The Essential Guide to Emergency Commercial Boiler Repair [2025]
A broken or malfunctioning commercial boiler system can disrupt your business. When your facility relies on a boiler, it’s best to catch problems before they spiral out of control.
By familiarizing yourself with boiler issues and emergencies, you can identify them before they occur & react quickly if they do. Knowing there’s a problem is only the first step – you’ll need to find a boiler service company you can rely on.
In this guide, we’ll highlight common problems that lead to emergencies, preventative maintenance, rental boilers, and emergency boiler service companies.
Troubleshooting Your Commercial Boiler System
In-depth knowledge of common boiler issues and their causes can help you diagnose problems effectively and efficiently. Let’s delve deeper into some prevalent boiler system concerns.
Boiler Not Starting, or Requires Manual Resets
One of the more obvious signs of your boiler not working properly is, well, it not starting or working at all. Though there are numerous reasons a boiler may not start, here are a few of the more common or more likely reasons.
The boiler may be locked out from a previous fault or failure. Boilers have two types of controls that can turn a boiler off. These are Automatically Resetting Controls (Operating Controls) and Manual Reset/Limit Controls.
Automatic Controls will reset themselves when the condition has passed and are normal. For example, on a steam boiler, your operating pressure control (also known as a “pressuretrol”), is designed to turn your boiler off once it hits the control’s setpoint and allow restarting once back below the setpoint by a set amount (known as the “offset”).
Manual Resets are tripped for more serious conditions, sometimes at a setpoint past the Automatic Controls. For example, a boiler High Limit Pressuretrol will have a setpoint higher than the Automatic Control. When this is reached and tripped, it could indicate an issue with the Automatic Control, which results in a lockout. This lockout requires an operator to manually reset the control before the boiler will restart.
Manual Reset lockouts can indicate a more serious issue, and troubleshooting should be part of the reset process to identify and correct any causes. Manual Reset Controls (of any kind, whether Pressure/Temperature, Water Level, etc.) should not be reset as part of the normal routine of starting the boiler.
Some other examples of manual resets, beyond High Limit Controls on boilers are: Manual Reset Low Water Cutoffs, Gas pressure switches, Flame Failure (pilot, or main flame), Combustion Air Proving Switch, Gas or Oil Pressure switches, etc. Some boiler controls provide annunciation, telling you exactly where the fault occurred. However, as mentioned before, any time a Manual Reset is tripped, the cause of the trip must be identified and repaired/corrected prior to resuming operation.
Your boiler may also not be receiving a Call for Heat. Whether your boiler is producing steam or hot water for a process, or comfort heating, all boilers receive what is known as a Call for Heat, i.e. a demand signal. This signal can come from a local control (Pressure or Temperature Control), a Lea-Lag panel, or the Building Management System. This signal is what tells the boiler to start up, in response to the demand. If this signal is disrupted your boiler will not start.
Your Boiler’s Operating Control may not be set correctly. If your boiler’s operating control setpoint is set too low, your boiler will not respond and add heat to the system. In some ways boilers are simple machines. The Operating Control tells the boiler when to add heat. If you set this control to 60PSIG, the boiler will only start once the pressure drops below that point (less the control’s differential, commonly 5PSIG). For example, if your system needs steam at 80PSIG, your boiler will only add heat once the pressure drops below 55PSIG. It will then run until the pressure reaches 60PSIG where it will turn off.
Leaking Fluids
There are numerous places around a boiler that may leak, or at least give the appearance of leaking – ranging from harmless and no cause for alarm to requiring emergency services for repairs.
Your boiler may be “sweating” at startup. Some might describe the boiler as sweating at startup. This is commonly caused by having a large, relatively cool boiler running at low fire during startup. These conditions can promote the condensing operation of the boiler. That is, the water vapor in the products of combustion is condensing due to the cool temperature. Steam (and conventional hot water) boilers are not designed for prolonged periods of condensing operation. The condensate is slightly acidic and will attack standard, mild steels. If this condition is transitory in nature, it is likely not a big problem, but it should be checked out by a competent boiler service technician. On firetube boilers, this may present as leaking from around the front and rear boiler doors.
Weeping Safety Relief Valves (SRV) can leak water. SRVs can weep if operated too close to their setpoint or due to wear and tear. Depending on how the SRVs are installed, they may give the appearance of water leaking from the top of the boiler if no Drip Pan Elbows were used. Steam boiler safety relief valves should be pressure tested annually to verify they operate correctly, but whether they need to be rebuilt annually depends on factors like boiler type, service, and local regulations, with some requiring removal and rebuilding every few years instead. A simple manual check on the test lever to ensure it lifts and seats properly should be done more frequently, such as quarterly for low-pressure boilers and monthly for high-pressure ones.
