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Boiler Vent Categories

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MEP Academy Instructor
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Boiler Vent Categories one through four, negative and positive pressure, condensing and non-condensing boilers
Boiler Vent Categories one through four, negative and positive pressure, condensing and non-condensing boilers

All certified boilers have a uniform test procedure to evaluate the vent system. The vent categories are determined to be either under a positive or negative pressure. They are also categorized by their possibility to condense water from the products of combustion. The ability of the products of combustion to condense into a liquid is related to the efficiency of the boiler. As the efficiency of the boiler goes up, the temperature of flue gases becomes cooler, increasing the changes of condensation.

If you prefer to watch the video of this presentation, then scroll to the bottom of the page.

Boiler Flue Vent Chart

Here we put together a simple vent chart to help you envision the requirements.

Boiler Flue Category Chart - Type I, II, III, and IV, Negative, Positive, Condensing and Non-Condensing Boilers
Boiler Flue Category Chart – Type I, II, III, and IV, Negative, Positive, Condensing and Non-Condensing Boilers

Category I Vents

The most used vent category is category One, which is where you might find the use of Type “B” vent materials. This is considered a non-condensing, negative pressure or negative draft system. Since the products of combustion are hot enough to stay above the dew point temperature there should be no condensate.

Type B Vents

Type B vents are designed specifically for non-condensing appliances that produce high-temperature flue gases not exceeding 400 degrees Fahrenheit. These vents operate under negative pressure, relying on natural draft to expel combustion gases. They are usually used with gas appliances with draft hoods.

Category II Vents

Category II vents also operates under a negative pressure like category I, but the flue gases are much cooler than a category one vent. The cooler products of combustion make the gases susceptible to condensation, so they’re located under the condensing side of the chart. Since condensation is possible, the material of the flue must resist the corrosive nature caused by the presence of moisture.

Category III Vents

Category III vents are considered positive pressure because they use a power exhauster for combustion and venting. Positive pressure vents create a unique risk because they can push combustion gases, including potentially harmful carbon monoxide, into the occupied or living space if there are leaks in the venting system.

Unlike negative pressure vents, which rely on natural draft to pull gases out, positive pressure systems actively force gases through the vent, increasing the likelihood of leakage if the venting system is not properly sealed and maintained. Since the flue gas temperature is high enough to avoid condensation, category three vents are in the non-condensing section of the chart.

When replacing a non-condensing boiler with a condensing boiler, several critical considerations must be made regarding the existing flue system. Condensing boilers operate differently than non-condensing boilers, primarily because they extract more heat from the exhaust gases, causing the gases to cool and condense before exiting the flue. The cooler temperatures my cause water to condense in the vent. 

Category IV Vents

Category IV also uses a forced draft positive pressure vent, but since the flue gas temperatures can reach temperatures below the dewpoint they’re classified as condensing type. The flue will also require that the material resist corrosion caused by the presence of moisture.

Direct Venting

Specialized venting systems, such as direct venting, use sealed combustion to draw air from outside and expel exhaust gases directly outdoors, enhancing efficiency and safety. This system typically consists of two separate pipes for intake and exhaust. Direct vent systems improve efficiency by not using indoor air for combustion and minimize the risk of indoor air contamination. 

In addition to enhancing efficiency and safety, direct venting systems offer several other benefits. They reduce the risk of back drafting, which can lead to the infiltration of harmful combustion gases like carbon monoxide into the living space. Direct venting also allows for more flexible installation options, as these systems can be vented horizontally or vertically, making them suitable for a variety of building layouts.

Furthermore, by using outdoor air for combustion, direct vent systems help maintain better indoor air quality and reduce drafts, contributing to a more comfortable indoor environment. Lastly, these systems are generally quieter and more aesthetically pleasing, with fewer visible exterior components.

Flue Material

A category One vent with a non-condensing boiler flue typically use double-wall type “B” vent materials. The double-wall helps maintain the flue temperature above the condensing temperature.

Condensing Boiler Flues must be made from materials that can resist acidic condensate and moisture, such as PVC, CPVC, Polypropylene, or Stainless Steel. Check the boiler manufacturers data to determine the required material. If converting from non-condensing boilers to condensing boilers then the existing metal flues may corrode due to the acidic nature of the condensate produced by condensing boilers. 

