Open Loop Solar Hot Water Heating Systems
Open loop systems directly heat the water. Open-loop systems work essentially by circulating water through the solar collectors via a small pump mounted on a water storage tank. The solar pump is activated by a differential thermostat controller that senses when heat is available in the solar collectors. The solar storage tank connects to the existing hot water heater and feeds the preheated solar water into the gas or electric hot water heater as hot water is used.
In regions where pipes can freeze, the solar collectors and feed lines are usually protected from freezing by automatic drain down controls. These Drain down systems allow the water in the pipes and panels to fall safely back out of the solar collectors and feed pipes to prevent freezing. These types of systems are "open loop" since the energy collection loop is not separate from the rest of the hot water system --i.e. the loop is "open" and sharing the same water.
strengths
Regular maintenance costs are associated less with open-loop systems because they don't use any special fluids or heat exchangers used with closed-loop systems. They are usually cheaper to install than closed-loop systems. Open-loop systems are more efficient at heating water than closed-loop systems, because water is directly heated from the solar panels.
weaknesses
The main weakness is related to the Drain-Down version of these systems. An open-loop systems' "drain down" freeze protection can fail, subjecting system owners to risk of substantial repair costs from freeze damage and property damage such as flooding from broken pipes. These costs can significantly outweigh the benefits of using this kind of system. A system drained-down for protection purposes can miss opportunities for providing high-performance benefits of solar hot water heating.
system configurations
Openloop and draindown systems are configured according to energy demands, solar energy availability and other factors at the point of installation. Openloop systems generally consist of at least these parts:
- 1: goldline-sb SB sensor, 10K
- 2: maidomist-71 MaidOMist Air Vent No.71
- 3: sensor wire
- 4: taco-006b4 Taco 006B4 Cartridge Circulator
- 5: watts-100xl4 T/P Pressure Relief Valve 212F,150psi
- 6: goldline-sb SB sensor, 10K
- 7: watts-100xl4 T/P Pressure Relief Valve, part of existing tank No.18
- 8: letro-sl2dw3 Letro SL-2DW3 Thermometer
- 9:watts-70a Watts 70A Tempering Valve
- 10: hot water output
- 11: cold water feed line
- 12: knob adjusts water temperature output
- 13: tomlinson-c-75 Thomlinson Quadflow bypass "H" valve
- 14: other-s480-075 NIBCO S-480 In-line Check Valve
- 15: solar panel inlet
- 16: watts-100xl4 T/P Pressure Relief Valve 212F,150psi
- 17: ksp-ks-40 KS-40 Crystal Clear Solar Panel
- 18: existing hot water tank, 40 to 60 gallon, electric or gas
- 19: rheem-rhm80p4 Rheem Storage Tank, 80gal, 4 port
- 20: goldline-gl30 Goldline GL-30 differential controller
not shown:
- copper piping
- pipe insulation
- a Letro LDF357B flowmeter (this flowmeter is recommended for diagnostics and monitoring, but not required for operation)
Draindown systems also include:
- a 2 solenoid valve drain configuration and a vacuum relief valve
sizing open-loop systems
For best results, systems should be matched according to energy use patterns.
King Solar offers this open-loop system kit to get you started saving energy:
- ERC-3 Solar Water Heating System for 3 or 4 people, powered by 110VAC
Sizing or configuring a domestic or commercial solar system that best fits your circumstances can be a challenging exercise. If you are uncertain, the best thing to do is send us your requirements.
Tell us:
- how the solar hot water heating system will be used. For example, will it be used in a home or as part of a boiler system in a commercial environment
- how many gallons of hot water are used per day. We can approximate by knowing how many people live in the residence, or how much heat is created per day by a boiler etc.
- where you are geographically located
Contact us for a price quote. We will reply within 48 hours with a suggested set of equipment specifications to meet your alternative energy needs.