Category Archives: plumbing

PEX

Cross-linked polyethylene, commonly abbreviated PEX or XLPE, is a form of polyethylene with cross-links. It is formed into tubing, and is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, and insulation for high tension (high voltage) electrical cables. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX has become a common alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.

Properties[edit]

Almost all PEX used for pipe and tubing is made from high-density polyethylene (HDPE). PEX contains cross-linked bonds in the polymer structure, changing the thermoplastic to a thermoset. Cross-linking is accomplished during or after the extrusion of the tubing. The required degree of cross-linking, according to ASTM Standard F876, is between 65 and 89%. A higher degree of cross-linking could result in brittleness and stress cracking of the material, while a lower degree of cross-linking could result in product with poorer physical properties.

Crosslinking improves the elevated-temperature properties of the base polymer. Adequate strength to 120–150 °C is maintained by reducing creep, the tendency to flow. Chemical resistance is enhanced by resisting dissolution. Low temperature properties are improved. Impact and tensile strength, scratch resistance, and resistance to brittle fracture are enhanced.

Almost all cross-linkable polyethylene compounds (XLPE) for wire and cable applications are based on LDPE. XLPE-insulated cables have a rated maximum conductor temperature of 90 °C and an emergency rating up to 140 °C, depending on the standard used. They have a conductor short-circuit rating of 250 °C. XLPE has excellent dielectric properties, making it useful for medium voltage—1 to 69 kV AC, and high voltage cables—up to 380 kV AC-voltage, and several hundred kV DC.

Numerous modifications in the basic polymer structure can be made to maximize productivity during the manufacturing process. For medium voltage applications, reactivity can be boosted significantly. This results in higher line speeds in cases where limitations in either the curing or cooling processes within the continuous vulcanization (CV) tubes used to cross-link the insulation. XLPE insulations can be modified to limit the amount of by-product gases generated during the cross-linking process. This is particularly useful for high voltage cable and extra-high voltage cable applications, where degassing requirements can significantly lengthen cable manufacturing time.

Preparation methods[edit]

The first PEX material was prepared in the 1930s, by irradiating the extruded tube with an electron beam. The electron beam processing method was made feasible in the 1970s but was still expensive. In the 1960s, Engel cross-linking was developed. In this method, a peroxide is mixed with the HDPE before extruding, the cross-linking taking place during the passage of the melted polymer through a long heated die. In 1968, the Sioplas process using silane was patented, followed by another silane-based process, Monosil, in 1974. A process using vinylsilane followed in 1986.

Raw material: XLPE powder used in rotational molding in a factory

Classification[edit]

North America[edit]

All PEX pipe is manufactured with its design specifications listed directly on the pipe. These specifications are listed to explain the pipe’s many standards as well as giving specific detailing about the manufacturer. The reason that all these specifications are given, are so that the installer is aware if the product is meeting standards for the necessary local codes. The labeling ensures the user that the tubing is up to all the standards listed.[1]

Materials used in PEX pipes in North America are defined by cell classifications that are described in ASTM standards, the most common being ASTM F876. Cell classifications for PEX include 0006, 0008, 1006, 1008, 3006, 3008, 5006 and 5008, the most common being 5006. Classifications 0306, 3306, 5206 and 5306 are also common, these materials containing ultraviolet blockers and/or inhibitors for limited UV resistance. In North America all PEX tubing products are manufactured to ASTM, NSF and CSA product standards, among them the aforementioned ASTM standard F876 as well as F877, NSF International standards NSF 14 and NSF 61 (“NSF-pw”), and Canadian Standards Association standard B137.5, to which the pipes are tested, certified and listed. The listings and certifications met by each product appear on the printline of the pipe or tubing to ensure the product is used in the proper applications for which it was designed.

Europe[edit]

In European standards. there are three classifications are referred to as PEX-A, -B, and -C. The classes are not related to any type of rating system.

PEX-A (PE-Xa, PEXa)[edit]

PEX-A is produced by the peroxide (Engel) method. This method performs “hot” cross-linking, above the crystal melting point. However, the process takes slightly longer than the other two methods as the polymer has to be kept at high temperature and pressure for long periods during the extrusion process. The cross-linked bonds are between carbon atoms.

