Introduction: Repair and Upgrade a Broken Radiant Infrared Heating Panel
This is an entry in the
Epilog Challenge 9
NOTE: These plug-in radiant heaters do not have built-in thermostatic controllers. The customer is required to either plug the heater into a pluggable thermostat or wire up a thermostat to control the heater from the outlet it is plugged into or associated wiring in the wall. We purchased a LUX WIN100 Programmable Outlet Thermostat for this heater when we got it. Thankfully, when the heater shorted out, it did not effect the thermostat. If you were to plug in a heater like this without a thermostat, it would probably burn out eventually from the continuous and unnecessary constant running.
DISCLAIMER: The instructions given in this guide will DEFINITELY VOID YOUR WARRANTY with the manufacturer. When working with anything electrical or with power tools, remember to play it safe and wear the appropriate safety gear. It is important to make sure all the electrical connections are thoroughly secure. If they do become loose, the high current may result in an electrical short and possibly a fire hazard. I am not a licensed electrician, so whatever you do, the onus of responsibility and liability is yours; I take no responsibility for any personal injuries or damage to your equipment that may result from attempting what is presented in the following instructions.
WHY NOT SEND IT BACK TO THE MANUFACTURER FOR REPAIR? When our heater failed to put out any heat after plugging it in this winter, I became painfully aware of what was meant by “limited” in a 5 year "limited" warranty. Basically the manufacturer told us that it would probably cost us at least $150 to ship it to them and very probably $300USD in shipping there and back if the heater did not have a factory defect from their perspective. This cost was just for shipping it within the same state where the manufacturer's facility is located. The heater itself retailed at $600-$650 and the manufacturer did not tell us what the repair cost would be, only stating that any repairs would only have a 90 day warranty. From what I could tell from searching on-line, I suspected the heater was probably electrically simple in design. I did not feel convinced that it was worth the cost or risk of sending it to the manufacturer for a simple repair and it turned out I was right. My only initial worry was that the actual heating element/s might have already been critically damaged, but the only way to know would be to pry open the case to determine the cause of the failure. Fortunately for me, the element was unaffected by the cause of the failures.
Step 1: Determine the Malfunction
First we need to determine if there is any continuity (closed circuit) within the heater's circuitry - this includes the heating element itself. Set a digital multimeter to the lowest resistance and then place the multimeter probes on the heater's power plug prongs to read the resistance at the neutral & hot plug contacts. Assuming the ambient room temperature is not at some crazy boiling temperature, the multimeter should show a lower resistance. In the case of this heater, if the elements are in normal working range, it should show 9-12 ohm resistance. As you can see in the picture, there is infinite resistance, which means there is an open circuit in the system. At this point, we still do not know why there is no continuity.
Step 2: Removing the Holding Rivets
Since we know there is no continuity, we need to open up the casing to inspect and test where the fault(s) might be. For this, you will need a flat-head screwdriver and optional duct tape if you want to protect the case from scratches from the screwdriver. Before we can open up the case however, we need to use a Dremel tool to grind out two rivets: one that holds the power cord support bracket on the back of the panel and the other a ground (GRN) rivet which electrically binds the front metal housing to the back of the case. Remember that this little rivet needs to be replaced later when we reassemble the case. You will be using a screw for that instead of a rivet.
Step 3: Opening the Case/Housing
The front face housing floats off the back of the case. After grinding the rivets away, you can now use the flat-head screwdriver to lift up the front housing edging, in order to separate the front from the back. Use your thumbs to brace the back of the edging. The case is made of aluminum, which makes bending relatively easy, but you should always pry back on the thickest parts between the holes/slots - not on the hole areas themselves. You only need to pry open three sides of the front housing in order to separate the two halves of the heater housing.
Step 4: Further Investigation - Part 1
It is always good practice when to doing something like this to label all the wires and take basic pictures - like the ones here - before pulling things apart. After carefully opening up the case, you will now be able to continue your continuity checking of the wires inside.
As you can see in these images, it was obvious there was a dead short sparking on the back of the casing.
It was hot enough to melt and burn up the scotch-lock connector/self-stripping tap connector (CN2) on the neutral side of the wiring.
In my opinion, the use of scotch-lock connectors on a 12-15 amp constant draw appliance like this is questionable. The problem with these connectors is that the only direct contact between wires is at the tiny thin surface of splicing metal in the connector. Couple this with a device that is constantly heating to high temperatures and then cooling and it is no surprise that the contact area would loosen over time. This increases resistance at the contact, generating more heat, as evident in the picture. Ultimately in this case, the connector melted away, creating a fire and shorting on the housing.
