Tip & How-To about Heating & Cooling

Free heat from your own furnace

To greatly increase the efficiency of all forced air heating systems use aluminum duct tape and tape all joints in the ductwork The hot air ducting from the furnace right to the register in the floor or walls should be air tight to keep heat from escaping .Also the cold air returns and all associated ducting should be taped at all joints to ensure maximum air flow . Taping all ducting will not only provide more heat to all rooms of your house it will also produce less dust from leaking cold air ducting which sucks in air and dust from areas typically not cleaned (wall and floor cavities) . I did this in my older home and found I had to close off some registers because of the huge increases of volume which provided extra heat volume for the rooms that needed it.The house is now consistantly warm in all parts

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Why can't I get air flow into rooms?

The problem may be at the plenum. If the ductwork is connected at the very top of the plenum it can't build up STATIC PRESSURE. If the plenum was on the floor in front of you, you would measure down 12-18", from top to bottom, and that's is where the ductwork should start on the plenum. It may be hard to understand but we are not supposed to connect any ductwork on the HEAD of the plenum, as well as 12-18" from the top. If your blower is forcing air pressure from the bottom, into the plenum, and we release that pressure by cutting openings in the top, the pressure does not build inside the plenum. but with the ductwork away from the top of the plenum, air is forced in from the bottom and pressure builds at the top allowing a higher STATIC PRESSURE inside the plenum. And that pressure is released into the ductwork at a higher velocity and more evenly per duct. Most installers don't know about static pressure and will attatch ducts at the top of the plenums box. The blower then has a lower pressure and, although you feel some air in the problem room, its not enough volume to condition the whole area. That's a tough fix by the way but if that's your issue, have it replaced and if done properly you will notice a difference. An 8" flex duct is around 220-240 cfm. Depending on your size of room it may be a large enough duct. Normal size bedroom(not master) is about a 7" with non-foam insulation. An 8" is common for a kitchen due to the heat load so your 8" to that room should be blowing good. You may also try to increase the blower speed, make sure your evaporator coil is clean, and at the plenum there should be dampers that you can control the air flow per duct. I've seen that %75 of the time, with poor air flow its the placement of the dunt at plenum. Hope this helps!

Jun 28, 2015 | Heating & Cooling

1 Answer

I have an Aprilaire 1750 installed inline with my upstairs central air system in the attic. The unit's ducting appears to be installed as indicated in the installation manual, but when the unit is running on very hot afternoons, it is sending hot air to registers that are being supplied by ducting hooked to the supply plenum directly across from where the conditioned air from the dehumidifier dumps in. This causes a 20 degree dif ference in air temperature coming from registers in different areas of the upstairs, Why am I getting this hot air from the dehumidifier?

Your dehumidifier is likely working correctly. When operating and removing moisture, a dehumidifier will supply warm/hot air to your house. Your dehumidifier moves less air than your A/C, so your supply ductwork in your house is oversized for the dehumidifier. This will lead to uneven feeding of your supply duct branches with just the dehumidifier operating.

Since your dehumidifier is installed in the attic, make sure that the ducting connected to it is well insulated. Also make sure that your dehumidifier cabinet is insulated. These actions will help prevent heat gain from the hot air in your attic.

Is your dehumidifier bringing in fresh air from outside? If the outside air is hot and humid, the dehumidifier will supply warmer air to your home.

Some people run their A/C fans continuously to help with the air distribution, but this is a bad idea since it increases energy usage considerably.


Aug 06, 2010 | Aprilaire 1700 Dehumidifier

1 Answer

Home heating issue! hot air is cold when it reaches top floor!

Just guessing, but I'll bet your 2nd floor duct work is in the attic, and uninsulated, wrapping all attic mounted duct work with R-13 insulation and sealing it with tape will help but there is still going to be a slug of cold air pumped into the upstairs rooms each time the furnace cycles.

Dec 11, 2009 | Better Living SPP High Efficiency...

1 Answer

Heat pump noise

the problem is with the air flow in the ductwork. try to find the piece of duct that does the actual "bang". If it is in the return air ductwork check to see if any furniture is blocking the inlet grills. if it is in the supply air check the heat registers and make sure that there not covered up as well. If the furnace has just been replaced it might need to have the speeds adjusted. The air handle is either producing to much air flow for the size of the duct and making a "balloon" out of the ducts or it can't get enough air and tries to "****" the ductwork together.

Jun 09, 2009 | Heating & Cooling

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