Free Central Heating

We may be hoping it stays too hot to need the central heating on our boat for a while but, sooner or later, we will need it working.

For the last two winters we have had free central heating on our boat, at least while the engine is running, after making one simple change. We’ve added an extra pump to the central heating circuit.

When the engine is running it heats the water in the calorifier through the first calorifier coil, with the rest of the engine heat wasted through the skin tanks as it heats the canal.

Free Central Heating Circuit

As originally installed the water in the calorifier can also be heated by the Webasto diesel powered central heating unit through the second calorifier coil.  We’ve now installed an additional pump, shown in red on the diagram, which pumps water around the central heating system without the Webasto unit using any diesel.

With the new pump switched on the engine heats the water in the calorifier through the first coil and the heat is picked up through the second coil and pumped through the radiators.  The new pump is wired with an on/off switch to the engine ignition circuit so it can only work when the engine is running.

The pump is a Jabasco 59510-0012 12v pump which has low resistance to water flow when switched off so the Webasto central heating will still work as normal when the new pump is switched off.

The result is that, within fifteen minutes of starting the engine, we have radiators throughout the boat which are hotter than when we run the Webasto unit, with no noticeable drop in the hot water temperature.

Whenever we are cruising, or just running the engine to charge the batteries, we have central heating available on demand, with no measurable running costs.

The Webasto unit can be used to keep the radiators warm during the evening, or to heat them in the morning.  And our stove can supply additional warmth too.

Don’t wait until it gets cold before fitting one yourself.