Review of Phase I Oilheat Chimney Venting Project Summary of Key Technical Issues Prepared by: Oilheat Manufacturers Association John E. Batey, PE Technical

Review of Phase I Oilheat Review of Phase I Oilheat Chimney Venting ProjectChimney Venting Project

Summary of Key Technical IssuesSummary of Key Technical Issues

Prepared by:Prepared by:

Oilheat Manufacturers AssociationOilheat Manufacturers AssociationJohn E. Batey, PEJohn E. Batey, PE

Technical DirectorTechnical Director

AcknowledgementsAcknowledgements

Oilheat Manufacturers Association (OMA) Oilheat Manufacturers Association (OMA) members supported this draft vent study.members supported this draft vent study.

We also thank Jamie Pye and the Maine Oil We also thank Jamie Pye and the Maine Oil Dealers Association for their valuable input Dealers Association for their valuable input and funding for this Phase I study.and funding for this Phase I study.

In additional, we recognize the important In additional, we recognize the important contributions made by Brookhaven contributions made by Brookhaven National Laboratory for many years of National Laboratory for many years of oilheat venting research. oilheat venting research.

IntroductionIntroduction

Technical concerns with chimney venting of Technical concerns with chimney venting of higher efficiency oilheat equipment have higher efficiency oilheat equipment have existed for the past 20 years. existed for the past 20 years.

Many of these remain unresolved. They need Many of these remain unresolved. They need to be resolved so that to be resolved so that consensus guidelinesconsensus guidelines can be developed to assist oilheat equipment can be developed to assist oilheat equipment manufacturers, installers, and code officials. manufacturers, installers, and code officials.

This initial report summarizes key concerns This initial report summarizes key concerns and areas where additional research is and areas where additional research is needed. needed.

OverviewOverview

Chimneys were required for early natural draft oilheat Chimneys were required for early natural draft oilheat equipment to draw in the combustion air and to vent equipment to draw in the combustion air and to vent exhaust gases.exhaust gases.

In the 1970s the average flue gas temperature was In the 1970s the average flue gas temperature was ~ 650F to 700F.~ 650F to 700F. After the 1970s, equipment efficiencies increased After the 1970s, equipment efficiencies increased

rapidly and flue gas temps dropped.rapidly and flue gas temps dropped. This increases the possibility of chimney damage from This increases the possibility of chimney damage from

flue gas condensation especially in older and larger flue gas condensation especially in older and larger chimneys.chimneys.

Existing oilheat chimneys are both lined and unlined Existing oilheat chimneys are both lined and unlined and code groups have begun to look into re-lining.and code groups have begun to look into re-lining.

The concerns are increasing as the efficiency of new The concerns are increasing as the efficiency of new heating equipment continues to rise. heating equipment continues to rise.

KEY QUESTIONS:KEY QUESTIONS:

How high can new oilheat equipment How high can new oilheat equipment combustion efficiencies go without combustion efficiencies go without incurring chimney damage?incurring chimney damage?

What is the current inventory of What is the current inventory of chimneys serving oilheat equipment?chimneys serving oilheat equipment?

Existing Technical Concerns and Past ResearchExisting Technical Concerns and Past Research

Past research on chimney venting of Past research on chimney venting of gasgas appliances identified a number of concerns appliances identified a number of concerns related to flue gas condensation and chimney related to flue gas condensation and chimney damage in mid- to high efficiency equipment. damage in mid- to high efficiency equipment. Chimney liners were recommended to increase Chimney liners were recommended to increase flue gas temperatures and lower condensation flue gas temperatures and lower condensation rates. (Ref 1,2)rates. (Ref 1,2)

Older gas chimneys are oversized and can Older gas chimneys are oversized and can experience flue gas spillage and moisture experience flue gas spillage and moisture condensation within the chimney leading to condensation within the chimney leading to chimney damage and potential safety concerns chimney damage and potential safety concerns

Technical Concerns and Past ResearchTechnical Concerns and Past Research

Key points include:Key points include:

