Uneven Heat: Testing Ceiling Radiant Heat /finding Cables/fix Cables - Electrical - DIY Chatroom Home Improvement Forum

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Old 10-03-2010, 02:03 AM   #1
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uneven heat: testing ceiling radiant heat /finding cables/fix cables

How do you troubleshoot ceiling cable radiant heat?

This high rise condo was built in the late 70's and all units have ceiling cable/wire heat. There have been various owners/renters and the ceiling has either fluorescent fixtures or track lighting in each room. It is unknown what precautions were made before the lighting was installed to avoid the cables.

There are 30 floors with 133 units from 1 bedroom to penthouses and also two level units. All units have two electrical meters. One for only the ceiling cable/wire radiant heat and a second electrical meter for everything else.

There is uneven heat with part of a room with detectable radiant heat (by looking up toward ceiling and feeling on ones face) and other parts of the same room where it is perceptibly cool with the thermostat on the highest setting. In addition to the subjective sensation multiple thermometers were placed in the room at waist and knee and floor level. The temperature was found to vary widely when the outside temperature was below 40 degrees with the heat on max. It was even more noticeable at an outside temperature of 20's where it was brutally cold in the dining room. There the temperature at the windows was 20 degrees and 2 feet away it was 40 degrees. At 8 feet from the window it was 60 degrees.

A laser pointing thermometer in this dining room had a ceiling temperature of 87 degrees. The temperature there though did not reflect working ceiling radiant heat. The adjoining living room was producing heat. Temperature at the window in the living room was in the 50's (no air entry possible at this window as it is sealed). The dining room has a sliding window with recently replaced weather-stripping.

The heat production/electicity consumption in the dining room and other rooms was tested by having the electric company view the electric meter while room heat was turned from off to on. Three rooms consumed electricity and there was no electric consumption in the dining room. This indicated that the laser pointing thermometer was reading warm temperatures either from a neighboring working area getting warm by convection or from hot air rising? So we plan to fix the heat in this diningroom by replacing the thermostat.

In the other rooms there is uneven heat. In the main bedroom at room entry it is in the mid 70's and 3 inches from the window on the other side of the room a thermometer was placed on the on the curtain handle and it was in the 20s. One foot from the window it is 40 to 50 degrees. Two to three feet from the window it was 50 to 65 degrees. Midway between the window and entry is the bed where the surface temperature is 65 to 69 degrees.

In the second bedroom/office the wall heat setting was also on the highest setting and as it got colder outside the inside temperature droped. The maximum temperature at waist level in the center of this room is 69 when the outside temperature is below 32 degrees. It is uncomfortable to sit within two feet of the west facing window. All rooms windows had their weatherstripping replaced on the sliding windows.

In the living room the temperature is very warm near the top shelf of the installed bookcases in the center of the room (mid seventies). Walking toward the west facing windows the temperature progressively drops. At approximately two feet from the windows at knee level the temperature was 65 degrees. Walking towards the north facing sealed window it was 50's two feet from the window at waist level when the outside temperature was 32 degrees.The inside temperature varies widely with the wall setting at 72 degrees (mercury thermostat)

The heat electric bill was the 5th highest in the building of 132 units of varying sizes. There are at least 30 other units facing north and west of similar size. And of the 132 units there are penthouse suites, and some two level units. Again all units have separate electical meters for the ceiling cable/wire radiant heat to make the comparison of only heat consumptions.

How can the ceiling radiant heat cables be tested in the bedroom to find the working and non working areas and then possibly splice a possibly broken/fractured cable/wire?

How do you tell if there is somehow a short or other problem causing the high electircal watts consumption with low room temperatures?

Are these ceiling heat cable/wires on all the time because of the non working portions and then the low temperatures sensed by the thermostat?

I do not understand the methods involved and would appreciate as much detail as possible. On internet searches I found various comments about: 1) test in warm weather before it is on all the time to better differentiate good/bad zones. 2) feel with hands 3) spray water 4) use a multimeter 5) go to the thermostat and make voltage/amp/resistance tests 6) infrared camera 7) laser pointing thermometer 8) ticker tester etc. What is the optimal method to test a concealed ceiling radiant heat cable system? If it is an infrared camera and that is unavailable or if someone to interpret the pictures in unavailable then what? How come the laser directing thermometer was unreliable to test the underlying cable/wire? Do we need both a contractor and an electrician? Please provide as much detail as possible. Thank you.

Last edited by martinradiant; 10-03-2010 at 04:00 AM. Reason: additional info
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Old 10-03-2010, 08:22 PM   #2
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somewhere on those ceilings there are box covers for the ends (sometimes the ends come loose )of the cables for attachment to the power from the tstat. With a little testing of the ohms, and rating of the cable, using owms law you should be able determine if some are bad. And by using a thermo imaging camera ucan find the cable in the ceiling, by turning it on. They do go bad, and if you have no attic as you say it can be messy to fix. I belive you can actually rent a thermo type camera.
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