Step 5: Further Investigation - Part 2 "Heating Element"
Even if everything else looks OK, we still need to determine that status of the other wires, the heater element and the thermal protector. This heater is a thin film infrared heating element with two parallel traced elements on a plastic substrate; the elements are traced one inside the other. As mentioned before, it should show 9-12 ohm of resistance if undamaged. To test this, we need to connect the two neutral (white) wires of the heater element to one of the probes of our multimeter and then the other two hot (black) wires to the other probe. As seen in the picture, we have around 10 ohm; so thankfully the main element was not damaged. The reason why the sparking and fire did not damage the element was because it occurred on the opposite side of the fire proof polyester fibreboard backing.
Step 6: Further Investigation - Part 3 "Thermal Protector"
Next we need to check the thermal protector switch (SW1). The best way to start is to remove the switch completely from the heater by clipping the wires. You will probably have to use a razor blade to CAREFULLY cut the hardened plastic on the backside of the switch, then very slowly and CAREFULLY bend back the plastic to pull the switch out.
WARNING: Do not put any force on the heater element side underneath; if you puncture or tear it, you might as well throw the whole heater away (or recycle it if you can). Do not attempt to peel off the old switch cover plastic or transformer tape because it will probably start tearing up the element backing with it. You can see I started to do this myself and decided it was not worth the risk of damage to the element underneath. Besides, as you will see later during reassembly, the old plastic actually came in handy for re-installing the new thermal protector.
The switch's main function is to protect the heater from getting too hot. When the heater is working perfectly, you should occasionally hear a little clicking or popping sound as the thermal protector opens and closes when it reaches the upper threshold and then cools back down to re-close the circuit. At room temperature, the thermal protector should be closed and therefore should have continuity. The testing picture shows this switch is stuck in a permanently open state (no continuity); it is damaged and needs to be replaced.
Step 7: FINAL ANALYSIS "Causes of Failure"
The inadequate scotch-lock connectors need to be replaced with something more robust. The thermal protector (SW1) needs replacing and we might want another circuit protection switch (SW2), just in case we have a similar fault in this heater.
Step 8: Is It Worth Repairing?
First: This heating element is a more expensive, printed metal element and not a cheaper carbon element. If the element turned out to be damaged, the answer would be to recycle the heater, but in this case the element itself was unaffected by the failures.
Next: can you purchase a replacement thermal protector (SW1) with roughly the same specifications as the original? Using a magnifying glass, read and record any codes on the thermal protector and try to identify the replacement part on-line. Fortunately, I was able to buy a three pack on eBay for $13.47 (including shipping).
I was feeling uneasy about the manufacturer's design, so I decided that a few small upgrades were in order. The first and most important is the replacement of the questionable scotch-lock connectors with more robust step-down butt connectors. Step-down butt connectors facilitate the different gauge wire sizes on either end. Also, adding flexible fibreglass insulation sleeving over the step-down connectors provides an added level of protection for the elements in case there is an (unlikely) failure or fire due to the new connectors. These connectors will provide a lot more contact area for the combined wires at the junctions and reduce the likelihood of loosening, overheating and subsequent failure. The second upgrade is an optional on/off rocker switch with supplementary protector (SW2). You could probably use any type that will not accidentally trip off during a minor power brown out in your house. I chose the following inexpensive item because it also had a neon lamp to help determine whether there was actual power going to the heater from our thermostat. The lamp is NOT an LED, which would require special circuity to deal with an alternating current. If your thermostat is doing its job correctly, you should see the light on this switch go on and off as the thermostat transfers power to the heater to keep things at the right temperature in the room. The added bonus is if there is a lengthy current spike, the switch's circuit breaker functionality will trip, protecting the heating element and possibly the thermal protector as well, or so I hope... The other thing - which is optional - is to install a GFCI outlet at the wall where the thermostat plugs in. This should provide protection if there was ever another dead short on the housing of the heater case and someone was to touch it accidentally.
The total cost for materials was around $78 (not including GFCI receptacle), or roughly half the cost of shipping the heater to the manufacturer one-way.
Step 9: Materials & Tools Required
The following are the items you will need if your heater is the same as mine. I've also included a short video you can download showing you how the new thermal protector functions when working properly. Note the clicking sound during the cooling stage as it re-engages the continuity and allows current flow again.
- CN1: 1x Step down butt connectors 22-18 to 16-14 AWG
- CN2: 1x Step down butt connectors 16-14 to 12-10 AWG
REPLACEMENT CONNECTORS (if needed):
- CN3,CN4,CN5,CN6,CN7,CN8 18-22 AWG butt connectors (Red)
- GRN: 1x 22-18 Gauge Vinyl Ring Terminal (Red) with a small nut & washer with 2 washers.
- GRN: 1x short steel or other electrically conductive screw to ground the front case to the back case.
