Hot Water Systems
Stroma – Hot Water Systems
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Water Heating
Main types
• From main heating system:
– Regular boiler and hot water tank
– Combi boiler
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From additional main system
From secondary heater
Electric immersion heater
Gas multi point heater
Electric instantaneous heater
Range cooker
Community heating
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Water Heating
• If the water heating is supplied by the :
– main system
– additional main system
– secondary system
It can be identified as such in the software
• Many hot water tanks have electric immersion heaters
fitted, but they are only used as a back up, and are not the
main way the water is heated
• Over the next few slides we will cover the different types of systems.
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Hot Water Cylinder & Boiler – Indirect
System
Immersion heater
To taps
Flow from boiler
From cold
water cistern
Return to boiler
Non Condensing Regular Boiler feeding
radiators and hot water cylinder.
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Conventional System
Header tanks
Indirect hot
water
cylinder
Sink
Sink
Boiler
Mains water supply
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Direct Cylinder
Immersion
heater
To taps
Flow from boiler
From cold
water cistern
Return to boiler
• Some older systems may not have the heat exchange coil in them
• These are known as ‘direct’ cylinders as the heated water goes directly
into the cylinder
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Electric Immersion - Dual
To taps
From cold
water cistern
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Sealed System
Indirect hot
water
cylinder
Expansion
vessel
Sin
k
Most condensing boilers are fitted in
a sealed system which has no
expansion tanks, just small
expansions vessels which take the
pressure in the system.
Sin
k
Boiler
Expansion
Vessel
Mains water supply
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Pressurised System
• Note the expansion
vessel above the hot
water tank and below
the boiler
• These are used to keep
pressure in the system.
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Encapsulated cylinders
• Encapsulated cylinders like
this becoming more
common, appear a lot in
recently built properties.
• Tend to have a hard casing,
cannot access insulation.
Try and get manufacturers
details in order to research,
manufacturers website tend
to have spec. It is fair to
assume 50mm of spray
foam insulation.
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Thermal Storage System
• A thermal storage water cylinder
reverses the normal process
• Cold water from the mains enters
the coil at the top of the tank and
is heated by the surrounding hot
water before outputting to the
taps.
• Hot water is therefore effectively
provided on demand and at
mains pressure.
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Gledhill System
• Although this system is
more efficient than a
standard central heating
system, RDSAP cannot
account for it.
• If you come across a
thermal storage system like
this then treat it as a
standard system with
regular boiler and hot
water tank.
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Multi Point Gas Water Heater
Normally:
• Older installations
• Supplies hot water only
• 3 pipes- gas pipe, cold water
supply, hot water draw off
• Often in properties with basic
heating system, e.g. gas fires
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Electric Instantaneous at Point of use Water Heaters
• In smaller properties you may
come across this method of
providing hot water.
• Usually a small unit located near
the sink in the kitchen or
bathroom.
• It heats the water as required,
like an electric shower.
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Water heating from additional
boiler
• A boiler can provide domestic hot water only
– if the specific boiler can be found on the boiler database it can be
entered as additional heating, with the floor area it heats entered as
0% and the water heating ‘from additional heating’
– If the boiler is not on the database it should be entered in the water
heating section only, and not as additional heating. The type of boiler
can be specified as
• Gas boiler/circulator for water heating only
• Oil boiler/circulator for water heating only
• Solid fuel boiler/circulator for water heating only
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Water heating from Range cooker
• If the water heating is supplied by a range cooker which does not provide
the main heating then it can be specifically identified in the water heating
• The following options are available:
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–
–
–
–
–
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Gas, single burner with permanent pilot light
Gas, single burner with automatic ignition
Gas, twin burner with automatic ignition pre 1998
Oil, single burner
Oil, twin burner pre 1998
Solid fuel, integral oven and boiler
Solid fuel, independent oven and boiler
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Water heating from community heating
• If the community heating is providing domestic hot water
only it can be specified in the water heating section as one
of the following options
– Hot water only community scheme – boilers
• This is the most likely option as most community heating is a
regular boiler system
– Hot water only community scheme – CHP
• This means the community system has combined heat and power,
you must be sure this is present before specifying it
– Hot water only community scheme – heat pump
• The community heating should be a heat pump rather than
standard boiler.
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Solar Water Heating
If a property has solar heated water there must be:
• Solar panels on roof
• A store (Hot water tank)
• Often additional controls
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How Solar Water Heating Works
Water heating system with solar
collector and twin coil tank
Solar collector
To taps
Flow from boiler
Return to boiler
Pump
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From cold water
cistern
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Solar Heated Water
 Solar water heating systems use the energy from the sun to heat
water, most commonly in the UK for domestic hot water needs.
 The systems use a heat collector, generally mounted on the roof in
which a fluid is heated by the sun.
 This fluid is used to heat up water that is stored in either a separate
hot water cylinder or a twin coil hot water cylinder inside the building.
 The systems work very successfully in all parts of the UK, as they can
work in diffused light conditions.
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Solar Heated Water
• There are two types of collector used for solar water heating applications:
- Flat plate collectors
- Evacuated tube collectors
The flat plate collector is the predominant type used in domestic systems as
they tend to be cheaper and more robust.
