Troubleshooting Electric Immersion Heaters

Element will not heat properly (all heater types)

# Problem Cause Solution
1 No power / electrical fusing Main disconnect in an off position; open protector(s) or defective circuit breaker on main; loose or disconnected wiring. Verify power and electrical connections by measuring voltage with a voltmeter and current with an ammeter. If three phase, measure all three phases. Test, reset or repair as required.
2 Open/overheated thermal protectors on heater Open protector will disable control/heater circuitry. See protector troubleshooting notes regarding thermal protectors in section 5 of this guide for details. WARNING: Do not operate heaters without thermal protection. Making sure that all power is off, test thermal protector(s) for continuity with an ohm or continuity meter. Test/ replace as required. If bimetallic (P2) style sensor, allow sufficient time for cooling before system reset or testing.
3 Missing thermal protector Protector removed during installation or prior servicing. WARNING: Do not operate heaters without thermal protection. Verify proper protector by product type/operating temperature and replace as required. (See catalog or installation sheet for available temperature ranges).
4 Thermostat not turning heater on (new installations) Thermal protector not connected to terminal blocks in control. Consult appropriate wiring diagrams and connect protector as required.
Improper Wiring Verify wiring with appropriate diagram and correct if necessary.
Single-phase power connected to lines L1/L2 instead of L1/L3. Correct power connection points and return to service
Possible defective thermostat. See appropriate control installation manual and troubleshooting notes.
Damaged or defective power switch Replace switch.
No power. See section 1 of guide for various causes of power disruption
5 Thermal protector(s) keeps opening (Protector 1 style). WARNING: Do not operate heaters withouth thermal protection. Low liquid level. Solution level must be maintained above the heater's hot-zone indicator standoff at all times to prevent the element from overheating. (note discoloration). Recommend the use of liquid level controls as the first line of defense against low level. Replace protector with proper rated protector. Consult installation sheets for details.
Buildup on heater sheath. Any deposit on the heater sheath will act as a thermal insulator and cause localized overheating. Inspect and clean heaters frequently. Check application, as de-rated heaters may be required in most solutions that buildup quickly. Replace protectors or recommend heater replacement as required. De-rate heaters to reduce the surface temperature. Consult installation sheets for details.
Watt density too high. Unusually heavy, viscous or poorly conductive fluids reduce heat transfer around the element, causing localized overheating. Check solution concentration or viscosity (may need chemical supplier’s MSDS sheets to verify). May be able to use higher temperature protectors or de-rate heaters to reduce opening. Replace protectors or recommend heater replacement as required. Consult installation sheets for details.
Protectors electrically overloaded. Excessive current flow through the thermal protectors will cause resistance heating through protector and a de-ration of the thermal set point. Rewire heater using a contactor or relay to energize the heater and wire protector in series with contactor coil/thermostat circuit. Higher temperature thermal protectors may be considered in some applications. Consult factory and installation sheets for details.
High temperature solutions. Due to the proximity of the protector to the element, viscous liquids or solutions over 180°F may cause protector to open prematurely. Replace protector with appropriate higher temperature protector. Consult installation sheets or catalog for details.
6 Protector 2 bimetallic thermostats opening at a low temperature. WARNING: Low liquid level. Solution level must be maintained above heater's hotzone indicating standoff at all times. Recommend the use of liquid level controls as the first line of defense against low level. Refill tank and reset P2 system.
Buildup on heater sheath. Any deposit on the heater sheath will act as a thermal insulator and cause localized overheating. Inspect and clean heaters frequently. Check application, as de-rated heaters may be required in most solutions that buildup quickly. Clean heaters and reset P2 system.
Heavy or viscous solution. Unusually heavy, viscous or poorly conductive fluids reduce heat transfer around the element, causing localized overheating. Check solution concentration or viscosity (may need chemical supplier’s property data or MSDS sheets to verify composition). May be able to use higher temperature sensors or de-rate heaters to reduce premature opening. Change P2 sensors/heaters as required.
Wiring of electrical load directly through bimetallic thermostat. Do not wire any heater load directly through the P2 sensor, as resistance heating and device failure will result. P2 sensors should only be wired into the holding coil circuit of some type of latching relay. Any sensor exposed to over a 2 amp load and/or over 240 VAC service should be replaced.