PEX-B (PE-Xb, PEXb)[edit]

The silane method, also called the “moisture cure” method, results in PEX-B. In this method, cross-linking is performed in a secondary post-extrusion process, producing cross-links between a cross-linking agent. The process is accelerated with heat and moisture. The cross-linked bonds are formed through silanol condensation between two grafted vinyltrimethoxysilane (VTMS) units, connecting the polyethylene chains with C-C-Si-O-Si-C-C bridges.

PEX-C (PE-Xc, PEXc)[edit]

PEX-C is produced through electron beam processing, in a “cold” cross-linking process (below the crystal melting point). It provides less uniform, lower-degree cross-linking than the Engel method, especially at tube diameters over one inch (2.5 cm). When the process is not controlled properly, the outer layer of the tube may become brittle. However, it is the cleanest, most environmentally friendly method of the three, since it does not involve other chemicals and uses only high-energy electrons to split the carbon-hydrogen bonds and facilitate cross-linking.

Plumbing[edit]

Radiant heating system manifold using PEX tubing

All pipes, including this copper exterior valve as well as PEX, can burst from freezing, although several reports suggest that PEX takes longer to burst under freezing conditions.

PEX’s flexibility means fewer connections, better water flow, faster and easier installations.

A PEX compression fitting makes it possible to join copper and PEX pipes by simply pushing them together for a watertight fit.

Brass crimp fittings, another popular type of fittings primarily used for connection PEX to PEX, PEX to Threaded pipes. 1.Drop Ear Elbows connect PEX and threaded pipe at a 90-degree 2.PEX to Copper Solder Adapter 3.PEX to Copper Threaded Adapter 4.PEX to Female Threaded Adapter 5.PEX Plug – terminate end of pipe 6.PEX to PEX Coupling 7.PEX to PEX 90-degree Elbow 8.PEX to Copper Adapter 9.PEX to Copper 90-degree Elbow 10. PEX x PEX x PEX 3-way PEX Tee.

Tools and fittings used in a plumbing installation with PEX piping. (1) crimping tool to squeeze a metal band to join a pipe and a fitting (2) compression coupling joining two 1/2 inch pipes (copper or PEX) (3) “T-joint” to connect 3/4″, 3/4″, and 1/2″ pipes (4) Copper-to-PEX 1/2″ connection (requires soldering) (5 and 6) tools to undo PEX connections (7) crimp rings to squeeze metal band to connect PEX to a fixture (8) PEX tube cutter.

PEX tubing is widely used to replace copper in plumbing applications. One estimate is that residential use of PEX for delivering drinking water to home faucets has increased by 40% annually,[2] and there is substantial evidence that PEX is or will soon become the dominant technology for carrying water in homes and businesses in the next decade or so. In 2006, The Philadelphia Inquirer recommended that plumbing installers switch from copper pipes to PEX.[1]

In the 20th century, mass-produced plumbing pipes were made from galvanized steel. As users experienced problems with the internal build-up of rust, which reduced water volume, these were replaced by copper tubing in the late 1960s.[3] Plastic pipes with fittings using glue were used as well in later decades. Initially PEX tubing was the most popular way to transport water in hydronic radiant heating systems, and it was used first in hydronic systems from the 1960s onwards.[2] Hydronic systems circulate water from a boiler or heater to places in the house needing heat, such as baseboard heaters or radiators.[4] PEX is suitable for recirculating hot water.[5]

Gradually, PEX became more accepted for more indoor plumbing uses, such as carrying pressurized water to fixtures throughout the house. Increasingly, in the 2000s, copper pipes as well as plastic PVC pipes are being replaced with PEX.[3] PEX can be used for underground purposes, although one report suggested that appropriate “sleeves” be used for such applications.[5]

Benefits[edit]

Benefits of using PEX in plumbing include:

  • Flexibility. PEX has become a contender for use in residential water plumbing because of its flexibility.[6] It can bend into a wide-radius turn if space permits, or accommodate turns by using elbow joints. In addition, it can handle short-radius turns, sometimes supported with a metal brace; in contrast, PVC, CPVC and copper all require elbow joints. A single length of PEX pipe cannot handle a sharp 90-degree turn, however, so in those situations, it is necessary to connect two PEX pipes with a 90-degree PEX elbow joint.
  • Direct routing of pipes. PEX can run straight from a distribution point to an outlet fixture without cutting or splicing the pipe. This reduces the need for potentially weak and costly joints and reduces the drop in pressure due to turbulence induced at transitions. Since PEX is flexible, it is often possible to install a supply line directly from the water source to an appliance using just one connection at each end.[2]
  • Greater water pressure at fixtures. Since PEX pipes typically have fewer sharp turns, there is greater water pressure at the sinks and showers and toilets where it is needed.
  • Lower materials cost. Cost of materials is approximately 25% of alternatives.[7][8] One account suggested that the price of copper had quadrupled from 2002 to 2006.[2]
  • Easier installation. Installing PEX is much less labor-intensive than copper pipes, since there is no need to use torches to solder pipes together, or to use glue to attach pipes to fittings.[7] One home inspector wrote that “Once you’ve worked with PEX, you’ll never go back to that other stinky glue stuff.”[9] Builders putting in radiant heating systems found that PEX pipes “made installation easy and operation problem-free”.[6] PEX connections can be made by pushing together two matching parts using a compression fitting, or by using an adjustable wrench or a special crimping tool.[2] Generally, fewer connections and fittings are needed in a PEX installation.[1]
  • Non-corrodible. PEX, unlike copper, is not subject to corrosion from minerals or moisture.[1]
  • No fire risk during installation. The oldest and most common method for joining copper piping is to solder pieces together using a torch. With an open flame there is always the risk of causing a fire in the surrounding structure, but PEX installation does not require a flame.[10]
  • Ability to merge new PEX with existing copper and PVC systems. Manufacturers make fittings allowing installers to join a copper pipe on one end with a PEX line at the other,[2] as well as giving options to reduce or expand the diameter of the pipes.
  • Longevity. The advantageous properties of PEX also make it a candidate for progressive replacement of metal and thermoplastic pipes, especially in long-life applications, because the expected lifetime of PEX pipes reaches 50 years. However, the longest warranty offered by any PEX producer is 25 years.
  • Suitable for hot and cold pipes. A convenient arrangement is to use color-coding to lessen the possibility of confusion.[9] Typically, red PEX tubing is used for hot water while blue PEX tubing is used for cold water.[1]
  • Less likely to burst from freezing. The general position is that PEX plastic materials are slower to burst than copper or PVC pipes, but that they will burst eventually since freezing causes water to expand.[11] One account suggested that PEX water-filled pipes, frozen over time, will swell and tear; in contrast, copper pipe “rips” and PVC “shatters”.[12] Home expert Steve Maxwell suggested in 2007 that PEX water-filled pipes could endure “five or six freeze-thaw cycles without splitting” while copper would split apart promptly on the first freeze.[13] In new unheated seasonal homes, it is still recommended to drain pipes during an unheated cold season or take other measures to prevent pipes from bursting because of the cold. In new construction, it is recommended that all water pipes be sloped slightly to permit drainage, if necessary.[13]
  • Environmental benefits. One account suggested that PEX used in radiant heating was better for the environment than copper, although it noted that the pipes were based on petroleum products.[8]
  • Pipe insulation possible. Conventional foam wrap insulation materials can be added to PEX piping to keep hot water hot, and cold water cold, and prevent freezing, if necessary.[14]

Drawbacks[edit]