Leaks are not uncommon around boiler Sight Glasses. Boiler sight glasses come in two main flavors, flat (sometimes known as reflex) and round shapes. Both rely on seals to keep the water/steam from leaking where the glass interfaces with the sight glass housing/fittings. Over time these seals can break down and begin leaking. Leaks typically start slowly, with little live steam escaping and a small drip, and can progress to blowing steam. Although initially, not necessarily an emergency, this condition should be corrected quickly, as it presents a safety hazard. Round style glasses are less expensive but do tend to leak more frequently (on high-pressure applications). It is worth considering upgrading to a flat sight glass arrangement to prevent frequent leaks and repairs.
There are obviously numerous piping/fitting connections around boilers, which can also leak. These leaks can be caused simply due to the nature and quality of the installation, or due to damage to the piping itself. If the leak is mechanical in nature, i.e. how the materials are joined, this can be a fairly straightforward repair to stop the leak. However, another cause can be due to poor water treatment, which can result in internal damage to condensate piping (channeling due to carbonic acid formation, or oxygen pitting). This sort of damage is repaired by replacing the damaged piping/fittings. However, if the root cause is not addressed, the damage will occur again and again. Leaks can also occur around modulating valves’ stems and pump seals. In general, whether or not a leak is an emergency depends on several factors, including: severity of the leak, risk of injury (steam or hot water versus cold water), risk of other damage (water dripping on electrical panels, for example), etc.
Leaking of boiler water from the pressure vessel is a serious issue and should be addressed promptly. Leaks from the pressure vessel can be at the tubes to tube sheet connection, due to damage to the tubes (wire drawing or oxygen damage), furnace to tube sheets connections (cracked welds), or cracking of the tube sheet. All of the aforementioned issues require R-stamp repair of the pressure vessel. Leaks may also happen at the mechanical connections where piping enters the boiler. If the leak here is simply a loose fitting, it can be repaired by tightening of the joint. However, if there is damage to the pressure vessel itself, it will require R-stamp repairs. As with troubleshooting mechanical reset controls, if your boiler is experiencing frequent leaks requiring repairs, the boiler’s operation/condition should be reviewed to diagnose the underlying issue causing the damage.
Beyond water-related leaks, boilers have the potential for fuel-related leaks. This includes gaseous fuels such as natural gas, or liquid based fuels such as #2 fuel oil. The potential sources of these leaks vary. They can range from leaking pipe fitting connections, valves (such as gas or oil shutoff valves), pressure regulators, etc. No matter the source, all fuel-related leaks should be treated as an emergency situation, given the combustible nature of the fuels. The boiler should be secured and a source of the leak should be identified and repaired before it is brought back online. The risk of leaks causing issues in the boiler room can be mitigated through routine testing of gas valves (gas valve leak test), and through gas train arrangement (Normally Open Vent Valves, for example).
Low or No Output, but Boiler Running
If your boiler is running but unable to keep up (either steam pressure or hot water temperature is not reaching the setpoint), there are some common places to look for an issue.
If your boiler is cycling on and off at low fire, your operating control may not be set to the correct pressure or temperature. As mentioned previously, regarding why the boiler may not start, if your boiler’s operating control setpoint is set too low, your boiler will not respond and add heat to the system.
If your boiler is driving too high a fire, but not able to keep up, there may be a tuning issue. If the burner is set up incorrectly, it may not be able to burn enough fuel to make the rate. Or, it may be tuned inefficiently, where too much of the fuel’s energy is wasted. A quick way to check efficiency is to look at stack temperature. In general, for a steam boiler, stack temperature will be roughly 100°F above the saturation temperature of the boiler water. If the temperature is much above this, it could indicate a tuning issue. One way to confirm fuel consumption meets the labeled input of the boiler is to measure gas flow. This can be done by clocking the meter over a period of time (taking a reading of the boiler room’s gas meter – make sure other users are turned off, or taken into consideration), or by installing a gas meter on the line feeding the boiler.
Outside of tuning, there are a couple of other potential causes of a higher stack temperature (lower efficiency). Two are fouling of the boiler’s water or firesides, or damage to materials in the boiler’s fireside (baffles). Fouling on the fireside is caused by soot, likely due to improper tuning. On the water side, fouling is due to deposits from the feedwater collecting on the boiler’s tubes. Both issues should be corrected/improved – corrected through cleaning and improved through better tuning and water treatment. For damage to the boiler’s fireside, this could simply be due to age-related stress damaging baffles meant to direct and control the flow of flue gases through the boiler for maximum efficiency. This damage should be repaired to improve efficiency, increase output, and save on fuel costs.
