Inspected this furnace today. There are two identical units in the crawl space. I only saw one plastic vent pipe for each to the exterior. The intake is at the furnace. I know some furnaces can use crawl space air for combustion air, but I always thought “direct vent” means two pipes, or the concentric pipe system.
One has a short piece of pipe, one looks like it’s been taped shut then a hole poked thru the tape?
Not sure if I should call this out or let it go?
Aside from the obvious things you need to report. EVERY TIME I see combustion air supplied in this manner, I look up the manufacturer’s instructions.
The second one is just FUBAR 
Is the crawl well vented?
Was it damp?
I always recommend to get combustion air from the exterior.
I believe there are High Efficiency units that are Non direct 1 pipe system that use only 1 pvc vent for exhaust but use the unconditioned air as its air source and are used primarily in crawlspaces and attics as long as the space is big enough for proper air intake amount
I totally agree Juan…especially the second one! The furnace is described as a Condensing Furnace, and according to info, it can use crawl space for combustion air if it’s single pipe venting. I don’t like the idea, because, to answer Chris Currins’ question, the crawl area is a little damp. It is large and well ventilated, but the condensing drains just dump below the furnaces on the crawl space floor.
The manufacture tag says “Direct Vent” furnace, which to me, needs exterior venting. I don’t want to call something out that may be okay, but I don’t want to let it go if it’s not okay.
My client is out-of-state and will rely heavily on my input since she could not attend the inspection. I still can’t see how the second one is okay, with that hole poked into the inlet pipe cover.
The second one is not ok The instructions will show specific ways that it needs to be done. I am sure that aluminum foil with a hole isn’t one of them.
What’s wrong with aluminum foil? This IS WV, ya know!! :|.)
Still looking for the installation manual. I think it’s too old (1992).
I may just informally suggest the exterior pipes be ran, even if not required by the manf.
I just don’t like to defer to a HVAC guy, if she has to get a HVAC guy to evaluate, why did she hire me, right? That’s why I’m trying to get this research done…
Thanks guys…
You could include all or part of this, most courtesy of Will Decker. I use some/all of it often.
Recommendation: High efficiency condensing furnaces may be installed with outdoor combustion air piped directly to the furnace. This is referred to as “direct vent” or “two pipe” installation.
Installation with air taken from around the furnace is sometimes referred to as “one pipe” installation - i.e. only the vent (exhaust) pipe is provided (What these furnaces are).
An important consideration in selecting one or two pipe installation is the quality of the combustion air. Indoor air is sometimes contaminated with various household chemicals, and/or high humidity levels, which can cause severe corrosion in the furnace combustion system. Some common sources of these chemicals are detergents, bleaches, aerosol sprays, and cleaning solvents. The air volume the furnace uses must be replaced with outdoor air that enters from somewhere else in the house (witch may not be desirable air to be bringing into the house).
If the furnace is operated without adequate air for combustion and ventilation, it may not perform properly. Excessive exposure to contaminated combustion air will result in performance related problems. As air leakage is the biggest weatherization issue, it is always best to take combustion air directly from outdoors. The recommended source of combustion air is outdoor air. Check with manufacturers installation requirements.
Excellent wording, Christoper, you rock…If you and/or Will don’t mind, I will use that comment. It’s a little lengthy for what I usually provide (only because I don’t think my clients’ attention span will absorb that much info), but I’m pretty sure it is how it needs to be explained to the client.
Thanks a bunch 
This is a good article about two pipe installation versus one pipe
Sure, feel fee to use all that you want. Will already gave his permission. Your right, this a lot more lengthy than most narratives I use, but in this case it does get the point across.
Good one thanks… Roy
Thanks guys…I actually had just read that article before posting, Yuri, as I was trying to gather some info on the subject…maybe great minds do think alike.8)
I just draw it in on my photo and leave it as a recommendation.
Very good info provided for those not able to do this on a report. 2 draw backs is nesting and location. This is now being taken care of by most new installations.