Puddlejumper Posted May 20, 2019 Share Posted May 20, 2019 Hi there Hope someone can help me. Our 3 way fridge decided to give up the ghost and I've replaced it with a 12v compressor fridge. To power it from the habitation battery I've taken a live feed from what was a 12v outlet socket so when the 12v is switched on the fridge is running. The original fridge feed from the relay which only works when the engine is running is currently disconnected can anyone tell me how to wire in the feed from the relay so the fridge is running while I'm driving. If I wire it into the fridge then all that happens is the relay constantly clicks so I'm guessing I either need to add a switch into the feed from the hab side or possibly a relay?? Any help would be much appreciated Thanks Link to comment Share on other sites More sharing options...
colin Posted May 20, 2019 Share Posted May 20, 2019 There shouldn't be a need to connect the original 12v lead unless your 12v habitation switches off when engine is running. Link to comment Share on other sites More sharing options...
Puddlejumper Posted May 21, 2019 Author Share Posted May 21, 2019 That's exactly what does happen, as soon as the engine starts the habitation supply goes off. Is this usual?? Link to comment Share on other sites More sharing options...
Stuwsmith Posted May 21, 2019 Share Posted May 21, 2019 My Bilbos campervan compressor fridge is wired directly to leisure battery (via 15A fuse) using substantial cross section wire. Fridge draws around 3.6A when running and has a low voltage cutout of 10.8 volts which is worth bearing in mind when considering wiring in a fridge. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 21, 2019 Share Posted May 21, 2019 I note that this was asked about on the wildcamping forum in August 2018. It might be worth forum-members looking at that thread before providing advice https://www.wildcamping.co.uk/forums/motorhome-questions-and-knowledge-base-/71574-12v-compressor-fridge-wiring.html Some of the information there is questionable. Switching off the 12V power-supply to a motorhome’s habitation-area when the vehicle’s motor is running became normal practice from the mid-1990s onwards - but only for UK-built motorhomes. The practice was introduced to provide ECM (Electro-Magnetic Compatibility) compliance and is often performed by a dedicated ‘isolation relay’ that can be disabled, assuming that relay can be found! (Doug, if you identify your motorhome - make, exact model, year of manufacture - it may be possible to provide more detailed assistance.) Link to comment Share on other sites More sharing options...
colin Posted May 21, 2019 Share Posted May 21, 2019 The majority of WC posts say connect straight to hab batteries (with own switch), that's the way to go. Link to comment Share on other sites More sharing options...
Puddlejumper Posted May 22, 2019 Author Share Posted May 22, 2019 Derek Uzzell - 2019-05-21 8:26 AM I note that this was asked about on the wildcamping forum in August 2018. It might be worth forum-members looking at that thread before providing advice https://www.wildcamping.co.uk/forums/motorhome-questions-and-knowledge-base-/71574-12v-compressor-fridge-wiring.html Some of the information there is questionable. Switching off the 12V power-supply to a motorhome’s habitation-area when the vehicle’s motor is running became normal practice from the mid-1990s onwards - but only for UK-built motorhomes. The practice was introduced to provide ECM (Electro-Magnetic Compatibility) compliance and is often performed by a dedicated ‘isolation relay’ that can be disabled, assuming that relay can be found! (Doug, if you identify your motorhome - make, exact model, year of manufacture - it may be possible to provide more detailed assistance.) Thanks for that, it's a 1991 Autosleeper Talisman GL on a Talbot Express chassis. Doug I guess it's not the end of the world as we invariably have it on EHU at home before we set off and get the fridge down to temperature it's just there is obviously the option of having it on while travelling and I'd like to use it. I think what happens is when it's wired up to run via starter circuit the power is also feeding directly into the 12V habitation side. I wondered if putting in a relay or two way switch would solve the issue? I'm not brilliant at designing electrical circuits but confident following a wiring diagram. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 22, 2019 Share Posted May 22, 2019 Generalised installation information for Waeco compressor fridges can be found here https://www.waecofridges.co.uk/pdf/CRX80_Manual.pdf You need to be able to run your Waeco fridge whether or not your motorhome is connected to an EHU and when the vehicle is static or being driven. The simplest and most logical way to achieve this is (as has been repeatedly advised) to connect the fridge directly to the leisure batteries, and not try to exploit the motorhome’s original wiring. Link to comment Share on other sites More sharing options...
