Radiant electric ceiling heat

Originally Posted By: smcintire
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I am looking for information for testing Radiant ceiling (electric heat). Other than using an infrared thermometer or checking continuity of the ceiling wire. Does anyone have any other tips on how or what to check icon_question.gif

Originally Posted By: Tom Turner
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Why test this type heat. SOP's exclude concealed items and your contract should too. To properly test this type heat you would have to make holes in the ceilings and this is beyond the scope of what we do.


Originally Posted By: smcintire
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why would you have to make holes in the ceiling?

Originally Posted By: smcintire
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sop(2.4. Heating

I. The inspector shall inspect:

A. The heating system and describe the energy source and heating method using normal operating controls.

Originally Posted By: Tom Turner
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You make holes in the ceiling to get to the wires to check continuity. I owned a house that had this type of heat and it seamed like every we tried to hang a lamp or flower pot we hit a heating wire and I would have an electrician repair it and that is what he had to do to properly make the repair.


Originally Posted By: smcintire
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I agree to make a repair you would have to make holes,but to check continuity you would use the wires at the thermostat. I also think that this method is beyond what we do. I am just looking for things that we can do to check this type of system.

Originally Posted By: rmagee
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I checked in “Electrical Inspection of Existing Dwellings”, a book written by the authors of “Code Check”

There is only one paragraph dealing with inspection of this type of system.

"Electric radiant heating panels, such as those imbedded in ceilings, can be very difficult to accurately test. Specialized equipment, such as infra-red heat detectors, can help see if the equipment is responding to the thermostats. If possible, the heat panels should be viewed from the attic space to look for any loose connections or damage."

This type of heat is common in my area. All I can do is use an infra-red thermometer to see if the ceiling heats up when the thermostat is activated. The attic idea is not very practical as most times the panels are buried under 12 inches of blown-in pink insulation.

Another type of system that is difficult to inspect is in-floor radiant heat where hot water pipes are imbedded in a concrete slab. During the summer, when the system has been off for an extended period it can take over 4 hours to get to the point where the heat starts to be noticed coming through the floor coverings.

Just the same way we can't properly check the operation of central air systems during the winter there are some systems that can't really be inspected in summer.

I guess that's why it's important to educate your clients on the limitations of an inspection and get a contract signed.

Rick Magee
Building Check Ltd.
Fredericton, N.B. Canada
"check with a professional"

Originally Posted By: smcintire
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thank you Rick and Tom for your input. Hopefully more people will post on this subject with there personal experiences and training.

Originally Posted By: jpeck
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You can check to see if it is ‘energized’ with a voltage detector, but that will not tell you if it is ‘working’.

Go to the panel, and put you clamp on ammeter on the fuse / breaker which is marked for that circuit. Go turn the thermostat 'on', go back and read the ammeter.

Your voltage sniffer will tell you if the ceiling heating wires are energized, however, a broken or cut through wire, and you will not have current flow. The clamp-on ammeter tells you if you have current flow, if you do, it is 'working', how well it is working if up to someone else to verify.

As others have said, no holes through a radiant ceiling, that could easily cut through or break a heating wire.

Jerry Peck
South Florida

Originally Posted By: smcintire
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Rick, thanks for the e-mail. I will do some reading on that site tonight. I think Jerry has the answer. I have talked with some other people and this seems to be the easiest way to check the system. It also sounds like it either works or it doesn’t. Thanks everybody. I will let you know tomorrow if it’s as easy as it sounds.

Originally Posted By: jtedesco
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Please accept this information only as a guide to the specific rules that I must follow when inspecting or installing this type of heating equipment in new occupancies.

I hope that this material is helpful.

V. Electric Space-Heating Cables

424.34 Heating Cable Construction.

Heating cables shall be furnished complete with factory-assembled nonheating leads at least 2.1 m (7 ft) in length.

424.35 Marking of Heating Cables.

Each unit shall be marked with the identifying name or identification symbol, catalog number, and ratings in volts and watts or in volts and amperes.

