Demand controlled kitchen ventilation (DCKV) is a building controls approach of slowing down kitchen exhaust fans and subsequent supply air in response to the actual cooking loads in a commercial kitchen. Traditional commercial kitchen ventilation systems operate at 100% fan speed independent of the volume of cooking activity and DCKV technology changes that to provide significant fan energy and conditioned air savings. By deploying smart sensing technology, both the exhaust and supply fans can be controlled to capitalize on the Law of Affinity for motor energy savings, reduce makeup air heating and cooling energy, increasing safety and reducing ambient kitchen noise levels.[30]
The summers here in Alexandria can range from almost pleasant to downright brutal. And you know as well as we do that it’s those latter days when your central AC or heat pump will decide to go down! But you don’t have to seek solace at the Waterfront or over at Cameron Run Regional Park. The secret to restoring your comfort lies with the certified specialists at HVAC & Plumbing Unlimited!
There was an unidentified beeping sound which I thought was coming from my indoor HVAC unit. The technician patiently spoke to me over the phone and we discovered that it was not the HVAC that was making the noise. The technician was extraordinarily helpful and polite as we spoke and he saved me a few hundred dollars since he helped me over the phone and didn't have to make an emergency visit. HVAC Unlimited is our "go to" company for all our heating and cooling needs!
Precision’s technicians are all NATE certified. This is the highest certification in the air conditioning industry. With that, we can take pride in saying that we provide the best AC repair Phoenix residents can get. Our technicians are thoroughly screened and tested before they begin work on your home. Our AC technicians provide top-notch Phoenix air conditioning repair, and proof of that is their ability to repair most every brand of HVAC equipment. These brands include Trane, Bryant, Ruud, Goodman, Amana, Precision, Armstrong, Carrier, Coleman, Honeywell, Janitrol, Lennox, Payne, Rheem, York, Goettl, American Standard along with many more.

Although HVAC is executed in individual buildings or other enclosed spaces (like NORAD's underground headquarters), the equipment involved is in some cases an extension of a larger district heating (DH) or district cooling (DC) network, or a combined DHC network. In such cases, the operating and maintenance aspects are simplified and metering becomes necessary to bill for the energy that is consumed, and in some cases energy that is returned to the larger system. For example, at a given time one building may be utilizing chilled water for air conditioning and the warm water it returns may be used in another building for heating, or for the overall heating-portion of the DHC network (likely with energy added to boost the temperature).[4][5][6]
In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, (de-) humidification, cooling, cleaning, ventilation, or air movement). In common usage, though, "air conditioning" refers to systems which cool air. In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC.[3] 

Air flow meter Aquastat BACnet Blower door Building automation Carbon dioxide sensor Clean Air Delivery Rate (CADR) Gas sensor Home energy monitor Humidistat HVAC control system Intelligent buildings LonWorks Minimum efficiency reporting value (MERV) OpenTherm Programmable communicating thermostat Programmable thermostat Psychrometrics Room temperature Smart thermostat Thermostat Thermostatic radiator valve
When your furnace isn’t regularly serviced it can operate less efficiently. This increases your energy bills and also prevents your furnace from keeping your home as warm as you like. Keep your furnace properly maintained with regular service. The national average furnace service cost is between $60 and $80. Companies may offer tuneup specials that cover all the necessary testing, tightening, measuring and cleaning to keep your equipment running at top efficiency. If you have a newer system, furnace service costs may be covered by your warranty. Outside of warranty, a basic tuneup might start at $58 and a more advanced maintenance cleaning could be over $120. Here are some signs your furnace may need service:
During the colder months of the year, the comfort of your home depends on the proper working function of your heating system. When your furnace breaks down or stops working properly, reach out to the heating experts at Horizon Services! We have nearly 30 years of experience providing reliable furnace repairs for homeowners throughout Delaware, Southern New Jersey, Southeastern Pennsylvania, and Northeastern Maryland. Our technicians are able to repair just about any type of home furnace using cutting-edge techniques and state-of-the-art tools. We can accurately diagnose the root of the issue and quickly get to work making the necessary repairs. We even offer same day service at no additional cost!
In 1758, Benjamin Franklin and John Hadley, a chemistry professor at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water. They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to speed up the evaporation. They lowered the temperature of the thermometer bulb down to −14 °C (7 °F) while the ambient temperature was 18 °C (64 °F). Franklin noted that, soon after they passed the freezing point of water 0 °C (32 °F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 6 mm (1⁄4 in) thick when they stopped the experiment upon reaching −14 °C (7 °F). Franklin concluded: "From this experiment one may see the possibility of freezing a man to death on a warm summer's day."[9]
In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a facility to be heated and cooled by a single piece of equipment by the same means, and with the same hardware.
If you live in a warmer climate, your air conditioner is likely one of the most essential pieces of equipment for your home. The best course is to perform regular routine air conditioner maintenance to ensure its smooth operation during the warmest months of the year. Annual tune-ups by a professional HVAC technician will increase the lifespan of your unit. When repairs are needed, be sure to hire a technician trained and certified in HVAC repair for best results. Following these guidelines will ensure that you are comfortable and cool through the summer season.
Most modern air-conditioning systems feature a dehumidification cycle during which the compressor runs while the fan is slowed as much as possible[citation needed] to reduce the evaporator temperature and therefore condense more water. When the temperature falls below a threshold, both the fan and compressor are shut off to mitigate further temperature drops;[clarification needed] this prevents moisture on the evaporator from being blown back into the room.[citation needed] When the temperature rises again,[clarification needed] the compressor restarts and the fan returns to low speed.

The Environmental Protection Agency (EPA) requires that all technicians who open a system containing a controlled refrigerant be certified to do so. There are four levels of certification, one of which is a “universal” certification to allow the HVAC technician to work on any type of equipment containing refrigerant. Your HVAC technician should be certified as “Level II Certified” at a minimum or, preferably, “Universal Certification” to work on your central air conditioner. Obtaining this certification information from your professional HVAC technician may be required in the event you are working with a realtor to sell your home. Costs for certification average $40 to $240.
Whether you have an electric or gas furnace, you shouldn’t have to suffer when your heater is not working. At Sears Home Services, our technicians fix many of the top furnace manufacturers. The issues you may face with your furnace can vary depending on the type of heating system. If you own an electric model and it isn’t working, some of the potential causes include:
The condensed, pressurized, and still usually somewhat hot liquid refrigerant is next routed through an expansion valve (often nothing more than a pinhole in the system's copper tubing) where it undergoes an abrupt reduction in pressure. That pressure reduction results in flash evaporation of a part of the liquid refrigerant, greatly lowering its temperature. The cold refrigerant is then routed through the evaporator. A fan blows the interior warm air (which is to be cooled) across the evaporator, causing the liquid part of the cold refrigerant mixture to evaporate as well, further lowering the temperature. The warm air is therefore cooled and is pumped by an exhaust fan/ blower into the room. To complete the refrigeration cycle, the refrigerant vapor is routed back into the compressor. In order for the process to have any efficiency, the cooling/evaporative portion of the system must be separated by some kind of physical barrier from the heating/condensing portion, and each portion must have its own fan to circulate its own "kind" of air (either the hot air or the cool air).
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