Frost Protection options with our Canal Boat

This is going to be our first winter with a canal boat, and I have been looking at how we can protect the boat against freezing.

I had a few options:-

  • I could drain all the water out of the boat, i.e. the water tank and the heating system. But we intend to visit the boat over the winter as a jumping off spot for visiting relations.
  • We do have mains power, so I could place some oil filled radiators in the boat, they would need an anti frost setting. This looks like a viable and popular option, but we have to prepay for electricity and I have no idea how much we would need.
  • The boat is fitted with a very effective diesel powered heating system, with radiators around the boat. At present, the control system is very primitive, with just an on/off switch, we have used it a few times. I would need to fit a frost thermostat to make it effective.

After much studying and asking questions on Facebook and the online forums, I decided to go with the third option and use the built-in diesel heater. We have a large diesel tank, so this I hope will last the winter.

Eberspacher Heater Switch
Eberspacher Heater Switch

Our boat is fitted with an Eberspächer D4W Hydronic water heater which heats the radiators and provides hot water when required, which in the summer is not often. It is controlled by a simple pull switch.

I then tried to source a 12v frost thermostat, from what I could see a 12v Honeywell frost thermostat part no 4111263a would do the trick. The prices of these seem to vary from each supplier, but in the end I selected PB Auto Electrics as the price and delivery seemed reasonable.

But when it arrived, it was the T4360 240v frost thermostat, A quick check with PB Auto Electrics and, they confirmed it was exactly the same device, I wish I had known before it would have made finding one a lot simpler.

NOTE: This type of thermostat is a very simple device, that uses a bimetallic strip as a switch when temperature changes see here for a more detailed explanation.

My plan was to fit the thermostat is parallel with the current switch, so I could still use the switch when needed, the frost thermostat could then operate independently when the internal temperature of the boat gets too low.

To install the thermostat, I made some extension leads from the switch to the new thermostat and mounted it on an internal wall near the control panel.

The switch had two wires attached, a yellow wire and a red wire. The red wire has 12V supply from the heater, and the yellow goes back to the heater to trigger it to start.

Inside Thermostat
Inside Thermostat

Inside the thermostat, I extended the red wire to terminal 1 and the yellow to terminal 3.

When you remove the cover of  the frost thermostat it revels a wheel with the temperatures marked on it, it is pretty much a normal  thermostat with a cover that stops adjustment.  To test the setup changed the setting to  above and below the current temperature.

Everything worked as expected, so I finally set it to between 3 and 4 degrees.

Before I left, I did take a photo of our fuel gauge, so I can see roughly how much diesel we use.

Next I will add  a frost protection switch, so I can isolate this in case of problems, I could have done this with the current switch, but I expect to add a normal thermostat later which will work with the switch or replace it.