Hot Water Cylinder: Stacking, Safety & Installation

Hot Water: Chapter 7

• Hot water is necessary for cleanliness and health in both personal hygiene and living areas.
• Some substances, fatty foods, require at least 60°C to dissolve them.

The Law

• The Building Act 2004 governs the building industry in New Zealand.
• The Act's goal is to improve control and encourage better construction and design practices.
• The objectives of the New Zealand Building Code correspond to the purposes of the Building Act.
• The Building Code outlines required building performance with a number of clauses, including G12.

Means of Compliance

• The Building Code includes clause G12 with compliance documents for hot water supply.
• G12 AS1 includes acceptable solutions for hot water supply installations.
• G12 AS1 also links to reference AS/NZS 3500 Part 4 as a verification method for meeting the Building Code requirements.
• All work on hot water services must conform to the Building Code.
• Clause G12 AS1 outlines that hot water services must meet the following "performance criteria" or mandatory requirements:
• Be delivered at a temperature that avoids the likelihood of scalding.
• Have adequate flow rates to sanitary fixtures and sanitary appliances.
• Avoid the likelihood of leakage.
• Allow reasonable access to components likely to need maintenance, including a means of isolation.
• Prevent the growth of legionella bacteria.
• Have safety devices on vessels used for producing/storing hot water to relieve excessive pressure and limit temperatures to avoid flash steam.
• The textbook covers methods of best trade practice and acceptable NZBC solutions.
• The book does not cover alternative certifying-level designs.

Building Code Requirements

• A building consent for a water heating installation requires that the installation complies with relevant Building Code sections.
• Relevant clauses include:
• B1 – Structure
• B2 – Durability
• E2 – External Moisture
• G12 – Water Supplies
• H1 – Energy Efficiency
• Clause B1 establishes the buildings support structure must support the loads for the building's lifespan.
• Clause B2 lays out durability requirements which state that water heating system components should last a minimum of 15 years.
• Components requiring maintenance or replacement may have a shorter expected life if identified in the owner's manual.
• Installers must provide information supporting a system's durability when applying for a Building Consent.
• Clause E2 requires protection of the structure's weatherproofing envelope to prevent external moisture from leaking into the building.
• Clause G12 protects the cold and hot water's purity and the safety of these water systems.
• G12 also includes acceptable solution G12/AS1, which consolidates the Building Code's various sections together.
• Clause H1 covers energy efficiency for all aspects of a building structure.
• Clause H1 sets our requirements for insulating hot water storage vessels and pipes
• Clause H1 references NZS 4305, which applies to domestic electrical/gas systems having a storage water heater capacity up to 700 liters.
• Minimizing pipe runs to conserve water/energy is included in Clause H1.

Hot Water Science

• Water changes when heated in various ways:
• Changes in volume
• Changes in boiling point
• Dissolves and expels gases
• Dissolves some solids
• May be corrosive
• Flows differently
• Liquid water is only slightly compressible.
• Standard piping or cylinders cannot restrain water if it is forced into a container or if it expands.
• Water expands when heated and when frozen, which will often burst pipes.
• Heated water becomes less dense, occupying a larger area, forming layers, hottest at the top and coolest at the bottom, a process known as stratification.
• Water's maximum density is achieved at 4°C
• The expansion of water above this temperate is not constant, it is greater at higher temps.
• Between 4°C and 100°C, expansion is approximately 4% of the original volume
• Incoming cold water averages 10°C, while hot water averages 65°C and within this range, water expands 2-3% of its original volume.
• Pascal's Law states that pressure universally transmits through a contained or confined fluid with undiminished force.
• Explosions may occur if heated water cannot expand where the force of an explosion depends on the material and structure of the container.

Boiling Point of Water

• Plumbers should be familiar with boiling water's temperature and pressure relationship.
• The Building Code requires people to be safe from injury associated with explosion cause by hot water, and the likelihood of flash steam production.
• Install any water heating system correctly to avoid excess temperature/steam production.

