Keep warm this winter

Keep warm this winter

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With winter in full swing, now’s the time to give your heating system a thorough health check. Peter Collard, marine heating systems expert at Eberspächer UK, shares some useful advice.

A good first assessment of your system’s health is to watch it on startup – if you notice your heater’s exhaust producing grey smoke or white diesel vapour when it’s trying to start, or your heater is taking two or three attempts to start, it’s time for a service. If you live onboard, I recommend having an accredited dealer inspect your heating system every one or two years. For occasional boaters that’s every three to four years. If your heater goes out when trying to start from cold, puffing a big cloud of white smoke across the marina, this can be a sign the flame tube is getting to the end of its life.

Is it safe to start?

Check your heater is actually safe to start – is the exhaust still in one piece? Flexible exhaust systems can get brittle over time and if knocked or disturbed during summer cruising or maintenance, can leak. Check the fuel system for leaks too, and ensure the combustion air pipe hasn’t been crushed. Is it a new boat to you? Check that a vehicle heater exhaust silencer hasn’t been fitted because it’s NOT gas tight or insulated and should never be fitted in a boat.

Water coolant

If your boat has a water heat system, similar to Eberspächer’s Hydronic range, check your water coolant. Before starting your heater, check the coolant fluid in the system – it’s more important than you may realise. If you neglect antifreeze, corrosion inhibitors can degrade or get used up. Radiators begin to rust internally and you risk the system ‘sludging-up’ and causing major internal damage. In some heaters, antifreeze is also used as a lubricant for the water pump and will stop calcification (limescale). If you are using a long-life coolant, your heating system should be drained down, flushed out, and fresh antifreeze water mix (Eberspächer recommend a 50/50 mix of any glycol-based product) added every five or six years (two to three years for standard antifreeze). Add one or two years if you use de-ionized water too. Never use more than a 50/50 mix or household inhibitors. And never add neat antifreeze into a single pipe header tank, it will just sit there in the tank fooling you into thinking your coolant system looks great.

Check fuel

If your boat hasn’t had much use over summer, fuel quality can be a concern. Is it old? Is there any sign of diesel bug? Fuel suppliers usually switch from summer diesel to winter diesel during September. Summer diesel is supposed to start waxing from -5°C, but this threshold can deteriorate. So when you need the heater it may fail due to fuel starvation. Ironically, by the time an engineer turns up, the temperature may have risen and the heater may well start first time! Eberspächer doesn’t recommend the use of an inline fuel filter for this reason: the paper element can block with wax just when you need the heater most. Rest assured, there is a small metal filter in the back of the fuel pump. If your fuel filter is blocking, cut two inches off your stand pipe or block it off and fit a shorter one. Use an anti-oxidant and fuel stabiliser to keep your fuel good until next summer and never tee into your engine’s fuel system.

Start the heater

Heaters may not start first time after sitting unused through the summer. The usual cause is trapped fuel in the heater’s copper fuel line, which can react with it and decompose. When copper fuel line is used, it generally has an extremely small bore size, usually 2mm internal diameter. A minute amount of diesel is surrounded by copper and within a few months, the copper can degrade the diesel and it will no longer ignite without compression. After two or three start attempts the heater will have pulled fresh diesel from the tank and you will be greeted by a brief cloud of smoke as the old diesel is burnt off. It’s a good time to check for exhaust and fuel system leaks too!

Finally, listen to your heater

The sound emanating from the exhaust should be clear, crisp and even: a steady roar; or, if fully silenced: a steady whisper. With the boards up, listen to the intake noise. This should be a steady whine. If you hear the whine changing erratically it can be a good indication that the blower motor won’t last through to springtime. If you’re thinking of fitting a heating system, the rule of thumb is that boats over 50ft may prefer a Hydronic system. Heat output ranges from 2.4kw up to 35kw. Prices for the smallest kit with seven-day timer start at £1,895, with installation costing approximately £522. For smaller boats there are four sizes of air heater, ranging from 2.2kw to 8kw with similar installation costs. Ultimately, this is specialist marine equipment and Eberspächer always advises you have it professionally installed to ensure a safe installation, avoid uneven distribution of heat, provide easier access for maintenance, and increase reliability. Money spent on installation is likely to save you cash in the long term.

Find out more

Eberspächer manufacture two different ‘systems’ for boats, both use air and diesel fuel mixed and ignited, within the heater’s internal combustion chamber to create thermal energy. The Airtronic range lends itself to more instant heat requirements by drawing in fresh or recirculated air which is heated and distributed to cabins and rooms via ducts and air outlets. For larger boats, the Hydronic range uses a heat exchanger to transfer its thermal energy to the boat’s own internal water system and provides a more consistent heat output akin to a domestic radiator/ convector based system. Eberspächer will be at the London Boat Show on stand CO73 – do stop for a chat, or visit


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