Heating Ventilating and Air Conditioning

Heating, ventilating and air conditioning (HVAC) refers to a system used in designing automotive or indoor environmental comfort. It uses ventilation air ducts to provide cooled or heated air to an automobile or a building through outlet vents.

15,506 Questions
Heating Ventilating and Air Conditioning
Electronics Engineering
Home Appliances

Which way should you set your ceiling fan to turn - in the summer and in the winter?

These recommendations depend on the height and size of the room, the season, and the activity taking place in the room.

Keep in mind that warm air rises to the top and cold air settles on the bottom. Air settles in layers from warm at the top to cold at the bottom, if left alone at equilibrium.

Ceiling fan recommendations:

In the winter

Set the fan to run counterclockwise (reverse; this looks clockwise as you are looking up). This will redirect the warm air from the ceiling and down the walls and into the living space where the people actually are. In a house, you would run the fan at a low speed so that you don't actually cool the warm air that you are moving downward. If you have a high ceiling, or are trying to heat a hall or a church, you may want to increase the fan speed so that the warm air will reach the living space as long as the fan speed does not create an unwanted downdraft at the people below.

In the summer

In a room of normal height (8 - 10 ft), you should operate your fan so that it turns clockwise (this looks counterclockwise as you are looking up), causing a more directed downdraft, especially with the fan running slightly faster. This causes a wind-chill effect because the skin evaporates slight amounts of water from the sweat glands and thereby provides cooling through the skin's surface. However, the air is only moved but not cooled! You may find that you can turn your thermostat down a degree or two and save more money on energy costs. The air blowing down won't actually cool the room though, so you should turn the fan off when there are no people (or animals) in the room.

In a high hall or church

It may be best NOT to run the fans at all in summer. This lowers the demand for cooling since the hot layer on top is an excellent insulation between the cool air near the floor (and the people) and the hot roof and outside.

A large, tall manufacturing hall would typically have different goals. There one would have a floor full of heat producing machinery plus the people operating it, working hard and welcoming a bit of a breeze. Then it would make sense to run the fans at fairly high speed to create a certain and directed downdraft. And with the shifts going throughout the days of the week, the fans should be running all the time and maybe in all seasons.

Finally, fans typically use 80-100 watts. When used properly, ceiling fans can really help to optimize the comfort level of the people and save energy and money.

Another user contributes this:

The important point from the previous answer is that fans are for cooling people. Advanced Energy (see the Related Link) says: "The most optimistic estimates I've seen on energy savings from ceiling fans peg the air conditioning savings at about 15%, assuming people do raise the thermostat setting and only run the fans when people are in the room, and taking into account the cost of energy used by the fan itself."

Home Improvement
Heating Ventilating and Air Conditioning

How much does it cost to build a wood burning fireplace?

1000000 vietnamese dong

Home Improvement
Heating Ventilating and Air Conditioning

Which direction should a ceiling fan go in the summer?

Fans should spin counterclockwise in the summer. The counterclockwise rotation pushes cool air down, while clockwise rotation can be used at a low speed in the winter to pull cool air up and push warmer air down.

Keep in mind, though, that ceiling fans don't actually cool rooms—they just create a breeze that has a wind chill effect, making you feel cooler. So you can turn the fan off if nobody's home.

Air Conditioning and Coolant
Heating Ventilating and Air Conditioning

Why does your home central air conditioner run but not blow cold air?

do you have your a/c set to fan? not a/c? otherwise you might need to contact your local a/c repair man and e will tell you you need a charge of freon in your system.


Why not to start checking the simple points like the filter, duct mechanism, etc.

Not so simple to give a "One Size Fits All" answer for but here are a few things to check.

1) when the system is running does the outside unit kick on? That is the condensing unit and supports the compressor which ultimately provides the cooling to the coil in the unit inside.

2) is the air filter dirty or do you have low air flow if so check the lines at the outside unit see if they're frosting or icing up. If they are try the air filter but if that still doesn't solve the problem call for service a low freon charge will cause icing.

3) if you have low flow but a clean filter check the "MERV" rating on the filter a merv 6-8 should be sufficient for most applications except cigarette smoke. The lower the merv # the less the resistance to air flow the larger the particle rating that it will filter in microns.

4) There are other components which can require servicing but they are normally handled by your service person unless you are familiar with HVAC repair. Have a Great day.