747 Posted May 22, 2019 Share Posted May 22, 2019 There should be existing wiring that powered the earlier fridge while driving. Take a supply from the leisure battery(ies) through a Relay so that the power source changes when the ignition is switched on or off. Any competent electrician could set that up. You have an old van which will have an old (and not very powerful) charging unit. You may need to uprate it to keep your batteries topped up as the new fridge will take more from the batteries. You have not mentioned if you have solar panels fitted, they would be a useful addition. Link to comment Share on other sites More sharing options...
Puddlejumper Posted May 22, 2019 Author Share Posted May 22, 2019 Yes I've got solar 240w and 220ah of leisure batteries. Fridge only pulls just under 1A when it's running so with sunny(ish) weather we can stay off grid pretty much indefinitely. I'll look at wiring a relay in. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 23, 2019 Share Posted May 23, 2019 When your Talisman motorhome was built 28 years ago it would have had a small 3-way Electrolux fridge, no solar-panels, a single leisure-battery of about 70Ah capacity and Zig-made electrical equipment that included a limited-output battery-charger. The Tabot Express’s motor’s alternator would not have been particularly powerful. Nowadays your Talisman has a 240W of solar-panel system and 220Ah of leisure-battery capacity (I note you said 330Ah on the Wildcamping forum). Auto-Sleepers would never have envisaged your Talisman’s 2019 specification and, unless you or previous owners have upgraded it, using the original wiring for purposes it was never intended for will, at best be inefficient and at worst be problematical. In principle, if your Electrolux RM212 fridge functioned OK on 12V when the motorhome’s engine was running, you ought to be able to connect your Waeco compressor fridge (which Waeco model is it?) to the wiring that supplied 12V power to the Electrolux fridge’s 12V heating element. But then your Waeco fridge would only operate when the motorhome was being driven unless you disabled the relay that interrupted the 12V supply to the Electrolux fridge when the motorhome’s engine was switched off. (It’s also worth mentioning that, in the 90s, it was common for a motorhome fridge’s 12V power to come from the vehicle’s starter-battery rather than from the leisure-battery.) As I understand it, you are currently powering the Waeco fridge from a habitation-area 12V circuit and have found that, when the motorhome’s motor is running, the habitation-area circuit goes ‘dead’. As I explained above, this policy became the norm for UK-built motorhomes (though I didn’t think Auto-Sleepers would have implemented it as early as 1991) but, as it nomally involves a simple ‘isolation relay’ triggered by a link to the vehicle’s ignition circuit, disabling that relay should keep the habitation-area circuit continuously ‘live’. (Disabling the isolation relay is a commonly used ploy to allow reading lights in the habitation area to be used while the motorhome is being driven.) However, even if you disabled the isolation relay, a major drawback with tapping into the original habitation-area circuitry is that this won’t have been designed to run a compressor fridge. Given how you’ve wired it up, I’m a mite surprised that your Waeco fridge operates satisfactorily as received wisdom (and advice in the Weaco installation instructions) is that such fridges should be connected to a battery using cables that are as short as practicable and - to minimise voltage drop - that the cable-diameter should match cable-length. This 2016 discussion refers https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Waeco-Won-t-Go/45765/ As you seem very reluctant to take the logical and simplest approach that will optimise your Waeco fridge’s performance - wire the Waeco fridge directly to the leisure batteries with ‘heavyweight’ cables with an On/Off switch in the live cable - I can only assume that there are persuasive reasons not to do this (eg. running the cables between fridge and batteries will be challenging). But that’s undoubtedly the best way to go. Link to comment Share on other sites More sharing options...
Alanb Posted May 23, 2019 Share Posted May 23, 2019 To add to Derek's excellent sumary, may I point out that a fuse should be included in the positive lead. This fuse should be as close to the battery, as reasonably practicable. Alan Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted May 25, 2019 Share Posted May 25, 2019 What can be done about this? My vitrifigo- Waeco compressor fridge makes ice in the cooling compartment at half thermostat setting or even lower. My Webasto the opposite keeps running hot at low thermostat setting. Are the thermostats of them adjustable? Link to comment Share on other sites More sharing options...
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