earthing point

[monzer]

Having a few electric niggles with various items on the van. One being the electric step buzzer not always working.

I removed a bent chequered plate that runs across the threshold of the hab door. There is a lot of wiring going from front of van to back underneath there and 2 earth wires are bolted on to it.

Now I am not the best with electrics but why are those earth wires connected to it? It will never be in contact with the chassis. It is screwed down but it would only be screwed in to the floor.

Or am I missing something?

 

[Phill D]

Probably supplies the earth to the step electrics assuming that the step is mounted to or connected to the plate.

 

[Phill D]

Or perhaps it’s a common point to join some of the earth wires

 

[monzer]

Probably supplies the earth to the step electrics assuming that the step is mounted to or connected to the plate.

I thought that but the steps not connected to it. This plate literally just sits on the floor.

 

[bertiebasset]

Maybe one wire is to earth the checker plate which is metal. 2nd wire may be to a light or something else.

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[Phill D]

I thought that but the steps not connected to it. This plate literally just sits on the floor.

Perhaps it is just used as a connection for earths coming from different parts of the van

 

[Wannabee]

Perhaps belt and braces protective earthing to the metal plate?

 

[monzer]

Perhaps it is just used as a connection for earths coming from different parts of the van

Yeah I guess it must be. I'm starting to think I've got an earthing problem in the 12v system and wondered if this had anything to do with it when I was investigating the step buzzer.

 

[tonyidle]

Perhaps it's utter stupidity on the part of the converter. Wouldn't be the first time.

 

[PP Bear]

Military vehicles have a variety of earthing straps that reduce the chance of static buildup etc. is it possible that they’ve added an earth point to prevent static on a floor plate as well

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[Wannabee]

Yeah I guess it must be. I'm starting to think I've got an earthing problem in the 12v system and wondered if this had anything to do with it when I was investigating the step buzzer.

Try disconnecting it, and then separately also a temporary earth to a known good earth point and see what effect it has. Might point you in the right direction.

 

[Phill D]

Try disconnecting it, and then separately also a temporary earth to a known good earth point and see what effect it has. Might point you in the right direction.

Or disconnect both and use a meter to check continuity to chsssis earth of each wire separately

 

[monzer]

Or disconnect both and use a meter to check continuity to chsssis earth of each wire separately

How is that done please?

 

[Lenny HB]

How is that done please?

Meter set to low ohm range, one lead to known earth point or chassis and the other on the end of the lead. In an ideal world it would read zero but it will probably read a few ohms. Just the leads will have a bit of resistance.

Before you test the wire hold the meter leads together then watch the display so you can see how it works.

 

[monzer]

Meter set to low ohm range, one lead to known earth point or chassis and the other on the end of the lead. In an ideal world it would read zero but it will probably read a few ohms. Just the leads will have a bit of resistance.

Before you test the wire hold the meter leads together then watch the display so you can see how it works.

I'm sure I can manage that but how will I interpret the results?

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[Phill D]

I'm sure I can manage that but how will I interpret the results?

If the meter stays at 1 then that lead is probably open circuit I.e. broken at some point along its length.
If the both read 0 or very close all is well .
Just connect them together if you are not putting the checker plate back.

 

[Lenny HB]

I'm sure I can manage that but how will I interpret the results?

By doing what I said in the second paragraph.

 

[monzer]

By doing what I said in the second paragraph.

Got that but I was just wondering if it does show up 1 on the meter then could that potentially be causing issues with other 12v stuff. Bear in mind I've no idea what these wires are for.

 

[Lenny HB]

Unless you can trace the wires to where they connect at the other end you won't know.

 

[monzer]

Okay I tried electrics but I'm about to give up. I was told by the people I bought the maxxfann from that I should run a 4.5mm cable from the battery to the back of the van to power the fan.

I went to the local caravan accessory place and they say you shouldn't use bigger than 2.5 in caravans or motorhomes and that you shouldn't use a run over 5 metres in length.

Such a faff!

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[Phill D]

As far as I know The max fan pulls about 4 amps when on maximum. So if 2,5mm cable is used the advised max run for an acceptable voltage drop would be 6m.

How far are you running the cable

 

[monzer]

As far as I know The max fan pulls about 4 amps when on maximum. So if 2,5mm cable is used the advised max run for an acceptable voltage drop would be 6m.

How far are you running the cable

6m van going from front to back (roughly) and floor to roof so I reckoned I'd need 6m at least. Probably more come to think of it.

 

[Phill D]

So if it’s 10m in total you will need 4mm cable

 

[monzer]

So if it’s 10m in total you will need 4mm cable

Which is what I was wanting but they guy in the shop didn't have any because he says you shouldn't use it. I did get the impression he was talking shite right enough

Anywhere online I could buy it?

 

[pappajohn]

It will be 4mm².....not 4.5mm²
That will be the real reason they don't have it.
I wonder how 12 mtr RVs manage if, as they say, 2.5mm² is the max size and only up to 5 mtrs. They're talking b0ll0cks.

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[autorouter]

I went to the local caravan accessory place and they say you shouldn't use bigger than 2.5 in caravans or motorhomes and that you shouldn't use a run over 5 metres in length.

Maybe he's heard that in relation to 240V mains cable. No point in using bigger than 2.5mm2 for that. However 12V power wires of 4mm2 and 6mm2 are common in MHs. Even for relatively low power like solar.

 

[Lenny HB]

I went to the local caravan accessory place and they say you shouldn't use bigger than 2.5 in caravans or motorhomes and that you shouldn't use a run over 5 metres in length.

I take it the dealer only sells Brit vans & Caravans where the wiring is always notorisly undersized.
What he told you is total BS, you can run any length cable you like just use a suitable size cable to keep the volt drop under 3%.

 

[monzer]

Cheers guys. So looks like I'll need a bit of 4mm cable as Phill D says. Won't have time to run it in before I go away unfortunately so top of the list when I get back.

 

[autorouter]

I removed a bent chequered plate that runs across the threshold of the hab door. There is a lot of wiring going from front of van to back underneath there and 2 earth wires are bolted on to it.

Now I am not the best with electrics but why are those earth wires connected to it? It will never be in contact with the chassis. It is screwed down but it would only be screwed in to the floor.

It's probably to comply with the rule that all exposed metal parts near 240V mains cables should be bonded to the protective earth. Just in case it chafes through one of the mains wires and becomes live. Very likely no actual electrical function at all.