The newer homes are sealed tight and are then equipped with "Air Exchangers".  Something may be amiss with it if you have one.

 

https://www.brighthubengineering.com/hvac/90595-basics-of-hvac/

The objective of HVAC are to control the temperature of air inside the designated “Air Conditioned" space along with control of moisture, filtration of air and containment of air borne particles, supply of outside fresh air for control of oxygen and carbon dioxide levels in the air conditioned space, and finally control of the movement of air or draught. All these factors comprise of a successful HVAC system. Air conditioning has changed over the years from just cooling of a space to the effective control of all the above parameters.

 

https://homes.winnipegfreepress.com/winnipeg-real-estate-articles/renovation-design/ASK-THE-INSPECTOR-Furnace-new-but-outside-air-intake-useful/id-1926

 

incomplete combustion, backdrafting or other issues that may cause safety issues in the home.

Unfortunately, the fresh-air intake you have described is the second type and does not provide direct combustion air to the furnace room, as it is directly connected to the return-air plenum for the furnace. This fresh air will enter the air circulation system of the heating system, which is separate from the combustion chamber on your furnace. Fortunately, you are correct that your new high-efficiency furnace should have an integral combustion-air intake duct that supplies air directly to the combustion chamber. Regardless, you should not be blocking or disconnecting this old duct just because you have upgraded your furnace. In fact, you should be doing the exact opposite.

Bringing in fresh air for the entire house through the return-air ducting on the furnace may help prevent a common problem when people upgrade their old heating appliances to high-efficiency units. Higher indoor relative humidity and window condensation often increase after upgrades to furnaces and installation of new windows. I get numerous calls and emails every year with this complaint. Tightening up the building envelope by replacing old, leaky windows and closing an old chimney flue after installation of a direct-vent furnace will trap warm air that used to leak out these two areas. This warm air can hold a significant amount of moisture, which will now remain in the home. Bringing in cold, dry, fresh air from outside is one way to prevent this issue from occurring. For that reason, leaving your old intake ducting in place is a very good idea.

 

Herb

2 hours ago, Gene Howe said:

But...but...but...air is pulled into the dryer by a fan which only runs when the dryer is operating. 

I don't understand how conditioned air builds enough pressure in a house to open the dryer vent. If it does somehow, I'd be worried about all the pilot lights and possible CO build up.  Sumpin' ain't kosher.

No pilot lights.  All electronic ignition. 

I don't think the fan is sealed, it is drawing room air, so if it is off,room air can flow  by the fan, into the dryer and out the vent if the atmospheric pressure is higher in the house than outside.

Herb

If the dryer door is not sealing that is how it is escaping from house and dryer vent.  Most of us now have one pilot light in the HW heater next to the furnance.  The new furnance should have sealed combustion.  When the AC comes on it creates drafts on the return side going back to the furnance and on the pressure side from the furnance out to the vents.  Because his air ducts are sealed in concrete there shold be no leakage.  So what I think is happening is that there is a vent near the dryer that is pushing it air into the drum and thus out of the house.  Please make sure the dryer door seals and stays closed.

1 hour ago, Michael Thuman said:

If the dryer door is not sealing that is how it is escaping from house and dryer vent.  Most of us now have one pilot light in the HW heater next to the furnance.  The new furnance should have sealed combustion.  When the AC comes on it creates drafts on the return side going back to the furnance and on the pressure side from the furnance out to the vents.  Because his air ducts are sealed in concrete there shold be no leakage.  So what I think is happening is that there is a vent near the dryer that is pushing it air into the drum and thus out of the house.  Please make sure the dryer door seals and stays closed.

When your dryer is running and the door is closed where is the air being exhausted entering the dryer ? Hint look at the louvers on the back.    Roly

39 minutes ago, Roly said:

When your dryer is running and the door is closed where is the air being exhausted entering the dryer ? Hint look at the louvers on the back.    Roly

 

and the air for the combustion comes from the louvers/access door on the front bottom.

Edited September 21, 20187 yr by HandyDan

My Dryer is electric, no pilot light, but it does have a light inside, does that count?

 

Herb

1 hour ago, Dadio said:

My Dryer is electric, no pilot light, but it does have a light inside, does that count?

 

Herb

Does the light go off when you close the door?

Houses of today are tighter than back yonder but don't forget all the exhaust fans a house has now a days so if a person is using natural gas there is usually enough air exchange through those vents when the fans are not running to keep a person from from dying of gas fumes...Also warmer air would go out the exhaust vents and not down through the dryer vent.

4 hours ago, Grandpadave52 said:

Does the light go off when you close the door?

I was wondering that too, I don't have one of those new phones that takes pictures, maybe some one here can put it in the dryer and turn on the dryer and let me know if the light stays on.

Herb

6 hours ago, Grandpadave52 said:

Does the light go off when you close the door?

yes says the neighbor's cat...

On 9/22/2018 at 12:35 AM, Stick486 said:

yes says the neighbor's cat...

A new recipe???

John

9 minutes ago, HARO50 said:

A new recipe???

John

shhhh....