Thermal cycling caused by low-level conditions. Repeated overheating degrades the switching point accuracy of the bimetallic sensors and may cause premature opening. Suggest the use of a liquid level control as the primary control device. Replace P2 sensor as required.
Bimetallic sensor does not reset. Possible defective protector or wiring problem. Verify wiring and test sensor for continuity at room and elevated temperature, and replace as required.
7 Heater blowing electrical protectors. Wrong protector size. Protectors must be sized in accordance with the rating information stamped on heater nameplate/installation tag. Replace with properly sized electrical protectors, as local codes require.
Wrong voltage applied to heater. Heaters operated at any voltage above the manufactured rating will increase in output and corresponding amperage draw. DO NOT OPERATE HEATERS ABOVE RATED VOLTAGE. Either replace the heaters with units matching the available voltage or provide correct voltage to the heaters.
Wrong voltage heaters supplied. Heaters operated at any voltage above the manufactured rating will increase in output and corresponding amperage draw. Check nameplate tag to verify model number and proper voltage requirements. If incorrect, replace heater. If they match, measure the resistance of each element and compare measured value against the theoretical value. Replace as required. Do not operate heaters above rated voltage.
Saturated/wet element insulation. Wet or saturated elements lose their electrical insulation and will leak voltage to ground, increasing the overall current draw. Measure resistance between ground/sheath and power lead wires of heater. Resistance should exceed 40 megohms @500 VDC. If below this value, check solution for compatibility before replacing heater as most wet elements are caused by corrosion perforations in the sheath.
Ground wire connected to power supply. This condition will result in a direct current flow to ground and a short circuit condition. Verify that the green ground lead is connected to a good earth ground, not the power supply. Correct wiring as required.
Improperly sized connection wire. Too small of gauge wire can cause resistance heating of wire and electrical connection. Check heater ratings and wire size employed. Replace wiring and connections per National Electrical Code.
Loose wire connection to protector. Loose connections can cause resistance-heating damage to wires and protectors. Check for any distortion or discoloration to wires or connection points and repair or replace as required.
Unbalanced load. Combining heaters of different wattage, or non-uniform groupings (not divisible by three for single-phase elements) will cause unbalanced electrical loads on one or more of the phases. Multiple heaters should be wired in single phase parallel or three phase Delta/Wye configurations. Reducing the unbalanced heater load can be accomplished by using uniform heater sizes and individual three phase elements.
8 Reduced output of heater Any time reduced output of an element is suspected, tests should be performed to measure the resistance of all the element phases (power off), the current draw across each power supply wire (with ammeter), and the voltage applied to the element (with volt meter). Low voltage. Any voltage below the design voltage of a resistance element significantly reduces the rated output of the heater. Measure the available voltage and compare it to the rating on the tag. Check and compare your incoming voltage vs. the voltage at the heater. If the difference exceeds 5%, consider increasing the wire size. Either replace the heater, add more elements to increase capacity or provide voltage to match the rating on the tag.
Wrong voltage heating element supplied. Heaters operated on lower than design voltage will decrease in output. Check nameplate to verify model number and proper voltage requirements. If wrong, replace heater. If they match, measure the resistance of each element to verify element and compare the measured value against the theoretical value. Replace as required.
One leg/phase out on three-phase power supply. This condition will apply full power to only one element, causing the heater to operate at about one half output. Check power supply and protectors. Repair/replace as required.
Open element on heater. Since many heaters have multiple internal heating element coils, it is possible that one element could be open. Measure the resistance with an ohmmeter and compare it to the theoretical value obtained using the nameplate volts and watts rating. If any leg varies by more than 10% of rated value, replace the heater.
Elements wired in a three-phase WYE connection versus a DELTA connection. This wiring method would de-rate the heater to one-third the rated output. Check nameplate rating and verify correct wiring to match rated element value.
Elements wired in series. This condition would cause the heaters to produce about one quarter the rated output. Check nameplate rating and verify correct wiring to match the rated value.
9 Voltage measured in tank. Heater insulation is wet and element is connected to an ineffective ground. Wet electrical insulation will allow some amount of voltage to pass to ground. If the ground connection is poor, the voltage will pass through the lowest resistance current path available. This is a hazardous condition. Shut off power and investigate source immediately. Make sure the ground connection is secure and that a conductive uninterrupted ground path exists to the ground source. Have a qualified electrician or testing service verify the grounding system. Remove or replace any non-copper or insulating material that exists in the path and test. Test heater insulation values as noted in section 7 and replace heater as required.