Chimney inspection is essential Chimney inspection is essential Sizing tables are needed for the new linersSizing tables are needed for the new liners Periodic vent inspections are recommended Periodic vent inspections are recommended Causes of chimney damage must be understood Causes of chimney damage must be understood

before reliningbefore relining Appliance must be sized to the actual heating demandAppliance must be sized to the actual heating demand Masonry chimneys showing damage should be relinedMasonry chimneys showing damage should be relined Vent table should be used to size the reliner when Vent table should be used to size the reliner when

mid-efficiency gas appliances are installed in an older mid-efficiency gas appliances are installed in an older masonry chimneysmasonry chimneys

For oil to gas conversions, careful cleaning of the For oil to gas conversions, careful cleaning of the chimney liner and debris removal is essential chimney liner and debris removal is essential

Technical Concerns and Past ResearchTechnical Concerns and Past ResearchVent II computer modelVent II computer model identifies when existing masonry identifies when existing masonry

chimneys are acceptable and when relining is needed. chimneys are acceptable and when relining is needed.

Unlined masonry chimneys deteriorated more rapidly than lined Unlined masonry chimneys deteriorated more rapidly than lined chimneyschimneys

Chimney crown damage due to freeze-thaw cycling was the most Chimney crown damage due to freeze-thaw cycling was the most common damage – the outdoor chimney crown was a good common damage – the outdoor chimney crown was a good indicator of chimney conditionindicator of chimney condition

Tall chimneys and cold climates contribute to increased Tall chimneys and cold climates contribute to increased condensationcondensation

For gas appliances, water vapor can condense in chimneys lined For gas appliances, water vapor can condense in chimneys lined with clay tile when exposed at outdoor air temperatures of 32F to with clay tile when exposed at outdoor air temperatures of 32F to 35F – (Note: 35F – (Note: oil is expected to condense at lower temperaturesoil is expected to condense at lower temperatures.).)

Dilution air is expected to reduce condensation rates in chimneys Dilution air is expected to reduce condensation rates in chimneys (Note: the difference in dilution rates between gas draft diverters (Note: the difference in dilution rates between gas draft diverters and oil barometric dampers needs to be examined.) and oil barometric dampers needs to be examined.)

Vent “wet time” was examined as a measure of vent condensationVent “wet time” was examined as a measure of vent condensation Dilution air decreases vent gas temperature, however, and the Dilution air decreases vent gas temperature, however, and the

benefit of higher vent gas temperature needs to be compared the benefit of higher vent gas temperature needs to be compared the reduction in dew point from dilution air.reduction in dew point from dilution air.


The Vent II model’s ability to predict condensation rates The Vent II model’s ability to predict condensation rates was verified by field tests and was the basis for was verified by field tests and was the basis for developing vent relining tables to guide installation of developing vent relining tables to guide installation of gas heating equipment.gas heating equipment.

Most clay tile lined chimneys that experiences problems Most clay tile lined chimneys that experiences problems had excessively long vent connectors, were high had excessively long vent connectors, were high chimneys, or did not have dilution air.chimneys, or did not have dilution air.

Clay tile pieces, mortar, or other debris in the chimney Clay tile pieces, mortar, or other debris in the chimney clean-out are signs of chimney damageclean-out are signs of chimney damage

Single gas-fired fan-assisted appliances Single gas-fired fan-assisted appliances should not be should not be ventedvented with unlined or clay tile lined masonry chimneys. with unlined or clay tile lined masonry chimneys.

Variability in chimney construction makes it difficult to Variability in chimney construction makes it difficult to determine dilution air ratesdetermine dilution air rates

Many existing masonry chimneys Many existing masonry chimneys were notwere not built to built to codecode. .


In 1994 local code officials in Oregon interpreted national In 1994 local code officials in Oregon interpreted national fire codes in a way that prohibited the use of unlined fire codes in a way that prohibited the use of unlined chimneys for new oil heaters, even though many had chimneys for new oil heaters, even though many had been operating without incident for decades. This been operating without incident for decades. This prevented the installation of new oil heating equipmentprevented the installation of new oil heating equipment unless the chimney was lined or rebuilt. (unless the chimney was lined or rebuilt. (Ref 3Ref 3))

This incident underscores the need for chimney This incident underscores the need for chimney venting research and guidelines for oil heating venting research and guidelines for oil heating equipment.equipment.


