Fresh air duct in home furnace


Old 12-19-00, 10:25 AM
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I have a Lennox Pulse, in the return air system there is a fresh air vent to the exterior. Is this a good or bad thing? With the extreme cold, with the flow vent closed the air still leaks threw. Would it be a bad idea to take it completely out and seal the holes?
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Old 12-19-00, 05:40 PM
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Check your local codes. The fresh air vent may be required. And if you have a 'tight' home this brings fresh air back in. Is your pulse heating ok?
Old 12-21-00, 05:13 AM
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Thumbs up Pulse

The house seems a lot warmer now that I plugged the exterior vent. The Pulse did not run more frequent, just the house being cold alarmed me. And the exterior duct work was very very cold to the touch. I guess I will leave it plugged until the weather warms a little.
What should the little silver dial be set to in the interior of the therostat?
Old 12-21-00, 04:45 PM
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Call a Lennox dealer to look at the pulse. A fresh air vent should not cause it not to heat. It definitely is not heating correctly.
Old 12-21-00, 08:21 PM
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a pulse furnace should be directly vented with 2" or larger pvc pipe. This is where your furnace gets combustion air and the other is for venting. If you had a vent pipe coming into the ductwork it could have a damper on it to reduce outdoor intake when necessary. If it was not connected directly to the return air duct it could have been for combustion air for the water heater or and other device that needs air.
Old 12-22-00, 08:17 AM
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Although I'm not a professional, I'm a fairly proficient DIYer...

I, too have a fresh air inlet in my return duct system for my HVAC unit...roof mount dual pak...

I just recently converted my water heater back to LPG from electric and am installing a gas cooktop and new vent hood in the kitchen...

While testing the vent hood, it suddenly struck me why that fresh air vent is allows outside air to replace the air I'm exhausting through the vent hood (and my bathroom exhaust fans) so as to not to create a negative pressure situation in the house where gas appliances (water heater comes to mind) start having exhaust gases sucked back into the house.

When I was running the hood, I noted a noticeable volume of air coming OUT of the return duct closest to the kitchen....that's when the light bulb went on...

I understand many new gas appliances have sealed combustion chambers with their own supply of fresh air so my advice may not apply to your situation but I thought the principle was worth mentioning...

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