What is the purpose of the vent open or closed on a window air conditioner? An open vent on a window air conditioner allows fresh air from outside to come into the home and circulate along with the cool air produced by the unit. A closed vent prevents warm, fresh air from entering the home. What is a furnace fresh air intake vent? How can you use a portable air conditioner without an exhaust hose? How do you clean an air conditioner? While an open vent is not ideal for efficiency, since the unit has to work harder to cool down the warm air, it does serve a purpose. Leaving the vent open refreshes stale air and removes odors from the room. Additionally, the vent makes it possible to run the unit on the fan-only setting, which simply pulls in air from outdoors on cool or mild days. How much routine maintenance does a window air conditioner need? At least once a year a window air conditioner must receive routine maintenance, or else the unit's performance and efficiency may degrade while the risk of...

What are the steps to install air conditioner window kits? To install an air conditioner in a double-hung window, lift the unit into the window, align the bottom flange with the outside edge of the sill, and then c... Are window air conditioners easy to repair on your own? Some portions of windows air conditioner units are simple to repair, but the compact design of window air conditioners might require users to disassemble a... How do you install an air conditioner in a basement window? Window measurements should be taken before buying the air conditioner, and when installing the air conditioner, it might be necessary to remove the window ... How do you light the pilot light on an Empire Corcho wall heater Model R-15? What are some benefits of waterless coolant? What is a simple comfort thermostat? How do you care for a hibiscus plant? What is the best way to cover a broken car window? Is a Peerless heater eco-friendly?Q: Should we block our crawl-space vents or keep them open?

Q: Some people tell me to block our crawl-space vents all the time to stop termites in the summer and heat loss in the winter. Other people say that I should be opening and closing the vents with the seasons. Which approach is right? —Jack Teasley, Williamsburg, VA. A: Tom Silva replies: I think working vents in crawl spaces are a good idea, and so do the building codes, which generally require them. These vents allow outside air to circulate under the floor in summer to prevent the moisture buildup that encourages mildew and rot. In winter, when the air is drier, the vents are closed to reduce the chance that the pipes in the crawl space might freeze. The simplest way to close foundation vents for the winter is to plug them from the outside with foam blocks made specifically for this purpose. Just remember to remove the plugs when the weather turns mild in the spring. As you do that chore, check to make sure that the vent screens are intact so that insects and other critters don't make a home under your house.

Automatic vents are less fuss. Air Vent makes ones that open at about 70 degrees F, close about 40, and don't require any electricity. You do not say whether your crawl- space floor is made of dirt or concrete, but if it is dirt, spread 6-millimeter plastic sheeting over it to help block that source of moisture.Your air conditioner, heat pump, or furnace probably uses a lot of energy. Heating and cooling makes up about half of the total energy use in a typical house. how to choose central air conditioning unitsFor air conditioners and heat pumps using electricity generated in fossil-fuel fired power plants, the amount you use at home may be only a third of the total. air conditioner window unit filterA question I get asked frequently is whether or not it's OK to close vents in unused rooms to save money. ac unit safety switch

The answer may surprise you. The photo above shows a typical vent for an ducted HVAC system (air conditioner, heat pump, or furnace). On the return side, you'll typically see plain grilles, but on the supply side, where the conditioned air gets blown back into the house, most HVAC contractors install registers like the one above. It has a lever of some sort that allows you to adjust the louvers behind the grille. You'd think that since it's adjustable, it must be OK to open or close it to suit your needs, right? The blower in your HVAC system is the heart of the air distribution. It pulls air from the house through the return ducts and then pushes it back into the house through the supply ducts. In high-efficiency systems, the blower is powered by an electronically commutated motor (ECM), which can adjust its speed to varying conditions. The majority of blowers, however, are of the permanent split capacitor (PSC) type, which is not a variable speed motor. In either case, the system is designed for the blower to push against some maximum pressure difference.

That number is typically 0.5 inches of water column (iwc). If the filter gets too dirty or the supply ducts are too restrictive, the blower pushes against a higher pressure. In the case of the ECM, a high pressure will cause the motor will ramp up in an attempt to maintain proper air flow. An ECM is much more efficient than a PSC motor under ideal conditions, but as it ramps up to work against higher pressure, you lose that efficiency. You still get the air flow (maybe), but it costs you more. The PSC motor, on the other hand, will keep spinning but at lower speeds as the pressure goes up. Thus, higher pressure means less air flow, and, as we’ll see below, low air flow can cause some serious problems. The important thing to remember here is that no matter which type of blower motor your HVAC system has, it's not a good thing when it has to push against a higher pressure. In a well-designed system, the blower moves the air against a pressure that's no greater than the maximum specified by the manufacturer (typically 0.5 iwc).