Heater ground lead connected directly to power. This condition would allow full voltage to pass through the ground lead to the path of least electrical resistance. This is a hazardous condition. Shut off power and correct condition immediately. Make sure that the green ground lead has not been mistakenly connected as a power lead. If so, test heater for damage to the element, correct wiring and return to service.
Stray voltage/current from other sources entering tank through heater ground. Voltage from other devices with ineffective ground connections may pass through the heater ground connection if it is of lower resistance than the original device. This is a hazardous condition. Shut off power and correct condition immediately. Test heater ground for voltage/current flow with heater power turned off to verify presence of flow. Locate source of voltage/current flow and correct condition

Metal Heaters

# Problem Cause Solution
1 Holes in heater sheath (Metal Heaters) Corrosion. (Chemical incompatibility) Usually either general etching along entire heated length, weld seam or solution interface areas. May also be seen as small irregular pits, patchy discoloration or cracks along the heater sheath. (Usually most severe in the heated areas.) Check chemistry or MSDS sheets and replace with appropriate sheath material.
Galvanic corrosion. Usually caused by dissimilar metals used during heater construction or between tank and heater sheath. (For example, a T304 S/S heater used in a T 316 S/S tank may cause corrosion on the T304 S/S material as the less noble metal on the electromotive chart [T304 S/S] will become anodic and corrode to the cathodic [T316 S/S] metal). Corrosion of this type may be seen as a general etching or pitting along the side of the heater facing the more noble metal (sometimes seen in oval patterns). In the case of a heater made with the same metal combinations, corrosion will typically start on the less noble metal, about 1/4" back from their junction. Usually, the relationship of more surface area of the noble metal will cause increased corrosion on the lesser surface area of the less noble metal. Replace heater or tank to match materials. Tank can also be lined with a non-conductive material to isolate heater.
Oxygen deprivation corrosion. Can be seen as pits or cracks under areas of buildup or in areas where metal parts overlap and prevent contact with oxygenated solution. (This oxygen is necessary to form the corrosion resistant oxide layer on metals.) Heaters should either be cleaned frequently to prevent this type of corrosion or replaced with a material and construction less prone to this type of attack.
Buildup. Any deposits on the heater sheath will insulate the element causing excessive internal temperatures. Darkened carbonized deposits and scorching are usually evident on heated portions of sheath. Element failure may result in arcing of the melting resistance wire to ground and will manifest itself as a series of longitudinal holes through the sheath along the hot zone. Clean heaters frequently in solutions that buildup on the heater sheath or consider de-rating replacement heaters to reduce surface temperatures and the buildup rate.
Overheating. Heater operated out of solution or used without the thermal protector or used in a viscous solution. Blue/black or golden discoloration over the hot zone of the element. Element may even arc to the sheath in a series of longitudinal holes. Verify that the correct watt density heater has been selected. Heater thermal protectors should be checked for correct wiring. Install liquid level controls and replace heater as required.
Holes around and above bumper/standoff (metal over the side heaters). Usually due to chemical attack on sheath, saturated element insulation and arcing to the sheath. Check compatibility of solution. Examine element for pitting behind protector thermal well caused by oxygen deprivation corrosion. Replace heater with appropriate sheath material as required.
Contact with electrically charged work. Contact of any metal heater with DC power within the plating tank will cause a discharge to the sheath, resulting in any of the following conditions: arc type hole through the sheath, increased corrosion in the area of contact or excessive buildup/plate-out depending on the polarity of the DC power in contact with the heater. Locate heater in the tank to avoid contact with charged work or protect the heaters from contact with a non- conductive guard material.
Holes in the Protector thermowell. Usually caused by moisture or fluids entering the junction box and migrating down the thermal well tube. Over time, this liquid will degrade the protector encapsulation and provide a current path and subsequent arcing to the metal thermal well. Replace heater or thermowell assembly as required. Make sure that the junction box is sealed and heater is not operated under the cover of a tank.
