Tag: Heating thermostat

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Part 2 – Fixing low voltage problems with our Heatmiser neo Stat 12V V2 Thermostat install

So we had a problem with our installation of the new Heatmiser thermostat. The thermostat is now positioned half way along the boat, before the old thermostat has been in probably the coldest part of the boa, much nearer the original heater controls. Now when the batteries are not fully charged the voltage drop on the 1 mm2 cable can to great to make the Eberspacher Diesel heater fire up reliably.

Problem solved by adding a remote relay

To fix this problem we needed to fit a relay where the old thermostat was positioned and use the Heatmiser thermostat ‘Call for heat’ signal to switch the relay, which would intern switch on the diesel heater.

Heatmiser with Relay
Heatmiser with Relay

The new wiring looks like the diagram above, with the relay much nearer to the heater there is minimal voltage drop from the relay to the heater, while the Heatmiser thermostat is still happy.

The relays I purchased at 12v automotive spec with a way over the top 30A switch capability. They come with a 30A fuse, this is replaced with a 1A fuse for this installation.

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New Heating Thermostat and Isolation Switches

Another quick trip to the boat last weekend to fit another thermostat this time so we can control the heat. Last time I fitted a frost thermostat that I wired in parallel with the heater on/off switch.

This time I added a normal household thermostat again in parallel, but I also added switches so we can switch off either of them and just use the original heater on/off switch.

Frost and Heating Thermostats
Frost and Heating Thermostats

For the moment I put small bit of insulation tape so I could label the switches.

Diesel Gauge
Diesel Gauge

Now with the heating thermostat we can leave the heating on low when we go out and return to a not so freezing boat.

Now we have been on the boat for two long weekends and left the frost thermostat on while we have been away and we have used almost ¼  of a tank of diesel, the tank hold 350 Litres or 77 Gallons, so we have used 80 Litres, plus a little mains electricity to keep it all running.

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