Condensing boilers often require smaller flue diameters due to lower exhaust gas temperatures and higher efficiency. The existing non-condensing flue size may need to be reduced to maintain proper draft.

Condensing boilers produce significant amounts of condensate that must be safely drained away. The condensate is acidic and may require neutralization before being discharged into the drainage system to prevent damage to plumbing and the environment.

Summary

When replacing a non-condensing boiler with a condensing boiler, it is essential to thoroughly assess and potentially modify the existing flue system to accommodate the specific requirements of the condensing boiler. This includes using appropriate materials, ensuring proper sizing and configuration, managing condensate, complying with codes and regulations, and potentially insulating and sealing the flue system.

Boiler Flue Categories Positive and Negative, Condensing and Non-Condensing

Why use Steam

By
MEP Academy Instructor
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0
steam heating and latent heat of vaporization
steam heating and latent heat of vaporization

Why use steam for heating? Steam is an excellent medium for heating due to its unique properties, particularly its specific volume and latent heat of vaporization. Here’s an explanation of why these properties make steam beneficial for heating.

If you prefer to watch the video of this presentation, then scroll to the bottom.

Specific Volume of Steam

Specific volume is the volume occupied by a unit mass of a substance, in this case steam.

Steam has a significantly larger specific volume compared to liquid water. This means that for the same mass, steam occupies a much larger space. When steam gives up its heat and condenses into water, it undergoes a dramatic reduction in volume, because water occupies much less space. 

Specific Volume of Saturated Steam. Increased pressure, reduces steam volume.
Specific Volume of Saturated Steam. Increased pressure, reduces steam volume.

Here we have 1 pound of steam at different gauge pressures. At 0 PSIG our specific volume is the greatest at 26.78 cubic feet per pound of steam. As we increase the pressure on the same pound of steam the volume gets smaller, and smaller. At 15 PSIG the volume is about half of that at 0 PSIG, and if we increase the pressure to 50 PSIG the volume decreases again by about half to 6.68 cubic feet per pound. Boilers are rated by their pressure, with low pressure considered 15 PSIG and less, and pressures over that are considered high pressure boilers.

We can see that if we drop the pressure from 50 psig to 15 psig, the same amount of steam now requires twice as much space or volume. By increasing the steam pressure, we can squeeze the same amount of steam into a smaller space. Now less look at how much energy steam holds at these different pressures.

Latent Heat of Vaporization for Dry Steam

The latent heat of vaporization is the amount of heat required to convert a unit mass of a liquid into a vapor without a temperature change. Steam holds more energy per pound than water. If we first look at water at 32 degrees Fahrenheit and the energy it takes to get that 1 pound of water to the boiling point of 212 degrees Fahrenheit, and then convert that pound of water to vapor we’ll understand the differences. 

Latent Heat of Vaporization for Steam at 0 psig is 970 Btu/Lb

A BTU is the amount of heat required to raise 1 pound of water, 1 degree Fahrenheit. This would require 180 BTUs to raise our water at 32 degrees to 212 degrees Fahrenheit. This means our 1 pound of liquid water at 212 degrees Fahrenheit holds 180 btu’s. We would then need approximately 970 BTU to convert the water at 212 degrees Fahrenheit to vapor at 212 degrees Fahrenheit, there is no change in temperature, just a change of state from water to vapor. The vapor holds 970 Btu’s, while the water holds only 180 Btu’s. This is one of the big advantages of using steam.

Steam carries a large amount of energy due to its high latent heat of vaporization. When steam condenses back into water on the surface of a heat exchanger, it releases this substantial amount of energy, which can be used for heating purposes. This energy release is highly efficient, making steam an effective medium for transferring heat.

Why Use Steam for Heating

The enthalpy of steam does not significantly change with an increase in pressure, which means that the total energy content (including both sensible heat and latent heat) of steam remains relatively constant across different pressures. This characteristic indicates that the efficiency of steam as a heat transfer medium is not primarily due to changes in its enthalpy with pressure. 

Instead, the primary advantage of using steam lies in its high latent heat of vaporization and the efficient heat transfer during condensation. These properties enable steam to transfer large amounts of energy quickly and effectively, making it a preferred choice for heating applications despite the relatively stable enthalpy across varying pressures.

