Review of Phase I Oilheat Chimney Venting Project Summary of Key

							  Review of Phase I Oilheat
  Chimney Venting Project
Summary of Key Technical Issues


          Prepared by:
Oilheat Manufacturers Association
         John E. Batey, PE
         Technical Director
         Acknowledgements

Oilheat Manufacturers Association (OMA)
members supported this draft vent study.
We also thank Jamie Pye and the Maine
Oil Dealers Association for their valuable
input and funding for this Phase I study.
In additional, we recognize the important
contributions made by Brookhaven
National Laboratory for many years of
oilheat venting research.
             Introduction

Technical concerns with chimney venting of
higher efficiency oilheat equipment have
existed for the past 20 years.
Many of these remain unresolved. They need
to be resolved so that consensus guidelines
can be developed to assist oilheat equipment
manufacturers, installers, and code officials.
This initial report summarizes key concerns
and areas where additional research is
needed.
                      Overview
   Chimneys were required for early natural draft oilheat
    equipment to draw in the combustion air and to vent
    exhaust gases.
   In the 1970s the average flue gas temperature was
    ~ 650F to 700F.
   After the 1970s, equipment efficiencies increased
    rapidly and flue gas temps dropped.
   This increases the possibility of chimney damage from
    flue gas condensation especially in older and larger
    chimneys.
   Existing oilheat chimneys are both lined and unlined
    and code groups have begun to look into re-lining.
   The concerns are increasing as the efficiency of new
    heating equipment continues to rise.
        KEY QUESTIONS:


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

What is the current inventory of
chimneys serving oilheat equipment?
Existing Technical Concerns and Past Research

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

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

Key points include:
   Chimney inspection is essential
   Sizing tables are needed for the new liners
   Periodic vent inspections are recommended
   Causes of chimney damage must be understood
    before relining
   Appliance must be sized to the actual heating demand
   Masonry chimneys showing damage should be relined
   Vent table should be used to size the reliner when
    mid-efficiency gas appliances are installed in an older
    masonry chimneys
   For oil to gas conversions, careful cleaning of the
    chimney liner and debris removal is essential
    Technical Concerns and Past Research
Vent II computer model identifies when existing masonry
  chimneys are acceptable and when relining is needed.
   Unlined masonry chimneys deteriorated more rapidly than lined
    chimneys
   Chimney crown damage due to freeze-thaw cycling was the most
    common damage – the outdoor chimney crown was a good
    indicator of chimney condition
   Tall chimneys and cold climates contribute to increased
    condensation
   For gas appliances, water vapor can condense in chimneys lined
    with clay tile when exposed at outdoor air temperatures of 32F to
    35F – (Note: oil is expected to condense at lower temperatures.)
   Dilution air is expected to reduce condensation rates in chimneys
    (Note: the difference in dilution rates between gas draft diverters
    and oil barometric dampers needs to be examined.)
   Vent “wet time” was examined as a measure of vent condensation
   Dilution air decreases vent gas temperature, however, and the
    benefit of higher vent gas temperature needs to be compared the
    reduction in dew point from dilution air.
    Technical Concerns and Past Research

   The Vent II model’s ability to predict condensation rates
    was verified by field tests and was the basis for
    developing vent relining tables to guide installation of
    gas heating equipment.
   Most clay tile lined chimneys that experiences problems
    had excessively long vent connectors, were high
    chimneys, or did not have dilution air.
   Clay tile pieces, mortar, or other debris in the chimney
    clean-out are signs of chimney damage
   Single gas-fired fan-assisted appliances should not be
    vented with unlined or clay tile lined masonry chimneys.
   Variability in chimney construction makes it difficult to
    determine dilution air rates
   Many existing masonry chimneys were not built to
    code.
Technical Concerns and Past Research


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


  This incident underscores the need for chimney
  venting research and guidelines for oil heating
  equipment.
Technical Concerns and Past Research

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

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

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

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



It is noted that for a steady state efficiency of
88%, a chimney height of 10 feet, and a flue
connector 10 feet long, that the highest firing
rate recommended is 0.75 gallons per hour.
Four and five inch liners are not
recommended.
Technical Concerns and Past Research

