OPINION: I was on Facebook the other day and something caught my eye: someone was using the fireplace to vent their portable air conditioner down the chimney. Brilliant, was my first reaction.
I live in a Victorian terraced house which can get very hot in the summer and trying to place a portable air conditioner near a window can be a real challenge. So using a permanent, open vent seems like a brilliant idea, and the unsightly hose can be tucked away out of the way.
It’s just that the more I thought about it, the less sense this idea made. Although I’ve found people online who say they’ve done this and it worked, there are clear issues that mean I wouldn’t do this.
It’s not just hot air
Before diving into the specifics, it’s essential to understand how portable air conditioners function. These devices don’t cool rooms by simply blowing air in; instead, they extract hot air from your space, channeling it through a hose to be vented outside. The cold air you feel is merely room air that has been stripped of its heat.
Moreover, modern portable air conditioners also dehumidify the room. The moisture extracted is typically expelled through the same exhaust hose, reducing the need for a collection tank unless in extremely humid conditions.
So hot, moist air comes through the hose and cool, dry air comes out the front vent.
Condensation drips down again
Hot, humid air is the main problem here. Chimneys are designed to handle very hot, dry air. Inserting the AC tube means the hot air comes into contact with the cooler chimney surface, causing moisture to condense and flow back up your chimney.
Not only will the drain create a damp environment, but it will also be messy and mixed with years of soot. That’s not a good idea.
If you have a stove and a lined chimney, that’s still not a good idea. You would have to seal the front of the furnace to insert the air conditioning pipe, but the hot air will condense in the liner and create water in your furnace.
Often you don’t know how good a chimney is
Not all fireplaces work, especially in old homes. The chimney may be blocked or blocked. In any case, there could be problems preventing hot air from escaping.
Distance is a real problem
If you somehow manage to jam the air conditioning pipe in the chimney, the warm air may not fully rise out of the chimney and some of it may flow back into your home.
Ideally, you want to completely seal the chimney, for example with insulation board and/or plyboard, with insulating tape around the edges. The air conditioning hose can then be led through a hole in your insulation into the fireplace room.
But there’s a secondary problem: distance. With a chimney, the hot air has to travel a long way. A typical Victorian home has a ceiling height of 10 or 12 feet. From the ground floor it’s at least 20 feet to the attic (just over 20 feet), and then you need even more to go past the roof line. So you’re looking at a good 30 feet or more in front of you.
Portable air conditioners have a maximum hose length of 1.5 m. Any longer than this can cause back pressure, which can overload the compressor. This reduces efficiency at best; In the worst case, the device could be damaged. To put it simply, portable AC units are not powerful enough to transmit power over the distances you would need in a fireplace.
Obtain proper window sealing
For all of these reasons, I would not use a chimney to exhaust a portable air conditioner, whether it works or not. A window is your best option. For sliding windows, many units come with a sliding bracket that can be attached to the bottom. However, for casement windows, it is easy to find window kits that will seal the window while leaving room for the hose. If you really don’t want to flaunt anything and want something much neater, you’ll need a properly installed split air conditioner instead.
For more in-depth insights and recommendations, refer to the original source here.
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