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Why is it, every time the Ac kicks in, it smells like the furnace kicking in? It feels like heat coming out at first, then cold.
DH says, oh, its just so hot (its in the 100--110 here), its pushing out hot air first. Hey, I disagree, that wouldn't make it smell like the furnace, and it doesn't get THAT hot in the AC duct between cycles.
Is this a combo a/c heating unit using the same ducts? Is the air handler located in a uninsulated attic? If so the ducts will heat up as soon as the a/c shuts off and the unit has to push that hot air out before the cold air can come out. The smell could be burnt dirt left over from when the furnce was last used and small amount migrate into the circulating air. Or it could be the smell of the dirt and dust all by itself. You need to clean the system including all parts of the air handler and the ducts, just changing a filter doen't remove anything already in the system.
Is this a combo a/c heating unit using the same ducts? Is the air handler located in a uninsulated attic? If so the ducts will heat up as soon as the a/c shuts off and the unit has to push that hot air out before the cold air can come out. The smell could be burnt dirt left over from when the furnce was last used and small amount migrate into the circulating air. Or it could be the smell of the dirt and dust all by itself. You need to clean the system including all parts of the air handler and the ducts, just changing a filter doen't remove anything already in the system.
Can we clean the system, or does it require one of those air duct cleaning services? If its just a smell, does it affect the efficiency of the AC? Our bills are sky-high. BTW, we're renting, this is a house, so the owner would have to do it and pay for it, we have a good relationship with the owner and don't want to change that!
While its not unusual for warm air to come out before the cool air, it is not normal for it to smell like the heat coils are coming on.
There is a slight chance that the heat coils are coming on at the same time as the a/c is coming on. You should probably have a HVAC tech take a look at it.
Sometimes when the ac/heater combo turns the air back on, it smells like something is burning. This is during the time of year when the air is used often being used and not just when just after the heat has been on. I clean the filter every month on schedule. What could be causing this?
Sometimes when the ac/heater combo turns the air back on, it smells like something is burning. This is during the time of year when the air is used often being used and not just when just after the heat has been on. I clean the filter every month on schedule. What could be causing this?
You clean the filter? Most filters are intended to be replaced, unless you have a high end and expensive cleanable filter system.
I have usually only noticed a burning smell when I first turn the heat on in the fall. The dust that has accumulated in the heating element burns off.
I have on occasion noticed a musty smell the first time the Air Conditioning is turned on, if it has been off for awhile. This is probably also related to dust & fibers that has collected on the cooling coils.
The first house we owned I was surprised to see that the AC coils had accumulated a 1/4" thick mat of cat hair and fibers after 13 years of owning the house, yes we had an Angora cat. That was in spite of our regular replacement of the standard air filters every 30 days. That mat of fibers was inhibiting the flow of air through the system. No wonder it was inefficient. I already had a contract in place to replace the entire system with one that was more energy efficient, otherwise I would have just had the coils cleaned to see how well it performed afterwards.
We replaced the HVAC and started using high efficiency air filters that should be replaced every 3 months, which I have done. I had our HVAC maintenance person check the coils last year when they were 15 years old, and they had hardly anything on them.
The second house we bought, the previous owner had 3 dogs and she did not go a very good job of cleaning the house. It smelled doggy. Even after having the tile floors and walls scrubbed, and the carpet replaced in the two rooms that had it, it we could still smell a doggy swampy odor when the AC turned on. I had the coils checked and they relatively were clean. The AC coils had been replaced a few years earlier, but not the heating equipment. The lined ducts also appeared to be clean, as far as we could see into them. The smell never went entirely away until we had the complete heating and AC system replaced, except for the ducts. So apparently the odor was in the heating system and air handling equipment. Air flows over that part of the system, even when it is turned off.
If you smell anything burning when the AC is on the first thing I would look for is the electric backup heat (if that's what you have for backup heat) coming on meaning the white wire (in most cases) is shorted to another power wire like the fan (green) or the condenser/heatpump contactor wire (yellow).
When this happens the backup heat will be on at the same time the cooling coils are working. It generally feels cooler in the home even if the temperatures are the exact same as when it's off, it's like a big dehumidifier at that point.
As far as HVAC smells is concerned, the most common smell is dirty sock syndrome and it's caused by bacteria that forms on the coils of heatpumps. Heatpumps have the cooling coils before the backup heat so the coil never gets hot enough to sterilize itself. In gas backup heat systems the coil is after the heat exchanger so the cooling coil will get well above a sterilization point over its use during the winter.
You also have to think about your particular system. Do the ducts run in the attic? If so it will take quite a bit of time for the duct work to cool off and during that time period you will be getting hit with attic temperature air as the ducts cool down. Some people with sensitive noses might smell hot ducts or you may even have a leaky return plenum that's pulling in hot attic air when it's most notable before the cooling coil gets to operating temperatures. It generally takes 5 minutes or longer for the cooling coil to get fully to its operating temperature.
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