As the pressure of steam increases, its specific volume significantly decreases, meaning that the steam becomes denser and occupies less space per unit mass. This reduction in specific volume with higher pressure allows for the use of smaller diameter piping to transport the same amount of steam energy.

Smaller pipes require less material, which reduces the overall material costs. Additionally, smaller piping is easier and quicker to install, leading to lower labor costs. This efficiency in piping size and installation makes steam systems economically advantageous in industrial and commercial applications.

Efficient Heat Transfer using Steam

When steam contacts a cooler surface, it condenses rapidly, releasing a large amount of heat almost instantaneously. This rapid condensation makes steam an excellent medium for delivering heat quickly and efficiently.

Steam provides uniform heating as it condenses at a constant temperature. This is particularly advantageous in processes requiring consistent temperature control.

Ease of Transport and Control

Due to its gaseous state, steam can be easily transported through pipes over long distances without significant heat loss. This makes it ideal for centralized heating systems where the heat source is distant from the application point.

Steam systems are relatively easy to control using valves and other mechanisms, allowing for precise regulation of heat delivery to different parts of a building or process.

Economic and Practical Considerations

Steam heating systems are often cost-effective, both in terms of initial setup and operational costs, especially in large-scale applications like commercial buildings and industrial processes.

Steam can be used in a variety of heating applications, from space heating in buildings to process heating in industries.

In summary, steam’s high latent heat of vaporization and large specific volume, combined with its efficient heat transfer capabilities and ease of transport and control, make it a highly effective and versatile medium for heating applications.

Why use Steam Heating

Top 10 HVAC Service Calls

By
MEP Academy Instructor
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0
See what the top 10 HVAC Service calls are and what the solutions are and the average cost to repair.
See what the top 10 HVAC Service calls are and what the solutions are and the average cost to repair.

Here are the Top 10 HVAC Service Calls, along with their typical solutions and estimated costs. Most of these problems occur due to poor installation, inadequate service procedures, or lack of maintenance.

#1 No Cool Air Flowing

Problem: Dirty air filters or blocked vents.

Solution: Replace air filters and clear any obstructions. Clogged and dirty filters restrict airflow and significantly decrease the system’s efficiency. When airflow is obstructed, air can bypass the filter, depositing dirt directly onto the evaporator coil, which impairs the coil’s ability to absorb heat. By replacing a dirty, clogged filter with a clean one, you can reduce your air conditioner’s energy consumption by 5% to 15%. Dirty filters also put additional stress on the indoor fan leading to fan failure.

Estimated Cost: $70 to $200

#2 Thermostat Issues

Problem: Malfunctioning or incorrectly set thermostat.

Solution: Calibrate, repair, or replace the thermostat. Approximately 25% of U.S. households use a smart thermostat. Smart thermostats are designed to be user friendly and energy efficient but can be incorrectly programmed. Issues can be related to thermostat complexity, user error, default settings, connectivity issues or lack of training.

Estimated Cost: $90 to $300

#3 Refrigerant Leaks

Problem: Low refrigerant due to leaks or improper initial charge.

Solution: Locate and repair leaks, recharge refrigerant. Inexperienced technicians can under or overcharge system with refrigerant. Make sure refrigerant charge matches the manufacturers recommendations, and don’t add refrigerant until system has been tested for leaks.

Estimated Cost: $200 to $1,500

#4 Poor Airflow

Problem: Blocked ducts, vents or dirty filters, or fan issues.

Solution: Clear blocked ducts, unblock vents, clean coil, repair or replace the fan motor.

Estimated Cost: $300 to $900

#5 Strange Noises

Problem: Loose or damaged parts, debris in the system.

Solution: Inspect and tighten components, remove debris, and replace damaged parts. Some reasons for noises can be worn bearings in the fan motor or the compressor can wear out over time, causing grinding or squealing noises. If your system has belts, worn or misaligned belts can cause squealing or screeching noises. Loose bolts, screws, or panels within the unit can vibrate and produce rattling noises.

Estimated Cost: $100 to $400

#6 AC Unit Won’t Turn On

Problem: Electrical issues, tripped breaker, faulty capacitor, or burned-out compressor.