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

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

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

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

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

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

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

Exhaust temperatures decrease as efficiency
rises. Chimney draft decreases as the flue gas
temperature drops. Also, the flue gas
temperature at the top of the chimney decreases
as the inlet gas temperature drops. In this way,
installing higher efficiency heating equipment
increases the probability of flue gas condensation
and related chimney concerns.
No specific guidelines now exist that are
commonly acceptable for existing
installations or for the installation of new
higher efficiency oil heating equipment.
Technical Concerns and Past Research


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

A venting report by Brookhaven National
Laboratory presented at the 1995 Oilheat
Technology Conference report contains chimney
venting tables for oil-fired appliances in Appendix
A.
It is noted that as the efficiency increases from
84% to 86% to 88%, the number of Not
Recommended (NR) cases increases indicating that
exhaust gas temperatures at the top of chimney
are considered to be too low. This occurs both for
the lower firing rates and for the taller chimneys.
(Ref 5)
Technical Concerns and Past Research

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

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

Reduction in smoke and combustion odors during
oil burner start-up and shut-down is very
important to enable side wall venting systems.
Research by Brookhaven has shown that
approximately two-thirds of the smoke produced
during cyclic operation is during burner starts and
stops.
Also, recent research with low sulfur and
biodiesel fuel blends suggests that these fuels
produce a significant reduction in PM and fuel and
combustion odors that could favor expanded use
of sidewall vent applications.
Technical Concerns and Past Research
Technical Concerns and Past Research

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

A basic chimney inspection check list is
presented. Some of this information may be
useful in establishing initial chimney venting
guidelines.
Technical Concerns and Past Research

An article entitled “Backdrafting Woes” in
Progressive Builder provides a means for
quantifying house depressurization and
backdrafting concerns to multiple exhaust fans to
with oil and gas powered heating equipment.
In a tight house the exhaust fans compete with
the chimney-vented appliance for air supply. In
some cases the heating appliance can
backdraft, if the negative pressure in the house is
excessive.
This work is based on many years of research in
Canada on house depressurization. This paper
begins to quantify house “air-tightness” and
exhaust fan air flow rates to house
depressurization.
    Technical Concerns and Past Research

    The chart that follows shows allowable exhaust
    flow rates for a range of house air-tightness
    ratings that produce safe and reliable chimney
    venting.
   A “house depressurization limit is calculated.
   When the total exhaust air flow is below this line
    the house is safe.
   When it is above this line the house may not be
    safe as chimney backdrafting may occur.
    House depressurization limits vary from house to
    house so this is not a general solution.
    However, it does illustrate the importance of
    treating the house and vent as a “system”, and
    can help to diagnose venting problems if the
    approach can be applied in a general way.
Technical Concerns and Past Research
Technical Concerns and Past Research



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

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

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

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

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

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

c.   Oil heating equipment efficiencies have
     increased substantially over the past three
     decades increasing concerns related to the
     suitability of existing chimneys. Average
     AFUEs have increased from 78 percent twenty
     years ago to the mid-80 percent range today.
     The US Department of Energy is considering
     increasing minimum efficiency levels even
     further which increases these concerns.
d.   Many variables impact the rate of condensation
     in individual chimneys as discussed in this
     report. There are no industry accepted
     guidelines for prescribing the maximum
     efficiency for heating equipment in chimneys of
     varying designs and sizes.
         Preliminary Conclusions

e.   Fire protection and building standards and
     codes require lined chimneys for new
     installations. Code inspectors and authorities
     having jurisdiction are free to interpret and
     enforce the provisions of fire and building
     codes. This has limited the installation of new
     oil heat equipment in the past.
             Recommended Actions
1.   Draft initial guidelines for oilheat equipment
     manufacturers and identify the need for additional
     research to address areas of uncertainty or concern.
     The information contained in this report and
     references are a starting point for this effort. OMA
     can play a key role in drafting these initial guidelines.

2.   Revise initial oil heat chimney guidelines based on
     review comments submitted by equipment
     manufacturers and installers, and other interested
     parties. Identify areas where additional information
     is needed so that research efforts can be planned
     and conducted.
3.   Develop a Project Plan with the goal of producing
     final guidelines for oil heat equipment and initiating
     and supporting new research.
STATEMENT OF NEED

The absence of industry consensus
standards for the venting of oil-fired
heating appliances leads to confusion in
the market which is an impediment to oil
use generally and to the upgrade of
existing systems with new, high efficiency
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