2 Swelled or split heater sheath (Metal Heaters) Caused by chemical attack, saturation of insulation and hydraulic expansion of magnesium oxide insulation as it converts to magnesium hydroxide. Replace heater with appropriate sheath material as required. Consult with chemical supplier for recommendation.
3 Heaters tripping GFP/ELCB circuits Usually caused by moisture trapped within the element insulation. Test insulation value with a meggar. Should measure a resistance of at least 50 megohms @ 500 VDC between the sheath and element. (Preferably greater than 200 megohms.) Replace heater if insulation value is less than noted above.
Defective GFP/ELCB circuit. Test by running a known good electrical load through the coil to verify operation. Replace as required
Low setting on GFP/ELCB circuit. Some ground fault devices have adjustable switch settings. Make sure these units are set for a minimum 5 Ma trip point.
Moisture within the junction box or thermal wells. Remove heater cover and inspect epoxy surface, thermal protector and thermal well for moisture or conductive plating salts. Clean/dry any deposits. Apply RTV sealant to gaskets or threaded areas and return to service.
4 Melted or overheated ground wires. Usually caused by a difference in potential between the heater ground connection and that of a DC power supply (rectifier). Test heater for permanent damage and repair/replace as required. Connect heater ground wire and rectifier ground to the same, verified ground source.
5 Metal plate-out on heater sheath Usually caused by either a difference in potential between the heater ground connection and that of a DC power supply (rectifier) or contact with charged components within the tank Inspect for contact between the heater sheath and plating tank cathode, work or parts accumulation on tank bottom contacting the heater sheath. Isolate components as required. If caused by a difference in potential between the heater ground and the rectifier ground, connect the heater ground wire and rectifier ground wire to the same verified ground source.
6 Physical damage to heaters. Heaters should be inspected for any physical damage prior to installation and during routine cleaning and maintenance. Shipping damages must be reported to both the factory as well as the carrier. Damage caused by improper cleaning can result in dangerous operation conditions. Do not operate damaged heaters. Heaters should either be returned to factory for repair or be discarded.
7 Sand or magnesium oxide powder found in junction box Usually caused by pressurized discharge of heater contents due to a corrosion of the sheath and vaporization of fluid that entered the element. Turn off power and remove the heater from service immediately as dangerous operating conditions may occur. Check application for compatibility before replacing heater.
8 Installation problems Heaters should be handled carefully and must be fully supported during installation. Using the power supply wires, flexible riser or metal riser as a handle during installation will cause damage to the wiring and internal components. Consult factory for possible repair. Do not operate damaged heater. Replace or discard as required.
9 Discoloration/blackening of heater sheath; heater is distorted or misshapen Heater was energized while out of solution. A titanium heater will exhibit a rainbow discoloration to the hot zone sheath. A stainless steel heater will turn its hot zone to a dark brown color. Certain design heaters will distort their shape. Ensure that the thermal protectors are properly wired to disable the heater when a high surface temperature is detected (when applicable). In addition, we recommend the use of a liquid level control is used to disable the heater when the liquid level drops to within 1-inch of the hot zone

Quartz Heaters

# Problem Cause Solution
1 Carbonized buildup inside heater sheath. Caused by overheating of vapors or fluids that have accumulated in the quartz heating tube. Loose cap or conduit fitting on heater. Carefully clean carbonized deposits from inside of quartz tube with damp rag on a wooded dowel. Replace o-ring on heater cap and apply a non-hardening silicone sealant to thread area and attach cover. Protect junction box area from dripping or condensation.
Degradation of junction box. Usually caused by excessive dripping of solutions such as chromic acid on junction box. Move heater in tank, install drip shield over junction box or replace heater with model built with a CPVC or chemically compatible junction box.
Junction box melted or distorted. Too high of solution temperature or heater operated in confined area. Improve ventilation/cooling air to junction box area or raise heater up slightly above tank to improve circulation. (as cold zone permits).
2 Buildup on the outside sheath of the element Usually caused by localized over heating or viscous solution. Since quartz heaters transmit most of their output through IR radiation, buildup of any type will cause overheating and reduced service life. Chemically clean any deposits from the sheath. Check the solution being heated, as a de-rated heater may be required.
3 Tube cracked off at solution interface Usually caused by severe thermal shock from localized overheating due to operation in air followed by displacement immersion into a fluid. This is a potentially hazardous condition. Shut off power and investigate immediately. Element should be inspected for corrosion and electrically tested before being returned to service. Replace tube as required. Make sure the thermal protector is operational and replace if necessary.
