Theory and troubleshooting using short modules packed with images to make learning quick and easy.
1 V (Volt) = 1,000 mV (millivolts)
1 V (Volt) = 1,000,000 µV (microvolts)
1 kV (kilovolt) = 1,000 V (Volt)
1 MV (megavolt) = 1,000,000 V (Volt)
1 A (amp) = 1,000 mA (milliamps)
1 A (amp) = 1,000,000 µA (microamps)
1 kA (kiloamps) = 1,000 A (amp)
1 µΩ (microhm) = 0.000 001 Ω (ohms)
1 mΩ (milliohm) = 0.001 Ω (ohms)
People often say heat rises, but that’s not entirely true. While hot air weighs less than cold air and will naturally rise, heat travels in all directions; from hot to cold. Heat flows between substances when there’s a difference in temperature. If you leave a 32°F ice cube sitting in a 69°F room, heat from the room will transfer into the ice causing it to melt. If both the ice cube and the room are both 32°F, no heat transfer will take place. Theoretically can extract heat from a substance until absolute zero, -459.67°F (−273.15°C) where all molecular motion would stop.
A British Thermal Unit (Btu) is a measurement of heat energy. One Btu is the amount of heat required to raise 1lb of water by 1°F. Btu per hour, or Btuh, is the capacity of a heating system such as a 40,000 Btuh furnace.
With air conditioning, you’ll often hear people express the cooling capacity in tons. The term, “tons,” or “tonnage,” is a Canada/USA refrigeration measurement. The ton of refrigeration is equivalent to using one ton of ice per day when using ice for refrigeration was the standard in the days before switching to mechanical refrigeration.
Sensible heat is the amount of heat, (molecular motion), you can measure with a thermometer. It’s the amount of heat you add or remove to a substance that changes a substance temperature but does not change the state of a substance.
Latent heat is heat added or removed that will change the state of a substance but does not affect the temperature of the substance. Water to steam is a change of state.
There are three types of heat transfer; conduction, convection, and radiation.
Conduction is the transfer of heat between objects that are in direct contact.
Example: A pot on a stove burner. As the pot absorbs heat, heat will transfer through the pot handle to your hand.
Convection is when a fluid, such as a liquid or air moves from one location to another and carries its thermal energy along with it.
Combustion is a rapid chemical reaction when oxygen combines with the fuel to produce heat. Lighting a match is combustion.
You require three things to produce combustion; heat, fuel, and oxygen. Since the air we breathe is only about 20% oxygen and 80% nitrogen, we end up having to supply much more air to get the oxygen we need.
Natural gas has the chemical formula of CH4. Natural gas, also known as processed natural gas, is a dry gas which means it has all the heavier hydrocarbons removed and stored in underground storage tanks for use. Natural gas has no color, no taste, no odor (your distributor adds mercaptan for safety which gives a rotten egg smell), is non-toxic (although you may die from insufficient oxygen if there is too much natural gas in the air), and is transparent.
Gas requires quite a bit of air for proper combustion since the air is made up of mostly nitrogen and only contains about 20% oxygen. For adequate combustion to happen, you require combustion air, excess air, and dilution air when using a draft device.
Combustion air is made up of primary and secondary air when speaking about perfect combustion. Since we strive for complete combustion in the real world, excess air is added to ensure combustion.
Combustion is a rapid chemical reaction when oxygen combines with the fuel to produce heat. By modifying any of the three, oxygen, heat, or fuel, you create an imbalance and can produce incomplete combustion.
Carbon monoxide (CO) and aldehydes are products of incomplete combustion.
Carbon monoxide is the most harmful product of incomplete combustion. It’s colorless, odorless, tasteless, and toxic. In large quantities, it can be combustible.
Boyle’s Law is a law for an ideal gas. An ideal gas is a perfect gas that follows all the gas laws. Ideal gases are hypothetical.
Boyle’s Law states that for a fixed amount of an ideal gas at a fixed temperature, P (pressure) and V (volume) are inversely proportional, which means at a fixed temperature, when pressure increases, the volume will decrease. If the volume increases, pressure decreases.