Each unit length of heating cable shall have a permanent legible marking on each nonheating lead located within 75 mm (3 in.) of the terminal end. The lead wire shall have the following color identification to indicate the circuit voltage on which it is to be used:

(1) 120 volt, nominal ? yellow
(2) 208 volt, nominal ? blue
(3) 240 volt, nominal ? red
(4) 277 volt, nominal ? brown
(5) 480 volt, nominal ? orange

424.36 Clearances of Wiring in Ceilings.
Wiring located above heated ceilings shall be spaced not less than 50 mm (2 in.) above the heated ceiling and shall be considered as operating at an ambient temperature of 50?C (122?F). The ampacity of conductors shall be computed on the basis of the correction factors shown in the 0?2000 volt ampacity tables of Article 310. If this wiring is located above thermal insulation having a minimum thickness of 50 mm (2 in.), the wiring shall not require correction for temperature.

424.37 Location of Branch-Circuit and Feeder Wiring in Exterior Walls.
Wiring methods shall comply with Article 300 and 310.10.

424.38 Area Restrictions.

(A) Shall Not Extend Beyond the Room or Area. Heating cables shall not extend beyond the room or area in which they originate.

(B) Uses Prohibited. Heating cables shall not be installed in the following:

(1) In closets
(2) Over walls
(3) Over partitions that extend to the ceiling, unless they are isolated single runs of embedded cable
(4) Over cabinets whose clearance from the ceiling is less than the minimum horizontal dimension of the cabinet to the nearest cabinet edge that is open to the room or area

(C) In Closet Ceilings as Low-Temperature Heat Sources to Control Relative Humidity. The provisions of 424.38(B) shall not prevent the use of cable in closet ceilings as low-temperature heat sources to control relative humidity, provided they are used only in those portions of the ceiling that are unobstructed to the floor by shelves or other permanent luminaires (fixtures).

424.39 Clearance from Other Objects and Openings.

Heating elements of cables shall be separated at least 200 mm (8 in.) from the edge of outlet boxes and junction boxes that are to be used for mounting surface luminaires (lighting fixtures). A clearance of not less than 50 mm (2 in.) shall be provided from recessed luminaires (fixtures) and their trims, ventilating openings, and other such openings in room surfaces. Sufficient area shall be provided to ensure that no heating cable will be covered by any surface-mounted units.

424.40 Splices.

Embedded cables shall be spliced only where necessary and only by approved means, and in no case shall the length of the heating cable be altered.

424.41 Installation of Heating Cables on Dry Board, in Plaster, and on Concrete Ceilings.

(A) In Walls. Cables shall not be installed in walls unless it is necessary for an isolated single run of cable to be installed down a vertical surface to reach a dropped ceiling.

(B) Adjacent Runs. Adjacent runs of cable not exceeding 9 watts/m (2? watts/ft) shall not be installed less than 38 mm (1? in.) on centers.

(C) Surfaces to Be Applied. Heating cables shall be applied only to gypsum board, plaster lath, or other fire-resistant material. With metal lath or other electrically conductive surfaces, a coat of plaster shall be applied to completely separate the metal lath or conductive surface from the cable.

FPN: See also 424.41(F).

(D) Splices. All heating cables, the splice between the heating cable and nonheating leads, and 75-mm (3-in.) minimum of the nonheating lead at the splice shall be embedded in plaster or dry board in the same manner as the heating cable.

(E) Ceiling Surface. The entire ceiling surface shall have a finish of thermally noninsulating sand plaster that has a nominal thickness of 13 mm (? in.), or other noninsulating material identified as suitable for this use and applied according to specified thickness and directions.

(F) Secured. Cables shall be secured by means of approved stapling, tape, plaster, nonmetallic spreaders, or other approved means either at intervals not exceeding 400 mm (16 in.) or at intervals not exceeding 1.8 m (6 ft) for cables identified for such use. Staples or metal fasteners that straddle the cable shall not be used with metal lath or other electrically conductive surfaces.

