Motor mover isolating switch

[Ratty3]

Hi
I am going to fit an isolating switch to my Motor mover at the weekend. Am I right in thinking it goes on the positive cable going from the battery to the mover control box? Does this affect the charging of the battery?

 

[Spurtle]

As you say, it should be fitted in the positive cable between the battery and the motor mover control box.

You should also have a suitably rated fuse in the same section of the circuit but , like the isolating switch, mounted outside the battery box. - the seperate section integrated into most caravan battery boxes where the 230v feed goes in is where most isolating switches are mounted but , if you can't, or don't want to put there, you can buy a dedicated isolator switch mounting box from Reich ..but that would mean cutting an extra hole in your pride and joy...

Any positive cable lying within the confines of the battery box should also be double insulated (heat shrink sleeving is perfect)

I serviced a caravan last week that had a standard 230v single gang light switch mounted inside the van being used as an isolator. Would have been interesting seeing someone trying to turn that off in a hurry.... :huh:

No excuses for not doing it properly

and it shouldn't affect the charging of the battery as the motor mover wiring is , or certainly should be, completely seperate from the domestic 12v positive supply from the battery.

 

[bertieboy1]

Spurtle,
Please explain why cable in battery box should be double insulated,after all it's only a 12 volt system.

 

[Damian]

Spurtle,
Please explain why cable in battery box should be double insulated,after all it's only a 12 volt system.

Because that is the requirement under the regulations, as is the requirement for cables to go through the battery box into the van through gas tight glands.
It may be "Only12v" but can draw around 20 Amps or so under full load.

 

[Spurtle]

The 'regulations' are that you should double insulate the positive cable within the battery compartment. That's what is contained within the NCC guidance for fitting motor movers & the fitting instructions from most manufactures.

During normal operation the current draw on most movers would be in the region of 20 to 30 amps but could potentially peak at 100amps plus and, given that all electricity is dangerous, whether AC or DC, I am quite happy to follow the guidelines.

 

[Woodentop]

The 'regulations' are that you should double insulate the positive cable within the battery compartment. That's what is contained within the NCC guidance for fitting motor movers & the fitting instructions from most manufactures.

During normal operation the current draw on most movers would be in the region of 20 to 30 amps but could potentially peak at 100amps plus and, given that all electricity is dangerous, whether AC or DC, I am quite happy to follow the guidelines.

Strange. My Powrtouch Evolution motors are marked 80A - which the manufacturer advises is the draw for both.

 

[Spurtle]

I was generalising, regarding the current draw.

Some mover systems will have a maximum total current draw under full load of 80 amps or less. Some of the Truma systems are quoted at 130amps max.

The important thing is that the primary power cable is sized correctly and protected from accidental shorting .
I would imagine that the reason for the double insulated positive cable requirement in the battery compartment is that the presence of the negative terminal of the battery, and its cable, makes for a very convenient ( or inconveniently) placed potential dead short.

 

[JohnM20]

I'm having a motor mover fitted but because we store our caravan with the battery box up against the house wall the isolator switch for the mover is being sited inside the caravan adjacent to the battery box and next to the mover's control box. The dealer has told me that "the law states that the switch MUST be within 18" of the battery box". Purely out of curiosity, is there such a 'law' ?

 

[RayS]

I really don't think there is a 'law' about this but,as ever, open to correction and to learn.

 

[ProfJohnL]

I am not aware of any law that makes that a requirement for mover isolator switches. Thats not to say there isn't one, but from an engineering and technical perspective I can see no reason for such a requirement.

As with any electrical circuit the circuit needs to be complete to allow current to flow. Break the circuit anywhere, and the current cannot flow. and that is what the isolator switches function is.

There are general conventions which suggest that for safety, automatic isolation of a circuit should occur as close to the power supply as possible. This is important for mains appliances to limit the amount of circuit that could still be live and pose a danger of electric shock, That would certainly be the case for the fuses or MCB's where their automatic function is to protect the wiring systems as much as the appliances, But the mover isolator switch is not an automatic disconnection device, but more of a convenience function.

 

[Spurtle]

There are guidelines from manufacturers, and a code of practice from the NCC on the installation of motor movers.......they also get a mention in the City & Guilds -Electrical Systems, Equipment & Circuits traning course

but can't think of anything specific that is enshrined in law, regarding such specific aspects of their installation as distance from battery to isolator ...... but , as mentioned previously, happy to learn otherwise

Don't like the idea of a cut off switch inside though.

 

[Damian]

Quote " The dealer has told me that "the law states that the switch MUST be within 18" of the battery box". Purely out of curiosity, is there such a 'law' ?

Simple answer is NO there is no such law.

Most movers come with pre cut lengths of cable for the various uses, and one of the cables from the isolator switch to the control box is relatively short, about 12 to 18 inches normally, and the usual site for the isolation switch is in the battery box under the mains inlet, to deter the use of mains power whilst the mover is being used.

The cables from the battery to the control box and isolator switch are quite long.

The installation of a mover is NOT the subject of any "Law", but is fitted with regard to a Code of Practice issued by the NCC.

 

[jignc]

When I fitted motor movers as a job the company said I could fit the isolating switch inside or outside but make sure the customer understands that the reason for fitting it in the battery box was so in an emergency you could switch it off from outside quickly.

I read recently that someone was driving their van with the mover but found that is was driving on its own regardless of the commands from the remote. They found the van next door was also being moved and both units must have been on the same channel. In this instance a quick access to the switch would have been a must.

 

[GStockton]

Just a small piece of information re Current draw of a Mover. On a single axle van up a slight slope is around 80 to 90 amps, a twin axle at 1600kg same slight slope draws 100 to 120 amps dc.

A good inexpensive DC clamp meter for you caravan fitters is the Alphatek TEK 632 worth a quick google.

 

[Martin_E]

Expanding on Damian's post......

The switch is fitted as near to the battery for the reason of loss of amperage, the further you go the thicker the cable required, but mover manufacturers supply one size cable (normally (or one size in and one size out)) so that restricts the distance the isolator can be fitted or even the control box.can be placed.

 

[ProfJohnL]

Expanding on Damian's post......

The switch is fitted as near to the battery for the reason of loss of amperage, the further you go the thicker the cable required, but mover manufacturers supply one size cable (normally (or one size in and one size out)) so that restricts the distance the isolator can be fitted or even the control box.can be placed.

I'm sorry Martin, but that simply is not true. The current in a circuit conductor is the same at all points in the circuit. It is determined by the potential difference (Voltage) and the resistance of what ever is in series including the conductor. The means of controlling the circuit by way of a switch can be any where in the circuit provided it breaks the circuit.. If you extend the circuit you may need to consider using a heavier gauge of cable, but when you consider that the same mover could be fitted to a variety of sizes, yet the manufacture only supplies one size of cable, in practice you would need only need to go fr thicker cable if you were looking at probably doubling the required length.

 

[Dustydog]

.My isolator is in the battery box as described by Damien. I always close the battery box door before using the mover.This stops it dragging on the ground in certain circumstances. No way can I call it an emergency off switch.If something goes wrong I doubt I'd have sufficient time to open the door fit the switch key and turn it off.
A friend has a Truma fitted. The isolator is not a switch but a 12n plug and socket arrangement.
So are we talking about an isolator or a safety dead man's handle switch?

 

[Damian]

The isolator switch is simply an isolator switch, in no way can it be sensibly be called a "safety feature" as such in respect of likening it to a dead mans handle, it is far too fiddly to do that.

The switch is there just to isolate the control box when the mover is not being used to stop any chance of the control box draining the battery.