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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
GALVANIC SCALE & METAL CORROSION
GAS BURNER FLAME & NOISE DEFECTS
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING COST SAVINGS METHODS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
HYDROGEN SULFIDE GAS
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVE, WATER HEATER
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMAL EXPANSION of HOT WATER
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISES
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER COMPARISONS, PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Solar water heaters: this article explains the basic components of solar hot water heating systems used to heat water for washing and bathing. Solar water heaters use renewable energy - sunlight - collected in outdoor rooftop or ground-mounted solar collectors to heat water which is circulated by a pump between a hot water storage tank and the panels.
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Solar water heaters use renewable energy - sunlight - collected in outdoor rooftop or ground-mounted solar collectors to heat water which is circulated by a pump between a hot water storage tank and the panels.
The upper end of a simple solar water heater collector is shown in our photo at left. Look closely and behind the corrugated plastic surface, at the top you can see the horizontal black tubing that moves water through the top end of this collector.
Solar water heaters have been in use for decades, with popular use at remote cottages or off-the-grid buildings and are likely to see increasing use in much of the world as energy costs continue to climb.
The schematic at above left (U.S. Department of Energy) explains a typical active, closed loop solar water heater hookup and shows the basic parts of a solar hot water system. The schematic at above right (U.S. DOE) explains a typical passive-batch solar water heating system, showing the batch collector containing a volume of hot water and located separately from a backup solar water storage or water heater tank.
[Click to enlarge any image]
Here are the key parts of solar hot water heating systems:
Our solar water heater photographs below show a convection-type solar water heater widely distributed in Mexico. The white water tank and the bank of solar heating tubes are initially filled with cold water.
As the sun heats water in the parallel heater tubes, warmed water rises by convection in the tubes and enters the storage tank while cooler water from the tank falls into the tubes for further heating. Heated water is drawn from a fitting at tank top while incoming cool water is fed into the tank bottom.
This system heats water and stores it in the reservoir tank using only natural convection with no pump required. Our second photo (below right) shows one of these systems installed.
As energy costs continue to increase the payback-time for the cost of solar panels and piping installation for solar hot water systems will continue to improve. The solar water heater system sketch is courtesy of Accu-Spect.
Especially in areas that receive adequate sunlight we should expect to see an increase in popularity of these systems.
This article series describes the characteristics of these water heating methods:
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: which is most efficient backup system for solar hot water?
The solar system I am pricing has one backup heating element, in the middle of the tank. I expect a lot of my use will be at night, therefore I was an efficient electrical system too. Would the performance of a supply tank with an element on the top and on the bottom, at traditional tank, be more efficient and supply more hot water than the single element, middle mounted heating element? - firstname.lastname@example.org
Interesting question Dan. I don't know - insofar as being able to cite an authoritative source without more research. But it may help to understand the role of dual heating elements in electric water heaters. The lower element warms all water in the tank, starting with cold water entering (cold water usually is directed to the tank bottom by a dip tube). The upper element boosts the ending temperature of hot water leaving the tank.
Question: Thermal slab with pipes deep in the concrete?
Current building regs here in Scotland dictate that I fit a thermal slab of at least 125mm thick as a floor in my house extension. I couldn't see the point of just relying on the sun through the window to heat it so I fitted under floor heating pipes.The slab is 250 mm thick,the pipes are 200mm below the surface,there is 170mm of "kingspan " between the membrane/subsoil and the edges are insulated with 5mm Kingspan.
I intend to fit a solar hot water panel to slowly,maybe over several days ,heat the slab,intending it to be a heatstore rather than a radiator ,say from a boiler system.
I can see from many posts on this site that my pipes are in too deep for a radiant system ,heated from a boiler,but I think that as a heated from below heat store it should provide a very stable source of heat to keep the room warm through the night or dull days( plenty of those in Scotland)
Lee, my experience is that pipes deep in the slab don't work well - which is reflected in the documents by experts in the radiant heating indusry. There are two heat transmission issues:
For technical details about placing heating tubing of any sort in to concrete slabs, see these articles:
Passive solar heated slabs: SLAB INSULATION, PASSIVE SOLAR
Radiant heat flooring design:
The R value is 5.100 M2.k/w.Yes the edges have 50mm of the same spec kingspan.The floor slab is encosed in the foundation wall and above ground level. Nothing much lost if it doesn't work,just the £70 for the barrier pipe.I will just have to fit a conventional radiator to the wall and connect the panel to the hot water tank if the heat goes down into the subsoil. Do you think that heat would rise through a solid ,as it does through a gas or liquid?
My aim is to help the thermal store by feeding heat in from below, I want the process to be slow( no avoiding that with the pipes in deep eh.)On reflection maybe midway up would have been better,but after the initial outlay for the panels ,the heat is almost free,might just need a few more. Thanks for you comment,will let you know if it works,probably won't be operational for 18 months or so.
Question: is it normal for the solar hot water panels to be empty or to collapse?
Are solar mats supposed to collapse when [the solar heating system] is turned off?
And is [the solar hot water heating system] meant to be and open air system or a closed system? - L.S. 1/22/2014
You are asking about solar hot water or solar heating systems that use a water-antifreeze mix. Among the many types of solar collectors are rubber tubes bonded in mats or gangs of tubing fed at either end by a connected rigid tube connected to the inlet and outlet piping for the system.
Depending on the manufacturer, these tub-mats are rather rigid and would look the same with or without water flowing, while others, made of softer plastic or rubber components may thin down when not under water pressure. In both cases the system stays full of water, not air, when the system is activated.
The solar hot water panel ends shown in my photographs just above are installed on a rooftop in Guanajuato, Mexico and are used to provide domestic hot water and to heat a spa or hot tub. This is a rigid mat, it does not "collapse" when water is not circulating. In fact there is so much solar gain on this roof that the owners have blocked off some of the solar collector tubing so that water is not overheated. Not shown in my photos is a pressure relief safety valve installed on the piping to release water in the event of an unsafe or over-pressure condition. You can see the solar water heater piping, a control valve, and the pressure-relief safety valve in this photo.
But in freezing climates and for some heating applications that are heating water for direct use, that is where an antifreeze mix is not being used in the solar heating system, the system is designed to drain-down when off in freezing weather, to prevent freeze-up. A drain-down solar design will indeed be virtually empty of water in that state: additional controls and air valves are installed on such systems to allow air in or to allow air to exit as required to prevent freezing.
I hope that with these details, if your question is not answered fully you can ask again with more information.
Questions & answers or comments about solar water heater systems: choices, properties, installation, maintenance & repair.
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