15 Ways To Increase Boiler Efficiency

One of the easiest ways for a business to reduce operating expenses is to use energy-efficient equipment. A great place to start lowering your monthly bills is to look at how recently you performed boiler maintenance and how efficiently your current boiler runs.

Before we get to our efficiency tips, we need to understand boiler efficiency.  The majority of heat is lost from your boiler in the stack or boiler water. The goal is to create conditions that generate the smallest possible amount of flue gas (exhaust gas that is expelled) at the lowest possible temperature. This results in increased boiler efficiency.

Think about it; the boiler draws in cool air, heats it up, and sends it out the stack.  A lower stack gas temperature is ideal because the higher the temperature, the more energy will be carried away by the flue gas.  On the other hand, the boiler system takes in cold water, heats it to steam, and uses the heat.  Anywhere we are losing heat, steam, condensate or hot water, we are losing valuable BTU’s.

Whether you rent or own a boiler, you need to save money. Here are 15 easy tips to help make your boiler system more efficient and save money on your monthly bills:

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1. Lower the Stack Temperature

Lowering stack temperatures may be as simple as a day/night set back that lowers the operating pressure on steam boilers or operating temperature on hydronic boilers when idling at night or on mild spring and fall days.

2. Install an Economizer

An economizer uses the otherwise wasted hot flue gas to heat feedwater on its way to the boiler.  If your steam boiler doesn’t have an economizer or your economizer isn’t working, this should be the first priority.  Economizers save fuel and the potentially damaging effects of feeding the boiler with cold water. For serious savings, see if a Heatmizer® is right for your boiler or domestic hot water application.

3. Tune the Burner Regularly

inspect boiler water side regularly and clean out mud legs and drumsAnother common issue occurs when it comes to boiler efficiency is not getting the right amount of air. For proper combustion of fuel inside the boiler, a certain amount of oxygen is required. If too little air is present, the carbon in the fuel will be incompletely oxidized, making carbon monoxide. This causes less heat to be released because the fuel isn’t completely burned, which lowers fuel use efficiency. Low air generates soot, smoke and carbon monoxide, all of which are very dangerous. Too much air also reduces efficiency.  The extra air is brought in cold and sent out the stack hot, wasting heat.

An optimal process provides just enough air for the fuel to burn safely. At Rasmussen Mechanical Services, we can measure the amount of air needed by using an O2 probe inserted into the stack and then tune the burner for optimum efficiency and fuel savings. However, in some facilities, the temperature of the air drawn into the burner varies with the seasons, requiring the burner to be tuned more frequently for maximum savings.

4. Install a Variable Frequency Drive

Not many burner fans or pumps exist out there today without VFD’s and not much new equipment is installed without it. However, if you haven’t heard of VFD’s or have a system that doesn’t utilize them, take note. The unbelievable power savings come from a concept known as the affinity laws for pumps and fans. Essentially, if your system has a fan or circulation pump being controlled by a damper or valve, your system may be wasting a lot of electricity when running at partial loads. A VFD lets your system control flow with fan or pump speed instead, and that’s where the magic happens.

5. Insulate your Valves

Many plants remove the insulation on valves in the boiler room for maintenance and never put it back because it is a hassle. However, exposing these large valves to the air causes a lot of heat loss and can make the boiler room unbearably HOT. Even with the record low gas prices, insulating these valves with a Heatmizer® Removable Blanket can save significantly, improve boiler room comfort and reduce the risk of burns while still allowing easy access for maintenance.

6. Clean the Fireside

Over time, soot may build up on the fireside of the boiler tubes, especially with older equipment.  This layer of soot acts as an insulator, bringing down the heat transfer rate and increasing fuel use. Because of the lower heat transfer rate, the hot gases pass through without transferring the heat to the water, increasing your stack temperature. Cleaning and inspecting your boiler tubes as part of your regular boiler maintenance will ensure that the soot remains minimal and improves the overall efficiency of the boiler.

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7. Preheat Combustion Air

The burner has to heat incoming combustion air with the flame. If the air introduced to the burner is warmer, it requires less fuel to make the same amount of steam in the boiler. A modest 40°F increase in fresh air temperature can save 1% of the fuel bill. If you run large boilers around the clock, this can really add up even with our historically low gas prices. In some cases, an air preheater can pay for itself in under a year.

8. Clean the Water Side

Keeping the waterside of your boiler clean and free of leaks requires diligent water treatment. Inspect your boiler waterside regularly and clean out any mud legs or mud drums to ensure good heat transfer from the metal to the water.  If your boiler water hardness is too high or treated improperly, or the boiler isn’t being blown down regularly, a scale will accumulate on heat transfer surfaces.  This scale will impede the heat transfer, reducing your boiler efficiency. The scale will also keep the water from cooling these heat transfer surfaces. If left untreated, the scale can cause the boiler to overheat, leading to costly boiler repairs and leaks.

