I bought a 12 year old Autotrail Cheyenne Motorhome in 2020. It was in great condition, but the electrics would have been regarded as a little dated even in 2008. The following series of posts discussed the various upgrades carried out. Some of the changes mentioned I later changed further in fact, so this is pretty much a Journel of Adaption
Part Four. Adding AC Cables and Control for Fridge and Water Heater
I mentioned previously about the additional AC Outlets the EasyPlus provides and I ran the cables in readiness to cable up? Time to put that plan into action!
Truma Ultraheat room heater
Firstly chopped the cable that went from the Sargent (Middle MCB) to the Truma Ultraheat and joined it to the Multiplus MCB 0 outlet. This actually makes the middle Sargent MCB redundant. If I had fitted a normal Multiplus, I would have reworked the Sargent innards to keep that breaker in place but using the EasyPlus Breaker Set meant that it would be easier to take the system back to standard at a later time if I ever wanted to.
In the case of the Ultraheat, I just made a direct connection from the EasyPlus Cable to the Ultraheat Cable as it only goes to one place and there is an Truma Control switch for that.
I then chopped the cables that went from the Sargent (End MCB) to the Truma Ultrastore and Thetford Fridge. This MCB also drives the pair of 240V lights and an extra socket I had previously added, so this is still relevant and more specific, which could be handy in practice.
Fridge and Water Heater
For these two, I want to be able to easily choose which device has any power available. The Ultrastores mains switch is right out the way under the cooker so awkward to get to. The Fridge socket is also behind drop-down door under the fridge and a bit of a pain to get to. The fridge itself has the energy selection control panel, but I want to be able to use auto-select without neccessarily using the 240V supply (so will switch to 12V automatically when moving as you are “strongly advised” against using Gas to power the fridge when moving) and would prefer to not get on hands and knees to unplug and plug in the fridge when I want to use/not use 240V.
Therefore, first step is to make some holes in the Electrics cupboard.
And then fitted a pair of AC Fused Spurs with Switches.
The Upper AC Switch is for the Boiler. The Lower AC Switch is for the Fridge. Both Spurs are fed by the outlet of the Auto-relay switching box (see the diagram below).
The top device is a standard dual-USB outlet. Added there as handy place to provide power to devices such as the rechargable torch and MiFi.
[SPOILER ALERT: The Fridge part of this modification changed after I replaced the 3-Way Thetford Fridge with a 240V Compressor Fridge. I am leaving this section showing the initial installation as it is all part of the ‘journey’ I went on modifying and updating the Motorhome]
What will this setup allow?
Well, there will be power to the Fused Spurs whenever the EHU is live, so I can use Hookup power for the Water and Space Heaters simply by flicking on the two switches on the Spurs. When there is no EHU live, then Inverter power to the Spurs is controlled by the Programmable Relay on the Cerbo – and I can set the Relay up so the Spurs are only connected in my chosen conditions – typically a battery State of Charge of over 80% or whatever I fancy making it (the Relay sends a +ve signal to the SSR and when active, the SSR switches on and the SC power goes to the Auto Relay).
The Truma Ultrastore works on Gas and/or Electric. When on Electric, a 850V AC Element is switched on to heat the 10L tank to 70C. On Gas, you can select the temp required between 30C and 70C. If you combine the two, it speeds up the heating process (from 15C to 70C, Gas only takes 34Mins, Electric only takes 45Mins, Gas + Electric takes 25 mins) so using potentially spare battery capacity not only saves you gas but can get you a tank of water for your shower faster. Or just run the heater on Electric for an extra 20 mins and use no gas.
The Thetford Fridge is either/or when it comes to Electric or Gas. It draws around 250W for around 75% of the time so not very economical when it comes to used electricity, but depending on what is coming from the solar it could be a handy use of spare and otherwise wasted harvesting.
Having the switches makes it very easy to chose where to direct the power, and having the relay cutting the power if the battery bank drops below the set value keeps the batteries well protected.
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