Heating Ventilating and Air Conditioning
Home Electricity
Home Appliances

Is it a fire hazard to leave a bathroom ceiling vent fan running?

Bathroom ceiling vent fans carry no warnings about continuous use. A fan in good condition, used in a good environment, will not heat excessively. However, a defective, older, or worn fan, or a fan that is binding or prevented from turning, or operated where airflow is blocked, can overheat, possibly dangerously. If a fan is making any kind of grinding or squealing noise, it should not be operated. A fan that does not turn freely should not be turned on. Such defective fans should be replaced, and it is good practice to replace any older ceiling fan (over six years) as a matter of course. They operate in harsh conditions, often ventilating moist or dirty, smoky air. A good quality, new fan will likely be quieter and more efficient, and it won't have the wear problems that can cause overheating. Potentially it is a fire hazard. Many vent fans use an open frame motor that depends upon air flow past it for cooling, and some vent fans are enclosed in plastic housings.

Over time, dust and lint can collect on this open frame motor, insulating it from the air flow and causing it to heat up. Eventually, if it gets hot enough, it can fail electrically and blow a spark. This spark can ignite the dust and lint, and if the housing is plastic the housing can ignite as well. This becomes a serious problem.

More here, about an actual case where this happened:


Heating Ventilating and Air Conditioning

Why do central A C line freeze?

The central AC line freeze due to evaporator coil. Because, This is the part of air condition system which transfers the inside to outside of the home. the two reason behind it it can freeze due to restricted air flow and lack of sufficient refrigerant. the result is that the air conditioner's evaporator coil cannot operate to properly dissipate heat, and in effect "overcools" itself. The result of this super-cooling is condensation and eventually ice from that condensation as it cools below the freezing point

Home & Garden
Heating Ventilating and Air Conditioning

How many cubic feet does one ton of air conditioner cooling?

5280 maximum

Heating Ventilating and Air Conditioning
Energy Conservation

Two ways you can save energy in space heating?

not heating space,by watering

Answer 2

The 2 most effective (but most expensive) ways are to replace your heating equipment with a more efficient unit and to insulate & air seal the building you live in.

Otherwise, close off rooms you aren't using and close the vents to them. Be sure to watch for mold, though, which can grow under those conditions. Use a programmable thermostat and turn the temp down when you are away.

Heating Ventilating and Air Conditioning
Home Electricity

Is a gas electric generator cheaper than public utilities?

Typical pricing of public utility will be always less than gas generator.

Heating Ventilating and Air Conditioning
Math and Arithmetic

How many BTU will it take to properly cool a 1200 sq ft home?

12000 btu = 1 ton

1 ton per 400 sq ft

1200 / 400 = 3

3 times 12000 = 36000 btu

Heating Ventilating and Air Conditioning

What area will a 15000 BTU propane heater heat effectively?

32x24 ft room with good insulation assuming cold like VT or MI.

Heating Ventilating and Air Conditioning

Can Air conditioner exhaust be used as heater?

its called a heat pump

Heating Ventilating and Air Conditioning
Wood-Burning Stoves

Can you burn cedar deck wood in wood stove?

Cedar- yes. Wood that has been treated to resist rot/insects, no. THAT wood has been treated with Chrome/ Copper/ Arsenic (known as CCA) and the smoke is VERY bad for you.

Air Conditioning and Coolant
Heating Ventilating and Air Conditioning

Why does air conditioners blow out white smoke?

You know somethings wrong when you see smoke! Disconnect the unit! Call someone who is competent and can diagnose and repair or replace it. Or let the system blow smoke until it catches fire then call the fire department the choice is yours .

Ok is it smoke, did it smell burned? Or was is a defrost cycle observed on colder days in heat pump systems? or was it a white vaporous cloud, after cloud dissipated was there signs of oil if so it was the ref charge

Home Improvement
Heating Ventilating and Air Conditioning

Can you burn wood in fireplace in California?

Due to air quality problems, there will be AREAS with CA where it is not permitted- and some areas where you cannot get a building permit to install one.

Air Conditioning and Coolant
Ford Ranger XLT
Heating Ventilating and Air Conditioning

How do you add freon to your air conditioner?

