HVAC for the Tech North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. HVAC - 1
A/C and Heating Components • Combination of many components • If linked properly, years of trouble free service. • If not, the possibility of uncomfortable customers and possibly the source of illness within the home.
Our HVAC Roots • 1895 Ernest Bryant and Ezra Smith approached Dave Lennox with an idea. • 1902 Willis Carrier invented the first dehumidifier for a painter from Brooklyn. • 1906 Carrier controlled temperature for a cotton mill in South Carolina. • 1952 Lennox got into the residential cooling market and has become an industry leader. • Without HVAC, productivity would decline, and we just wouldn’t be as nice.
What is a BTU? • British Thermal Unit • Heat needed for 1 Lb water 1 degree F • 1 BTU = 1 Large kitchen match • BTUH is Quantity and Time • 12,000 BTUHs per Ton of A/C • 3 ton A/C can remove approx 36,000 kitchen matches of heat in one hour. • A 3 ton A/C system does NOT weigh 6000 lbs.
Physics of Air • Heat travels from warmer to cooler • Moisture transfer is from wetter to drier. • The air conditioner is a mechanical device that collects heat from an undesirable location and conveys it to a more desirable location, namely inside the house to outside the house.
The six elements of total comfort 1. Air Circulation How air is moved through the ductwork and through the house. 2. Humidity Too much too little effects and solutions 3. Even Temperature No large temperature swings throughout the home 4. Fresh Air Ventilation, why bring in outside air? 5. Filtration What is a good filter? 6. Quiet Who wants a noisy A/C or heater?
Component of an A/C System • The Compressor is the heart of the system • Its job is to compress the gas and forces it around the system.
Metering device • Controls the flow of refrigerant • Fixed metering device has a small hole called an orifice. • When water is sprayed it hits the skin and as it evaporates it removes heat.
Metering Device • The TXV also controls the flow of refrigerant • It opens and closes automatically based on the need to give the unit maximum efficiency.
Metering device Evaporator • Evaporates the refrigerant and absorbs the heat from the home. • About 35-45 degrees • Dehumidifies • Drains water collected from the home.
Blower • Blower moves a specified amount of air through the ductwork and throughout the home. • If it cannot, the unit works harder and performs less. • As efficiencies increase, proper airflow becomes more critical.
Condenser Coil • The condenser coil is where the heat that was absorbed into the refrigerant is rejected from. • The refrigerant is cooled down and condensed back into a liquid.
Condenser Fan Motor • Pulls outside air across the coils to cool the refrigerant and exhaust the heat away from the home. • Newer blades are tapered for quietness.
INDOOR Blower #4 OUTDOOR Fan #6 Evaporator Coil #3 Condenser Coil #5 Compressor #1 Metering Device #2 6 Components of an A/C system
Lineset, Refrigerant lines • Carries refrigerant from the evaporator to the condenser and back again. • Sizing is important RTM • Insulated on the suction line • Might have a drier. • Measured I.D.
Driers • Liquid drier, for the little, liquid line collects moisture and debris. Used whenever system is opened. • Suction line filter, is used after burnouts or when needing to collect large amounts of debris.
INDOOR OUTDOOR The blower blows cooler air back into the room Heat from the house is discharged outdoors Warm air, from the house, goes in to the Return air The condenser fan motor, to cool the condenser coil, draws in outdoor air Airflow • The blower picks up heat from the home and the evaporator absorbs it into the refrigerant. • The condenser fan discharges this same heat from the condenser coil to a more desirable location.
Package units • As the name implies, a package unit is an A/C and possibly heating system with all the components packed into a single package. • Ties into ductwork through the roof or a wall.
Ductwork Install once for a lifetime The straighter the better If it leaks air its not good enough • Metal duct • Ductboard • Flexible
Duct Cleaning • Rotating brush with vacuum attached. • Negative pressure system that uses brushes and whips to move dust toward a remote vacuum system. • Neither system is effective unless a visual inspection of the ENTIRE duct system is accomplished. • Ducts should ideally never have to be cleaned.
Heat pump • A heat pump works just like an A/C in the cooling mode but in the heating mode causes the refrigerant to flow backwards. • (Turn a window unit around into a window backwards)
Heat pump Heating • By reversing the flow of refrigerant the two coils, evaporator and condenser, are reversed. The refrigerant now flows from the compressor to the indoor coil first where the refrigerant condenses and then flows to the outdoor coil where it evaporates.
Heat pump Defrost • The out door evaporator will now ice up. • The system must now defrost. • The defrost sensor senses ice or a very low temperature on the outdoor coil. • The sensor tells the circuit board to start a defrost. • The unit now has the refrigerant flow just as it did in cooling. • The refrigerant warms the outdoor coil until the ice melts and it shifts back into the heating mode.
Heat pump Efficiency • A heat pump when compared to electric heat is approximately 3 times more efficient to operate. • (3 COP, Coefficient of Performance) • When compared to gas heat they are close to the same. • Local gas and electric prices dictate the efficiency of each.
Humidity • Humidity is measured in Percentage of Relative Humidity (%RH) or the amount of moisture in the air compared to how much moisture the air can hold at any given temp.
Humidity • Moisture that is in the air is a form of heat (Latent Heat). • The higher the humidity usually the more uncomfortable you are in the cooling season, but it can make us feel warmer in the heating season as well.
