Silicon Carbide Hot Surface Igniter Repair

The hot surface igniter (HSI) serves as an effective replacement for gas furnace spark plugs by allowing low voltage electricity to pass through it and heat it up.

Once heated to its operating temperature, an HSI produces a rectified DC signal to verify there is flame present and maintain the main open gas valve position.

1. High Voltage

Hot surface ignitors are spark-producing igniters designed to handle high voltage. Common uses for these igniters include laboratory furnaces for burning off gases that would otherwise become combustible and gas heaters to light the flame, but it’s also often seen used on range tops, ovens or any other cooking or heating devices.

Service technicians may be taken aback when one of these igniters fails, as old-style silicon carbide hot surface igniters were quite delicate and required careful handling to avoid breaking. Dropped at an inopportune moment can result in their brokenness leading to no heat calls being filed.

Silicon carbide (SC) igniters are being replaced with universal SN igniters that offer much better quality and durability, often lasting 3-5 times longer. Their smooth non-porous ceramic surface easily distinguishes these newer igniters. Many manufacturers now offer kits to retrofit older furnaces with these more reliable universal SN igniters.

If a customer is experiencing repeat igniter failures, their service technician should conduct a visual inspection of the ignitor. Chafing and burns should be carefully observed along with corrosion or moisture build-up on electrical connections; continuity testing of an igniter provides evidence of its integrity.

Cracked igniters are one of the main culprits behind failed ignitors and can be detected using a multimeter to test for continuity. If an igniter reads open or infinity on its continuity testing, it has likely become cracked and should be replaced immediately.

An improperly functioning HSI can result in intermittent sparks, damaging its ignitor. Furthermore, it may reduce life span of igniter by prompting premature failure at lower temperatures. A cracked HSI could also be due to excessive voltage or power surge; should this occur, notify the power company to reduce it immediately.

Cracked HSIs often present an additional challenge: their spark gap may be too narrow or wide for optimal operation. To identify this, manufacturers offer special tools called spark gap testers which allow for accurate measurements.

2. Dirt or Grease

Hot surface ignitors differ from spark igniters in that they do not cause ignition issues when exposed to dirt or grease, although if left contaminated it may become difficult for it to provide an efficient flame signal to gas valves resulting in early failure and replacement being necessary.

Silicon carbide hot surface ignitors typically last from five to ten years before needing replacing, though some rare ones can last even longer. Over time, wear will lead to the formation of a thin oxide layer on its surface which serves to seal in SiC grains beneath it and slow further oxidation while simultaneously weakening flame signal and stopping it from opening the gas valve.

If your silicon carbide ignitor is performing below expectations, there are some simple tests you can perform to identify what the problem may be. First, look for cracked ceramic insulators; these could potentially protect the wire from heat without proper protection against shorting to ground and therefore could be the source of its malfunction.

Verify that the igniter and sensor are in their proper places, without touching other components that might cause overheating. Furthermore, check that your sensor isn’t obscured by coverings like blankets or other materials which might obscure it from view. If a problem remains undetected then replace both of them accordingly.

One way to resolve this problem is to install an ignitor made of silicon nitride which is resistant to dirt and grease build-up. Ignitors made from this material are more robust, consume less energy, outlive their predecessors by 2-7 times longer, consume less power consumption overall and last two or seven times longer, making them an excellent upgrade choice in both new furnaces as well as retrofit applications.

Honeywell now offers a universal module replacement kit featuring the high-quality Supco IG402K flat HSI as part of their field service solution for various furnace applications, providing quick solutions for common ignitor problems with one cost-effective set of modules to rapidly replace them all at once. The kit includes the HSI, module adapters and wiring harnesses needed to quickly address any potential ignitor problems quickly – ideal for quickly solving them quickly! It replaces many OEM Ignitors such as White Rodgers modules (F767A series), Robertshaw products among many others.

3. Overfired Gas Valve

Silicon nitride (SN) igniters that are increasingly replacing hot surface ignitors offer long lifespan and exceptional strength compared to their predecessors, and can stand up against most elements. They make an excellent upsell opportunity for existing furnace customers as one universal replacement igniter can replace hundreds of OEM ignitors at an incredible value.

SN Igniters feature an insulated ceramic base to protect its contacts and wires that connect with it, plugging directly into a 24V ignition module which sends out signals via the ignitor to open gas valves to mix fuel with air for combustion. Once connected to the 24V module, if successful the igniter heats up with time delay before lighting both pilot and main burners simultaneously.

As the igniter heats up, current is passed through it to provide current for combustion to close its contacts and ignite. Once at operating temperature, a sensor on the module will detect this and send a signal to open a gas valve – usually for seconds; once enough time has passed for it to detect flame, both igniter and gas valve will turn off automatically.

After several cycles, the ionized gases within an igniter may build up and cause problems with its contacts, which could ultimately prevent it from reaching operating temperature and result in contact points burning out. This may be caused by various causes including high supply voltage which could damage or burn out an igniter – in this instance contacting your power company may help; they should consider lowering this figure immediately.

Another potential cause is an improper ignition control. If the ignition control is defective and does not properly transmitting signals to the gas valve, then its opening will never occur. You can check for this by measuring voltage between HSI lead and ignition control which should be 120V; additionally it must be connected with furnace chassis using moisture-resistant No 18 wire suitable for continuous duty grounding.

4. Overheating

Silicon carbide hot surface ignitors may be quite long-lasting, yet they may experience issues that require repairs. Thermal overload occurs when an ignitor becomes overwhelmed with too much heat; often caused by dirty or greasy surfaces on its ignitor itself but could also stem from loose wiring or open switches – professional repair services will be able to restore full functionality and minimize future risks with these issues.

Professional technicians will be able to quickly identify and address heating system problems before they have an opportunity to impact other components. They can test ignition controller and wiring connections to ensure proper functioning; additionally, they may search for dirt accumulation that could contribute to thermal overload issues.

If the ignitor in your furnace is experiencing persistent problems, it may be worth upgrading to a different model. Modern furnaces use silicon nitride igniters which are much more reliable and use less energy when operating; additionally, these last 2-7 times longer than silicon carbide ones; you can purchase one from HVAC equipment dealers or online.

When replacing an older-style silicon carbide (SC) ignitor, technicians should take special care not to damage its ceramic base. Newer universal replacements are designed to match original size and shape so they can fit directly into furnace without retrofitting; however, they should only be handled using clean hands due to being fragile. Damaging an ignitor may result in inaccurate temperature control as well as delayed or misfired ignition causing misfired ignition which in turn could impact production output negatively.

Make sure the ignitor is properly situated by checking its positioning with respect to flame sensor immersion in combustion stream; otherwise it could send incorrect signals back to ignitor causing errors that must be rectified by either bending sensor bracket/insulator or moving the flame sensor as necessary.