You need EPA certification to purchase and use any refrigerant that has an Ozone Depletion Potential (ODP*) greater than zero. These would include any refrigerants containing chlorine compoundssuch as R12 (CFC12 - formerly used in cars and trucks) or R22 (HCFC22 - no longer used in new central or window A/C units, but still in use in most existing units). Many other refrigerants also contain chlorine compounds, but these two are the ones you will find in most older home or automotive equipment.The problem with chlorinated refrigerants is that once they enter the atmosphere and are broken down by solar action, the chlorine molecules break free and can eventually damage the earth's ozone layer. The ozone layer is "way up there" and serves to block the most harmful solar radiation which causes skin cancer, etc. Although that's a very basic and simplified explanation, it works well enough for our purposes here. For these reasons, and up to this point, the above quoted answer is partially correct.

However, not all refrigerants contain chlorine, and those that don't contain chlorine have zero ODP*. Two examples would be R134A, used by most vehicle manufacturers, and R410A (one trade name is "Puron") now used by most residential A/C manufacturers. If you do some digging on the EPA web site, you will find that sales and use of R134A and R410A and a few other refrigerants are not currently restricted by the EPA, and it is legal for anyone to purchase them if the state they're in allows it. (You must also be aware of any state and local regulations.)

You should also know that your equipment may not need more refrigerant - the problem may have a different cause - and you can't just add any kind of refrigerant, since equipment is designed to use only certain refrigerants and oils. Adding the wrong ones can do serious damage to the compressor and other expensive components.

As for adding refrigerant to your own equipment: in most cases, it's not a good idea unless you have the tools, training, and experience for the job. There are risks to your personal safety, risks to the equipment if serviced improperly, and risks to the environment if refrigerant is allowed to escape. Also, regarding the environmental risks, the EPA makes it absolutely positively crystal clear that it is illegal to deliberately release ANY refrigerant, even non-chlorinated refrigerants, into the atmosphere. All refrigerants also have a global warming potential (GWP), so that is also an environmental consideration.

As mentioned earlier, you may check the EPA web sites to verify this information, and also to keep up-to-date on the latest regulations.

Window air conditioners are not designed to allow adding Freon. They are charged at the factory and hermetically sealed, so they shouldn't have any leaks or require recharging for the service life of the unit. If a window air conditioner no longer cools adequately it is most likely due to dust buildup on the coils, or eventually, the compressor wearing out and and becoming inefficient. If the unit has been used extensively, but otherwise maintained, the compressor may be suspect if the unit is over 10 years old.

Central air conditioning units have fittings on them with Schrader valves, similar to those found on automotive air conditioning systems. There is a high pressure side valve and a low pressure side valve. Refrigerant is added on the low pressure side, preferably while the compressor is running. A technician will use a special gauge manifold that allows monitoring of high side and low side pressure simultaneously while adding refrigerant from a portable cylinder.

Current regulations require an HVAC license to purchase and use refrigerants such as R12, R22 and R134a, generally called "Freon", although technically, not all refrigerants are sold under that brand name. There are alternatives, such as Duracool, which can be freely used in systems originally designed for R12, R22 or R134a, without having to change seals or lubricants, and can be purchased and handled without an HVAC license. Duracool-type refrigerants are essentially highly refined propane, and are thus flammable, so they need to be handled with care. Otherwise, they are environmentally friendly and non-toxic.

Try cleaning your coils first, not just the outside. Most service techs never clean the (evaporator) that's above your furnace because it is tough to do. Clean first before you assume anything. One reason it may be dirty is if you have indoor pets.

You can add freon to the low side of your a/c. When the gauges are attached to the system, you can use the third hose to attach to the freon can. Make sure you leave the can upright so as to add only the gas. Don't turn the freon can upside down to add liquid as this can lock up the compressor and then you will have to call the a/c repairman.

More information:

First, you need to be EPA certified unless you are charging your own appliance, and if adding certain types of refrigerants, certification is required to purchase the refrigerant as explained above. You need to know what kind of refrigerant. [ R22 R143a etc. ] On a home system a good set of gauges and connect properly on a 22 unit low side is blue, suction line is larger in size pipe. High side red smaller diameter. Connect both hoses check pressures if their is no reading the compressor is not running. If compressor is running on a 22 unit the high side red should be 225 to 275 should not go above 350 psi or it will cause damage your unit more or cause a rupture low side should be from 60 psi to 80 psi don't go any higher to much freon is no good and will cause higher temp. Be careful because were talking high pressures you should have a certified tech. do this if you add freon you must have a leak it dose not evaporate their is no winter summer freon its a sealed system and should never need refrigerant.