  • Degradation from sunlight. PEX tubing cannot be used in applications exposed to sunlight, as it degrades fairly rapidly.[15] Prior to installation it must be stored away from sunlight, and needs to be shielded from daylight after installation. Leaving it exposed to direct sunlight for as little as 30 days may result in premature failure of the tubing due to embrittlement.[15]
  • Perforation by insects. PEX tubing is vulnerable to being perforated by the mouthparts of plant-feeding insects; in particular, the Western conifer seed bug (Leptoglossus occidentalis) is known to sometimes pierce through PEX tubing, resulting in leakage.[16]
  • Problems with yellow brass fittings. There have been some claimed PEX systems failures in the U.S., Canada and Europe resulting in several pending class action lawsuits. The failures are claimed to be a result of the brass fittings used in the PEX system. Generally, builders and manufacturers have learned from these experiences and have found the best materials for use in fittings used to connect pipe with connectors, valves and other fittings. But there were problems reported with a specific type of brass fitting used in connection with installations in Nevada that caused a negative interaction between its mineral-rich hard water[17] and so-called “yellow brass” fittings.[5] Zinc in the fittings leached into the pipe material in a chemical reaction known as dezincification, causing some leaks or blockages.[17] A solution was to replace the yellow brass fittings, which had 30% zinc, with red brass fittings, which had 5% to 10% zinc.[17] It led California building authorities to insist on fittings made from “red brass” which typically has a lower zinc content, and is unlikely to cause problems in the future since problems with these specific fittings have become known.[5]
  • Initial adjustment to a new plumbing system. There were a few reported problems in the early stages as plumbers and homeowners learned to adjust to the new fittings, and when connections were poorly or improperly made, but home inspectors have generally not noticed any problems with PEX since 2000.[18]
  • Limited adhesives for pipe insulation. One source suggested that pipe insulation, applied to PEX using certain adhesives, could have a detrimental effect causing the pipe to age prematurely; however, other insulating materials can be used, such as conventional foam wrap insulation, without negative effects.[14]
  • Fitting expenses. Generally, PEX fittings, particularly the do-it-yourself compression ones, are more expensive than copper ones, although there is no soldering required.[2] Due to the flexibility of PEX, it generally requires fewer fittings, which tends to offset the higher cost per fitting.
  • Potential problems for PEX radiant heating with iron-based components. If plain PEX tubing is used in a radiant heating system that has ferrous radiators or other parts, meaning they are made out of iron or its alloys, then there is the possibility of rust developing over time; if this is the case, then one solution is to have an “oxygen barrier” in these systems to prevent rust from developing. Most modern installations of PEX for heating use oxygen barrier coated PEX.
  • Odors and chemical taste in potable water.[19]
  • Possible health effects. There was controversy in California during the 2000s about health concerns. Several groups blocked adoption of PEX for concerns about chemicals getting into the water, either from chemicals outside the pipes, or from chemicals inside the pipes such as methyl tertiary butyl ether and tertiary butyl alcohol.[20] These concerns delayed statewide adoption of PEX for almost a decade. After substantial “back-and-forth legal wrangling”, which was described as a “judicial rollercoaster”, the disputing groups came to a consensus, and California permitted use of PEX in all occupancies.[21][22] An environmental impact report and subsequent studies determined there were no causes for concerns about public health from use of PEX piping.[21]

Government approvals[edit]

PEX has been approved for use in all fifty states of the United States as well as Canada,[1] including the initially reluctant state of California, which approved its use in 2009.[5] California allowed the use of PEX for domestic water systems on a case-by-case basis only in 2007.[23] This was mostly due to issues with corrosion of the manifolds, not the tubing itself, and was allowed in California when used in hydronic radiant heating systems. In 2009, the Building Standards Commission approved PEX plastic pipe and tubing to the California Plumbing Code (CPC), allowing its use in hospitals, clinics, residential and commercial construction throughout the state.[5] Formal adoption of PEX into the CPC occurred on August 1, 2009, allowing local jurisdictions to approve its general use,[24] although there were additional issues, and new approvals were issued in 2010 with revised wordings of the 2007 act.[25]

Competitors to PEX[edit]

Alternative plumbing choices include:

  • Aluminum plastic composite are aluminum tubes laminated on the interior and exterior with plastic layers for protection.[1]
  • Corrugated stainless steel tubing, continuous flexible pipes made out of stainless steel with a PVC exterior and are air-tested for leaks.[1]
  • Polypropylene Pipe, similar in application to CPVC but a chemically inert material containing no harmful substances and reduced dangerous emissions when consumed by fire. It is primarily utilized in radiant floor systems but is gaining popularity as a leach-free domestic potable water pipe, primarily in commercial applications.
  • Polybutylene (PB) Pipe is a form of plastic polymer that was used in the manufacture of potable water piping from late 70’s until 1995. However, it was discovered that the polyoxymethylene (POM or Acetal) connectors originally utilized to connect the polybutylene tubes were susceptible to stress enhanced chemical attack by hypochlorite additions (a common chemical used to sanitize water). Degraded connectors can crack and leak in highly stressed crimped areas, causing damage to the surrounding building structure. Later systems containing copper fittings do not appear to have issues with hypochlorite attack, but polybutylene has still fallen out of favor due to costly structural damage caused by earlier issues and is not accepted in Canada and U.S.

