Energy efficiency for gas-fired
and oil-fired domestic heating
and hot water systems
Session 3:
Non-condensing and
condensing boiler installations,
and requirements relating to
space heating primary circuits
type and design for gas-fired
and oil-fired wet heating
systems
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Session Objectives and Activities
During the session you will
• Familiarise yourselves with the ‘Guide to condensing boiler
installation assessment procedure for dwellings’ and
associated parameters
• Complete calculations relating to boiler installations
• Research requirements related to space heating primary
circuits types and design for gas-fired and oil-fired wet heating
systems
• Discuss websites and information you have found
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Introducing the condensing boiler installation
assessment procedure for dwellings
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Gas-fired and oil-fired domestic central heating must use condensing boilers
in most circumstances
Where installation of a condensing boiler may be difficult, an assessment
should be completed to see if a non-condensing boiler would be allowed
‘The Guide to the Condensing Boiler Installation Assessment Procedure for
Dwellings’ explains the assessment procedure
If it is suspected that a building may not be suitable for a condensing boiler,
a standard form must be completed to assess whether a non-condensing
boiler can be fitted for a specified fuel.
Appendix G of Part L of the Building Regulations is the form
for assessing when non-condensing boilers are permitted.
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
The condensing boiler installation assessment
procedure for dwellings – assessment criteria
The following criteria must be considered:
• Dwelling type
• Existing boiler fuel
• New boiler fuel
• Existing boiler type
• Existing boiler position
• In the lowest cost option, is the new boiler positioned
in a different room from the existing boiler?
• New boiler positioned in a different room to the
existing boiler?
• Extended flue (longer than 2m) necessary?
• Condensate pump or soakaway necessary?
This will lead to an assessment score.
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Circumstances when non-condensing boilers are
permitted in domestic heating systems
In residential buildings, a non-condensing boiler is allowed only if:
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an existing boiler is being replaced within 3 years of installation
under the manufacturer’s or installer’s guarantee
OR
The assessment form shows a score above 1,000 giving evidence
that installation of a condensing boiler has been assessed as
impractical or uneconomic.
Note that a score above 1,000 does not prohibit installation of a condensing
boiler.
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Possible difficulties with condensing boilers
There are a number of possible difficulties with installing condensing
instead of non-condensing boilers.
Compared to non-condensing boilers, condensing boilers:
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discharge gasses from the flue terminal which are cooler, less buoyant
and often form a visible plume
discharge gases which may wet surfaces too close to the terminal, or
be a nuisance to neighbouring property or people passing nearby
cannot use a flue designed for a non-condensing boiler or share a flue
with a non-condensing boiler
form liquid condensate within the boiler which must be discharged to a
suitable drain or soakaway
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Key websites
If you are unsure where to look for regulatory information and guidance, try one
or more of the following websites:
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UK government Planning Portal www.planningportal.gov.uk
•
Building and Engineering Services Association (B&ES) www.b-es.org/b-esconnections/technical/
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Energy Saving Trust www.energysavingtrust.org.uk/organisations
•
Scottish and Northern Ireland Plumbing Employers’ Federation
www.snipef.org/
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Welsh Government www.wales.gov.uk/topics/planning
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Chartered Institution of Building Services Engineering www.cibse.org
Do not feel you must limit your search to these sites if
you have ideas of others worth exploring.
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Key points from ‘Guide to condensing boiler
installation assessment procedure for dwellings’
From 1st April 2005, revised Approved Document L1 of the Building
Regulations sets down revised guidance for the efficiency of hot
water central heating gas and oil boilers installed in new and
existing dwellings.
Appendix G of the revised Approved Document L1 is the Condensing
Boiler Installation Assessment Procedure, which is to be used in
cases where it is expected to be impractical or too costly to install a
condensing boiler.
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Key web pages
You may have found a range of websites that contain relevant information.
Note the key websites in your course folder for future reference.
Tutor to add specific websites if felt helpful
Websites, regulations and standards are frequently updated so you may want to revisit
websites and conduct further research in future to ensure you are always using the
latest information.
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 – non-condensing and condensing boiler installations, and requirements
relating to space heating primary circuits type and design for gas-fired and oil-fired wet
heating systems
Worksheet
Students should work individually to complete a heat loss / demand / boiler
sizing worksheet with a set of example parameters.
Example worksheets are available from various energy providers,
manufacturers, trade associations and/or government websites.
One example suggested for use in this session is available from The Energy
Saving Trust – CE54, available to down load via this link:
http://www.energysavingtrust.org.uk/Publications2/Housingprofessionals/Heating-systems/Domestic-heating-sizing-method-2010edition
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Session 3 Potential Solutions
Property 1
Property 2
Property 1
A = 168.8 W/K
A = 155 W/K
U = 28.5 WK
B = 159.4 W/K
B = 321 W/K
T = 35.8 KW
C = 87 W/K
C = 250 W/K
V = 35.8 KW
D = 288 W/K
D = 250 W/K
E = 376.2 W/K
E = 214.5 W/K
F = 1080 W/K
F = 1190 W/K
G = 32,400 W
G = 35,000 W
H=-
H = 39.9 W/K
I=-
I = 255 W/K
J=-
J = 255 W/K
K=-
K=-
L=-
L = 5830 W/K
M = 3000
M = 3000
N = 3000
N = 5830
Property 2
U = 30.5 WK
T = 41.2 KW
V = 41.2 KW
Energy efficiency for gas-fired and oil-fired domestic heating and hot water systems
Next session:
During the session you will:
• Research compliance standards and parameters for hot
water storage vessels
• Research requirements relating to the preparation and water
treatment of hot water systems and wet central heating
systems
• Research requirements relating to the commissioning of hot
water systems and wet central heating systems