 |
InspectAPedia® |
InspectAPedia
|
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair | Ask a Question or Search InspectAPedia |
This article explains the cause, diagnosis, and cure of gas heater or gas appliance igniter problems that cause bangs, whooshes, noises, clicking, or failure to ignite properly. Some of these conditions are dangerous. We also discuss both gas igniters and gas regulators on gas fired heating equipment and LP or Natural Gas Pressure Regulators used on building appliances such as gas fired furnaces, boilers, water heaters, and stoves: How to Inspect & Test LP or Natural Gas Valves Regulators, or Gas Controls at Appliances. The gas igniter troubles discussed here apply to some models of gas appliances including heaters, water heaters, electric ranges, clothes dryers, etc. where an automatic or pilot less gas ignition system is used. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. Questions & Answers on Diagnosing & Repairing Noisy Gas Igniters on Heating EquipmentThis article series provides descriptions and photographs of unsafe gas piping, regulators, or controls on heating systems, indications of unsafe or improperly operating gas appliances, gas meters, and other gas installation defects. This document also provides free sample draft home inspection report language for reporting defects in oil and gas piping at residential properties. General safety warning: improper installation and even improper inspection and testing methods involving natural or "LP" gas can involve dangerous conditions and risk fire or explosion. If you smell gas you should leave the building immediately and should do so without doing anything that could create a spark such as operating a light switch or telephone. From a safe location, call your gas company's emergency line and/or your fire department. The text provided here is a working draft and may be incomplete or inaccurate Question: Noisy gas burner igniter worry: when the valve opens it sounds like a hammer hitting a metal pipe
May I ask your opinion on intermittent pilot valves for gas furnace? My furnace works perfectly. However, when the valve opens it sounds like a hammer hitting a metal pipe...Is it possible the electronic ignition is sending more than 24 volts to the valve solenoid and that's why it makes such a loud noise on opening? There's a box that regulates and sends the 24 volt electronic signal to the pilotless ignition that I've thought about replacing. About your pro bono advice, I'm 60 years old, no job, no pension and would appreciate any advice. - R.K., MI Reply: Short answer: the gas burners may need cleaning, the system may be unsafe, you need a service call
First we ought to rule out a dangerous noise that can be heard when the gas furnace ignites. Properly when the thermostat calls for heat the igniter lights a pilot that then ignites gas when it is released into the burners. If burners are dirty or clogged, the gas flame may not be igniting across all of the burner tubes as quickly as it should. A result could be incomplete ignition and a banging sound when the accumulated gas finally ignites. You should be able to detect this problem by observing with care just what happens during a heater on-cycle. Watch out for sooty gas burners: If you see soot on or around gas burners such as shown in our photo (above) you should shut off the equipment (it is unsafe) and call a heating service technician promptly. And if this is the problem, a service call that includes cleaning rust and debris off of the pilot and igniter, or rust and debris off of the burners and checking their adjustment might fix the trouble. If the gas burner tubes include flame crossover slots, those are intended to assist the spread of flame from the first ignited gas burner tube over to the other tubes. Be sure those slots are cleaned as well. Be sure to also ask your service tech to check the proper operation of all of the heater safety controls while s/he is there. Watch out: in boiler school our instructor came to class one night with his previously full-beard shaved off. His eyebrows looked odd too. He explained that he was kneeling by the burner, watching too closely when the flame was igniting. A flashback burned off half of his beard and one eyebrow. He had to finish the job himself with a razor. Don't get your face too close to the gas burners while inspecting for trouble during flame ignition. There might be a different problem, a delay in igniting the pilot itself, though that is probably less common. What Causes the Bang, Kaboom, or Loud Whoosh When the Gas Burners are Igniting?A "bang" or "kaboom" (as some folks describe it) sounds very dangerous, if that's what you've got. It can signal that you are getting "delayed ignition" of the gas in your combustion chamber. If the gas valve opens and sends gas through the burners but actual ignition is delayed, gas accumulates, then ignites with an explosion when the spark finally occurs. The risk is a damaged, cracked heat exchanger leading to a costly furnace replacement, or worse, a dangerous heating system leaking potentially fatal carbon monoxide into the building. A loud "whoosh" during burner flame ignition may be caused by the same burner clog and debris problem, especially if it's heard earlier in the development of this dirt and debris difficulty.