PEX-AL-PEX[edit]

PEX-AL-PEX pipes, or AluPEX, or PEX/Aluminum/PEX, or Multilayer pipes are made of a layer of aluminum sandwiched between two layers of PEX. The metal layer serves as an oxygen barrier, stopping the oxygen diffusion through the polymer matrix, so it cannot dissolve into the water in the tube and corrode the metal components of the system.[26] The aluminium layer is thin, typically 1 or 2 mm, and provides some rigidity to the tube such that when bent it retains the shape formed (normal PEX tube will spring back to straight). The aluminium layer also provides additional structural rigidity such that the tube will be suitable for higher safe operating temperatures and pressures.

PEX tool kit[edit]

A PEX tool kit includes a number of basic tools required for making fittings and connections with PEX tubing. In most cases, such kits are either bought at a local hardware store, plumbing supply store or assembled by either a home owner or a contractor. PEX tools kits range from under $100 and can go up to $300+. A typical PEX tool kit includes crimp tools, an expander tool for joining, clamp tools, PEX cutters, rings, boards, and staplers.[further explanation needed]

Other uses for PEX[edit]

  • Artificial joints. Highly cross-linked polyethylene is used in artificial joints as a wear-resistant material. Cross-linked polyethylene is preferred in hip replacement because of its resistance to abrasive wear. Knee replacement, however, requires PE made with different parameters because cross-linking may affect mechanical strength and there is greater stress-concentration in knee joints due to lower geometric congruency of the bearing surfaces. Manufacturers start with ultra high molecular weight polyethylene, and crosslink with either electron beam or gamma irradiation.
  • Dental applications. Some application of PEX has also been seen in dental restoration as a composite filling material.
  • Watercraft. PEX is also used in many canoes and kayaks. The PEX is listed by the name Ram-X, and other brand specific names. Because of the properties of Cross-Linked Polyethylene, repair of any damage to the hull is rather difficult. Some adhesives, such as 3M’s DP-8005, are able to bond to PEX, while larger repairs require melting and mixing more Polyethylene into the canoe/kayak to form a solid bond and fill the damaged area.
  • Power cable insulation. Cross-linked polyethylene is widely used as electrical insulation in power cables of all voltage ranges but it is especially well suited to medium voltage applications. It is the most common polymeric insulation material. The acronym XLPE is commonly used to denote cross-linked polyethylene insulation.
  • XLPE automotive duct

    Automotive ducts and housings. PEX also referred to as XLPE is widely used in the aftermarket automotive industry for cold air intake systems and filter housings. Its properties include high heat deflection temperature, good impact resistance, chemical resistance, low flexural modulus and good environmental stress crack resistance. This form of XLPE is most commonly used in rotational molding; the XLPE resin comes in the form of a 35 mesh (500 µm) resin powder.

  • From Wikipedia, the free encyclopedia

water heater electric

the electric water heater begins around 1850 with an experiment that was created in which both water and bath, on the underneath side, were heated by gas jets. An Englishman Benjamin Maughan, however in 1868 invented the first instant water heater called “The Geyser”, a device where the water was heated as it flowed into the bath. They were known to be quite dangerous.

Maughn’s invention influenced the designs of a Norwegian mechanical engineer by the name of Edwin Ruud, who immigrated to Pittsburg. Ruud who invented the electric water heater (automatic storage) in 1889, founded the Ruud Manufacturing Company, which is still in operation today, and pioneered the advancement of water heaters, in both the residential and commercial market.

The Water Heater is still sometimes referred to as a geyser in the UK. Other terms include: an electric water boiler, electric dispensing pot, or electric water urn.

There are various kinds of water heaters. The most common water heaters are the storage water heaters. Instantaneous (tankless) water heaters are newer on the market, and newer still, solar water heaters.

