CIBSE publishes several guides to HVAC design relevant to the UK market, and also the Republic of Ireland, Australia, New Zealand and Hong Kong. These guides include various recommended design criteria and standards, some of which are cited within the UK building regulations, and therefore form a legislative requirement for major building services works. The main guides are:
If your furnace’s motor runs but the blower doesn’t move air, the belt that connects the two probably has broken. Replacing it is an easy fix. First, turn off all power to the unit and turn off the gas at the gas valve that serves the furnace. Remove the door on the front of the furnace cabinet to give you access to the blower (it might be on a slide-out drawer.) Check the number stamped on the belt and get an exact replacement from a home center or heating supply outlet.

Gas furnaces and heaters have control shutoffs to prevent gas leaks, but they are not fail-safe. If you smell gas in your house, do not turn any lights on or off, and do not try to shut off the gas leading to the furnace. Get out of the house, leaving the door open, and immediately call the gas company or the fire department to report a leak. Do not re-enter your home.


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]
Air conditioner inverter Air door Air filter Air handler Air ionizer Air-mixing plenum Air purifier Air source heat pumps Automatic balancing valve Back boiler Barrier pipe Blast damper Boiler Centrifugal fan Ceramic heater Chiller Condensate pump Condenser Condensing boiler Convection heater Cooling tower Damper Dehumidifier Duct Economizer Electrostatic precipitator Evaporative cooler Evaporator Exhaust hood Expansion tank Fan coil unit Fan heater Fire damper Fireplace Fireplace insert Freeze stat Flue Freon Fume hood Furnace Furnace room Gas compressor Gas heater Gasoline heater Geothermal heat pump Grease duct Grille Ground-coupled heat exchanger Heat exchanger Heat pipe Heat pump Heating film Heating system High efficiency glandless circulating pump High-efficiency particulate air (HEPA) High pressure cut off switch Humidifier Infrared heater Inverter compressor Kerosene heater Louver Mechanical fan Mechanical room Oil heater Packaged terminal air conditioner Plenum space Pressurisation ductwork Process duct work Radiator Radiator reflector Recuperator Refrigerant Register Reversing valve Run-around coil Scroll compressor Solar chimney Solar-assisted heat pump Space heater Smoke exhaust ductwork Thermal expansion valve Thermal wheel Thermosiphon Thermostatic radiator valve Trickle vent Trombe wall Turning vanes Ultra-low particulate air (ULPA) Whole-house fan Windcatcher Wood-burning stove
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:
For residential homes, some countries set minimum requirements for energy efficiency. In the United States, the efficiency of air conditioners is often (but not always) rated by the seasonal energy efficiency ratio (SEER). The higher the SEER rating, the more energy efficient is the air conditioner. The SEER rating is the BTU of cooling output during its normal annual usage divided by the total electric energy input in watt hours (W·h) during the same period.[33]
Turn off the gas supply valve, typically located by your gas meter on the gas inlet pipe. Turn off the gas by rotating the valve one quarter turn with an adjustable wrench. When the gas is off,  the valve’s oblong stem points perpendicular to the inlet pipe. Then call your gas utility or the fire department from a remote location. Do not return to your home until you know it is safe.
Should you need to replace an air conditioning unit, Abacus Plumbing recommends Lennox brand of air conditioning and heating systems. Lennox systems offer the highest level of home comfort at the lowest possible cost of operation. Additionally, these systems are praised by consumer publications and meet or exceed all government standards for efficiency. Learn more about installation »
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
R22 (also known as HCFC-22) has a global warming potential about 1,800 times higher than CO2.[62] It was phased out for use in new equipment by 2010, and is to be completely discontinued by 2020. Although these gasses can be recycled when air conditioning units are disposed of, uncontrolled dumping and leaking can release gas directly into the atmosphere.
Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration", with each approximately equal to the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as 12,000 BTU per hour, or 3517 watts.[32] Residential central air systems are usually from 1 to 5 tons (3.5 to 18 kW) in capacity.
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