combustion air and exhaust appear merged

[Michael Inwards]

good day americas finest.....a mid efficiency furnace with combustion air and exhaust pipes was looking nice and typical to me but theres only one pipe exiting the roof which looked about four inch, and had what looked something like a draft hood, (larger then the bottom pipe so it wasnt simply an adapter) and on top of that a reduced pipe, perhaps 1 1/2 (roof was too steep to walk and I'm getting this via binocs and silly me I didnt take a pic) so when I looked in the attic they were joined by T or something...again couldnt get close but at least got a pic. can these be joined? doesnt that suck exhaust products back as combustion air? only theory I can come up with is there is some kind of pipe within pipe device so theres only one hole in the roof. the 'draft hood' looking dealy, maybe a rain deflector for combustion air? well I seek the opinions of those more experienced then I.
mike in MN

[Christopher Currins]

pipe within pipe device

That's what you have.

[Christopher Currins]

CONCENTRIC VENT TERMINATION KIT

[Bob Elliott]

Originally Posted by ccurrins

CONCENTRIC VENT TERMINATION KIT

Yep, and surprised I do not see them more often with cat 4 furnaces.

One hole is easier than two.

[Marcel Gratton]

Originally Posted by minwards

good day americas finest.....a mid efficiency furnace with combustion air and exhaust pipes...

A mid efficiency furnace using a pvc flue...

[Bob Elliott]

Originally Posted by mgratton

A mid efficiency furnace using a pvc flue...

I doubt it.
Must be a typo.

[Steven C. Waskewicz]

90% efficiency and greater are condensing furnaces, and require two pipes for intake air and exhaust, and can use PVC due to their lower stack temperatures.

[Robert J. OConnor]

Originally Posted by swaskewicz

90% efficiency and greater are condensing furnaces, and require two pipes for intake air and exhaust, and can use PVC due to their lower stack temperatures.

Yes, but keep in mind that many manufacturer's permit the intake on a 90%+ to be a plastic mesh like cover right at the unit (special part supplied with the equipment) if the space is big enough to provide sufficient "combustion air" (called single pipe venting)

And the exhaust has to be PVC or a special stainless steel (very expensive) due to how corrosive the flue exhaust/condensate is. Typical galvanized single wall or double wall type B/L vent shouldn't be used on the higher efficiency units because of that.

JMO & 2-Nickels ...

[ROBERT V. YOUNG]

Just a question.
The galvinized pipe to the right. Any perpose in the system?
Attachment 47902

[ROBERT V. YOUNG]

Mr.C those 2 nickels you keep given = a dime you know.
Would not the proper use of the phrase be, JMO & a dime?

[Michael Inwards]

thanks for all that input, I greatly benefit. no it was no 'typo' when I said mid effeciency....I was just displaying my lack of experience which I exhibit freely in the midst of pros to be able to learn. I thought this to be mid because it had 'glow plug' but the burners where right out in the open...i could easily reach right in and burn my little pinkies. I thought high eff was totally enclosed. so again Im open to all input....since I plan to someday be the best darn inspector in the area....have to hurry, 55 old right now so thanks for the help. straighten me out on the mid/high eff

[ROBERT V. YOUNG]

Michel.
You will do fine.
You attitude is commendable. The ability to see ones errors is most important.
I made and still make errors. We are all human.
Great question. Keep asking.

[Robert J. OConnor]

Originally Posted by ryoung7

Mr.O those 2 nickels you keep given = a dime you know. Would not the proper use of the phrase be, JMO & a dime?

It's a US thing, eh ... ... and sometimes it's a quarter due to inflation ...

Originally Posted by minwards

... Im open to all input....since I plan to someday be the best darn inspector in the area ....

And you will get there if you keep asking good questions about things you dont understand or haven't seen before ...

Originally Posted by minwards

I thought this to be mid because it had 'glow plug' but the burners where right out in the open...i could easily reach right in and burn my little pinkies. I thought high eff was totally enclosed.

Typically the combustion chamber on a 90%+ high efficiency furnace would be enclosed. What was the make and model for the furnace?

[Greg W. Mathias, CCHI]

Originally Posted by minwards

thanks for all that input, I greatly benefit. no it was no 'typo' when I said mid effeciency....I was just displaying my lack of experience which I exhibit freely in the midst of pros to be able to learn. I thought this to be mid because it had 'glow plug' but the burners where right out in the open...i could easily reach right in and burn my little pinkies. I thought high eff was totally enclosed. so again Im open to all input....since I plan to someday be the best darn inspector in the area....have to hurry, 55 old right now so thanks for the help. straighten me out on the mid/high eff

If you have some time, take the advanced HVAC course offered here. I just finished it and learned alot about the different units.
http://www.nachi.org/hvacclass2008.htm

[ROBERT V. YOUNG]

Thanks for reminding me to finish my advanced course.
Mr. Mele or (Mr.Apple)and Kenton as the streight man do a great job of explaning the HVAC system in detail.
Be prepared for a 4 or 5 part course last time I looked.
Bring you note pad with you.Loads of detialed education.
HAY NO TALKING IN CLASS.
Take your books young man and sit in the front where I can watch you better. who me!!
Attachment 47912 sorry teacher.sorry class.