electric heat section 6
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23 terms
Terms | Definitions |
|---|---|
 to produce heat and deliver it ot a specific area | what is the job of an electric furnace? |
| using the temperature rise method | what is the easiest way to determine what the air flow of an electric furnace actually is? |
| subtract the temperature of the air entering the furnace from the temperature of the air leaving the furnace | how is the furnace TD calculated? |
| the therometer would pick up radiant heat produced by the elements and would cause a higher reading | why should you not place the thermometer where it can "see" the coils of the element? |
| at the furnace disconnect | where can the voltage and amp draw of the furnace be obtained? |
| fan motor adds heat to the circulated air | why should you be sure to measure the total current- including the fan motor amperage? |
| measure each set and add to get the total amperage | what should be done if the furnace has more than one set of power lines? |
| (volts X amps X 3.41) divided by (1.08 X temp rise) | what is the formula for calculating the furnace CMF? |
| furnace data plate | where can the minimum allowable CMF for a particular model furnace be found? |
| (230 X 30 X 3.41) / (1.08 X 28) = 778 | what is the CMF of an electric furnace that draws 30 amps, at 230 volts, and the temperature rise is 28 degrees? |
| the return air section | what is one of the most often neglected parts of the heating systems? |
| the total free area of the grills and registors could be too small | how could registers and return air grilles prevent sufficient air movement through the system? |
| turn off the electrical power | before removing any of the furnace panels, what should the owner be cautioned to do? |
| thermostat operation, location and operation of the electrical disconnect and power suppley fuses, and filter maintenance | wht three items should be explained to the customer before leaving an installation? |
| more air is needed to keep the heating elements form overheating (if elements start to glow red, they will burn out) | why is the discharge air temp not as hot with an electric furnace ans it is with a gas or oil furnace? |
| 3.41 | what is the number of btus per watt? |
| 62.4 X 240 X 3.41 = 51113 | what is the btu output of an electric furnace whose amp draw is 62.4 amps at 240 volts for all three elements? |
| find amp draw of one element (240 / 23 = 10.43 amps) then (3 X 10.43 = 31.29 amp draw of 3 elements) then ( 31.29 X 240 X 3.41 = 25608) | what is the btu output for the elements of an electric furnace which is using 3 elements rated at 240 volts with resistance of 23 ohms per element? |
| volts X amps X square root of 3 X 3.41 | what is the formula for finding the btu output for 3 phase electric heating elements? |
| 480 X 23 X 1.72 X 3.41 = 64751 | what is the btu output of a 3 phase electric furnace with each leg drawing 23 amps while supplied with 480 volts? |
| 12000 | how many btus equal 1 ton? |
| 400 | how many cmf equal 1 ton? |
| 500 | how many square feet equal 1 ton? |
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