(G) Dry Board Installations. In dry board installations, the entire ceiling below the heating cable shall be covered with gypsum board not exceeding 13 mm (? in.) thickness. The void between the upper layer of gypsum board, plaster lath, or other fire-resistant material and the surface layer of gypsum board shall be completely filled with thermally conductive, nonshrinking plaster or other approved material or equivalent thermal conductivity.

(H) Free from Contact with Conductive Surfaces. Cables shall be kept free from contact with metal or other electrically conductive surfaces.

(I) Joists. In dry board applications, cable shall be installed parallel to the joist, leaving a clear space centered under the joist of 65 mm (2? in.) (width) between centers of adjacent runs of cable. A surface layer of gypsum board shall be mounted so that the nails or other fasteners do not pierce the heating cable.

(J) Crossing Joists. Cables shall cross joists only at the ends of the room unless the cable is required to cross joists elsewhere in order to satisfy the manufacturer?s instructions that the installer avoid placing the cable too close to ceiling penetrations and luminaires (lighting fixtures).

424.42 Finished Ceilings.

Finished ceilings shall not be covered with decorative panels or beams constructed of materials that have thermal insulating properties, such as wood, fiber, or plastic. Finished ceilings shall be permitted to be covered with paint, wallpaper, or other approved surface finishes.

424.43 Installation of Nonheating Leads of Cables.

(A) Free Nonheating Leads. Free nonheating leads of cables shall be installed in accordance with approved wiring methods from the junction box to a location within the ceiling. Such installations shall be permitted to be single conductors in approved raceways, single or multiconductor Type UF, Type NMC, Type MI, or other approved conductors.

(B) Leads in Junction Box. Not less than 150 mm (6 in.) of free nonheating lead shall be within the junction box. The marking of the leads shall be visible in the junction box.

(C) Excess Leads. Excess leads of heating cables shall not be cut but shall be secured to the underside of the ceiling and embedded in plaster or other approved material, leaving only a length sufficient to reach the junction box with not less than 150 mm (6 in.) of free lead within the box.

424.44 Installation of Cables in Concrete or Poured Masonry Floors.

(A) Watts per Linear Foot. Constant wattage heating cables shall not exceed 54 watts/linear meter (16? watts/linear foot) of cable.

(B) Spacing Between Adjacent Runs. The spacing between adjacent runs of cable shall not be less than 25 mm (1 in.) on centers.

(C) Secured in Place. Cables shall be secured in place by nonmetallic frames or spreaders or other approved means while the concrete or other finish is applied. Cables shall not be installed where they bridge expansion joints unless protected from expansion and contraction.

(D) Spacings Between Heating Cable and Metal Embedded in the Floor. Spacings shall be maintained between the heating cable and metal embedded in the floor, unless the cable is a grounded metal-clad cable.

(E) Leads Protected. Leads shall be protected where they leave the floor by rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or by other approved means.

(F) Bushings or Approved Fittings. Bushings or approved fittings shall be used where the leads emerge within the floor slab.

(G) Ground-Fault Circuit-Interrupter Protection for Heated Floors of Bathrooms, and in Hydromassage Bathtub, Spa, and Hot Tub Locations. Ground-fault circuit-interrupter protection for personnel shall be provided for electrically heated floors in bathrooms, and in hydromassage bathtub, spa, and hot tub locations.

424.45 Inspection and Tests.

Cable installations shall be made with due care to prevent damage to the cable assembly and shall be inspected and approved before cables are covered or concealed.

Joe Tedesco, NEC Consultant


Originally Posted By: smcintire
This post was automatically imported from our archived forum.

Just to let everyone know that posted on this subject. I ended up checking each zone at the main panel with an amp meter. I also checked ceilings for damage and warned the client about installing anything in the ceiling that could damage the wiring.