Some things to know:

#1. Don't burn your fingers, it hurts, real bad.

#2. Don't overcharge, even a little too much and you wont' remove humidity and it will never cool.

#3. He didn't mention bleeding out the air from your lines before charging after hooking up the cylinder, let that air into your system and you are causing more trouble.

If you want to do typical home improvement type things, if you are a DIY guy, stick with changing your filter monthly, make sure your drains are clear, and change/ check your thermostat batteries. anything else you are playing with high voltage, and freon.

I have had plenty of customers that decided to change their thermostat themselves to save $50. They shorted out the board, ended up costing themselves a $500 repair.

I would listen to the advice freezer-burn hurts an makes your finger black, and did you need to add refrigerant or take some out? Remember also to reclaim the refrigerant in an" EPA "approved cylinder. If you over load your compressor it will fail. If the compressor burns out it may have a chemical reaction with the refrigerant and produce acid in your system. Now you have a real mess at that point! All the refrigerant has to be removed, the compressor / motor replaced, the system purged, the oil replaced the refrigerant replaced, a run up of the system to check that it is running properly. I believe I would leave the servicing to the technician who has extensive (hours of class room and field experience) training.

Check cooling coil/evaporator(in the door unit)if there is ice built up then feel the air vent. If you do not feel air, it means your vent is blocked and you may need to clean the air vent. You probably have a leak. You need r22 test gauge and hose, reamer, tube cutter and flaring kit.

Check the suction pressure (big tube at out door unit) and remove 2 way cap and 3 way cap valve then connect the blue hose at service port 3 way valve (port located at left or right depends on the manufacturer.) You will get pressure about 40-45 psi (air conditioner is running) then use an Allen key(hexagonal wrench) to close 2 way valve (small tube or gas discharge side) wait 1-2 minute cooling operation then close 3 way valve (suction tube or big tube) immediately shut off air conditioner and pull out power chord. You may need 2 people one at in door unit and the other at out door unit. This method is to keep remaining gas inside the compressor/condenser. Then leak check, open 2 way valve about 90 degrees hold it for 10 seconds then close it. Measure the pressure and keep it open for 5-10 minutes. If the pressure does not indicate the same as when it was first measure it means that you have a leakage. For air conditioners 1- 5 years old, the leakage will happen at the copper tubing connection and improper flaring. Then you will need to clean the in-door and out-door unit. Use a spanner or wrench to loosen the copper flare nut at the out-door unit and in-door unit (inside insulation) then use PVC tape to cover all copper pipes to prevent dirt from going inside. Lift up out-door unit and use coil cleaner detergent. Wait 5 minutes then flush with water. Remove indoor front panel then disconnect out-door unit cable at front panel in door unit. Lift up indoor unit to disengage the hook and pull out the indoor unit, then clean the cooling coil, cover electrical parts with plastic. The last step is that you need to cut (use cooper cutters) the copper pipe on the flare nut connection (low side with big tube and high side with small tube) in-door connection and out-door connection. Then you will need to remove the burr from cut edge using reamer and make sure metal powder does not go in. Make a flare after inserting the flare nut onto the copper pipes. You can install the unit back now. Check the low side pressure of the unit. If the pressure is between 55-67 psi no need to charge it. Before u charge r22 gas u need to to purge air inside piping/tubing by using leakage check method. Just use the service port so their will be no need to use test gauge. Crack open 2 way valve for 10 seconds then close it. Now push the pin(same as a tire pin) at the service port 3 way valve for 3 seconds repeat this three times. You may need to purge all air inside test gauge and hose. Then check gas leakage using same method that was already explained. CHECK suction pressure 55-67 psi in running mode and set it to the lowest temperature (16 Celsius/27 Fahrenheit) and pipe length below 10 feet should be okay. If it is not okay, you will need r22 gas tank. Connect yellow hose to r22 tank and middle connection at test gauge. Then fully open tank valve and crack open blue stem at test gauge (do not exceed 60 psi to prevent flooding the compresser) for 30 seconds to 1 minute then close it. Measure the pressure for 1-3 minutes. Repeat this step until you get 67 psi in running air-conditioner or u can feel the suction pipe to see if it is cool. If your unit already empty you need r22 lubrication and weight scale put r22 gas-tank on the scale and read at out-door unit tag how much the manufacturer recommends the weight should be. Then u need to fill the yellow hose with r22 lubrication about 5-10 milliliters. Repeat charging method that has already been explained and measure the weight of the gas according to the manufacturer and then you are done.