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Solar Heated Water
Evacuated tube collectors are generally more expensive due to a more
complex manufacturing process (to achieve the vacuum) but
manufacturers generally claim better winter performance.
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Solar Water Heating
• Where solar water heating is present there may be a control panel,
these are easily identified by the symbols on the screen
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Solar Water Heating
• If this system is present there will be a ‘yes/no’ option in the
software. Selecting ‘yes’ will give you the option to enter
further details.
• As with other manual entries, documentary evidence must
be supplied in order to do so
• Selecting ‘no’ will assume the default value, which is a 3m2
flat glazed panel on a south facing roof
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Solar water heating - software
Stroma – Hot Water Systems
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Solar water heating
• Extended Data to be collected:
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–
–
–
–
–
–
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Collector type – flat plat, evacuated tube or unglazed
Area of panel (aperture) in m2
Tilt
Orientation
Over shading
Zero loss efficiency – this figure should be in the system documentation
Heat loss coefficient - this figure should be in the system documentation
Solar store combined – is the store part of the existing hot water cylinder
Total hot water volume – if the store is combined, record the cylinder volume
Dedicated solar volume – if the store is separate, record the separate cylinder
volume
– Solar circulating pump – is the pump powered by electricity, PV or unknown
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Solar water heating
• RdSAP convention 9.09 states:
– Documentary evidence is required to over-write collector or solar
stone values except that orientation, tilt and overshading can be
overwritten with visual evidence
– If the panel/collector details are available but the solar store
information is not, the default values can be used for the solar store
– If the solar store is combined and details are being recorded the
volume of the combined cylinder must also be recorded.
Stroma – Hot Water Systems
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Waste Water Heat Recovery
• What is it?
– A waste water heat recovery system (WWHRS) uses a heat exchanger to
recover heat from waste warm water as it flows through the waste plumbing
system
– This is used to pre-heat the cold water feed of a shower, combi boiler or hot
water cylinder.
– The energy recovered depends on the temperature of the cold water feed to
the dwelling (which varies by month) and the number and type of systems
that are installed
• It is unlikely to be retro-fitted at a property, so it is more likely to be
found in modern properties
• You will need documentary evidence to include it as it is unlikely to be
visible
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Waste Water Heat Recovery
Stroma – Hot Water Systems
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Waste Water Heat Recovery
As with FGHRS, WWHRS can only be recorded if it can be found in the database
• Up to two of these systems can be entered
• WWHRS only work in conjunction with mixer showers
•
You will need to determine the following:
– Number of rooms with bath and/or shower (any shower)
– Number of rooms with mixer shower and No bath
– Number of rooms with bath and mixer shower
This information is collected for every survey regardless of the
presence of WWHRS. This data determines the recommendation
for a WWHRS
Stroma – Hot Water Systems
© Stroma Development Ltd 2013 | Version 1.2
Waste Water Heat Recovery
• Identifying mixer showers
– Mixer showers take water from both hot and cold water supplies.
– They mix the hot and cold together to reach a desired temperature.
– They generally flow faster than electric showers
• Instantaneous electric showers are not included in the mixer
shower count, except for ‘Number of rooms with bath and/or
shower’ field
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© Stroma Development Ltd 2013 | Version 1.2
Waste Water Heat Recovery
• RdSAP convention 9.08 states:
– Include only if found in database. When the model cannot be found
no default option is available but the presence of the device should
be recorded in site notes
– Number of rooms with bath and/or shower includes rooms with only
an electric shower. If two showers found in a room count as one.
– Only mixer showers count for waste water heat recover. Mixer
shower means a shower where the hot water is provided by a boiler
(combi or regular), heat pump or immersion heater. A mixer shower
attached to bath taps is recorded as a mixer shower only if there is a
permanent bracket over the bath and there is a shower curtain or
screen.
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Hot Water Cylinders
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Hot Water Tanks - Insulation
• The thickness of the insulation
should be measured at a point
where you can get through to the
cylinder.
• With spray foam find an area
where the foam has been cut
away for connecting pipes
• If the insulation thickness falls
between two options in the
software then go with the lesser
of the two.
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© Stroma Development Ltd 2013 | Version 1.2
Cylinderstat
• The only control a DEA is concerned with on a hot water tank is the cylinder
stat.
• Usually to be held onto tank by wire
• A common misconception is that a TRV can count as a cylinderstat.
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Combined Hot and Cold Water Storage Unit
Mains feed
Hot water
Cold
feed
Flow from boiler
Return to boiler
Immersion
heater
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Typical Hot Water Cylinder Sizes
• Getting the Cylinder size
is crucial in your
assessment this guide
will help you
• Normal Size 90 – 130
Litres
• Medium Size 131- 170
Litres
• Large Size
> 170
Litres
Stroma – Hot Water Systems
Dimensions H x
W
Litres
825 x 450
110
900 x 400
96
900 x 450
120
1050 x 400
115
1050 x 450
144
1500 x 450
218
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Software
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Any questions?
Stroma – Hot Water Systems
© Stroma Development Ltd 2013 | Version 1.2