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Introduction
The HVAC system is what we use on a daily basis. Any problem in the HVAC system can be a pain in the neck. Well, cold air coming from returns causing a draft is one of those common problems. It’s annoying but fixable.
So, why does cold air coming from returns cause a draft to happen?
The most common issue for cold air coming from returns is clogged air ducts. In that case, maintenance is the best way to avoid it. Another reason is the heating coil and fan getting stuck. To solve it make sure there are no loose connections. Exhaust duct getting blocked is also at fault here.
Now that was a quick glimpse at all the reasons why cold air might come from returns. Below I go into more detail.
Why is Cold Air Coming from Return Ducts?
There are mainly 3 parts to a household HVAC system. The machine, supply duct, and return duct. The machine has cooling compressor and heating coils. It also has a fan so that the air can be pushed through. And sometimes there is an exhaust duct with the return duct.
The Duct is Filled with Dust
The first reason of why cold air is flowing from return ducts can be a dusty/clogged duct.
The return duct sucks air from the room. In case your room is dusty or dirty frequently, plenty of dust can get collected.
Source: stackexchange
Solution
Maintenance is the best way to stop dust from clogging the vents. You don’t need to do the maintenance every year or so. Once in every 5 years will work just fine in this case.
Also, you don’t need to do the maintenance by yourself. There are professionals out there who can do the job for you. But if you feel confident, you can also try to clean yourself. There are full cleaning kits available in the market.
If you are looking forward to buying a cleaning kit, you can check the links below. Both of these kits come with everything you need to clean with.
| Products | Features | Buy Now |
| Nu-Calgon Evap Foam No Rinse Evaporator Coil Cleaner | Liquefies dirt, oil and grease very quickly in the system | Check Price |
| K&N HVAC Filter Cleaner | Removes filter clogging to prevent low pressure lockout | Check Price |
| Frost King ACF19 Foam Coil Cleaner | Cleans fiter, coil, and fan blades | Check Price |
| Klima-Cleaner Air Conditioner Cleaner | Improves the cooling efficiency | Check Price |
All of these cleaning kits are really handy to use. Also, these kits will last you a long time.
The Heating Coil is not Working
The heating coils heat up the air and the fan passes it through the supply vent. So, if the coil doesn’t work, the air won’t be heating up. So you need to check on the heating coil. The heating coil is located inside the machine.
But, cold air coming through vents when the furnace is off will happen if the seal isn’t right. The exhaust or the air intake needs to be closed when the furnace is off.
A partially functional coil can work during the day but not at night. Since days are warmer, the night wind is much colder. That is why many face their AC not working at night.
Also, if you are thinking about blocking cold air return vents in winter, then don’t. It can burn the coil because of overheating.
Solution
Usually, the loose connection is a big issue with these coils. If you are using the machine extensively, the connections can burn out sometimes. But the coil itself can burn out as well. In that case, changing the coil is the best decision.
The Circulation is not Working
The complete HVAC system heavily depends on the circulation of air. The circulation starts from the supply duct and gets back through the return duct. If the circulation isn’t working properly the air will not be cooled or heated properly.
Blocking cold air return vents in summer is an important issue as well. But it can put stress on the machine since air cannot pass freely.
So, how can we solve this issue?
Solution
If the circulation isn’t working right, there might be a problem with the fan. The fan is responsible for going in through the return duct. Also, the air comes through the supply duct. In that case, repair the fan or replace it.
You can use the Panasonic WhisperFit DC Retrofit Ventilation Fan. It has a smartflow technology with ECM motor.
Again, air cannot move freely if the duct is clogging up. Dust usually sticks on the walls of the duct. And over a period of time, dust accumulates and puts stress on the fan.
Changing the HVAC system filter can help increase air circulation.
The Exhaust Duct has been Blocked
The exhaust duct exists in some modern HVAC systems. The exhaust duct sits with the return duct. Its purpose is to let some hot air pass by so that new cold air can circulate inside the room. If the exhaust is blocked, air blowing out of the intake vent can happen.
If the exhaust isn’t closed correctly, cold air coming from ac vents in winter can happen. So, how to stop cold air from vents? It’s really easy, just make sure a good seal and keep the intakes and exhausts closed.
So, what to do if the exhaust duct is blocked?
Solution
If the exhaust duct is blocked, only the existing air can circulate in the room. And eventually, a cold draft from the air vent will dominate the room.
Solving the exhaust duct blocking issue is simple. The exhaust duct is located along with the return duct. So check on the duct and see what the problem is. If dust is clogging the duct, then clean the duct and run the system again.
And that’s everything you need to know about HVAC systems cold air coming from returns. Apart from these, also keep in check what size of return you’ll be needing for 3.5 tons. If kept in check, these technical things can go a long way.
Frequently Asked Questions (FAQs)
Where to put the Seals on so that Air won’t Escape the Room?
You can use caulk and rubber seals so that air won’t escape the room. For extra effectiveness, you can tint your windows so that sunlight heats up the room.
How to Change the FIlters on the HVAC System?
To change the filter on the HVAC system go down to the machine. Then pull on the servicing door. There is usually one filter on the air intake and one behind the coils. Take the latches off and pull on the filter to take them off. Insert the new filter and tighten them in their place.
How to Fix Leaks on Air Ducts?
To fix leaks on air ducts use duct tape to fix leaks on air ducts. If you see the damage is small, duct tape will work fine. But if the air duct came completely apart, then you need a new duct. Take the new duct, insert it in the broken area and seal it with tape.
Endnote
That is everything you need to know about, cold air coming from returns causing a draft.
Always remember to turn the power off. Otherwise, there are risks of getting electrocuted.
Good luck fixing your HVAC system!
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.