Well, simply put a calorifier on a narrowboat is a marine water heater.

Usually cylindrical in shape, calorifiers are a useful way of recovering waste heat and transferring it into domestic water systems. Waste heat comes from the heated coolant in the engine cooling system. The calorifier is plumbed into the engine coolant re-circulation system and uses a series of coils inside the tank to heat a body of water contained in the main shell of the tank.

This is very much like your standard central heating copper immersion heater in the airing cupboard. Remember them!

Like the domestic cousin, the marine calorifier can also have a 230VAC immersion element as a back up and can be linked in to most narrowboat central heating systems such as gas fired, forced air combustion and even the back boiler on a multi-fuel stove to make use of the excess energy these systems produce.

Commonly installed in the engine room, calorifiers come in a range of shapes and sizes, vertical or horizontal. Location becomes only a matter of efficiently connecting it to services.

Sizes range from 20 litres up to a whopping 120 litres and often two calorifiers can be linked in tandem to straddle the swim if required. The only restrictions in size and location being the power of the available energy to heat the water and the availability of water itself.

When sizing your calorifier on your narrowboat, you need to ensure you have an adequate electrical supply. Most calorifiers will come with a pre-installed 1kW immersion heater. Check our batteries & electrical information chapters for advise on battery and inverter sizing and the correct wiring specification. Refer, as always, to the manufacturers instructions at all times when installing calorifiers.

One thing worthy of note. Most calorifiers have copper internal coils for a balance of efficiency and cost. If you have a central heating with an aluminum heat exchanger or if there is aluminum any where in the system, you will need a calorifier with stainless coils. It’s that old favourite, galvanic corrosion and the interaction between two different metals in water. This will cause internal corrosion of the system unless all metal system components are matched  in accordance with the manufacturers installation instructions.