Storage Tank Water Heaters:

This is typically the kind of water heater you saw growing up, the big white tank often beside the furnace. Tank type water heaters come in different varieties – gas, oil electric. This refers to the type of burner used to heat the water. Energy efficiencies between the different types of burners on the tank water heaters can differ greatly. In this tank, cold water is used to fill the tank, and an element, usually near the top bottom inside the tank is used to heat it. In between the inside tank and the outer shell is often insulation to help keep the water hot, without the elements having to do all of the work.

Instantaneous Water Heaters:

Instantaneous Water Heaters, also called Tankless Water Heaters are just that. They do not have a tank, and therefore are thought to be more energy efficient. Sometimes they are called an in-line water heater, as it only heats the water it needs as it passes through, and therefore energy is not wasted by heating extra water all day that is not in use.

Other terms for Tankless Water Heaters is Combination Water Heaters, Combi Boilers, Continuous Flow Water Heaters, Inline Water Heaters, Flash Water Heaters, On-Demand Water Heaters or Instant-On Water heaters.

These particular Water Heaters are rapidly gaining in popularity and will soon become the standard. Often, one main Tankless Water Heater will be installed near the furnace, and supplemental smaller Tankless Water Heaters will be situated in tactical spots, such as a far reaching bathrooms, etc to be located right where the water is being used. This strategy saves water as well as energy, thereby making this option one of the most efficient, as well as saving on space.

Solar Water Heaters:

If you’re fortunate enough to live someplace sunny most of the year around, a solar powered water heater may be an option for you. Solar collectors are typically installed on the exterior of the building on the roof or nearby. If insufficient sunlight or at night, an automatic sensor turns off and keeps the remaining water from cooling.

For colder climates, you’re not out of luck. The evacuated tube collector solar powered water heater is an alternate type of solar water heater, smaller and deemed more efficient, also roof mounted, is said to work very well in cold climates.

True to its name, the evacuated tube collector solar powered water heater has a row of glass tubes which contain heat conducting rods. Inside the heating rods is antifreeze, which is in a circulating loop. The heat is captured and transferred into a heat exchanger. The result is excellent, with very low heat loss due to the fact that once the inside coating has absorbed solar radiation, the air has been evacuated from the glass tubes to create a vacuum.

By: Stephan Bevan

Article Directory: articledashboard.com

Water Heater

Storage water heaters (tank-type)[edit]

Main article: Storage water heater

Gas furnace (top) and storage water heater (bottom) (Germany)

In household and commercial usage, most North American and Southern Asian water heaters are the tank type, also called storage water heaters, these consist of a cylindrical vessel or container that keeps water continuously hot and ready to use. Typical sizes for household use range from 75 to 400 liters (20 to 100 US gallons). These may use electricity, natural gas, propane, heating oil, solar, or other energy sources. Natural gas heaters are most popular in the US and most European countries, since the gas is often conveniently piped throughout cities and towns and currently is the cheapest to use. In the United States, typical natural gas water heaters for households without unusual needs are 40 or 50 US gallons with a burner rated at 34,000 to 40,000 BTU/hour.[2] Some models offer “High Efficiency and Ultra Low NOx” emissions.

Another popular arrangement where higher flow rates are required for limited periods is to heat water in a pressure vessel that can withstand a hydrostatic pressure close to that of the incoming mains supply. In North America, these vessels are called hot water tanks, and may incorporate an electrical resistance heater, an air source heat pump, or a gas or oil burner that heats water directly.

Where hot-water space heating boilers are installed, DHW cylinders are usually heated indirectly by primary water from the boiler, or by an electric immersion heater (often as backup to the boiler). In the UK these vessels are called indirect cylinders, or direct cylinders, respectively. Additionally, if these cylinders form part of a sealed system, providing mains-pressure hot water, they are known as unvented cylinders. In the US, when connected to a boiler they are called indirect-fired water heaters.

Compared to tankless heaters, storage water heaters have the advantage of using energy (gas or electricity) at a relatively slow rate, storing the heat for later use. The disadvantage is that over time, the water inside the tank cools down, activating the heating system to heat the water back up. Additionally, when heavy use exhausts the hot water, there is a significant delay before hot water is available again. Larger tanks tend to provide hot water with less temperature fluctuation at moderate flow rates.