This initiated an OMA project with the This initiated an OMA project with the collaboration of state oil heat associations to collaboration of state oil heat associations to supply input at the National Fire Protection supply input at the National Fire Protection Association technical committee meetings for Association technical committee meetings for installation of oil burning equipment. installation of oil burning equipment.

OMA led a group of oil heat associations that OMA led a group of oil heat associations that recommended revisions to NFPA-31 to allow new recommended revisions to NFPA-31 to allow new oil heat equipment to be installed. The revised oil heat equipment to be installed. The revised standard included provisions for a preliminary standard included provisions for a preliminary chimney inspection and draft tests when the new chimney inspection and draft tests when the new appliance was installed. (appliance was installed. (See Attachment A - See Attachment A - Action Plan and OMA Tech UpdateAction Plan and OMA Tech Update) )


NFPA-31 was also revised to include oil heating NFPA-31 was also revised to include oil heating equipment equipment Venting TablesVenting Tables with relining with relining recommendations developed by Brookhaven recommendations developed by Brookhaven National Laboratory National Laboratory as Appendix Eas Appendix E. .

These tables are based on a vent model These tables are based on a vent model developed by BNL for oil heat equipment. The developed by BNL for oil heat equipment. The tables present recommendations for chimney tables present recommendations for chimney liners but are liners but are not requirementsnot requirements as they are as they are contained in the appendix of the standard. contained in the appendix of the standard.



It is noted that for a steady state efficiency of It is noted that for a steady state efficiency of 88%, a chimney height of 10 feet, and a flue 88%, a chimney height of 10 feet, and a flue connector 10 feet long, that the highest firing connector 10 feet long, that the highest firing rate recommended is 0.75 gallons per hour. rate recommended is 0.75 gallons per hour. Four and five inch liners are Four and five inch liners are notnot recommended. recommended.


Ref 4 Ref 4 was developed by engineers at Brookhaven was developed by engineers at Brookhaven National Laboratory and focuses on National Laboratory and focuses on reliningrelining recommendations for masonry chimneys. It is recommendations for masonry chimneys. It is recommended for existing masonry chimneys to recommended for existing masonry chimneys to improve draft and reduce flue gas condensation improve draft and reduce flue gas condensation when new higher efficiency heating equipment is when new higher efficiency heating equipment is installed. installed.

Inspection of the existing chimney liner is Inspection of the existing chimney liner is recommended before installing a new appliance. recommended before installing a new appliance. Many existing chimneys are oversized for the new Many existing chimneys are oversized for the new more efficient boilers and furnaces that operate more efficient boilers and furnaces that operate with much lower exhaust gas temperatures than with much lower exhaust gas temperatures than older equipment.older equipment.


One of the key criteria implicit in the BNL One of the key criteria implicit in the BNL recommendations is the need to maintain a recommendations is the need to maintain a minimum exhaust gas temperature (95F to 120F) minimum exhaust gas temperature (95F to 120F) at the top of the chimney to reduce condensation at the top of the chimney to reduce condensation and chimney damage. and chimney damage.

Laboratory and field testing to verify these Laboratory and field testing to verify these minimum temperatures and validate the OHVAP minimum temperatures and validate the OHVAP model was never conducted. model was never conducted. Laboratory and field Laboratory and field testing is needed to validate the findings of the testing is needed to validate the findings of the OHVAP model before it can be used with OHVAP model before it can be used with confidence.confidence.


30 to 40 years ago flue gas temperatures of oil-30 to 40 years ago flue gas temperatures of oil-powered boilers and furnaces ranged from 650F powered boilers and furnaces ranged from 650F to 700 F. to 700 F.

Typical fuel oil firing rates were 1.25 to 1.50 Typical fuel oil firing rates were 1.25 to 1.50 gallon per hour range. gallon per hour range.

Modern oil heating equipment has much lower Modern oil heating equipment has much lower flue gas temperatures (400 F to 450 F) and lower flue gas temperatures (400 F to 450 F) and lower firing rates (0.75 to 0.85 gallons per hour) as firing rates (0.75 to 0.85 gallons per hour) as equipment efficiencies rose and house heat loads equipment efficiencies rose and house heat loads reduced.reduced.