Your boiler may be equipped with a manual (potentiometer) firing rate control. Some boilers will have manual firing rate control. This control is designed to allow an operator (or technician) to manually drive the boiler to set firing rate. This is useful for tuning a boiler, but if left in the manual position, it will limit the boiler’s output to whatever firing rate the potentiometer is set to.
Your boiler may have a Low Fire Hold Control. Low Fire Hold Controls (LFH) are designed to protect boilers from rapid startup from cold. For certain boiler designs, a rapid warmup will cause damage to the boiler vessel. The LFH measures either water temperature or steam pressure and does not allow the boiler to go above low fire until the set temperature/pressure is reached. This means the boiler cannot create steam (or sufficient temperature hot water) to provide your system until the boiler is at a safe temperature, even though the boiler is on and running.
Low Water Condition
If your boiler continually shuts off on low water or you notice low water in your sight glass, there are a couple of potential causes.
Your boiler feedwater pump may be undersized or failing. Feedwater pumps are sized to provide enough water to equal the amount of water leaving the boiler as steam, plus a safety factor (this factor varies based on the type of feedwater control), at a pressure equal to your boiler’s safety relief valve (SRV) plus 3% (by code) so that water can be added to the boiler in the event the SRV’s are lifted. It does sometimes occur that someone may mistakenly size a replacement feedwater pump based on the boiler’s operating pressure. This is dangerous as a pump sized this way will not be able to add enough water to the boiler at higher pressures. A good way to quickly check for this is to look at the boiler’s feedwater pumps’ ratings label. This label will show you the pump’s output (pressure and flow rate) at its design setpoint.
The pressure rating will be in FTHD (feet of head), and the flow rate will be in GPM (gallons per minute). To convert your boiler’s pressure to FTHD, multiply its SRV setpoints x 1.03 (safety factor) x 1.10 (to account for piping losses) x 2.31 (PSIG to FTHD). Flow rate, you take your boiler horsepower rating and multiply it by 0.069, or the boiler steam output (in lbs/hr or pph) x 0.002. This will give you the evaporation rate in GPM, then multiply this x 1.5 (safety factor). Lastly, compare the number you calculated to the pump’s rating label. If the pump is less than these numbers, there is a potential sizing issue. Note: even if the numbers do meet or exceed what is on the pump’s label, there may still be a sizing issue, depending on pump condition, if the pump has been modified, piping layout, etc.
High Water Condition
If your boiler trips out with high water in its sight glass, it is equipped with a High Water Cutoff (HWCO). The job of the HWCO is to protect the steam system from the boiler’s water level getting too high. If a boiler’s water level gets too high, it increases the risk of carryover, which is water being pulled out of the boiler with the steam, or wet steam. If the water level gets too high, you can start introducing more water into the steam header, which can create issues with water hammer. Water hammer occurs when slugs of water are pushed along by steam at high velocities. As this water reaches fittings/elbows in the system, it imparts large amounts of energy into the piping and piping supports. This is dangerous as the piping can be damaged and potentially broken loose from its supports.
High water conditions can be caused by a few different issues, such as sudden load changes and leaking modulating feedwater valves. A sudden load change on a steam boiler temporarily drops the boiler’s steam pressure. As the pressure drops, the size of the steam bubbles in the boiler water increases, leading to a higher observed water level (this is known as “swell”). If your boiler is equipped with a modulating feedwater valve, this can also fail over time and experience what is known as “leak by”. This is where the valve does not fully close off, allowing a low flow of water to leak by the valve into the boiler, slowly raising its level. One cause of this is requiring too much pressure drop across the feedwater valve. For example, many feedwater valves have a maximum pressure drop rating of 50PSIG. If your feedwater pumps are deliver 170PSIG to the FW valve (to meet previously mentioned requirements for feedwater pumps), but the boiler operates at 90PSIG, the feedwater valve is being asked to take a pressure drop of up to 80PSIG. Over time, this high pressure drop at low valve openings can cut the valve’s seat, creating a path for a leak.
Noisy Operation
Boiler rooms are generally noisy places, with combustion noises and the sound of fans and pumps operating. But there are normal noises and abnormal noises. High pitched squeals or grinding noises from motors can indicate a motor is failing. Noise from the burner’s fan wheel area can indicate an out of balance fan wheel (potential for damage to the wheel, or dirt buildup on the blades).
A deep rumbling or pulsing noise when the boiler’s burner is firing can indicate poor tuning, or be caused by mechanical issues such as the aforementioned dirty fan blades, blocked louvers or combustion air openings, improperly set stack damper, etc. A proper inspection and tune-up is the best way to find the root cause of combustion noise, to begin repairs and re-tuning.
Using an Industrial Boiler Rental During an Emergency
Emergencies can take a facility’s boiler system offline. Rental boilers offer a reliable and flexible solution, minimizing your facility’s downtime when things go wrong.
