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Each KW will produce 3,413 BTU per hour. This fact and the Chart above should prove helpful in making Heater Selections. Knowing what Heat Rise to expect will aid you in educating customers using Electric Heat for the first time. As an example, 10 KW of Heat in a Southern Home with 3 Tons (1200 CFM) of Air Conditioning may well do the Heating job. The customer may complain because the outlet air is just about body temperature and he feels no heat. Save costly call backs by being ready with Chart figures to explain that a 26.3' rise at 1200 CFM will do a proper job, etc. When ordering, always specify Heaters rated for the Supply Voftage that you will have. The BTU output is directly related to the square of the Voftage as in the formula:

Power in Watts = Voltage squared divided by Resistance
Note how a 240 Volt Heater would have to be derated with a lower input Voltage.

A 240 V rated Heater with a supply of 230 V will yield only 92% of its rated output.
A 240 V rated Heater with a supply of 220 V will yield only 84% of its rated output.
A 240 V rated Heater with a supply of 208 V will yield only 75% of its rated output.
A 240 V rated Heater with a supply of 120 V will yield only 25% of its rated output.

Unlike a motor, Heater Amperage draw goes DOWN with Lower than rated Supply Voftage.

RULE OF THUMB ON MINIMUM AIRFLOW REQUIREMENTS

Approx. 65 CFM per KW is needed with Heater Inlet Air 77'F as with straight cooling. Approx. 120 CFM per KW is needed with Heater Inlet Air 110'F as with Heat Pump.

Check our Installation Manual for final Airflow determination which could be somewhat less but the above is a conservative "Rule of Thumb' if the Heater fills the Duct.

HEATER PERFORMANCE FORMULAS

MULTIPLIERS FOR DETERMINING THE AMPERAGE DRAW OF DUCT HEATERS

SELECT CAREFULLY AND SAVE !!!
Substantial cost increases result when additional elements, controls and/or circuits are required. We are not sug- gesting that you purchase less capacity than you need but sometimes the lower KW will be quite adequate and save you a bundle!!!

Example: If an 11.5KW Heater @ 240V 1 @ will do the job, why use the 12KW Heater @ 240V costing at least 40% more because it is over the allowable 48 Amps per Circuit and requires costly Overcurrent Protection.

Example: If the situation is right and a good safe job can be done, it might be well to consider the installation of separate Heaters, each rated less than 48 Amps and not requiring Overcurrent Protection from the factory. Possibly a Heater in each duct branch or more than one Heater in the main duct could be used. Our Heaters are Listed so that this may be done in a ganged fashion to fill the cross- sectional area or one after the other if the inlet to any Heater is 110'F or less.

FIELD WIRING OF DUCT HEATERS
Field Wires to Heater Controls Compartments or Fuse Panels must be Copper suitable for 75'C (1 67'F). In the following table we show actual maximum load permitted which is 80% of the total ampacity of the wire when there are 6 or less conductors in a conduft and 70% when the conductors exceed 6. U.L. requires that a neutral be counted as a conductor in units rated 120 or 277 Volts. However, they do not require that you count grounding wires.

Note: Heaters with built-in fusing are designed to accept field electrical supplies as follows: 1 Ph. 20 to 48A @ 208 to 600V-1 Supply 1 Ph. 49 to 144A @ 208 to 240V-1 Supply 3 Ph. 24 to 48A @ 208 to 600V-1 Supply 3 Ph. 49 to 96A @ 208 to 240V-1 Supply 3 Ph. 97 to 144A @ 208 to 240V-1 or 3 Supplies 3 Ph. 49 to 96A @ 300 to 600V-1 or 2 Supplies

Option: Item just above - 1 Supply most other heaters have provision for 48A, or 96A supply circuits in multiple. Heaters requiring circuit fusing are also available with smaller control boxes and a seperate U.L. Listed Remote Fuse Panel. Consult Factory for additional information.

TEMPERATURE EQUIVALENT TABLE

For other equivalents not listed in table use following formulas: Fº=Cº X 1.8 + 32º Cº=Fº - 32º / 1.8

	Electric Resistance Heat Values can be found by direct application of Ohm's Law and other known electrical values or equations. Formulas and applications considered are limited to those of benefit to people involved in sales or service of Electric Duct Heaters. In Formulas and Applications considered below: The square root of 3 (3) = 1.732
	P = Watts E = Volts KW = 1,000 Watts	I = Amps R = Ohms 1 KW = 3,413 BTUH

FORMULAS AND APPLICATION:

CONNECTING TO HIGHER VOLTAGES
NEVER connect a Heater to a higher voltage than the Data Plate ratingl Just as the output drops with lower applied voltage, it increases even more rapidly with a higher voltage.

1. Amp Draw is now over the 48 per circuit allowed bu UL and NEC
2. The Element output is now at 1/3 more than factory design limit.
3. Contactor and other component capacities may be exceeded.
4. Safe Wattage Density may now be exceeded and Heater short cycles.
5. UL Label and Warranty are VOID!!
6. Product Liability passes from us! YOU WILL HAVE PROBLEMS!!!

RESISTANCE IN OHMS CALCULATED FOR VARIOUS HEATERS

You are not generally required to know the Ohms of Elements in a Heater unless you need replacement(s) and, even then, you would specify the KW, Voltage, Phase etc. from the Heater Data Plate with the KW per Element determined by dividing total KW by the number of Elements. Sometimes it is necessary to know the Ohms for replacements, particularly for Three Phase Heaters. You may measure the total Ohms of two or more pieces and, when possible, supply nameplate data, Element coil O.D. etc. A review of some sample formulas below will show that it is important to be able to distinguish between Delta or Star (Wye) Three-Phase construction.