HJ Cooper SS Mains Pressure Thermosiphon Coiled Hot Water Cylinders

Model: MS-CT

HJ Cooper Stainless Steel Mains Pressure Thermosiphon Single and Twin Coil Hot Water Cylinders


Wetback is something that is mostly associated with an old house with a low pressure copper cylinder connected to an old wood burner. With an HJ Cooper thermosiphon cylinder you can now have a new modern house with mains pressure water heated by your wetback fire, saving you money on your power bill.

Peace of mind
This range of electric mains pressure hot water cylinders comes with a 10 year warranty on the inner cylinder, and is backed by Rinnai after sales service and support.

Thermosiphon coil for wetback
The water is circulated through a coil (see below image) inside the cylinder by a thermosiphon effect i.e. warmer water rises and cooler water falls, creating a natural flow. This means there is no need for a pump to circulate the water, you can still heat your water even if there’s a power cut!

Single or twin coil?
You will need a twin coil cylinder if you are connecting to a wetback fire and a glycol solar system. If you are connecting to a wetback fire and/or a potable solar system then you will need a single coil hot water cylinder. A single coil cylinder has an extra eco connection that can be connected to an open loop (potable) solar system, or a hot water heat pump.

Twin coil systems: Running cost savings
Save money on power in summer using solar water heating through one coil, and in winter heat the water by the webtback fire with the second coil.

Designed for high temperatures
The duplex stainless steel inner cylinder means it can be used in solar systems with high incoming water temperatures.


Mains pressure stainless steel thermosiphon single coil (all dimensions are in mm)


Mains pressure stainless steel thermosiphon twin coil (all dimensions are in mm)


Suitable for:
• Indoor installations
• Mains and low pressure systems
• Domestic and commercial water heating applications

Not suitable as a pool or spa heater.

Model Codes and Capacities: Single Coil MS250550CT20 = 250 L (2 kW)
MS250550CT30 = 250 L (3 kW)
MS300550CT20 = 300 L (2 kW)
MS300550CT30 = 300 L (3 kW)
Model Codes and Capacities: Twin Coil MS250550CCT20 = 250 L (2 kW)
MS250550CCT30 = 250 L (3 kW)
MS300550CCT20 = 300 L (2 kW)
MS300550CCT30 = 300 L (3 kW)
Please ask in store for details on different element configurations and thermostat options.
Construction • High grade duplex stainless steel inner cylinder
• Galvanised steel outer casing
• CFC free polyurethane foam insulation, compliant with NZ MEPS
Connections • Hot and cold water connections ¾ " (20 mm)
• Coil connections ¾ " (20 mm)
Coils Wetback thermosiphon coil 25 mm diameter. Auxiliary coil 25 mm diameter.
Element Incoloy 825 alloy sheath element positioned at the bottom of the tank.
• 250 L: 2 kW* or 3 kW
• 300 L: 2 kW* or 3 kW
* Twin element options available
Thermostat Robert Shaw 30 A contact auto reset thermostat
TPR TPR supplied, factory set to 850 kPa and 90 °C
Weight: Single Coil 250 L = approx. 51.5 kg (empty)
300 L = approx. 61.5 kg (empty)
Weight: Twin Coil 250 L = approx. 56.5 kg (empty)
300 L = approx. 66.5 kg (empty)


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