The ideal system also has low duct leakage. The typical system, however, is far from ideal. Although most systems are rated for 0.5 iwc, the National Comfort Institute, which has measured static pressure and air flow in a lot of systems, finds the typical system to be pushing against a static pressure of about 0.8 iwc. Now we're ready to address the question of closing vents. When you start closing vents in unused rooms, you make the duct system more restrictive. The pressure increases, and that means an ECM blower will ramp up to keep air flow up whereas a PSC blower will move less air. Most homes don't have sealed ducts either, so the higher pressure in the duct system will mean more duct leakage, as shown below. The more vents you close, the higher the pressure in the duct system goes. The ECM blower will use more and more energy as you do so. The PSC blower will work less but not move as much conditioned air. In both cases, the duct leakage will increase further. In addition to moving air, your air conditioner, heat pump, or furnace is also cooling or heating that air that flows through the system.

The air passes over a coil or heat exchanger and either gives up heat or picks up heat. In a fixed-capacity system—and most are—the amount of heat the coil or heat exchanger is capable of absorbing or giving up is fixed. When the air flow goes down, less heat exchange happens with the air. As a result, the temperature of the coil or heat exchanger changes. If air flow is low, it'll dump less heat into the coil in summer, and the coil will get colder. If there's water vapor in the air, the condensation on the coil may start freezing. You might even end up with a block of ice, as shown in the photo below. And ice on the coil is really bad for air flow. It's also bad for the compressor as not all of the refrigerant evaporates and liquid refrigerant makes its way back to the compressor. If you want to have to buy a new compressor, this is a good way to do it. Same thing if you have low air flow over a heat pump coil in winter. You could get a really hot coil, high refrigerant pressure, and a blown compressor or refrigerant leaks.

Similarly, low air flow in a furnace can get the heat exchanger hot enough to cause cracks. Those cracks, then, allow exhaust gases to mix with your conditioned air. When that happens, your duct system can become a poison distribution system as it could be sending carbon monoxide into your home. Let me now summarize the problems I've described above that can result from closing vents in your home. The first thing that happens is the air pressure in the duct system increases, which may give rise to these negative consequences: You're not guaranteed to get all the problems that apply to your system, but why take the chance. I recently wrote about all the IT folks who are trying to follow in Nest's footsteps and profit from the home energy efficiency movement. I used the Aros smart window air conditioner as the example of companies that think you can solve problems just by creating a product with a smartphone app. Well, meet a more malignant idea: the E-vent. (You can find it easily enough by searching on the term "Kickstarter E-Vent.")

It's just a Kickstarter project right now, and maybe it won't get funded. If it does get funded, however, it will be subject to all the problems I described above. It doesn't matter whether you close the vents by getting up on a ladder in your home or from the beach in Cozumel. It's still a bad idea. The E-Vent page on Kickstarter says they monitor the air temperature and open vents if the temperature gets too cold while air conditioning or too hot while heating. Of course, that’s not going to work unless they monitor the temperature right at the coil or heat exchanger. And that still probably wouldn’t work because there’s a wide range of acceptable temperatures for different systems. This is an HVAC product developed by people who don't know some very important principles of heating and air conditioning. Let's hope they don't kill anyone. The fundamental problem here is that closing supply vents in your HVAC system changes what comes out in particular locations. It doesn't change what the blower is trying to do.

Nor does it change the amount of heat the air conditioner, heat pump, or furnace is trying to move or produce. It's possible you may be fine closing a vent or two in your home, but it will depend on how restrictive and leaky your duct system is. If it’s a typical duct system with 60% higher static pressure than the maximum specified, closing even one vent could send it over the edge. If it’s a well designed system with low static pressure and sealed ducts, you shouldn’t have a problem as long as you don’t try to close too many. The only way something like this could work is if closing a vent signaled the blower to move less air and the air conditioner, heat pump, or furnace to move or produce less heat. (Properly designed zoned duct systems do this by using variable speed ECM blowers with multi-stage systems.) Otherwise you're subject to those 7 unintended consequences, one of them potentially deadly. The Sucking and the Blowing — A Lesson in Duct Leakage- Understanding Air Leakage