In large commercial occupancies such as grocery stores, refrigeration is a necessary part of the business model. Coolers, refrigerators, and freezers line several isles containing produce, frozen food, meat, and dairy products. Connecting these indoor components to compressor and condenser units requires several hundred feet of refrigerant lines. These lines are typically field-installed copper pipe with many brazed joints. Pressure testing connections before beginning equipment startup is essential. The cost of refrigerant, malfunctioning equipment, environmental hazards, and the safety of occupants are good reasons to ensure leakproof refrigeration systems. Additionally, most mechanical codes and the Environmental Protection Agency (EPA) require pressure tests for new piping installations.
Sometimes it takes a dramatic event to institute real change. In the case of the COVID-19 pandemic, building ventilation systems could potentially be forever changed. Here, we attempt to predict how ventilation systems might evolve in the aftermath of the coronavirus and what those changes will mean for HVAC professionals.
Its 95 degrees on a hot, humid day. A service repairman, working on your HVAC, opens the door to your vented crawlspace. He observes ductwork dripping with water, mold on floor joist, and termite tunnels on the crawlspace walls. He services your air conditioner and recommends you call an exterminator. Why are you having all these issues in your crawlspace? Could it be that the naturally vented crawlspace doesn’t work anymore? Some people would say, it never worked. Why is this?
When we see the acronym HVAC, most only think of heating and air conditioning. But the V is for ventilation, an important role when considering the air quality in buildings. Indoor air quality is achieved through ventilating and filtering air in a space. The International Mechanical Code’s definition of ventilation is “The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, a space.” When we supply fresh air to spaces and remove stale air, we improve the breathing air quality for the occupants. When air is “conditioned”, it means several things that include removing or adding heat, cleaning the air, removing moisture, and replacing air.
In the recent past, a mechanical contractor could install very inefficient appliances and equipment with no thought to energy costs. Energy rates were cheap; therefore, mechanical codes did not address energy usage. Mechanical code emphasis was on installation integrity, clearance to combustibles, and service space requirements. The installed equipment was very heavy and overbuilt. That all changed in the late 20th century due to several economic and environmental factors. These factors created a new buzzword: energy conservation.
The combining of fuel, air and an ignition source creates combustion. This combustion process is utilized in furnaces and water heaters to heat air or water. Byproducts of combustion are carbon dioxide, water, occasionally carbon monoxide and other gases.
The mini-split heating and cooling system was an idea that evolved from the basic window air conditioner. Window units are simple installations that offer room by room temperature control if enough are installed. However, window units are noisy. To minimize noise, the window unit compressor was moved to a remote location using refrigerant lines to connect to the inside fan-coil. As a result, the mini-split system was born. This product first saw mass appeal in Asian markets. Today these systems are found throughout the world and has become a big player in the domestic HVAC market.
There is an old joke among HVAC contractors. When bidding on a replacement system for a customer, step back 100 feet from the house and hold up your hand. If three fingers will block the view of the house, install a three-ton unit. If it takes four fingers to block the view, then install a four-ton unit. That meager attempt at humor does highlight an issue that has been kicked around since the beginning of the industry. Are load calculations necessary? If so, how do you properly size a heating and air conditioning system for a house or commercial building?
Back in the rural south, around 1940, power companies would mail flyers to their customers at the beginning of summer. These flyers would give tips on how to stay cool during the hottest days ahead. Some of the tips were; grow ample shade around your residence, stay inside during the hottest part of the day, use open windows for increased air circulation, and keep wet towels available to cool your forehead and neck. Homes, in those days, were designed to facilitate air movement. Large porches and arched ceilings in hallways enhanced air currents that moved freely through the structure. These conditions were the norm for homeowners before the availability of affordable air conditioning.
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