Originally Posted By: rmoore This post was automatically imported from our archived forum.
Dave…
I did a double-take on the first one I saw like that too. I can't remember the manufacturer now, as it was quite some time ago, but when I researched the installation instructions I found that the outside intake was optional. The ones I have seen with only one pipe have all been in unfinished basements, so efficiency probably isn't harmed that much by using interior air for combustion. Still...for the price of a length of pipe, you would think they would all use exterior combustion air.
So...with the caveat that the manufacturers specs are the last word, it's probably OK. Just make sure it's the intake that's missing! 
-- Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com
Originally Posted By: dbush This post was automatically imported from our archived forum.
Yeah Rich, I talked to Erby and Joe Myers and they both told me the same thing. I just had never seen one like that. It was the Intake that was missing; but thanks for looking out for me.
Originally Posted By: Lee Hammerstein This post was automatically imported from our archived forum.
High efficiency furnaces come in two types. One is “sealed” combustion and the other is “open” combustion. The sealed combustion furnace has the burners sealed inside so you do not have access to the flames unless you disassemble the cover, though there is usually a sight glass to view the flame. The open combustion furnace has no such sealed compartment and after removing the furnace door, you could access the flame with no further disassembly.
Every sealed combustion furnace I've seen or installed required the intake be installed.
On open combustion furnaces the intake is optional and really just for show when installed as it uses the air inside the building for combustion as well as some of the air that passes through the intake.
Trane and American Standard are two companies that sold a lot of the open combustion furnaces. Looking at the outside cabinet of the open versus sealed they look identical.
Originally Posted By: apolillo This post was automatically imported from our archived forum.
my 2 cents…
It should have a pipe and an elbow to prevent small articles getting sucked in. Picture a kid with a matchbox car or some other small item. It could easily get lost in there.
Originally Posted By: rmyers1 This post was automatically imported from our archived forum.
“Be Careful” in your judgement if it’s “only the intake” piping which appears to be missing, must be OK.
Remember…all gas appliances require proper volume of combustion air.
The best way to determine if any gas appliance has adequate combustion air is simply math. ( National Fuel Codes)
Cubic feet of area x 20= BTU
Example: An (open) space or basement area 30L x 30W x 8H =7,200cuft
7,200 x 20=144,000 BTU
Now add in the usual hot water heater and maybe a clothes dryer.
You may find that in fact you have a confined space which requires an outside air supply.
In Chicago we find in excess of 90% of gas appliance are being improperly installed. a very serious problem which our Energy suppliers are trying to address.
How many Mech Rooms do you see of this size?
Try this simple math, you may be amazed. Check your own home.
If you need further clarification on this, please feel free to contact me directly.
Originally Posted By: Gary Reecher This post was automatically imported from our archived forum.
rmyers1 wrote:
Just another quick thought for you to consider.
Most developers, home builders, or what ever you prefer to call them are selling looks and not (large unconfined spaces) for a mech room.
You cannot even go by that logic or code either. There have been incidences of new construction where a water heater is back drafting in the open basement when the furnace blower was operating for air conditioning. The scary thing was the furnace was only one pipe pvc. Venture to say what is going to happen when the furnace is turned to heat mode 
Originally Posted By: rmyers1 This post was automatically imported from our archived forum.
You just answered your own question sir. If the furnace blower sucked out the exhaust for the water heater, then (the furnace system was improperly installed). Being in the A/C mode I would suggest the filter rack did not have a cover. Also hoping no return air vent in basement area, or very poor return air ductwok. Certainly hope the occupants are still alive. Just think of what happens when the gas burners of the furnace come on, then also sucking combustion air and fumes back into itself, to circulate thru the home. Thats another problem with the newer homes, they are built so tight, to conserve on energy, it causes a multitude of other problems. This is why it is so important to use the simply formula. As an HVAC Engineer, with 40 years practical experience, I can positively tell you this simply formula I previously provided my fellow NACHI member works. Test it out on your next job. May be a source of extra revenue for your company, correcting the other guys screw up. I would invite you to visit our NACHI educational sites. These sites are free to the public. As an HVAC Service Tech, you are a prime future candidate for our industry, Home Inspections. Good Luck
Originally Posted By: rmyers1 This post was automatically imported from our archived forum.
Here’s another one for you to think about.
A vintage condo building with 520 units. recently when the owners began turning on their A/C, (G/E Package Terminal Units with backup electic heat), several of them leaked onto the floor. All the units were properly installed. All the units were serviced and no problems found. The only major projects the building had recently completed was installation of newer style windows.
Think about it and let me know your thoughts.
Originally Posted By: Gary Reecher This post was automatically imported from our archived forum.
In the case I referenced the return ducts leaked. No supply registers in the basement and no combustion or makeup air. If the original installing company had taken the time to take draft and electronic combustion readings and went through a complete system test with worst case scenario operation these problems would have been uncovered.
Now to your condo problem. Since windows were changed and the problem started. It sounds like air leaks were sealed and a negative room pressure problem is not allowing to drain properly whenever kitchen or bathroom exhaust fans or clothes dryer are operating.
Originally Posted By: rmyers1 This post was automatically imported from our archived forum.
Excellent diagnosis.
In this case , we found that over a period of years so many people had plugged up the bldg vents, which are located in the kitchens and baths that it would cause negative pressure on certain days. Once we suggested the Building Engineer to go thru the entire building (520) units, and remove all the articles being used to plug these vents…Problem solved. People thought that during the Winter, cold air was being allowed to enter their condo thru these vents. On our initial visual inspection, we found ladies underpants, socks, towels, newspapers, duct tape, so many novel items being used to block the vents.This is an actual case. of a building which we have an exclusive, unit only, inspection contract with. Prior to asking our opinion the building had spent several thousand dollars to HVAC companys, trying to determine what was wrong with the A/C systems.They were very impressed with our quick resolve, especially when it didn’t cost them anything. just a simple question…I also suggested they should direct our inspection reports to the proper persons, because many of them had already reported on the potential problem.The Building Engineer with his $200,000 plus salary and free condo, being slightly embarrassed, is now required by the Condo Board to read each and everyone of our Home Inspection reports…Your Very Good.
Maybe you should consider relocating to Chicago. Work year round. If your as good as you appear to be, you could enjoy a very lively business in this area. Chicago needs good HVAC contractors.