The two could be related: if there is a shortage of combustion air the burners could be producing a bit of soot that in turn clogs the burners and leads to a bang or whoosh sound when the gas furnace or boiler burner ignites. But if the root problem was improper combustion air to the heater or improper air mix adjustment at the burner tubes themselves, that problem would have probably been present from day one of the heater's installation. If your heater has worked well for some time and now is developing noise, check the advice we gave at the start of this note. Watch out: a heating appliance might have adequate combustion air only when the utility room door or some other nearby door is open. If the service tech adjusts and tests the system with the door open, the system may look just fine. But when s/he leaves and shuts the door to the utility room there might be inadequate combustion air. Details about diagnosing and correcting gas or oil appliance combustion air problems are at Combustion Air Defects Watch out: also for the presence of soot anywhere in, on, or around the gas burners. If the system is producing visible soot its operation is improper and very dangerous as production of potentially fatal carbon monoxide is probably going on. While natural gas and LP gas normally burn clean, a chimney or draft or combustion air problem can lead to very rapid system clogging, soot, and potentially fatal heating system troubles. Sources of Heating System 24V Transformer NoiseQuestion: [continued] My first note should have mentioned that I narrowed the hammer on a pipe sound to the actual valve by shutting off the natural gas supply and reproducing the sound without an actual ignition. However, I would guess you answered my question on improper voltage going to the ignition because your note did not even mention that as a possible issue. I did replace the valve last fall. New Honeywell equivalent valve. You guessed it same issue. Maybe even a little more noisy than the 20 year old original. I will look into a transformer replacement. Reply: I have never seen a heating system coil develop a defect that led to high voltage coming out of a furnace or boiler 12V or 24 V transformer, so I didn't suspect that cause. According to our electrical expert Paul Galow (Galow Consulting), the transformer is very unlikely to be the root cause of the sound you describe, and a more likely cause, if you have indeed traced the sound to the valve itself, is a mechanical problem in the valve that means it needs replacement. The output voltage of a transformer is determined by the input voltage and the number of wire turns in the transformer winding. To double the output voltage of the heating system 24V output transformer you'd need to have cut or shorted the transformer in a way that eliminated half of those turns. Such a defect would be not only unusual but it would more likely lead to burn-up of the device and it would stop working altogether. You could replace the 24V transformer as an experiment - they are quite inexpensive, but it doesn't sound as if the trouble lies there. Transformers do make noise, but more likely they make a 60-cycle buzzing or humming sound. The transformer often has a core made up of laminated metal components. If the glue fails the core can vibrate, causing a hum. So while we don't rule out some bizarre defect that causes the transformer to send an overcurrent to the gas valve mechanical solenoid that opens to actually send gas to the burners, it's not likely and more likley is wear or something breaking inside the mechanical parts of the solenoid itself. Now to the Gas Solenoid Valve ItselfWith all those safety warnings and dirty burners out of the way, if you do not see any burner troubles and you can trace the clicking hammering noise really right to the gas solenoid valve, it probably needs replacement. As you have made clear that you are hearing a loud hammer-click that seems to come right from the gas solenoid valve itself, it sounds as if there lies a mechanical defect. We [DF] fixed a humming transformer by whacking it once with a hammer. Not very elegant and certainly not recommended by a repairman, but the humming quit for another year or so. About replacing the solenoid valve, given that your previous replacement didn't last: It's a bit subtle but Watch out for Batches of Bad HVAC Replacement PartsWatch out: I [DF] have bought and replaced heating and air conditioning system replacement parts (and for that matter car parts) only to find the new parts were defective. Worse still is to go back to the same store, buy another new part, only to find it's defective too. Keep in mind that often all of the replacement parts of a given part number that are stocked at a local supplier often arrived in the same box, on the same day, and came from the same production run. So if one of them is bad, sometimes all of them are. Try buying the part somewhere else when you replace it, or check the lot numbers on the package to see if you can get a part from another production run. See Gas Regulators for Appliances for details on how to inspect and test LP or natural gas regulators and controls. Suggestions for Diagnosing Gas Igniter Problems on Stovetops
Case History of LP Gas Stove Chronic Igniter Troubles, Diagnosis, & Repair
Turning on the gas burner is supposed to cause it to ignite automagically. But instead the burner blows, blasts, or never ignites, and the igniter clicks continuously. Or the burner will ignite, but the igniter won't stop clicking. There are plenty of explanations around about how these gas flame igniters work and how they are smart enough to turn off after the flame ignites. If you ask ( CONTACT us) we'll add that information here. But below we focus on how to repair igniters that are just maddeningly bad behavers. Problems & Fixes for Automatic Gas Flame IgnitersWe are using a gas range top for this example but these defects or some of them can occur on other automatic or electronic ignition gas fired appliances. The gas burner top is askew as we show in our photographs below, perhaps after it has been removed (say for cleaning) and has not been properly and squarely replaced. Look closely to be sure your stovetop parts are properly seated, especially if they were removed for cleaning. Notice those two pins sticking up on the burner base in our photo at below-right? Notice those two half-round indentations in the burner cap (shown upside down in the lower portion of the same photo ?) Those tell you how to align the burner top properly. Even a small misalignment can prevent proper gas burner operation, and like many gas appliance defects, may be unsafe too.
The gas flame igniter becomes cracked and short-circuits or fails intermittently - the repair solution is to replace the igniter element with a new one. Cooks who often allow pots to boil over and spill water on the hot igniter may contribute to this failure - we're not sure, but in our opinion it's a poor product design that cannot tolerate typical events that occur in the home. The gas flame igniter wiring becomes wet by using too much liquid when cleaning the stove top. In this case the igniter may fail to stop clicking, or may fail to ignite the burner until the wiring has dried. Use less liquid and don't spill liquids into the stove top interior. We have seen these wires short and melt inside the stovetop. Watch out: as our photos below illustrate, water or other liquids spilling onto electrical wiring inside of a range top can cause a short circuit.
At above left we show the interior of this gas range top. The blue box at top center is the control module. At above right you can see that one of the stovetop's internal connectors was shorting to the metal body of the range enclosure.
Our photo at above left shows the shorted stove wiring connector, and at above right, the arc-burn into the steel of the stove top interior, confirming that the connector was shorting to the grounded stove body. Water leaking into the range top interior caused this failure. We re-wired the appliance (using the proper high-temperature-rated electrical wiring materials) and we made sure that the wiring was supported off of the metal range top interior surfaces to prevent a recurrence of this problem. Watch out: when disassembling appliance parts - some stove gas burner parts are made of soft case metal. If in disassembly or reassembly you strip the threads on these parts you may not be able to reassemble the gas burners safely and those larger part assemblies will need replacement. The gas igniter control module may itself fail and need replacement. This is a more costly part, and in our experience is less often the problem than the items above. Frequently Asked Questions (FAQs)... Ask a Question or Search InspectApediaUse the search box below to ask a question or to search the InspectApedia.com website. Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
| ||||||||||||
The Home Reference Book - the Encyclopedia of Homes