Exhaust temperatures decrease as efficiency Exhaust temperatures decrease as efficiency rises. rises. Chimney draft decreases as the flue gas Chimney draft decreases as the flue gas temperature dropstemperature drops. Also, the flue gas . Also, the flue gas temperature at the top of the chimney decreases temperature at the top of the chimney decreases as the inlet gas temperature drops. In this way, as the inlet gas temperature drops. In this way, installing higher efficiency heating equipment installing higher efficiency heating equipment increases the probability of flue gas condensation increases the probability of flue gas condensation and related chimney concerns. and related chimney concerns.

No specific guidelines now exist that are No specific guidelines now exist that are commonly acceptable for existing commonly acceptable for existing installations or for the installation of new installations or for the installation of new higher efficiency oil heating equipmenthigher efficiency oil heating equipment. .


The chimney has a fixed heat loss rate. If the The chimney has a fixed heat loss rate. If the firing rate is reduced, less heat flow enters the firing rate is reduced, less heat flow enters the chimney, and therefore, (for the same chimney chimney, and therefore, (for the same chimney heat losses) the exit gas temperature is lower. heat losses) the exit gas temperature is lower. This can contribute to condensation and chimney This can contribute to condensation and chimney damage by using appliances with lower fuel firing damage by using appliances with lower fuel firing rates.rates.


A venting report by Brookhaven National A venting report by Brookhaven National Laboratory presented at the 1995 Oilheat Laboratory presented at the 1995 Oilheat Technology Conference report contains chimney Technology Conference report contains chimney venting tables for oil-fired appliances in Appendix venting tables for oil-fired appliances in Appendix A. A.

It is noted that as the efficiency increases from 84% It is noted that as the efficiency increases from 84% to 86% to 88%, the number of Not Recommended to 86% to 88%, the number of Not Recommended (NR) cases (NR) cases increasesincreases indicating that exhaust gas indicating that exhaust gas temperatures at the top of chimney are considered temperatures at the top of chimney are considered to be too low. This occurs both for the to be too low. This occurs both for the lower firing lower firing ratesrates and for the and for the taller chimneystaller chimneys. (. (Ref 5Ref 5))


Field testing and validation of the BNL OHVAP Field testing and validation of the BNL OHVAP model is needed before it can be model is needed before it can be recommended for use.recommended for use.

However, the vent tables supply valuable However, the vent tables supply valuable insight into potential chimney venting insight into potential chimney venting concerns for high efficiency oil heating concerns for high efficiency oil heating equipment in conventional masonry equipment in conventional masonry chimneys. Research is needed to fully chimneys. Research is needed to fully evaluate chimney performance at lower flue evaluate chimney performance at lower flue temperatures and at lower firing rates.temperatures and at lower firing rates.


Smoke and OdorsSmoke and Odors

Reduction in smoke and combustion odors during Reduction in smoke and combustion odors during oil burner start-up and shut-down is very oil burner start-up and shut-down is very important to enable important to enable side wall venting systemsside wall venting systems. .

Research by Brookhaven has shown that Research by Brookhaven has shown that approximately two-thirds of the smoke produced approximately two-thirds of the smoke produced during cyclic operation is during burner starts and during cyclic operation is during burner starts and stops. stops.

Also, recent research with Also, recent research with low sulfurlow sulfur and and biodiesel biodiesel fuelfuel blends suggests that these fuels produce a blends suggests that these fuels produce a significant reduction in PM and fuel and significant reduction in PM and fuel and combustion odors that could favor expanded use combustion odors that could favor expanded use of sidewall vent applications.of sidewall vent applications.



The The Advance Oil Heat – “A Guide to Efficiency Advance Oil Heat – “A Guide to Efficiency Improvement”Improvement” that was written by Brookhaven that was written by Brookhaven National Laboratory and the Energy Research National Laboratory and the Energy Research Center about ten years ago includes discussions Center about ten years ago includes discussions on chimney venting.on chimney venting.

A basic chimney inspection check list is A basic chimney inspection check list is presented. presented. Some of this information may be Some of this information may be useful in establishing initial chimney venting useful in establishing initial chimney venting guidelinesguidelines..


