M R   S E R I E S   D U C T   H E A T E R S
I N S T A L L A T I O N   M A N U A L

These Duct Heaters may be used with Heat Pumps, Cooling Units, or with any Forced Air System. They are suitable for Zero Clearance Installations in vertical or horizontal duct systems.  Downflow units have specific labels.

MODEL NUMBERING SYSTEM: The letters MR mean Manually Resettable Thermal Switches and are used for the secondary protection. The next group of numbers designates the minimum Duct Size with the side to be cut first and the length of the insertion next.Numbers following the first dash indicate the KW. The -1 or -3 following denotes single or three phase. S or F on the end would designate Sequencing Relays or Flanged Construction.

EXAMPLE: MR816-5-1 means a Manual Reset Type Heater to go in the 8" side of an 8" x 16" Duct, 5KW, 1 Phase.

Heaters may be ganged in order to fill a duct. For example, two 12" x 24" heaters may be used to fill a 24" x 24" duct. They should not be used so the outlet air from one becomes the inlet air of the next unless the inlet to the second is below 110 deg. F. Air Flow should be sufficient for the sum of both Heaters. See the Air-Flow limit chart on the other side of this instruction sheet.

These Duct Heaters MUST be installed according to the following Guidelines:

1. At least 4 Ft. downstream from air source or elbow. If closer than 4 Ft. may require turning vanes, baffles or other devices to assure an even distribution of air over the face of the heater.
2. At least 2 Ft. before an elbow or may require devices as in #1.
3. Transitions to and from a Duct Heater should be limited to 20% of the duct area per linear foot.
4. Always mount in the side of a vertical or horizontal duct. NEVER MOUNT FROM TOP OR BOTTOM OF A HORIZONTAL DUCT!
5. All duct materials must be suitable for 250 deg. F. operation.

The air duct should be installed in accordance with the Standards of the National Fire Protection Associationfor the Installation of Air Conditioning and VentilatingSystems Pamphlet No. 90A and No. 90B.

Locate the Heater so that it is completely accessibleand that normal ventilation is assured.

Installing the Heater consists of cutting an opening in the duct that will clear the heater frame enclosure. Insert heater and fasten to the duct through mounting holes in the control box. Observe all labels as to direction of air flow, wire sizes and type, and rated voltages.

The amount of air curtain between the Heater Element(s) and Limit Switch(es) must not be reduced by internal Duct Liner within 1 ft. before or after the Heater. In Fiber Glass Duct Systems, a metal sleeve inside the duct to Heater Terminal Box is not flush with the air stream, nuisance cycling may result.

Field connected wires entering the Heater Controls Compartment must be Copper suitable for 75 deg. C. (167 deg. F.). Field wire the Supply and Control circuits in accord with National and Local codes and use the wiring diagram supplied with each heater as a guide. Never use a fan delay with these duct heaters.

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