4 Tube cracked or broken off near bottom Usually caused by tube/element assembly being physically hit or jarred, which forces the element into the tube. This type of damage typically matches the location of the bottom spacer ring or outside radius of the outer two elements. When hit from the inside, cracks normally radiate outward with a larger opening on the outside of the tube. This is a potentially hazardous condition. Shut off power and investigate immediately. Element should be inspected for corrosion and electrically tested before being returned to service. Replace the tube assembly as required. Verify that the thermal protector is operational and replace if necessary. Make sure that the replacement heater has a guard installed and that the heater is moved to a safer location in the tank.
5 Tube cracked or section broken out near center This type of damage can also be the result of severe jarring particularly if the broken tube section matches the spacer locations. If the tube is broken in an area away from the spacers, check for cracks that lead to a larger hole on the inside of the tube. The tube being struck by an object in this area would cause this condition. This is a potentially hazardous condition. Shut off power and investigate immediately. Element should be inspected for corrosion and electrically tested before being return to service. Replace tube as required. Make sure that the thermal protector is operational and replace if necessary.
6 Tube etched or has porous appearance on outside surface Usually caused by operation in either a highly alkaline solution or one containing fluoride. Check with chemical supplier for proper sheath material selection. Do not use quartz heaters in this type application, as a similar future failure will result. Element maybe able to be reused in another application provided it is inspected and electrically tested.
7 All three legs of element open, failure after a short period of operation (less than one day) Usually caused by operation at higher than rated voltage, however, operation out of solution will cause similar failure. Elements operating at high surface temperatures will exhibit a bluish tint over the entire hot zone. Check that the voltage being applied matches the nameplate. If it does, check the voltage code stamped on the top 2" of the metal tubular element to make sure it matches the rated voltage. Remember that some elements are designed with various voltage and wiring combinations to achieve the rated voltage. Verify these findings with the factory technical sales representatives.
8 All three legs of element open, failure after an extended period of time Usually the result of overheating caused by low liquid level, solution viscosity or buildup on either the inside or outside of the tube. Element will exhibit darkening over the entire hot-zone with a bluish hue near the cold/hot transition area. Check thermal protectors to verify operation and wiring, correct as required. Verify solution concentration and operating temperature. Replace elements as required. Clean deposits off of both inside and outside surfaces of quartz tube.
9 One leg/element open. Usually caused by a loose connection or bad element. Check wiring connections and retest element. If resistance remains open, replace element.
10 Bluish spots or discoloration in cold zone transition area. Usually caused by a bad pin weld termination. Replace element.
11 Holes/melting of metal element sheath Usually caused by operation in a viscous solution at high temperature or with tube surfaces covered with some type of buildup. Check application, replace with de-rated heaters and clean as required.
12 Guard melted or distorted. Usually caused by operation with low liquid level. Test thermal protectors and verify wiring, operation and positioning. Remove any moisture from the thermal well that could cause corrosion or delay the protector response.
13 Guard material cracking at weld seams or solution interface. Incompatible solution. Check solution for temperature and chemical compatibility with polypropylene. Switch to fluoropolymer or CPVC guards as required.
6 Physical damage to heaters. Heaters should be inspected for any physical damage prior to installation and during routine cleaning and maintenance. Shipping damages must be reported to both the factory as well as the carrier. Damage caused by improper cleaning can result in dangerous operation conditions. Do not operate damaged heaters. Heaters should either be returned to factory for repair or be discarded.
7 Sand or magnesium oxide powder found in junction box Usually caused by pressurized discharge of heater contents due to a corrosion of the sheath and vaporization of fluid that entered the element. Turn off power and remove the heater from service immediately as dangerous operating conditions may occur. Check application for compatibility before replacing heater.
8 Installation problems Heaters should be handled carefully and must be fully supported during installation. Using the power supply wires, flexible riser or metal riser as a handle during installation will cause damage to the wiring and internal components. Consult factory for possible repair. Do not operate damaged heater. Replace or discard as required.
