and would like to have the air intake on my high efficiency furnace brought out doors (it is currently inside right beside the furnace). I have been told that according to new code that I will need to use Type BH ClassII PVC pipe which they are currently selling at Lowes. They do not however sell any couplers or elbows in this type of PVC. Can I use standard PVC parts to couple the pieces together? I have a Lennox G43UF furnace, and according to the installation manual this can be done as long as the pipe is in the same pressure system as the exhaust and within 6". Any guidance would be greatly appreciated.

[JohnnyG]

Just curious as to why you'd want to do this? If I'm not mistaken, that intake is for *combustion* air only so I'm not sure what difference it would make where it comes from?

[TKG26]

You are not required to use SYSTEM 636 on the air intakes. So you can infact use ABS or any PVC out there.

The code only applies to the exhuast system on newly installed nat gas appliances as of August 2007 in ontario. The air intake is not a problem. Excisting installs can continue to use abs or pvc as long as its air tight and not damages. IF found cracked it cannot be repaired only replaces with the new approved system 636(type BH classII pvc)

FYI 636 can not be mixed with other pvc and requires the use of 636 primers and glues only

Hope that helps

http://www.ipexinc.com/Content/EN_CA..._System636.asp


FYI if you already have a 4-5" combustion air vent from the outdoors in the furnace room you do not need to "2pipe" your furnace to finish your basement... 2piping is the prefured way to vent a furnace though as it ensures less contaminents from the home go through the heat exchangers. Normally a combustion air is there to serve both the water heater and the furnace. So if you do infact add the second pipe to your furnace you will still need that combustion air vent for you water heater.

[57]

that intake is for *combustion* air only so I'm not sure what difference it would make where it comes from?

Drawing combustion air for furnaces (or fireplaces) via a pipe directly from outside helps because then the air is used directly for combustion without cooling down the house. If you use house air for combustion, this air is drawn from warm air inside the house which has had energy expended on it to heat it. The delta energy is the cost of heating that amount of combustion air, which is not insignificant.

My fireplaces are the same - most people find that when they have a fire - especially an inefficient wood fireplace without glass doors and combustion air intake, the house can often be cooler, except for right in front of the fire, due to the combustion air being taken from warm air in the home. If the fireplace draws combustion air from outside and the warm air is prevented from being used for combustion (by the glass doors), the efficiency rises dramatically.

[JSA]

So if you do infact add the second pipe to your furnace you will still need that combustion air vent for you water heater.[/QUOTE]

Thanks for everyones input. TKG26, my hot water heater does not have a seperate air intake, however if I enclose my "furnace room" and leave proper venting to the area via registers as per the instructions for the water heater is this not sufficient for combustion? I thought that I read that each opening must be 1" in size per Btu/h and not less than 100", is this correct?

[TKG26]

Ill take a look in my code book when i get a chance. But im pretty sure in a modern constuction home that a water heater less then 50,000btu's requires a 2" combustion air...


IF you have combustion air it is probably because your in a tight home. ITs there to ensure that your house does not go into a negative pressure when you have the fireplace on,exhaust hood running,bathroom fan runing and dryer running that the water heaters vent does not reverse...
At the minimum go with those openings. as suggested by the manual(made and printed in the usa) local codes(canadian) previal. Ill post back when i get a look at my code book.

[JSA]

Thanks for your replies TKG26,
My hot water tank is a Superflue Model #6G60NVH-02, 42000 BTU. According to the specifications in the manual, Confined spaces less than 50 cubic feet per 1000 BTU/Hr have a CSA venting requirement (near the ceiling and floor) of 1 inch squared per 1000 BTU/Hr. My possible eventual space for the furnace room will be approximately 4.5'D * 8.5'W * 8'H which will be shared by the furnace. This is one of the reasons why I would like to have the furnace intake terminated outside. Will proper venting according to specifications be OK in a room this size? Your suggestions would be greatly appreciated as my Wife and I are expecting our first child and I would like to make part of the basement a play area.

[TKG26]

Ok read through the code book today. ITs as clear as mud! LOL Bottom line a tank under 50,000btu's DOES NOT require outdoor combustion air but as your manual states needs access to free air from the the structure so follow the guidelines in the manual and put in some lover vents top and bottom of the door.. (please excuse my error in post #6)

The combustion air vent tables actually do state that a 3" comb air is required for appliances under 50,000btus but having worked with the utility and new home builders i know alot of pressure was put on the code writers to give the tanks liniancy with comb air..

Anyway to clarify. IF you 2 pipe the furnace you dont need comb air for the tank if its the only other appliance in that room, but lovered air intakes comunicating with the rest of the basement is needed. But as mentioned before why are you agains simply boxing in the room and using the combustion air vent that you have now? IF its 5" round its more then adequate and you can stuff it between the furnace return air and the furnace so the air is not dumping at the floor.

With all that said im not in your home to give you 100% Accurate info.. If you have natural draft fireplace or wood fireplace a jenaire exhuasting range you may opt to keep combustion air in the room. Those are strong sources of draft and can turn a home negative...


When is your annual furnace maint due? If its almost due have a HVAC tech in for your maint and have him or her confirm what i have said.. Being there in person is the safest way to give accurate info.