Solution: Check and reset breaker, replace capacitor, inspect wiring, or hit the reset button located in compressor’s access panel if available. On hot days it’s not uncommon for the high-pressure limit switch to shut the system off to protect the compressor or draw excessive amps that cause the breaker to trip. Compressors can burn-out due to many issues such as electrical spikes or inconsistent voltage levels, faulty wiring or components, low refrigerant charge or contaminated refrigerant, operating in extreme weather, normal wear and tear.

Estimated Cost Electrical Issues: $100 to $350

Estimated Cost burned-out Compressor: $1,500 to $2,500 or more depending on type and size of compressor.

#7 Water Leaks

Problem: Clogged drain line, frozen evaporator coils.

Solution: Unclog drain line, thaw coils, ensure proper insulation. A clogged drain line could also reduce the unit’s capacity to reduce humidity levels. 

Estimated Cost: $150 to $500

#8 Unpleasant Odors

Problem: Mold or mildew in the ductwork or unit.

Solution: Clean ducts, replace filters, clean drain pan, and check for mold. Cleaning ducts enhances HVAC system efficiency by improving airflow and reducing energy consumption. It helps reduce odors by removing dust, mold, and pest residues. Additionally, it significantly improves indoor air quality by reducing allergens, mold spores, and other pollutants, contributing to better respiratory health and overall well-being for the occupants. Regular duct cleaning is a crucial part of maintaining a healthy, efficient, and comfortable indoor environment.

Estimated Cost: $300 to $700

#9 Frequent Cycling

Problem: Thermostat issues, dirty filters, improper refrigerant levels, oversized air conditioner. Oversized air conditioners can cause the system to cycle on and off frequently, a phenomenon known as short cycling which causes rapid cooling, inadequate dehumidification, increased wear and tear, higher energy bills, and temperature fluctuations. 

Solution: Adjust thermostat settings, replace filters, check refrigerant levels.

Estimated Cost: $100 to $400

#10 High Energy Bills or Lack of Cooling

Problem: Inefficient system, dirty coils and bent fins.

Solution: Clean coils and comb any bent fins. Dirty coils and bent fins can cause various issues such as reduced cooling efficiency, higher energy consumption, and potential system freeze-ups. The typical solution involves cleaning the coils, where the cost will depend on the severity and accessibility of the coils. Regular maintenance to keep the coils clean can prevent many related problems and ensure the system operates efficiently.

Estimated Cost: $150 to $500

These costs are approximate and can vary based on location, the specific HVAC system, and the service company rates. Regular maintenance can help prevent many of these issues and extend the lifespan of the HVAC system. Let us know in the comments below what your top 3 service call complaints are, and the typical cost to repair.

Top 10 HVAC Service Calls and their Cost to Repair

How to Calculate EER SEER HSPF

By
MEP Academy Instructor
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0
Energy Efficiency Standards SEER2
Energy Efficiency Standards SEER2

When buying a car, you might look at how many miles per gallon the car can achieve when comparing which car is more efficient. This is an indication of its ability to convert fuel into a certain distance traveled. A similar ratio in the HVAC industry is used to indicate how efficient an air conditioner or heat pump is at using electricity to produce BTU’s.

Beginning on January 1, 2023, the US Department of Energy (DOE) has changed to a new rating system where different regions of the United States are divided up. There are now Northern and Southern regions with varying efficiency ratios. Any air conditioners installed starting in 2023 and after in the Southwest and Southeast regions of the United States must meet the new SEER2 energy efficiency standard.

SEER2 Energy Efficiency Standards Map
SEER2 Energy Efficiency Standards Map

Regions matter because different standards are based on the climate needs of customers living in the North, Southeast, and Southwest regions. People in southern climates, where air conditioners are used more frequently, require more energy-efficient systems. Therefore, depending on your geographical region and HVAC needs, split system air conditioners, heat pumps, and single-package systems may have varying efficiency standards.

Energy Efficiency Ratio (EER)

The Energy Efficiency Ratio (EER) measures the efficiency of an air conditioning system or heat pump. It indicates how effectively the unit converts electrical energy into cooling output. Specifically, EER represents the ratio of the cooling capacity (in British Thermal Units per hour, or BTU/h) to the power input (in watts) at a given operating condition.