An article entitled “Backdrafting Woes” in An article entitled “Backdrafting Woes” in Progressive Builder provides a means for Progressive Builder provides a means for quantifying house depressurization and quantifying house depressurization and backdrafting concerns to multiple exhaust fans to backdrafting concerns to multiple exhaust fans to with oil and gas powered heating equipment. with oil and gas powered heating equipment.

In a tight house the exhaust fans compete with the In a tight house the exhaust fans compete with the chimney-vented appliance for air supply. In some chimney-vented appliance for air supply. In some cases the heating appliance can backdraft, if the cases the heating appliance can backdraft, if the negative pressure in the house is excessive. negative pressure in the house is excessive.

This work is based on many years of research in This work is based on many years of research in Canada on house depressurization. This paper Canada on house depressurization. This paper begins to quantify house “air-tightness” and begins to quantify house “air-tightness” and exhaust fan air flow rates to house exhaust fan air flow rates to house depressurization. depressurization.


The chart that follows shows allowable exhaust The chart that follows shows allowable exhaust flow rates for a range of house air-tightness flow rates for a range of house air-tightness ratings that produce safe and reliable chimney ratings that produce safe and reliable chimney venting. venting.

A “house depressurization limit is calculated. A “house depressurization limit is calculated. When the total exhaust air flow is below this line When the total exhaust air flow is below this line

the house is safe. the house is safe. When it is above this line the house may not be When it is above this line the house may not be

safe as chimney backdrafting may occur. safe as chimney backdrafting may occur.

House depressurization limits vary from house to House depressurization limits vary from house to house so this is not a general solution. However, house so this is not a general solution. However, it does illustrate the importance of treating the it does illustrate the importance of treating the house and vent as a “system”, and can help to house and vent as a “system”, and can help to diagnose venting problems if the approach can be diagnose venting problems if the approach can be applied in a general way. applied in a general way.



This work is important because it shows This work is important because it shows the interaction between the house and the the interaction between the house and the venting system that directly impacts the venting system that directly impacts the operation of chimney and venting system.operation of chimney and venting system.


A Brookhaven National Laboratory report in May 1991 A Brookhaven National Laboratory report in May 1991 summarizes the current state of chimney venting research: summarizes the current state of chimney venting research:

““The occurrence of low vent-system temperatures, acid The occurrence of low vent-system temperatures, acid corrosion and the corrosion and the potential for corrosion in the vent potential for corrosion in the vent system is an issue of major importance system is an issue of major importance for oil-fired for oil-fired heating equipment. The areas of immediate concern heating equipment. The areas of immediate concern include the corrosion of metal vent connectors and include the corrosion of metal vent connectors and chimneys in the field operation of mid- to high-efficiency chimneys in the field operation of mid- to high-efficiency equipment… Based on this work and validation efforts on equipment… Based on this work and validation efforts on vent design programs, recommendations for oil-fired vent design programs, recommendations for oil-fired residential equipment categorization will be provided to the residential equipment categorization will be provided to the industryindustry.” .”

This work has not been completed as US Department This work has not been completed as US Department of Energy funding was re-directed away from vent of Energy funding was re-directed away from vent research to other projects. research to other projects.

Preliminary ConclusionsPreliminary Conclusions

a. Masonry chimneys that are unlined or lined with a. Masonry chimneys that are unlined or lined with clay tile may degrade over time if excessive flue clay tile may degrade over time if excessive flue gas condensation occurs after installing new oil gas condensation occurs after installing new oil heating equipment with lower exhaust gas heating equipment with lower exhaust gas temperatures and reduced fuel firing rates.temperatures and reduced fuel firing rates.

b. Chimneys serving natural gas fired heaters began b. Chimneys serving natural gas fired heaters began to experience condensation concerns as Annual to experience condensation concerns as Annual Fuel Utilization Efficiencies reached 82 percent. Fuel Utilization Efficiencies reached 82 percent. Oil equipment operates with about 4 percent less Oil equipment operates with about 4 percent less heat loss due to water vapor in the flue gas heat loss due to water vapor in the flue gas (latent heat). Therefore, as oil appliances (latent heat). Therefore, as oil appliances approach AFUE efficiencies in the upper 80 approach AFUE efficiencies in the upper 80 percent range, then increased chimney percent range, then increased chimney degradation through excess flue gas degradation through excess flue gas condensation is more likely to occur. condensation is more likely to occur.