With a wide array of boiler sizes and capacities on hand, rental companies can cater to the diverse needs of various industrial facilities. They provide expert guidance in selecting the appropriate temporary boiler based on capacity requirements, expected duration, and other factors specific to the facility.
Whether you have a short-term (generally one month is the minimum rental period) or long-term need (up to years), rental boilers can be modified and adjusted to accommodate evolving situations, making them a versatile solution for fluctuating demands.
In times of peak demand or emergencies, rapid deployment becomes a critical factor. By working the a boiler service provider that offers rental boilers, your facility can adapt with a temporary boiler to maintain operations.
They also offer swift responses to any additional emergencies or breakdowns that might occur during the rental period, further enhancing their value as a reliable partner during challenging times.
When you rent from professional boiler rental companies, compliance, safety, and reduced operational risk are assured. These companies strictly adhere to stringent safety regulations and requirements, providing a safe and compliant work environment.
One consideration, if you want to plan ahead for potential emergencies, or if you know there are times when you will need a rental boiler or boiler plant (for example, if you have planned downtime or need to satisfy high peak demands), is prepiping of rental connections. It takes time to install piping to hook up a rental boiler; if it is an emergency situation, this time costs money. You can prepipe connections to your existing steam, feedwater, and condensate systems to reduce the amount of time it takes to connect a rental boiler.
Prevent Commercial Boiler Emergencies
Commercial boiler emergencies can disrupt your business operations and pose significant safety risks. However, these emergencies are often preventable with proactive maintenance and regular inspections.
Our industrial boiler preventative maintenance schedule can offer some insight into a routine that maintains boiler health. Below, we’ve covered the core elements of maintaining a healthy boiler and avoiding emergencies.
Regular Maintenance and Service Appointments
Regular boiler maintenance is the cornerstone of a healthy system. Routine service appointments with professional technicians should be scheduled to detect potential problems before they escalate.
During these inspections, technicians perform comprehensive checks, clean the system, and make necessary adjustments to optimize performance. This preventive step not only ensures your boiler’s longevity but also enhances its efficiency and reliability.
Regular Visual Checks
Performing regular visual checks in the areas surrounding the boiler can help detect early signs of leaks, corrosion, or other potential problems. Be vigilant for signs like water stains, rust, or unusual odors.
Immediate attention to these abnormalities can prevent further damage, safeguarding your boiler system against potential emergencies.
Daily Boiler Operation
You should turn on your boiler system daily, even during periods of low demand. This prevents issues arising from prolonged inactivity. Regular operation keeps the system active, preventing components from seizing up or developing problems due to lack of use.
This simple daily practice can significantly contribute to the smooth running of your boiler system.
Annual Checkups
Beyond routine maintenance, annual checkups performed by experienced professionals are critical for the proper functioning of your boiler system. Thorough inspections allow technicians to scrutinize all components, test safety features, and carry out any necessary repairs or replacements.
This proactive approach helps avoid unexpected breakdowns and emergencies, ensuring your boiler system remains in optimal condition year-round.
Regular Boiler Cleaning
Over time, dust, debris, and sediment can accumulate within your boiler system, negatively impacting its performance. Regular professional cleaning services can effectively remove these deposits, ensuring optimal heat transfer and preventing potential fire hazards.
A clean boiler operates more efficiently, reducing the risk of unexpected breakdowns and emergencies.
Monitor Energy Expenses
Keeping a close eye on your energy expenses can provide valuable insights into your boiler system’s efficiency. If you notice a significant increase in energy costs – without a corresponding increase in boiler usage – it could indicate an issue with your system.
Promptly addressing these issues can prevent emergencies, save on energy costs, and enhance the overall efficiency of your boiler system.
Employee Education
Educating your employees about boiler safety and maintenance is another effective preventive measure. Provide training on identifying warning signs such as unusual noises, leaks, or strange odors, and encourage them to report any concerns immediately.
By fostering a culture of awareness and proactive reporting, you can address potential issues before they escalate, further enhancing your boiler system’s safety and reliability.
Finding Professional Commercial Boiler Repair Services Near You
When it’s time to call in the professionals, consider the following tips:
Research and Gather Recommendations: Look for online reviews and testimonials, and ask fellow business owners for recommendations.
Check Licenses and Certifications: Ensure potential service providers comply with industry regulations and standards.
Check Experience and Expertise: Look for services with a solid track record and experience handling various boiler models and types.
Insurance and Liability Coverage: Make sure the boiler repair service has adequate insurance coverage to protect your business from potential liabilities.
WC Rouse & Son has been providing fast, efficient, expert boiler services for over 70 years. With 24/7 emergency services, boiler rental services, and expert technicians, we’re ready for any situation.
Don’t wait for an emergency to strike – contact us today to schedule a check-up with an expert boiler technician!