What is "Super heat"?

You will hear and see this term all the time in reference to refrigeration. Simply put it is the difference between the temperature of a vapor line in relation to the temperature scale on a pressure gauge for a particular refrigerant or how much liquid is feeding the evaporator in relation to how fast it is being boiled off. for example (R22) if the suction gauge reads 70 psi then the evaporating temperature is 41 degrees but if the tubing is 51 degrees then you have 10 degrees of Superheat. A typical range for residential air conditioning is 8-18 degrees with some error based on extreme conditions. Once you understand Superheat you can diagnose obvious problems. For example a system that is under charged or has a stuck (closed) metering device will have high super heat (over 20 degrees) at the compressor and a system that is grossly overcharged or has a dirty indoor coil will have very low Superheat about 3-7 degrees with low suction pressure and the suction line will be very cold. It is ok and quite normal for the Superheat to change dynamically while the system is running, you will have to interpret what you are seeing.

What is "Sub cooling"?

Sub-cooling is similar to Superheat but happens in the condensing portion. Refrigerant when condensing will happen at a particular temperature which is very close to the temperature scale corresponding to head pressure for a given refrigerant. After the refrigerant is condensed it will try to assume ambient temperature but will never reach it. The difference between liquid line temperature and condensing saturation temperature is Sub-cooling and is a very good indication of "refrigerant level", but only when proper Superheat is indicated or you could have a misleading indication. Typically 20 degrees of Sub-cooling is desirable and the closer the liquid line temperature is to ambient the better (indicating an efficient system). Checking Sub-cooling in the heat mode of a heat pump has to be done carefully because you have influence of the space between the indoor coil and the point of measurement. For best heating you will want most of the refrigerant to be condensing in indoor coil without backing it up with refrigerant.

As a general rule Sub-cooling = Refrigerant charge quantity, Superheat = Refrigerant cycle performance. Check both!!!

Heating Ventilating and Air Conditioning

What is ac tonnage for tempstar acs036a2c1 fba036gc1?

3 ton

Heating Ventilating and Air Conditioning

How does dark curtain keep room cooler?

they deflect heat

Home Improvement
Heating Ventilating and Air Conditioning

How deep does a fireplace need to be?

Most building codes require that the firebox be at least 20 inches deep (except for a different style of fireplace, called a Rumsford, which can be 12 inches) Check YOUR local building codes. Also, make sure that the chimney extends the proper height above your roof or the fireplace won't draw.

Heating Ventilating and Air Conditioning

What is the abbreviation of TR represented in Air Conditioners?


Air Conditioning and Coolant
Heating Ventilating and Air Conditioning

Do central air conditioners need a return vent?


Microsoft Windows
Heating Ventilating and Air Conditioning

Can you install a window air conditioner in a crank out window?

Generally speaking, this would be difficult to do.

Air Conditioning and Coolant
Heating Ventilating and Air Conditioning

Will a new r22 coil work with 410 refrigerant?

An R22 coil will work properly with R410A only ifseveral conditions are met.

First, the manufacturer of the coil must specify that it will work with both refrigerants. R410A systems operate at about 40 to 70 % higher pressure than R22 systems.

Second, the new coil must be equipped with an inlet control (either a thermal expansion valve or orifice) that is intended for R410A. The new coil may not use a capillary tube metering system to control refrigerant flow into the evaporator coils.

Third, the tonnage, or Btu capacity, of the coil and control device, and the EER/SEER of the coil must match those same ratings for the condensing unit.

Fourth, if the new coil has been used in an R22 system, it must be thoroughly flushed clean of oil, and must be refitted with the proper control valving for R410A.

Heating Ventilating and Air Conditioning

What is the tonnage and seer of a Tempstar nac060aka9 ac unit?

It is a 5ton 10 SEER

Home Improvement
Heating Ventilating and Air Conditioning

Should you close attic vents during the winter?

Attic ventilation can be as important in the winter as in the summer. The vents allows the air space in the attic from having a build up of moisture. With the vents closed, there could be times the humidity in the attic would be high enough to cause mold and mildew on the lumber, especially the roof sheeting. In the summer the vents allow heat to be vented out and in the winter they allow moisture to be vented out. Not an expert? Just been in the HVAC & insulation biz for 41 years Eric S.


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