Relative Humidity • If the Relative Humidity is too high, we can have moisture problems. Fungus can grow, dust mites thrive, and a host of other undesirable conditions can occur. • If the Relative Humidity is too low, we lessen those detrimental effects but now we can have static electricity, skin disorders, nose bleeds etc. another group of issues we must consider. • Lennox has chosen 25-50% as the optimum range for both comfort and IAQ issues
Filters • Filters can be grouped into two major categories the ones that protect the equipment and the ones that protect our customers. • Particulate can be grouped into the big stuff that floats around that our noses can filter and the small stuff that floats around that our noses can’t filter. • Problem; homes contain tremendous amounts of small particulate.
Filters The graph below shows the incidence of health problems that can be aggravated by airborne particulates. By reducing the airborne particulates in the home, we can help to reduce the incidence of these health concerns.
Filtration • Arrestance The percentage of the big dust that a filter can remove before becoming fully loaded. • Dust Spot The percentage of the small dust that a filter can remove before becoming fully loaded. • MERV Minimum Efficiency Reporting Value A rating 1-16 a filter receives after 6 different tests, with different sized particulates, rating the filter at worst case scenario.
Typical Ratings for Various Filters MERV Type of filter Average Dust Spot MERV 1-4 Fiberglass, Disposable Panel, 20% Washable metal/synthetic, Self charging (Passive) MERV 5-8 Pleated, Media panel, Cube 20-35% MERV 9-12 Extended pleated 40-75% MERV 13-16 Electronics 80-95% HEPA 99.9%
Recommendation for filtration • Lennox has chosen to use a MERV 8 as its target minimum for recommendations. • Lennox’s HEPA Bypass is the best product for particulate filtration
Recommendation for Purification • Lennox’s Pure Air system has a MERV 10 filter to catch dust, UV bulbs to sterilize germs, and a catalyst to help eliminate odors
Ventilation • The V in HVAC is one of the most overlooked areas in our industry • By bringing in outdoor air we can provide fresh air to dilute the toxic air in our homes. • It is estimated by the EPA that the air inside the home is 40 to 100 times more polluted than outdoor air. • Off gassing is when products let off VOCs, (Volatile Organic Compounds) into the air we breathe. • The recommended methods for controlling these VOCs are to: • Remove products from the living space. • 2.Ventilate.
Ventilation • HRV is typically used in northern climates because it will not dehumidify the incoming fresh air. • ERV is typically used in southern climates where we must dehumidify the fresh air being brought into the home.
Wiring, Voltages • 110, 115, or 120 volt home voltage for Gas Furnace. • 210, 220, 230, or 240 volt High voltage for Electric heat, Heat pumps, and Condensers. • 24 volt control voltage Thermostat, low voltage.
BanT A/C and Heat 123-555-0987 Perfection USA Thermostat • The brain of the system • Can control, temperature, humidity, set back times and temperatures, and continuous fan for filtration needs. • Bimetal and electronic • Non-programmable and programmable • 5/2 and 7 day program
Primary and Secondary Drains¾” PVC Pipe Key words • Down • Straight • Secure Three primary Drains • 90% Furnace • A/C evaporator coil • Humidifier Secondary drain should be installed when over conditioned space.
Other types of Heating • Electric Heat Similar to a hair dryer Least expensive to install Most expensive to operate • Gas Heat and Oil Heat Gas and Oil furnaces take the fuel and ignite it, with the fuel burning in a chamber the chamber gets very hot. The blower is now turned on and the air from the home is moved around the chamber heating the air. The warm air is now blown into the home.
No matter what fuel type, Natural gas, Liquid Petroleum, or Fuel Oil, the Heater (furnace) has a primary job of introducing warm air into the living space when temperatures fall outdoors, and the home begins to loose heat through the walls, floors and ceilings.
Types of Ignition • Standing pilot. A pilot light that burns and ignites the fuel for the burner to burn. • Was used in heating for many years • Still used on water heaters • Being replaced with more efficient means of ignition. upon.
Types of Ignition • Electronic ignition. Uses an electrical spark to ignite the burners. • Does not require the burning of fuel for a pilot light as it lights the burners directly. • Sometimes-called spark ignition. • Used on some gas stoves, Bar B Que grills, and some brands of gas furnaces. • Oil furnaces use electronic ignition almost exclusively.
Types of Ignition Hot surface ignition or HSIhas become the predominant form of ignition. Uses electricity to heat up a surface until it becomes hot enough to light the burners. A basic form of this is the automobile cigarette lighter.(Remember those?) Uses an electrical current to make the coil glow red hot to be used as an ignition surface. Many different types of surfaces have been tried and are being improved
Oxygen Fuel Heat Proper combustion • Fuel • Oxygen • Heat
Heater Locations • Horizontal • Attic • Crawlspace • Upflow • Closet • Basement • Mechanical room • Garage • Attic • Downflow, Counterflow • Closet • Mechanical room • Package • Roof • Side of Home
Vent piping • Single wall metal pipe used as a connector or a starter piece. • Double wall Type B vent pipe used for 80% efficient and less units. • Schedule 40 PVC is used on 90% efficient, positive pressure venting and combustion air.