Avoiding the Creation of Steam

• In an open container waters will boil to become steam at 100°C at sea level.
• Boiling points rise significantly if water boils under pressure.
• Changing liquid into steam uses a lot of energy, which creates violent forces if the water has high pressure and temperature.
• Heated water expands aggressively as it turns to steam, because gas occupies more space than liquid.
• Steam inside the water storage unit can also collapse the vessel.
• Steam condensing back into water inside a storage unit creates a vacuum and collapses the cylinder

Types of Water Heaters

• A comparison of basic types of water heaters can be found in the Basic plumbing services skills textbook on pages 308–313.

• Water heaters can either are single-point-use, or act as a central storage heater.

• For buildings, occupancy rates, location and usage will determine if a localized or central system would be best.

• Supplying hot water to a tap with pipe runs is referred to as a dead leg.

• Because heat losses from pipework are excessive, displacing cold water requires significant hot water, making this uneconomical.

• The Building Code's clause H1 defines maximum and minimum draw-off points flows.

• To avoid this, install single-point electric or gas heaters.

• Water heater options:

• Instantaneous water heaters

• Storage water heaters (high, medium, or low pressure)

• Heat exchange (coil) storage water heaters

• Boiling water heaters

Water Capacity

• System capacity is determined by average water use, 40-60 liters per person per day is an common factor to size hot supply.
• Variables for determining hot water capacity:
• Number of people served
• Number of appliances using hot water, and in particular showers
• Dwelling's size
• Winter cold water temperatures
• Users' standard of living
• Users' habits
• Use of spa baths
• Size a water heater according to a homes accommodation potential not current residential amount.
• Design the system to accommodate 'peak load'; The maximum number of hot water users making the maximum hot water system demand.
• Peak demand can be calculated with:
• Flow rate tables from the Building Code,
• Manufacturer's information, such as Rinnai determining their systems peak flow as 30–40 l/hr.
• Factor in that appliances like washing machines use hot water similar a person plus, and allow another person for a second bathroom in the estimation

Types of Energy Sources

• The water heater will be decided by the type of available energy source, which includes fuels that can be burnt.
• To achieve best running costs and convenience, use a combination of one or more of these energy sources:
• Electricity, including single-phase immersion elements and three-phase electrode boilers
• Solid fuel, including wood, coal, and pellets
• Gas, either LPG or Natural gas
• Steam, including geothermal
• Oil
• Solar, either as solar gain from collectors or heat pumps
• Choosing the right energy source depends on fuel availability rates, predicted fuel costs, and technology efficiency.
• Ex: Gas heaters have increased from ~80% to 95% efficient recently
• Energy sources can be controlled or uncontrolled.
• Controlled regulate heat input.
• Ex: Electric cylinders use a thermostat often over temp cut off.
• Uncontrolled heat water up to boiling.
• Ex: Solar heat source. Water will continue rising with the energy source available.

Water Heater Construction

• G12 Requirements (Hot Water Cylinder Configuration )
• There Building Code has requirements for water heater construction and the effects of Temp and pressure on water heater construction.
• Unit standards require system installation, maintenance, and commissioning.
• Ex: AS/NZS 3500.4:2003 Plumbing and drainage Heated water services, Clause G10 Piped Services, and Clause G12 Water.
• Complies with standards and regulations Ex: NZBC clause G12 AS1 and lists regulations in Table 5., such as:
• Low-pressure electric copper storage water heaters (complies with NZS 4602), design, and insulating for 6.5 L - 450 for pressures that go up to 120 kPa or 12m in height.

NZS Compliance

• Above copper water heaters in vertical position or open-vented must comply with G12 and NZS 4603.
• If valve-vented, comply with NZS 4607.
• Electric storage water heaters beyond those covered by 4602 must comply with NZS 4606.
• NZS, Parts 1-3, specifies general requirements for storage water heaters of 6.5-630 liters, temperature control, allowable heat loss, and type/routine testing schedules. Gas-fired models are in the Gas Regulations".

Materials

• Some cylinders are principally only made with one material such as copper, copper cylinder, or stainless steel.

  • Copper is most commonly made for with medium to low pressures, while medium thick cylinders are for medium pressures.

