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A commercial hybrid heating system can be the perfect option for your next boiler room upgrade. In this latest blog post from Patterson-Kelley, “Commercial Hybrid Heating Systems, Explained in Less Than 700 Words!” you’ll see how a hybrid heating system can help you save money on your initial investment, while still operating at the highest levels of efficiency.

 

Commercial Hybrid Heating Systems, Explained in Less Than 700 Words!

Eventually, all commercial heating systems need to be replaced – and whether you replace one unit, or five, it will require a significant investment in time and money.  In upgrading your system with the latest technology can offer in condensing equipment, high system efficiency, building management and connectivity, the cost to retrofit your boiler room can escalate quickly.

Fortunately, there is an additional option. You can choose to update your boiler room while saving on installation cost and optimizing your heating system efficiency by considering a hybrid system approach.

 

What is a Commercial Hybrid Heating System?

Hybrid systems consist of one or more condensing boilers, combined with one or more non-condensing boilers that perform the same function. It is designed to both, accommodate building loads, and provide instant savings on the cost of installation.

The design of a hybrid system is calculated to handle the building load with the condensing boiler(s) until it can no longer condense or maintain high efficiency levels. Condensing boilers are more efficient when maintaining lower temperatures and lower percentage of boiler modulation (1-50%). Once they begin exceeding certain parameters, they become less efficient.

In a hybrid system, the temperature required to heat the building on a given day would be used to calculate the building load and size the unit(s) accordingly. For example, an engineer would select a specific building and calculate the energy required down to a specific outdoor temperature without exceeding 150°F boiler temperature. When the system calls for 150°F and below the condensing boiler will run, but when the system calls for 151°F or above the non-condensing boilers will kick-in to accommodate the load. This is assuming that the system will operate at a 30° delta T, so that the return temperature is at 120°F to 130°F. This will cause the condensing boiler(s) to provide high efficiency to the best of its capacity.

 

Proper Control of a Hybrid Heating System

Applying the right control to a hybrid system design is extremely critical for proper boiler sequencing, and to attain the most condensing run-time during boiler operation. The end user must be able to prioritize the start sequence of the boiler system. In the case of mild weather, the condensing boilers must have priority in satisfying building load requirements. When the weather changes, and the outdoor temperature drops below the point of boiler condensation (90%+ efficiency), the control should engage the non-condensing boiler(s).  At this point the difference in efficiency between the two types of boilers should be about 1-1 ½ %. The condensing boiler will now be operating at 88%, while the non-condensing boiler operates at 86.5-87% efficiency.

 

Why Install a Hybrid Heating System?

The benefits of installing a hybrid system include increased savings on installation costs and maximized efficiency. A non-condensing boiler can be about 40% more cost effective than a condensing boiler. When replacing a multi boiler system, purchasing a multiple condensing boilers can become more expensive than a combination of condensing and non-condensing boilers.

 

Prevent Challenges with a P-K Hybrid System Solution

Lacking a good boiler control system that can effectively manage the boiler input based on the temperature requirements of a building can become a great disadvantage when setting up a hybrid system. In which case, the building loads would need to be calculated in a way that a portion of the boiler plant will be condensing and the other portion will not be condensing.

In the past, setting up a hybrid system could have been intimidating for both the system designer and the installer. Those times are over! With recent boiler technology breakthroughs, controls are now able to achieve boiler sequencing and manipulate loads based on the type of boiler and temperature requirements.

The Patterson-Kelley NURO® Touch-Screen Control has the flexibility to control hybrid system applications. Just with one click within the settings option, the control can walk you through the easy steps of setting up the appropriate parameters. Even if the boilers are connected to a building management system, properly setting the hybrid system with the NURO® control can be a piece of cake!

Next Steps?

Interested in more information on the Nuro system and how it might help your clients? Give us a call at 800-355-7061 and we’d be happy to answer any questions or help you with the engineering specifications.

One of our most trusted brands, Patterson-Kelley, provided us with this great explanation breaking down turndown in commercial boilers.

Boilers are rated on thermal efficiency, which is simply the chemical energy added to the boiler, divided by the energy added to the boiler water. As more energy is transferred from the hot gas into the boiler water, the thermal efficiency increases and the temperature of the hot gas decreases. Turndown ratio plays a key role in this energy transfer. Many engineers and owners have been intentionally mislead regarding turn-down ratio’s and this article will dispense with the misleading information and down right nonsense about turn-down ratios and efficiencies!

Almost all boilers are tuned to add excess air, which ensures ideal combustion of the fuel for proper air-fuel mixing. The excess air can also prevent the burner from overheating by “pushing” the combustion flames off the burner.

When energy from the hot gasses is transferred to the boiler water, the gas temperature dips below the dew point, which causes vapor to become liquid. The energy released from the conversion is picked up by the boiler water and results in a significant boost in efficiency.  Every pound of condensate from flue gases condensing adds approximately 1000 btu’s to the boiler water. However, dry flue losses and loss of vapor can result in energy loss.

Energy loss can be readily calculated if the amount of CO2 and O2 in the flue gas and the stack temperature is known.

 With the evolution of boiler technology, manufacturers have found a way to offer units with multiple firing rates, and units that can modulate seamlessly between fixed low fire rates and fixed high fire rates. The fixed fire rates are defined as the boiler turndown capacities, and modulation is accomplished by reducing the air and gas flow into the boiler.

