Help understanding my electrics

[sprie]

Sorry about this, but I have no manuals for this, and the previous owner couldn’t help.

I have this fuse box and a controller (with 1 relay and 2 fuses).

The van has an original set of circuits (e.g. some lights, fridge) and a previous owner added some 3-pin plugs & fluorescent lights.

There is an inverter (with an on-off switch) adjacent to the leisure battery, and there is a solar panel on the roof (with a control panel I haven’t even looked at yet).

I have replaced the old leisure battery with a brand new, fully charged one.

All the electrical items/sockets work when I plug in the external supply.

When I unplug this external supply, the original circuit works, but the 3-pin circuit does not.

Given this (and the photo attached), can anyone tell me

1. what each of the flip switches does on the fuse box
2. what is the relay for
3. is there a way to find out if the 3-pin circuit should work running from the battery
4. what is the inverter for?

Sorry to be so ignorant, but I haven’t been able to deduce the answers, and I am guessing this is fairly basic stuff,

Many thanks

 

[oldiesontour]

The inverter has to be on to convert the leisure battery power to mans power , depending on how it's wired to the van the man's sockets may become live via a switch or relay or it may just have an inbuilt socket.
By flip switches do you mean those on the right of the phot..if so they are MCB s (a type of resettable mains fuse) up is on

 

[LithiumConvert]

It is normal for the 230volt 3-pin sockkets to work only on hookup.

A standard inverter will have its own 230volt 3-pin socket - note the power limit of the inverter.
and a single battery may well not support the power output of the the inverter

 

[pappajohn]

The switches in the white box are 240v mains trip switches and control 3 pin sockets, fridge, possibly boiler, battery charger etc.
Unless the inverter has been wired with a changeover switch the white box is only live on 240v hookup.
I would think the inverter is a stand alone, low power unit with just one 3 pin socket built in so all the other 240v mains things will only work on hookup

 

[starquake]

The switches in the white box are 240v mains trip switches and control 3 pin sockets, fridge, possibly boiler, battery charger etc.
Unless the inverter has been wired with a changeover switch the white box is only live on 240v hookup.
I would think the inverter is a stand alone, low power unit with just one 3 pin socket built in so all the other 240v mains things will only work on hookup

Agree, as with only one leisure battery the chances of running anything meaningful on the system is nil. By meaningful I mean a TV or laptop charger will probably work for a few hours.

You won't run a Microwave (well for long) or an airfryer type device on a single leisure battery as you will be drawing well beyond the design capacity of the battery. Most have a 20A max draw per battery, so around 240-300W. If you draw over this rate, you quickly will cause the leisure battery to die.

If you have a lithium battery you can ignore the above and run a Microwave potentially on a single battery.

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[autorouter]

There is an inverter (with an on-off switch) adjacent to the leisure battery,

There are a few different ways to wire in an inverter. It converts 12V DC battery power to 230V AC mains power like you get from a house mains socket. The simplest way to wire an inverter is to wire the DC input to the battery, and plug a mains appliance directly into the socket on the inverter.

Another way is to wire in a few sockets, for example a mains 4-way extension, into the inverter output. The next step is to wire the inverter output socket to a trip switch in the mains consumer unit, and have a trip switch just for inverter sockets.

There are other options, including an automatic switchover for the sockets: using the external supply when available, and automatically switching over to inverter power when the external supply is unplugged.

Maybe you could post a few photos of the setup, someone could probably tell you what system you have.

One comment on the trip switches in the photo. The left switch has a Test button, which means it is an RCD, that protects against electric shock and earth leakage. The other two trip switches look like MCBs, a C20 and a B20 (it's hard to read the writing on them). They protect against any overcurrent faults.

The RCD probably switches off both the MCBs if there is an earth leakage fault. It can be used as a mains switch to turn off the whole mains supply. The two MCBs will control two different circuits - if one trips, the other will still be working.

The C20 or B20 means they are 20A trips, which is a bit high for a motorhome. Mostly in a motorhome they will be 6A,10A,13A or possibly 16A, but not 20A. A normal mains hookup cable and connectors will be good for 16A, and usually have a maximum 16A MCB to protect the input. The 20A trips are only just over the limit, and you should swap them for 16A or less when you get the chance. It's easy, and not expensive.

If you do this, make sure you get double-pole MCBs, not single-pole ones. The ones in the DIY stores are all single-pole and are no good for this. You need to get them from a specialist electrics store like CEF, or maybe a caravan accessories shop will have them.

 

[sprie]

Many thanks Oldiesontour, lithiumconvert, papajohn, starquake, autorouter.
Your replies were very helpful. I will do some more investigations and take a steer from your advice.
atb
Ian

 

[autorouter]

To take an overview, most motorhomes don't have an inverter. The habitation ciruits run on 12V DC power from a leisure battery. The leisure battery is charged from the mains electric hookup (EHU) whenever the hookup is p[lugged in.

The 12V habitation circuits include the lights, water pump, and the control boards for the fridge, water heater and space heater.

Any 3-pin mains sockets won't be powered, except when the hookup is plugged in.

The idea is that you can park in the middle of a field, with no mains hookup at all, and still have lights, stay warm, have a hot shower, use the toilet and have a cold beer - no mains required at all. The main heating/cooling power is usually from gas, for the water heater, space heater and fridge.

If you have an inverter, that will be an extra, usually a few mains sockets powered by the inverter from the battery. As I mentioned before, sometimes the sockets switch over from hookup mains to inverter mains when the hookup is unplugged.

But whatever the hookup mains situation, the habitation circuits should all run on 12V DC from the battery.