9 Discoloration/blackening of heater sheath; heater is distorted or misshapen Heater was energized while out of solution. A titanium heater will exhibit a rainbow discoloration to the hot zone sheath. A stainless steel heater will turn its hot zone to a dark brown color. Certain design heaters will distort their shape. Ensure that the thermal protectors are properly wired to disable the heater when a high surface temperature is detected (when applicable). In addition, we recommend the use of a liquid level control is used to disable the heater when the liquid level drops to within 1-inch of the hot zone

Fluoropolymer Heaters

# Problem Cause Solution
1 Fluoropolymer sheath melted, split or distorted Heater operated with low liquid level without proper thermal protection. Check/test wiring and thermal protector to verify operation. Repair/replace heater as required.
Heater operated at higher than rated voltage. Check/verify power supplies and compare to nameplate rating of element. Correct voltage and replace heater as required.
Viscous or concentrated solution. Dense or concentrated solutions impede heat flow from the elements and can cause localized overheating and damage to the fluoropolymer sheath. Increased mixing of the solution near the element can reduce the problem but replacement of the heater with a de-rated/more open design is preferable.
Buildup on the sheath. Any buildup between the formed passes on a Fluoropolymer heater will cause localized overheating and can cause melting of the sheath material. Periodic cleaning can reduce the buildup and overheating. Open type designed, over-the-side model heaters should also be considered as replacement options. Vari-power heaters can be considered for low power requirement installations. Bottom designs with tight spacing should be avoided in any application where buildup or sedimentation is possible.
Operation in liquids that polymerize or crystallize when heated. Buildup on the fluoropolymer sheath will limit heat transfer, causing localized overheating which may melt the sheath. These solutions can only be heated with de-rated heaters or through indirect type heating methods. Either replace heaters with open, derated design (2.5 WSI or less) or switch heating methods.
Thermal protector pulled up out of position during installation or replacement. The thermal protector only measures the sheath temperature directly adjacent to where it is mounted. The thermal protector must be fully seated into base of the thermal well to work properly.Verify installation of thermal protector. Replace heater as required.
Thermowell tubes full of solution. Any fluid inside the Thermowell will act as a coolant and delay the switching point of the protector device until the fluid is boiled away. Care should be taken to ensure the well is not damaged, the heater junction box is sealed properly, and that the excessive moisture is prevented from entering. Periodic inspection of the interior of the junction box and thermal well should be considered in unusually wet installations or in solutions operating over 180 degrees F. If solution is found in the Thermowell, a pressure test (5 PSI) should be performed to verify integrity.
Thermowell retainer bracket removed, out of position or damaged. Since the retainer bracket holds the thermal protector against the element at the top of the hotzone, damage to or misalignment can affect the response time and performance of the protector. Reposition the bracket and Thermowell if heater is serviceable. Replace heater if necessary.
Localized overheating caused by operation in a confined area. If fluoropolymer heaters are operated in too small of an area that effectively limits their ability to dissipate the energy they produce, localized overheating and melting may occur. The heater should either be moved to a more open area or solution circulation should be added to assist in heat transfer. Replace heater if necessary.
Improper forming clearance or compressed passes on the element. Formed elements should not be contacting adjacent passes under any type of pressure. While incidental element contact normally will not cause problems, compressed elements in high temperature or viscous fluids will cause excessive localized overheating and melting. Usually element contact spots can be opened up by hand forming. If contact pressure remains the element should be returned to factory.
2 Swelled or split heater sheath (any location). Usually caused by damage to the fluoropolymer sheath near the swelled area, which allows solution to enter and chemically attack the heater sheath. Solution then saturates the magnesium oxide insulation and hydraulically expands the insulation as it converts to magnesium hydroxide. Determine the cause of damage and replace the heater with a guarded model. See section 3, "Damage to fluoropolymer sheath" (third item).
3 Swelled or split heater sheath at the hot zone transition. This condition can be caused by one or more the following conditions. Low liquid level. Operating an element out of solution for a short period of time without the thermal protector connected will cause swelling or melt damage to the fluoropolymer covering. Solution can then enter, corrode the heater sheath and hydraulically expand the element. Recommend the use of thermal protection devices and liquid level controls with replacement heaters.
Repeated low level incursions. Repeated low level conditions even with a thermal protection device will cause degradation of the fluoropolymer sheath and increased permeability in any exposed area. Moisture or chemistry can then permeate through the damaged area and will be concentrated at the hotzone transition point. Over time this fluid will cause corrosion and hydraulic expansion failure in this area. Recommend the use of liquid level controls with replacement heaters to prevent repeated low level exposure.