- SW2: 3x 22-18 AWG Fully Covered Insulated Female Push-On Terminals
REPLACEMENT SWITCH (SW1):
- Sensata/Klixon 7AM series thermal protector: 7AM029A5
- Cantherm: Thermal Cut-outs/Bimetal Thermostats: CD79F11005A
- Type A Radial Lead, standard 18AWG
- NC, (120VAC,22 Amperes)
- Low Resistance Bi-Metal 70 OHM/cmf: Opening Temperature 110C
NEW (ROCKER SWITCH with SUPPLEMENTARY PROTECTOR) (SW2):
- equivalent component SPST, Circuit Breaker/Switch with internal neon lamp (NOT LED!)
- Current Rating (A) 15
- Voltage Rating DC (VDC) 50
- Voltage Rating AC (VAC) 250
UPGRADED WIRING (NOT SHOWN):
- SW2: 4 feet: 3 or 4 Conductor cable, 16AWG O/S with 300V-600V rating
- 1 foot: Techflex Insultherm Ultraflexx fibreglass sleeving -or- fire proof equivalent
- Kapton, Transformer tape or other high temperature electrical tape.
- 2x Nylon Cable Ties (Zap Straps)
- Duct tape (to protect heater case from scratches)
- Blanket or cardboard to place the heater on while working.
- GFCI (Ground Fault Circuit Interrupt) Outlet - OPTIONAL
- Safety Goggles
- Wire stripper
- Ratchet Crimper
- Wire cutter (NOT SHOWN)
- Flat-head screwdriver (NOT SHOWN)
- Dremel tool & grinding bit (NOT SHOWN)
- Digital Multimeter -or- continuity checker (NOT SHOWN)
- Magnifying glass (NOT SHOWN)
- Power drill & drill bit (NOT SHOWN)
- Felt marker (NOT SHOWN)
- Sandpaper (NOT SHOWN)
Step 10: Fire Protection for Step-Down Butt Connectors
The circuit diagram above, along with this picture of the final connection, should make reassembly easy for you. Just remember to put the Techflex sleeve over one end of the wire before crimping the two ends closed on the step-down butt connectors. You can then close up the ends with the Kapton tape.
Step 11: Installing New Thermal Protector
As previously mentioned, leave the original plastic from the damaged thermal protector attached to the back of the heating element. Cut off the new switch's plastic cover instead and then slip the new switch (SW1) into the old plastic on the element and secure it with Kapton or transformer tape.
Step 12: Installing Rocker Switch With Supplementary Protector (SW2)
If you decide to include the rocker switch with supplementary protector (SW2), then you will need to drill an appropriately sized hole in the power cord support back bracket.
If you are not installing this feature, then you can follow the original circuit diagram and ignore connector (CN8) and forgo any additional modifications to the back bracket.
NOTE:Don't do like I originally did and crimp the Female Push-On Terminals on the new SW2 cord before feeding the cord through the new hole in the back bracket.
Step 13: Final Wiring After Repair and Upgrading
Here we have the final wiring for the project. As mentioned before, if you were not installing the rocker switch with supplementary protector (SW2), then your layout would look like the original wiring diagram near the start of these instructions.
Step 14: Testing of Wiring
Before closing up the case, make sure everything is working correctly. Just as in the very beginning, attach leads from your multimeter to the electrical power plug prongs (hot & neutral) and then flip the SW2 into the on position; you should see the same resistance as when you were originally testing the heating element for damage.
Step 15: Ground Protection of Case
IMPORTANT: Start by sanding down any paint on the back of the inside of the case where the power cord support bracket is connected. You need bare metal for a good ground wire contact with the case metal. Reconnect the ground wire onto the back housing using the small bolt, nut and washers to re-secure the bracket.
Test before closing up: If it all looks good, you might still want to see if everything functions smoothly before closing up the case. Plug it into a wall outlet for 5 minutes to see if you smell anything melting or burning. If all seems well then go ahead and close it up.
Step 16: Closing Up Case and Grounding Front Housing
Now carefully return the back case back into the front housing and using your thumbs, push the edging closed to secure the two halves back together. The final thing is to screw a connective metal screw into the rivet whole that was ground out at the beginning during disassembly. This screw provides a (GRN) between both halves and should be tested for continuity at the plug end prong as seen in the picture.
Step 17: Final Testing
Almost done. With multimeter or continuity checker, check to make sure everything is working fine as seen in the pictures. If everything is OK then you can use two small zap straps to secure the rocker switch's (SW2) cord to the existing power cord on the back of the heating panel. DONE!
FYI: I tried to file a report online with the buggy and frustrating U.S. Consumer Product Safety Commission website without success. I then tried to send a report via email with a pdf attachment of the “Safety Report” form taken from their own website and they were unable to read the file due to software incompatibilities on their end.
We have a be nice policy.
Please be positive and constructive.