Volume storage water heaters in the United States and New Zealand are typically vertical, cylindrical tanks, usually standing on the floor or on a platform raised a short distance above the floor. Volume storage water heaters in Spain are typically horizontal. In India, they are mainly vertical. In apartments they can be mounted in the ceiling space over laundry-utility rooms. In Australia, gas and electric outdoor tank heaters have mainly been used (with high temperatures to increase effective capacity), but solar roof tanks are becoming fashionable.

In temperate zone countries, where ambient temperatures are seasonally colder, tiny point-of-use (POU) electric storage water heaters with capacities ranging from 8 to 32 liters (2 to 6 gallons) are made for installation in kitchen and bath cabinets or on the wall above a sink. They typically use low power heating elements, about 1 kW to 1.5 kW, and can provide hot water long enough for hand washing, or, if plumbed into an existing hot water line, until hot water arrives from a remote high capacity water heater. They may be used when retrofitting a pump and recirculating plumbing in a building is too costly or impractical. Since they maintain water temperature thermostatically, they can only supply a continuous flow of hot water at extremely low flow rates, unlike high-capacity tankless heaters.

In tropical countries, like Singapore and India, a storage water heater may vary from 10 L to 35 L. Smaller water heaters are sufficient, as ambient weather temperatures and incoming water temperature are moderate.

Tankless heaters[edit]

The inside of a hydraulically operated two-stage tankless heater, heated by 3-phase electric power. The copper tank contains heating elements with 18kW maximum power.

Tankless water heaters—also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters—are gaining in popularity.[citation needed] These high-power water heaters instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. Copper heat exchangers are preferred in these units because of their high thermal conductivity and ease of fabrication.

Tankless heaters may be installed throughout a household at more than one point-of-use (POU), far from a central water heater, or larger centralized models may still be used to provide all the hot water requirements for an entire house. The main advantages of tankless water heaters are a plentiful continuous flow of hot water (as compared to a limited flow of continuously heated hot water from conventional tank water heaters), and potential energy savings under some conditions.

Stand-alone appliances for quickly heating water for domestic usage are known in North America as tankless or on demand water heaters. In some places, they are called multipoint heaters, geysers or ascots. In Australia and New Zealand they are called instantaneous hot water units. In Argentina they are called “calefones”. In that country “calefones” use gas instead of electricity. A similar wood-fired appliance was known as the chip heater.

A common arrangement where hot-water space heating is employed, is for a boiler to also heat potable water, providing a continuous supply of hot water without extra equipment. Appliances that can supply both space-heating and domestic hot water are called combination (or combi) boilers. Though on-demand heaters provide a continuous supply of domestic hot water, the rate they can produce it at is limited by the thermodynamics of heating water from the available fuel supplies.

From Wikipedia, the free encyclopedia

water heating

Water heating is a thermodynamic process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. In industry, hot water and water heated to steam have many uses.

Domestically, water is traditionally heated in vessels known as water heaters, kettles, cauldrons, pots, or coppers. These metal vessels that heat a batch of water do not produce a continual supply of heated water at a preset temperature. Rarely, hot water occurs naturally, usually from natural hot springs. The temperature varies with the consumption rate, becoming cooler as flow increases.

Appliances that provide a continual supply of hot water are called water heaters, hot water heaters, hot water tanks, boilers, heat exchangers, geysers, or calorifiers. These names depend on region, and whether they heat potable or non-potable water, are in domestic or industrial use, and their energy source. In domestic installations, potable water heated for uses other than space heating is also called domestic hot water (DHW).

Fossil fuels (natural gas, liquefied petroleum gas, oil), or solid fuels are commonly used for heating water. These may be consumed directly or may produce electricity that, in turn, heats water. Electricity to heat water may also come from any other electrical source, such as nuclear power or renewable energy. Alternative energy such as solar energy, heat pumps, hot water heat recycling, and geothermal heating can also heat water, often in combination with backup systems powered by fossil fuels or electricity.

Densely populated urban areas of some countries provide district heating of hot water. This is especially the case in Scandinavia and Finland. District heating systems supply energy for water heating and space heating from waste heat from industries, power plants, incinerators, geothermal heating, and central solar heating. Actual heating of tap water is performed in heat exchanges at the consumers’ premises. Generally the consumer has no in-building backup system, due to the expected high availability of district heating systems.

From Wikipedia, the free encyclopedia