Damage to the fluoropolymer sheath. Cuts, nicks or damage to the fluoropolymer sheath at any location will allow solution to come in contact with the exposed heater sheath. This heated fluid will vaporize and tend to condense at the hotzone transition point. Over time, this fluid will cause corrosion, sheath penetration and hydraulic expansion failure in this area. Recommend careful handling and the use of guards on replacement heaters to reduce the incidence of damage.
High solution level. High solution levels, which allow contact with the junction box, can break down the epoxy and internal seals and allows solution to enter the element. This fluid may cause an electrical short circuit and will cause corrosion of seals and the element with a resultant hydraulic expansion failure in this area. Replacement heaters should be blocked up slightly to prevent reoccurrence or solution level should be maintained at an appropriate level.
Improperly sealed flex lead junction. Fluoropolymer heaters will develop a positive internal pressure between the metal element and fluoropolymer sheath when energized and a partial vacuum while cooling. Improperly sealing the end of a flex lead option heater will allow moist air to enter and condense on the element during this cooling cycle. This moisture will accumulate over time at the flex lead/hotzone transition causing damage to the electrical connections and hydraulic expansion and failure of the insulation. Replacement heaters must be properly installed by user to prevent this damage from reoccurring. Rigid risers or the use of small potted junction boxes can alleviate this problem as well.
4 Section of element that's completely missing Usually caused by combination of physical damage to the fluoropolymer sheath and corrosion on the element. Subsequent arcing and electrical discharges melt away section of the element until the electrical protectors open. Properly sized protectors, good grounding and the use of GFCI circuits will reduce the potential of this type of failure.
5 Melting or distortion of junction box at the element insertion point Usually caused by moisture within element insulation which condenses on interior of epoxy seals creating a current path to ground. Large current flow in this area heats the element melting the junction box and surrounding epoxy sealant. Properly sized protectors, good grounding and the use of GFCI circuits will reduce the potential of this type failure.
6 Cracks in internal epoxy encapsulation Usually caused by an electrical discharge between the element and ground or between phases of the power connection. Check heaters for damage to the element sheath or for indications of high fluid levels, which may have caused solution leakage (see section 3, "Damage to fluoropolymer heater sheath", third item). Replace heater as required.
7 Holes in the Thermowell tube Moisture or fluid entering the junction box and migrating to and accumulating in the Thermowell will degrade the thermal protector allowing a current path and arcing to occur to the thermal well tube. Any fluid inside the Thermowell will also act as a coolant and delay the switching point of the protector device until the fluid is boiled away. Care should be taken that the heater junction box is sealed properly and that excessive moisture is prevented from entering. Periodic inspection of the junction box and thermal well assembly should be considered in unusually wet installations and solutions operating above 180 degrees F. If solution is found in the Thermowell, a pressure test should be preformed to verify integrity. Periodic inspection and possible relocation of the heater to a more protected location can reduce the potential of future problems.
8 Guard material cracking at weld seams or solution interface Check solution for temperature and chemical compatibility with polypropylene. Switch to fluoropolymer or CPVC guards as required.
9 Heaters tripping GFP/ELCB circuits Usually caused by moisture trapped within the element insulation. Test insulation value with a meggar. Should measure a resistance of at least 50 megohms between the sheath and element. (Preferably greater than 200 megohms @ 500 VDC). If lower than noted value, replace the heating element, as field repairs are impractical and temporary.
Defective GFP/ELCB circuit. Test by running a known good electrical load through the coil to verify operation. Replace as required.
Low setting on GFP/ELCB circuit. Some ground fault devices have adjustable switch settings. Make sure the units are set for a minimum 5 Ma trip point.
Moisture within the junction box or thermowells. Remove heater cover and inspect epoxy surfaces, thermal protector and Thermowell for moisture or conductive plating salts. Clean/dry and remove any deposits. Apply RTV sealant to gaskets or threaded areas and return to service.
10 Fluoropolymer sheath on single element or phase of the heater melted Usually caused by a combination of operation with low liquid level and one leg of the power source open (blown protector, open breaker or single phase wiring). Replace heater and correct power/wiring problem.