c. Oil heating equipment efficiencies have c. Oil heating equipment efficiencies have increased substantially over the past three increased substantially over the past three decades increasing concerns related to the decades increasing concerns related to the suitability of existing chimneys. Average suitability of existing chimneys. Average AFUEs have increased from 78 percent twenty AFUEs have increased from 78 percent twenty years ago to the mid-80 percent range today. years ago to the mid-80 percent range today. The US Department of Energy is considering The US Department of Energy is considering increasing minimum efficiency levels even increasing minimum efficiency levels even further which increases these concerns.further which increases these concerns.

d. Many variables impact the rate of condensation d. Many variables impact the rate of condensation in individual chimneys as discussed in this in individual chimneys as discussed in this report. There are no industry accepted report. There are no industry accepted guidelines for prescribing the maximum guidelines for prescribing the maximum efficiency for heating equipment in chimneys of efficiency for heating equipment in chimneys of varying designs and sizes. varying designs and sizes.


e. Fire protection and building standards and e. Fire protection and building standards and codes require lined chimneys for new codes require lined chimneys for new installations. Code inspectors and authorities installations. Code inspectors and authorities having jurisdiction are free to interpret and having jurisdiction are free to interpret and enforce the provisions of fire and building enforce the provisions of fire and building codes. This has limited the installation of new codes. This has limited the installation of new oil heat equipment in the past. oil heat equipment in the past.

Recommended ActionsRecommended Actions

1. Draft 1. Draft initial guidelinesinitial guidelines for oilheat equipment for oilheat equipment manufacturers and identify the need for additional manufacturers and identify the need for additional research to address areas of uncertainty or concern. research to address areas of uncertainty or concern. The information contained in this report and The information contained in this report and references are a starting point for this effort. OMA references are a starting point for this effort. OMA can play a key role in drafting these initial guidelines. can play a key role in drafting these initial guidelines.

2. Revise initial oil heat chimney guidelines based on 2. Revise initial oil heat chimney guidelines based on review comments submitted by equipment review comments submitted by equipment manufacturers and installers, and other interested manufacturers and installers, and other interested parties. Identify areas where additional information parties. Identify areas where additional information is needed so that research efforts can be planned and is needed so that research efforts can be planned and conducted.conducted.

3. Develop a Project Plan with the goal of producing final 3. Develop a Project Plan with the goal of producing final guidelines for oil heat equipment and initiating and guidelines for oil heat equipment and initiating and supporting new research. supporting new research.

STATEMENT OF NEEDSTATEMENT OF NEED

The absence of industry consensusThe absence of industry consensus standards for the venting of oil-fired standards for the venting of oil-fired

heating appliances leads to confusion in heating appliances leads to confusion in the market which is an impediment to oil the market which is an impediment to oil use generally and to the upgrade of use generally and to the upgrade of existing systems with new, high efficiency existing systems with new, high efficiency equipment specifically.equipment specifically.

1. Field measurements of surface temperatures on inner walls of selected chimney systems

• Logged over 1 week time periods• Correlated with weather conditions• 12 sites targeted – lined masonry, steel, one- and two- story, “good” and “problem” sites• 8 or more measurement points along length of vent, local data loggers

Purpose:• To begin to establish criteria for what is acceptable with oil• To develop and demonstrate simple temperature measurement method• Identify need-for and scope-of a more comprehensive field test

2. CFD Simulation of Model Chimney Systems

• Commercial Fluent Code, 3-D, transient• Model and run several of field test sites

Purpose:• Evaluate low-cost modeling method• Validation against field results

3. Initial Draft of Preliminary Guidelines

• Develop initial guidelines based on Draft Phase I Report• Prepare “strawman” guidelines for industry review• Collect, review , and incorporate industry comments• Identify specific areas where additional research is needed

Purpose: • Develop preliminary venting guidelines• Identify the need for addition research for formulating final guidelines

Documents

Review of Phase I Oilheat Chimney Venting Project Summary of Key Technical Issues Prepared by: Oilheat Manufacturers Association John E. Batey, PE Technical