The benefit of this modulation is threefold; it reduces cycle losses, it reduces the wear on the components, and it can potentially lead to higher thermal efficiencies.

Impact of Turndown

This begs the fundamental question – wouldn’t a boiler with extreme turndowns be much more efficient than one with 5:1 turndown?  The answer to that is ‘NO’! And the proof of that is a simple engineering calculation that anyone can verify for themselves (shown below).

To achieve high turndowns the boilers are tuned to deliver greater amounts of excess air at low firing rates to keep the burner from overheating. The additional excess air will significantly reduce the dew point of the water in the flue gas and alter the losses in the dry gas.  To illustrate this effect, the example used in Figure A is updated to reflect a 20:1 turn down where the O2 is set to 11% (corresponding to a CO2 of 5.6% and 97% excess air).  The results are highlighted in Figure B below.

Note that the dew point has been lowered from 130.6° F to 117° F  and the boiler is no longer in the condensing range.  This represents a 3.7% DECREASE in overall efficiency and this is just the beginning of the bad news! 

When excess air well above 50% is used in the boiler, it impacts the stability of the combustion flame which can lead to excessive flame failures, nuisance trips and cycle losses.

The P-K Analysis

Realistic boiler modulation rates have helped improve the overall boiler system efficiency from reduced cycle losses and increased thermal effi­ciencies. Extreme turndown produces the opposite effect. Boil­er plant designs must factor in actual (not extrap­olated) boiler efficiencies through the firing range of the equipment and matching the expected plant loads with the right boiler size selections.

Interested in learning more? Reach out to us at sales@buymeinc.com

Going to be at the 2019 AHR Expo?

Dave Connors, Patterson-Kelley’s Trainer and National Accounts Manager will be giving an exclusive presentation at the 2019 AHR Expo. Be part of his “The Dirty Little Secret Associated with High Turndown” presentation to get a new perspective on the controversial topic.

Join Dave Connors on Wednesday, January 16th between 1:45 PM and 2:05 PM at Theater A – Room C101 of the Georgia World Congress Center. 

As an owner or as a design engineer, you want to be sure that your boiler selection will operate at peak efficiency, under all conditions. Thermal efficiency is simply the chemical energy added to the boiler, divided by the energy added to the boiler water. As more energy is transferred from the hot gas into the boiler water, the thermal efficiency increases and the temperature of the hot gas decreases. Turndown ratio plays a key role in this energy transfer. Many engineers and owners have been intentionally misled regarding turndown ratio’s and this article will dispense with the misleading information and down right nonsense about turndown ratios and efficiencies!

Patterson-Kelley, one of our most trusted brands of boilers, has published a blog post on the advantages and disadvantages of high turndown. We are sharing that post below as well as their explanation of how Patterson-Kelley will introduce 10:1 turndown without sacrificing system efficiency.

Commercial Boiler Efficiency

Placing system efficiency at the forefront of commercial boiler acquisition continues to be a trend in the heating and water heating industry. Manufacturers are racing ahead to push the limits of technology by offering aggressive turndown capabilities approaching, and even exceeding 20:1, at the detriment of system efficiency.

In an age where energy conservation is important and condensing boilers are increasingly being adopted, the dewpoint plays an important role in system efficiency because it determines whether the boiler will condense or not, as well as how much condensation will occur. The dewpoint is the atmospheric condition below which water droplets condense and dew can form, releasing heat that can then be absorbed back into the system. Condensation can occur at up to 130º F depending on pressure and humidity. The returning water in the heating system is used as the cooling medium; as the temperature of the returning water drops, the amount of condensate increases.  The potential amount of condensate estimated at 100,000 BTU’s per hour is one gallon, if the boiler is operating at reduce temperatures.

Heating System Flexibility

Although heating systems are designed to meet peak loads, they spend most of their run-time hours off peak. Along with efficiency, flexibility is an important factor in boiler operation. As the building loads change, the heating system must be flexible enough to change with it. In the instance where the heating system is sized at a higher capability than is required, the flexibility of a boiler could accommodate the imbalance by turning down the input to match the load. This has become the key driving factor in the high turndown story.

Traditionally, turndown has been the limiter of efficiency. To maintain stable flames, excess air is introduced which depresses the dewpoint of natural gas. The dirty little secret associated with high turndown is that, in most cases, the boiler is no longer condensing.

Aggressive turndown capabilities usually lower the dewpoint and reduce the window of opportunity to condense due to excess air. The 970 BTU/lb. of condensate that engineers expect to get from the system, will continue to go straight up the flue.

Excess air to achieve highest possible efficiency:

  • 5 – 10% for natural gas
  • 5 – 20% for fuel oil
  • 15 – 60% for coal


A Patterson-Kelley Solution

Due to technology improvements, Patterson-Kelley will introduce 10:1 turndown capabilities for the first time during 2019. Patterson-Kelley has achieved higher turndown with a unique process that allows the gas valves to reliably turn down without adding large amounts of excess air, resulting in flexibility and efficiency. This method delivers a 10:1 turndown rate while preserving the dewpoint of a 5:1 turndown rate, which helps maintain high condensation levels. This higher turndown capability will provide designers the ability to match input to building loads without sacrificing reliability. No more nuisance flame failures that have traditionally plagued high turndown boilers.

You can see the original post here.

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