Chapter 27.19 Electric Heating Systems

Evidence shall be submitted that adequate electrical service will be available and provided by the local utility company.  The labeled voltage of the equipment shall be within 5 percent of the service voltage provided.

A.  The total rating (or adjusted rating) of heat emission devices in each room or space to be heated shall equal or exceed the calculated B.T.U. heat loss of such room or space, except that in bedrooms to be heated, a tolerance of not more than 20 percent less than the calculated B.T.U. required to offset the B.T.U. heat loss from such room will be allowed providing such deficiency is made up in other areas regarded as living area when computing the total calculated B.T.U. required for the dwelling.

B.  The total rating (or adjusted rating) of the heat emission devices shall equal or exceed the calculated B.T.U. aggregate heat loss of all the rooms or spaces heated where used as living quarters.

C.  The output in B.T.U. of each heat generating and emission unit shall be computed at the location where the electrical energy is converted to thermal (heat) energy.  The conversion of electrical energy to thermal (heat) energy shall be considered at an efficiency of 100 percent providing the labeled voltage of the equipment is within 5 percent of the service voltage.  Where the labeled voltage of a heat generating or emission unit is greater or less than 5 percent of the service voltage, an adjusted rating of the heat generating or emission unit shall be used in determining the B.T.U. output.

The adjusted B.T.U. rating =
3413 X (Service voltage)²
(Label voltage) 2 X KW name plate rating

(Repealed by Ord. No. 144049; passed and effective July 14, 1977.)

For self‑contained heating units in the form of electric floor furnaces which are intended to heat spaces other than the room or space in which the device is located, the following requirements shall apply:

A.  The distance between the heater outlet and the center of any space to be heated by it, shall not exceed 18 feet (20 feet for kitchens) measured through the center of the intervening openings;

B.  There shall not be more than one doorway and one archway between the heater outlet and any space or room to be heated by it;

C.  A return inlet shall not be located in the bathroom, in a space used for storage purposes or in any other confined space;

D.  A separate manual disconnect shall be provided for each heating device;

E.  Thermostatic control shall be provided within the heated space, except that no thermostatic control shall switch any combination of heater elements totaling more than 7 kilowatts simultaneously;

F.  Heating units of any type located in halls where openings are provided with doors, or in other limited areas which may confine the heat output of the device, shall be provided with thermostatic control or other air temperature limiting device, located within a hall or other limited area, to control the air temperature of the hall or other limited area in which the heating unit is located.
(This may be a thermostat located in the hall or other limited area containing the heating device, arranged to operate in series with other thermostatic controls located elsewhere.)

G.  An unobstructed passageway, not less than 2 feet in width, shall be provided on at least one side of a flat register type floor furnace, to permit passage without stepping over or on the register.

H.  Flat register floor furnaces shall not be placed closer than 6 inches to any wall.  Wall register floor furnaces shall not be placed closer than 6 inches to a wall corner.  Floor furnaces shall be placed so that a door in the open position, or draperies and similar combustible materials, cannot be closer than 12 inches to the register.

(Amended by Ordinance No. 187432, effective December 4, 2015.)

A.  Central heating systems of the forced air type shall conform to the general installation requirements of this Title.  The equivalent KW capacity of such a system shall equal the calculated heat loss of the living quarters of the dwelling in B.T.U. per hour, at design conditions, plus not less than 10 percent greater than the total building heat loss in size, when it is the only source of heating.  The total output of such a system in B.T.U. shall be computed at the location where the thermal (heat) energy is converted and/or transferred to the circulated air.

B.  For resistance electric heating elements the conversion of electric energy to thermal (heat) energy shall be considered at an efficiency of 100 percent.

C.  For electrically operated heat pump equipment, acceptable evidence of equipment heating performance characteristics shall be provided and the equivalent KW capacity determined therefrom.

A.  Resistance cable shall not be installed in walls.

B.  Cables may be installed in ceilings or poured masonry floors.  Cables shall not extend beyond the room in which they originate.  Cables shall not be installed in closets, over cabinets which extend to the ceiling, under walls or partitions, or over walls or partitions which extend to the ceiling, except that single runs of cable may pass over partitions where embedded.  This requirement shall not prohibit low‑temperature heat sources in closets to control relative humidity.

C.  Cables shall be separated at least 8 inches from lighting fixtures, outlets and junction boxes, and 2 inches from ventilating openings and other such openings in room surfaces, or sufficient area shall be provided to assure that no heating cables will be covered by surface mounted lighting units.

D.  A separate manual disconnect shall be provided for each space heated.

E.  Thermostatic control shall be provided in each heated space, except that no individual thermostatic control shall switch any combination of heaters totaling more than 7 kilowatts.

F.  Thermostatic controls shall not be installed on cable until the wattage has been inspected by a Building Official and approval posted on the job.

A.  Prefabricated conductive panels shall not extend beyond the room in which they originate.

Nothing in the regulations contained in this Chapter shall prohibit the installation of other types of permanently placed electrical heat‑generating and emission units not presently covered herein when such units are approved by the Underwriters’ Laboratories, Inc., and installed in a manner approved by such Laboratories providing they meet the general provisions of this Chapter and further that a separate disconnect shall be provided in each heated space, except that no individual thermostatic control shall switch any combination of heaters totaling more than 7 kilowatts.

Installation of resistance heaters in air ducts shall be permitted, subject to the following requirements:

A.  A heater which is to be installed in an air duct or plenum shall be approved for the purpose and shall be installed in the manner approved for the equipment;

B.  Each such heater installation shall be provided with approved controls, consisting of an air‑flow switch or pressure differential switch, which will disconnect the power supply to the heaters in the case of failure of a normal air flow across the heaters for any reason, such as blocked filters, motor failure, broken belts, shafts, or other driving equipment, etc., and shall be provided with an approved temperature‑limiting control.  In addition, a supplementary independent control shall also be provided in each duct heater to prevent overheating.  This device shall be manually resettable or replaceable;

C.  They shall not be located outdoors, unless specifically approved;

D.  They shall not be installed in downflow systems;

E.  Except for approved heater assemblies used in conjunction with a heat pump or central air conditioner, the heater shall not be located closer than 4 feet to the flange of the heat pump or air conditioner unit;

F.  Two or more duct heaters may be installed in a group in duct work when specifically approved for this purpose and under such restrictions as may be necessary to ensure safe operation;

G.  Duct heaters shall be approved for zero clearance from combustible materials, except that the terminal and/or control box of a duct heater shall have a minimum access clearance of 24 inches to permit servicing and adjustment to the controls;

H.  An inspection panel with an area of not less than 140 square inches and a minimum dimension of 5 inches shall be provided in the duct immediately adjacent to, and on the upstream side of, each electric duct heater.  The panel shall provide access for cleaning dust and debris from the heater and means for checking concealed heat limiters.  The panel shall be marked, “Disconnect heater before removing this panel.”

1.  EXCEPTION: An access panel will not be required for electric duct heaters of the slide‑out type if they are supplied by flexible conduit and ‑

a.  Are readily removable.

b.  Weigh less than 50 pounds.

c.  Have a maximum dimension of 3 feet for that portion which extends into the duct,

2.  A separate access panel will not be required where the electric duct heater is located within one foot of a removable room grill and the heater is removable through the grill opening;

I.  Duct and plenum heater controller equipment shall be accessible with the disconnecting means installed at or within sight of the controller.