• Stainless steel: Suitable corrosion/stress properties.

  • low-alloy duplex steel with strong strength and lower costly 2304 Duplex.
  • Steel medium costs that contain corrosive resistant 2205 Duplex.

• Systems that source from high chlorine supply in high ppm, or 50, may need stain steel with anode.

• System should use the same/similar materials, but it is unavoidable when there are copper cylinders and independent cast iron boilers.

• Zinc alloy often is brazed with joints (Copper Cylinders)

• Standard Cylinder can be available with inlets and water entry can come at the bottom or via side entry.

• Multiple inlet: 2 extra inlets useful when fitting with heater & solar pump in future.

• One/More coils for purpose made cylinders when there's indirect heating.

Effect of Pressure on Cylinder Configuration

• The cylinders need tags to see if its subject to what pressure for designed operations. Cylinder can damage if pressure exceeds.
• There can be a water heater make in Zealand that contains enameled jacket which can also be looked at as mains units.
  • Either tested for pressure or rated or to resist main pressure can be featured by labels.

Check labels

• Label of cylinders maximum working pressure is at 7.6 m from medium height, and the test pressure in kPa test is 120.
• kPA is label pressure rated which is what can be found in mains.
• Overexposure cylinders (copper based) can become dangerous. see faults.
• Extra strength dome ends made with Older cylinders with sides. Corrugatons for encasing from dense foam.
• Vitreous have bottoms/tops to resist pressure.

Effect of Temperature on cylinder Configuration

• Limits temperature to save consumers. And to prevent steam. See avoidance-steam" for more detail.
• Temperature in hots tanks has matieral properties limit on them. (Ex: steel lined needs maximum temp) Therefor unsuitable for connection/source(s).

Other Requirements and Notes

• Components need protecting from access heat(s) ex valve designs with temp control,
• There are several makers as their components very due unit/fuel used
• Simplist Water heater that does not have controller or heat/energy = inefficient.
• Devices are then heat with gasses (burner) or electric (element) or boilered that use(s) pellets to burn".

Electric Heat System

• Generally use a lower power/energy to solid/gas burners. Takes longer for temperatures at source of powers limit.
• Older ones =1 kW. Now newer fitted 3kW/2kW. Select right rating replace what there is failure.
• more powers pull out larges current with electricity. Regular home wiring that carries 2 kW.
• Electrics can had example for, 27kW three phase wiring is requires.
• A 4m2 solar heat will at two kW/ hr. Gas heater (instant) are at 55kW also pellet are 200 max.

Storage Water heater

The need metals are to make with both (cylinders or water quality). When metals come close corrosion will corrode those that are weaker". -

• Nicel elements on metal cylinders low.
• Tin for glass in metal and mains are pressure
• Incalloy provide better protection than has "hards" hardness".

Tin Plated Elements

• Cylinder: metal glass liners.
• Tin steel make and solution (mag) is closeness.
• elements plating will fast (Anodes) and make claim(s) void.

Nice plating Element

• necessary cylinder heater cylinder =metal needs use Nickel plated to prevent water corrosion over time.
• Using is not correct design & use can (corrosion) on element unnes.
• Inalloy Is used area that's heavy on h20s, to resist and prevent water corrosion, & High Alloy

Low Incoloy

• Solutsions and problems for are that have minerail (ultimate). Reduce failure from square CMS is build up

Quick Recovery

• Quickness by gas unit for storage unit. Can can design 2nd to add as high element provide at top.
• This includes extra at 2nd, near the quick and fast and heater". Also by the dual.

Quick Recovery with Diagram

• Quick recover with special enclosing to elements.

The switches and Control units

• Units boil electric can off its powers when boil
• Also with that the heat water has 3 term use insulation Simplist controls
• The heater will also with select temp. The powers switch itself and the power or temp. Also when hot

Explore hot water cylinder concepts including 'stacking' and overheating risks. Learn about installation standards (G12 AS1), suitable pipe materials, and the importance of rust inhibitors in closed systems. Discover heat trap functions and heat retention methods for open vented systems.