9. Return Condensate to the Boiler

Condensate is formed as the steam transfers its heat and condenses. It would be irresponsible to waste this byproduct because it is clean water without dissolved solids or gasses that are ready for use again in your boiler. The water is already hot and therefore requires significantly less fuel to make it into steam again. Reusing the condensate also reduces how much cold makeup water, chemicals, and treatment is required for your boiler. Lastly rerouting condensate back into the feedwater system can reduce wastewater treatment and sewer costs.

For an even larger efficiency increase, consider a high-pressure condensate return system on your largest steam users. This keeps your condensate at a higher pressure, and because it doesn’t flash, you return more water at a significantly higher temperature directly to your boiler.  Contact Mechanical Construction Services to see if this is right for your process.

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10. Recover Heat from Boiler Blowdown

Much like the return of condensate to the boiler, recovering the heat from the boiler blowdown can increase boiler efficiency. The blowdown valve is used to remove boiler water which contains soluble and insoluble solids. It helps reduce the level of dissolved solids in the boiler water to prevent the boiler scale. Unfortunately, when it removes hot water, it also wastes energy. Installing a blowdown heat exchanger, flash tank or combination of the two can help recover some of this energy for your boiler system. Using heat recovery to cool down the blowdown and heat up your make-up water will improve energy efficiency.

11. Control Blowdown Rate

Blowdown removes impurities, like water hardness, from the boiler and is required to keep the boiler surfaces clean. However, blowdown also removes heat from the system.  Water enters the system cold, is heated up to the boiler temperature, and is removed in the blowdown hot. Some boiler systems are fitted with continuous blowdown that does not change with boiler load. To control the heat being sent down the drain, blowdown should be limited only to the amount necessary to control the dissolved solids. For serious savings, control dissolved solids with an automatic blowdown valve. By only blowing down when it is required, you can save a lot of energy without risking costly damage to your boiler from the scale.

12. Reduce Excess Air

Boilers require excess air in order to complete combustion. Although necessary, the amount of excess air can result in totally different efficiencies for your boiler. Too little excess air and the boiler will build up soot and dangerous carbon monoxide, while too much excess air reduces efficiency. Fortunately, there are automatic combustion control systems that can intelligently monitor required air quantities for your combustion systems. As discussed above, tuning can keep your burner running at its best, but it is limited to the best your old burner can offer.

Combustion can produce byproducts like soot and ash

Upgrading to a high-efficiency burner will save a significant amount of fuel and pay for itself many times over.  Ask us about a burner retrofit if your burner is more than 15 years old, runs at higher than 3% stack O2 at any point, or uses linkages.  In many cases, a burner upgrade can save over 10% on your gas bill!

13. Reduce Carry-over

Carry-over is boiler water that leaves the boiler in the steam but is still water.  It carries impurities such as dissolved solids with it. First off, these impurities are then deposited around the steam system inside intricate devices like control valves and pressure regulators, causing a lot of damage and increased maintenance.

As for efficiency, this moisture reduces the BTU content of the steam at the end-use. Essentially, this is more water that was heated in the boiler but did not give off useful heat before going to the condensate system. Carry-over can be caused by a number of things, and the solution depends on the cause. Suspect operating practices such as bringing loads on fast, high TDS, or poor separation equipment as a culprit.

Learn more about carrying over in our blog, How Boiler Feedwater Quality can Affect Boiler Operations.

14. Survey Steam Traps

Stuck, worn out, or just broken steam traps can stick open, allowing valuable steam to blow right through into the condensate system. If you want to ensure you are running at peak efficiency, survey your steam traps regularly and replace broken or sticking traps. Don’t know how or don’t have time? We can find any malfunctioning traps and replace them, saving you time, and saving your company money. Contact us to get started.

15. Reduce Steam Usage

It may seem obvious, but the best way to save on fuel and electricity to your boiler is to reduce steam usage in your processes. Insulating piping and tanks heated by steam, for example, can significantly reduce steam usage, and therefore, fuel usage. High-pressure condensate systems can reduce steam usage at your deaerator AND fuel usage in the boiler.

Ensuring your boiler efficiency is key to controlling your monthly bills. Having a knowledgeable company service your burner, boiler, and steam system regularly will help you ensure that your boiler is as efficient as possible. Let Rasmussen Mechanical Services help you prolong the life of your equipment and work toward preventing repair costs down the road. If you’re convinced that our services are needed, head over to our contact us page and send us a message!

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