Electric Heating Basics HVAC
Last Updated on Monday, 01 February 2010 16:03 Written by <a href='/jomsocial/62-iamrichard/profile'>Richard</a> Friday, 29 February 2008 09:20
Electric Heat Basics
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Electric heating can take many different forms. Electricity drives a heat pump to generate heat, electricity powers resistance heating strips to produce heat in an electric furnace, and electricity can power heating elements to make radiant heat for radiant heaters, or electric heating elements can heat fluid like water for providing heat for domestic use hot water, in a loop system, or in a hot water coil. Electric heat is very diverse and is used in many different applications from residential, to commercial, to industrial.
Measuring Electric Heat and Sizing Considerations
Converting electricity to heat, 1 watt of electricity produces 3.415 BTUs (British Thermal Units). Therefore, when an HVAC company sizes the heat load for your home they will estimate the amount of BTUs necessary for your structure or space to be heated and determine the amount of KW's (Kilowatts) needed to produce enough heat to satisfy the heat load demand for your structure. So if you needed 34,000 BTUs to satisfy the heat load demand for your structure the HVAC contractor would select a 10 KW heat strip for your air handler or 10 KW's of electric heating strips to satisfy the heat load demand for your structure. This will also determine the size of wire and breaker needed for 10 KW's of heat strips plus other secondary loads in the unit such as a fan and controls. It is important to properly size the wire and the overload breaker for the specific load according to the amperage draw of the strips and all the electrical loads in the units. If the size of the wire is too small the wire can get very hot, melt the insulation on the wire, and cause an electrical fire or a dead short. If the breaker is not properly sized nuisance trips will happen or, if oversized, the breaker will not trip when a dangerous situation exists. There is usually more than one safety control for electrical heat strips to protect against dangerous conditions. Heat strips also are equipped with thermal limits so if they get too hot for the conditions the control circuit is interrupted disengaging main power to the electrical heat strips.
Electric Heat Advantages and Disadvantages
The main disadvantages of electric heat are electric heating strips produce dry heat which causes dry air conditions in the structure and the cost of powering the electric heat strips is usually more than the cost of using other fuels to heat the structure. Aside from the cost the low humidity issue can be overcome by installing a humidifier in the structure to maintain optimal humidity conditions. Low humidity creates problems such as static electricity and makes the average human feel cooler when the humidity is low. The temperature can be 75 degrees Fahrenheit but many of the people occupying the structure feel cold. Adding humidity to the structure can help people feel warmer and therefore make it possible to keep the thermostat at a lower setting which results in using less energy to heat the structure.
The main advantages of electric heat are:
- Installation cost for electric heat are lower than other types of heating systems
- There is less danger from electric heating applications because electric heat does not burn fossil fuels so it doesn't produce dangerous gases such as carbon monoxide or CO2. No special considerations for primary combustion air are necessary nor does a flue have to be installed to vent combustion gases. Electric heat also does not consume oxygen to produce heat.
- Since electric heat does not burn fossil fuels to produce heat there is no soot or dirt from the combustion process to worry about.
- Individual zones can be set up to control different areas of the structure so when a particular area of the structure is not occupied the thermostat can be set to a minimum set point. This is good zone and demand control and can result in savings on the power bill for heating certain areas of the structure.
Electric heating systems can be ideal for many different applications and is commonly used today in many different applications. Electricity is widely available and highly reliable which makes electric heat a good option for a heating system. While the initial cost for installation is low and the operation of an electric heating system can be high an electric heating system can be zoned so that energy savings are realized over other types of heating systems. Electric heat makes for a reasonable alternative to other types of heating systems and if installed and sized properly can offer years of comfortable and reliable heat.
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