Why does my furnace have a fresh air intake?

[firecontrol]

This is where it gets confusing.
Specs for Mobile homes are they the same as those for Manufactured Homes!

As I understand it: A manufactured home and a mobile home are one in the same due to the fact that they are transportable on their own frames. Modular homes are different in they are delivered on flatbed trailers and have no means to be transported by themselves.

A definition I found was: "According to the Manufactured Housing Institute’s National Communities Council (MHINCC), manufactured homes[2]

are homes built entirely in the factory under a federal building code administered by the U.S. Department of Housing and Urban Development (HUD). The Federal Manufactured Home Construction and Safety Standards (commonly known as the HUD Code) went into effect June 15, 1976. Manufactured homes may be single- or multi-section and are transported to the site and installed." (Wikipedia)

I guess the difference would be a stick built on site home has the ability to be inspected at all the different phases of the construction process to make sure it complies with the local/state requirements. A manufactured home can be built (in a factory) thousands of miles away in a different state and jurisdiction and brought in and set on some form of foundation.

[firecontrol]

All the mobile homes in Houston I've ever worked on, has a special roof jack, the introduces fresh air for combustion down one area of the jack, and releases flue gasses out the other area. I have installed many of these, they are confined to the combustion chamber, they have no effect at all on your ac. Maybe some of you are talking about the old school ones, where two pipes are run down into the furnace area, one lower than the burners and one higher, I haven't see any like that around here since the 70's.

On the mobile home furnaces I'm talking about there are two connections on top of the furnace. 1st is the large metal concentric style chimney consisting of a large appoximately 8" diameter galvanized pipe coming into the center of the furnace top. This larger pipe brings in the combustion air to the burner and is sealed to it's mating connection inside the furnace. Inside this larger pipe is the smaller diameter 4-5" pipe that the flue gases use to exit the home via the furnace roof jack.

"Usually" to the left side and to the front of the furnace top is an insulated 4" flex that connects to the top of the furnace and empties into the blower compartment on the top of the furnace. I've seen two different styles, one was the old Coleman Blend-aire that had a power ventilator on the roof that was connected at this point and it had it's own control panel inside the furnace. The other type was simply a damper motor of some kind that opened when the furnace blower ran and closed when it wasn't.

[teddy bear]

The fresh air's function is to keep the pollutants from all of the materials in your from building up in your home and renew oxygen.
During mild weather and temperatures, even leaky homes may only get a fresh air change in 10-15 hours. When a home is occupied, Indoor Air Quality experts suggest a fresh air change in 3-5 hours to purge indoor pollutants and renew oxygen.
The cost for fresh air change is <$1 for 24 hours. If a home occupied for 12 hours, you are <$.50 a day for cooling and dehumidifying. Your choice.

Crawl into a plastic bag and leave a note near by to have the ones that find you post us on what happened.

10% of the population is very sensitive to this. 50% can not tell the difference.
As you get older, oxygen levels mean more.
Next maintain <50%RH to avoid mold and dust mites.
The ultimate control is a CO2 meter set low enough to detect occupancy with natural infiltration. This will reduce ventilation needs another 25%. Anytime the outside wind and stack effect are high even air tight home may not need much fresh air.
None the less filtered fresh air is important for long life and comfort. I have seen repeated major improvements in sensitive occupants health and comfort by keep the fresh air flowing and maintaining <50%RH
Hope this helps.
Regards Teddy Bear

[pacnw]

HUD has jurisdiction over manufactured homes and has mandated fresh air ventilation for as long as I can remember, or at least since they identified the health risks of formaldehyde out-gassing and other indoor air contaminates.

As for the code specific to requiring fresh air intakes, I can only speak to my state. Either you provide a "Skuttle" style fresh air intake to the HVAC forced air system or you install a whole home HRV/ERV or you don't pass inspection on new home construction.

Your latest post states your state only requires that an exhaust fan run 24/7, how does the air that the fan(s) are exhausting get replenished into the home?
If this was directed to me, I am strictly referring to a stick built home/built on site/timber frame home. We don't understand no intake of outside air, but yet exhausting air with the potential of pulling the house into a negative(slight possibility, really).


For 30+ years I've seen every mobile home style furnace installed in a manufactured home located on the main floor and a standard efficiency style has had a 4" vent connected to the blower compartment and terminated outside.

.

[thracianspec]

Thanks all for your input, as you can see here in the picture there is nor does there ever appear to have been a damper. I have seen the mixair type with damper, but I have 2 of these furnaces with no damper.

Again, I'm just perplexed how outside 100 degree air helps cool your house when you're trying to pull in cooled air from the return?

I agree fresh air is important, but is this the answer for other A/C systems?

I have some contacts at the manufactured home company and I'll just have to ask them how their HVAC system was intended to work.

[martyinlincoln]

All systems are required to have fresh air intake here . The most common way is just like yours,outside air brought directly to the return. It only brings in enough air to balance what's leaking out elsewhere. In large commercial buildings an entire system can be dedicated to heating/cooling the amount of make up air brought in.

[pacnw]

Again, I'm just perplexed how outside 100 degree air helps cool your house when you're trying to pull in cooled air from the return?

It has NOTHING to do with heating or cooling!!!!

It is simply ventilation air. Not only does it dilute the VOCs, but it is also combustion air for any fuel burning appliance(furnace, cook stove, etc) that does NOT have its own direct access to outside.