EER Calculation

EER = Cooling Capacity (BTU/h) / Power Input (W)

EER is typically measured under specific conditions: an outdoor temperature of 95°F, an indoor temperature of 80°F, and 50% relative humidity. This standardization allows for a direct comparison of different units under the same conditions.

Seasonal Energy Efficiency Ratio (SEER)

The Seasonal Energy Efficiency Ratio (SEER) measures the overall energy efficiency of an air conditioning system or heat pump over an entire cooling season. Unlike the Energy Efficiency Ratio (EER), which is calculated at a single operating condition, SEE considers the variations in temperature and cooling demand that occur throughout the season. It represents the ratio of the total cooling output (in BTUs) to the total electrical energy input (in watt-hours) over the cooling season.

SEER Calculation

SEER = Total Cooling output over a Season (BTU) / Total Electric Energy Input over a Season (Wh)

SEER ratings provide a standardized way to compare the energy efficiency of different air conditioning units and heat pumps, considering the varying cooling demands throughout the cooling season. This helps consumers and professionals make informed decisions when selecting HVAC equipment for energy efficiency and cost savings.

Heating Seasonal Performance Factor (HSPF)

The Heating Seasonal Performance Factor (HSPF) measures the efficiency of heat pumps in heating mode over an entire heating season. It represents the ratio of the total heating output (in British Thermal Units, or BTUs) to the total electrical energy input (in watt-hours) during the heating season. HSPF provides an indication of how efficiently a heat pump converts electricity into heat over a range of conditions and temperatures experienced throughout the heating season.

HSPF Calculation

HSPF = Total Heating Output (BTU) / Total Electric Energy Input (Wh)

HSPF provides a comprehensive measure of a heat pump’s heating efficiency over a typical heating season, helping consumers and professionals make informed decisions about equipment that offers better energy savings and performance in various climates.

The new SEER2 Standards

The calculation for SEER2, like the original SEER, is designed to measure the overall energy efficiency of an air conditioning system or heat pump over a cooling season. While the fundamental formula remains similar, SEER2 incorporates updated testing conditions and procedures to better reflect real-world performance.

SEER2 Calculation

SEER2 = Total Cooling Output (BTU) / Total Electric Energy Input (Wh)

Key Differences in SEER2 vs SEER Calculation:

1. Updated Testing Conditions

SEER2 includes more representative testing conditions that reflect a wider range of operating environments and load profiles, considering part-load and variable load conditions more accurately.

2. Improved Measurement Techniques

SEER2 employs updated measurement techniques to account for variations in system performance, cycling losses, and other factors that impact efficiency under real-world conditions.

3. Standardized Load Profiles

SEER2 uses standardized load profiles that mimic the fluctuating cooling demands typical of an entire cooling season, offering a more comprehensive assessment of system efficiency.

Example Calculation

If an air conditioning system provides 60,000 BTUs of cooling over a season and consumes 4,000 watt-hours (Wh) of electricity during that time, the SEER2 would be calculated as follows:

SEER2 = 60,000 BTU / 4,000 = 15

Application

Regulatory Standards: SEER2 is used to set minimum energy efficiency standards for new HVAC systems, ensuring they meet contemporary performance requirements.

Product Comparison: Consumers and professionals can use SEER2 ratings to compare the efficiency of different air conditioning units and heat pumps, aiding in the selection of more energy-efficient models.

Energy Savings: Higher SEER2 ratings indicate better energy efficiency, which translates to lower energy consumption and cost savings over the cooling season.

By incorporating more realistic testing conditions, SEER2 provides a more accurate measure of an HVAC system’s seasonal energy efficiency, helping to promote the use of systems that are more efficient and environmentally friendly.

Uses of EER, SEER and HSPF

Performance Assessment: These calculations offer a standardized way to compare the efficiency of different air conditioners or heat pumps. A higher value indicates better energy efficiency.

Energy Cost Savings: HVAC Equipment with higher ratings use less electricity to produce the same amount of heating or cooling, leading to lower energy bills.

Environmental Impact: More efficient air conditioners or heat pumps reduce overall energy consumption and greenhouse gas emissions, contributing to environmental sustainability.

Regulatory Compliance: In many regions, building codes and energy standards specify minimum efficiency ratio requirements for air conditioners and heat pumps. Compliance with these regulations ensures that installations meet energy efficiency standards.

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