Adjustable trip device for EHU

[RayS]

I remember seeing somewhere a device which you could connect between caravan and site bollard or inside caravan which is an adjustable circuit breaker. I would like to have on that I could set at say 5 amps on European sites to avoid inadvertent tripping of site supply e.g. by using the higher power on the hair dryer or water heater - it's usually a go to the office and get the box unlocked job to get thhings reset - not good in the middle of the night or when in the middle of morning wash and brush up.
Would appreciate any leads (sorry about the pun) to finding details.

It seems you can buy 5 amp MCBs so perhaps a waterproof junction box containing one would be possible, leaving the caravan RCD in full control of any faults. I am aware of the need for qualified inspoction and testing etc. which will not be a problem

 

[ProfJohnL]

I remember seeing somewhere a device which you could connect between caravan and site bollard or inside caravan which is an adjustable circuit breaker. I would like to have on that I could set at say 5 amps on European sites to avoid inadvertent tripping of site supply e.g. by using the higher power on the hair dryer or water heater - it's usually a go to the office and get the box unlocked job to get thhings reset - not good in the middle of the night or when in the middle of morning wash and brush up.
Would appreciate any leads (sorry about the pun) to finding details.

It seems you can buy 5 amp MCBs so perhaps a waterproof junction box containing one would be possible, leaving the caravan RCD in full control of any faults. I am aware of the need for qualified inspoction and testing etc. which will not be a problem

I have considered this, and was unable to find a practical device, that didn't cost the earth. But I have also considered the idea of having a consumer unit inside the caravan that has two MCB's in parallel a 10A and a 6A in parallel, would in theory allow you to select , the 6A one for 6A sites, 10A one for 10A sites and both 10 & 6A together for 16A sites, but and it's an unknown but at this stage, if there MCBs would share the current correctly on dual mode setting.

 

[bertieboy1]

Prof,
Only thing wrong with you idea is it won't work - supposing the current through each circuit breaker was equal you would never be able to draw more than 12 amps. Better have three CB's one 4,one six and one 16Amp and only use one at a time.

 

[Hutch]

Gents , just let the girls have their hair done a day before going away, then complement them the next day as to how nicemit is and make the tea then following morning with the whistlening kettle, . 6 amp hook ups a pain but can be done.

 

[ProfJohnL]

Only thing wrong with you idea is it won't work - supposing the current through each circuit breaker was equal you would never be able to draw more than 12 amps. Better have three CB's one 4,one six and one 16Amp and only use one at a time.[/quote]

Hello Bertie,
That was my concern, but as becasue it all depends on how the MCB actually works; I have done some more research and:

Unlike fuses, where the fuse link presents an electrical resistance which is heated by the flow of current, an
MCB's to the BS specifications principally use and electromagnetic detector and actuator which will react in about 2.5mS This means the electrical resistance of the MCB is intrinsically low, and is not substantially different for MCB's of different current ratings. This would mean that supply current for the load would be shared by each MCB almost equally, rendering the parallel pair idea unsafe and in reality useless.

It would as you suggest be better to have 3 separate MCB,'s which would be switched into circuit to suit he incoming supply limits.

 

[chrisn7]

Ray - Perhaps you are thinking of the Alde Load Monitor, which can be set to activate at various amperages between 6 and 17 amps?

 

[Martin_E]

If you had a 10A and 6A and ran them together (16A) then you would be overloading the caravan by the time you add the other two breakers into the equation (2x C6) 28A the inlet is normally clearly marked 16A max

 

[ProfJohnL]

If you had a 10A and 6A and ran them together (16A) then you would be overloading the caravan by the time you add the other two breakers into the equation (2x C6) 28A the inlet is normally clearly marked 16A max

I think you have misunderstood the concept. My original idea which I conceived before doing full research was based on the concept that you could increase the current bearing capacity of a wired fuse holder by adding extra lengths of fuse wire. Each wire would have a resistance and as such the combination of fuse wires would work like paralleled resistors, and share the current . I hasten to add I never did this in installations but we did do this for product development testing. I would also add that it never worked out quite as expected as the consistency of the fuse wire was not especially good, and different gauges of wire often had different melting points.

However the having done a little research into British Standard MCBs, their method of operation is not dependant on the resistance or the melting point of a link, but it utilises the magnetic flux density of a current passing through a coil, and the compression load of a spring. These can be chosen far more accurately than forming a piece of fuse wire. Crucially the design presents a minimal resistance to the load current which is largely independent of the maximum current the design is rated for. Consequently if you try to operate two or more MCBs in parallel for the same circuit , you will get unpredictable operations of the MCB's at varying currents under the maximum combined rated load.

It is for this reason I have discounted the idea of running two or more MCB's in parallel for the incoming supply.

The concept of having an MCB rated for each generic site's current rating (for example 3A 6A 10A and 16A breakers) a is more plausible. Whilst I may have not stated it, the switching would have to be arranged to prevent more than one MCB being in circuit at any one time.

However another alternative would be have a plug in modular approach where the incoming supply had an electrically safe connector where a 3,6,10,or 16A module could be plugged in by the caravanner.

Ideally (in my view) would be a device that had pre programmed current ratings that could be easily selected by the user.

I do know that several companies have looked at an microprocessor controlled automatic load shedder which would automatically turn off less important circuits or appliances if a heavy demand appliance is turned on, so for example, Items like the fridge, water heater and space heater , would be turned off when teh kettle is turned on, on the basis that teh time it takes to heat the kettle will be no more than a few minutes, and in that same time the loss of power to those selected items will not compromise their long term function. There are several problems with this in practice, as some items reset to their OFF condition if power is taken away. So there would have to be a large degree of inter manufacturer agreement on control standards for this to happen, although we are seeing systems like Hive in the domestic market, which could cross over into the caravan world, and I am aware that Truma now offer mobile phone apps for some of their products, so perhaps its not so pie in the sky as it may at first seem.

 

[Dustydog]

Prof
Would it be wrong to introduce another consumer unit into the circuit between the EHU entry point and the caravan's own consumer unit using say a 5 or 6 amp mcb . He could then change the mcb to 10 or 16 amps as the need arises.
Ok probably too simple to be sensible I'll go back to my Bonio

 

[RayS]

I think this was the device or something very like it. But a more bassic and cheaper item which just tripped the entire caravan supply at the caravan before the bollard breaker tripped would be better..
looks like a clamp round type ammeter with an output to a relay would be fairly simple to make and install.

(Reply to Chrisn7)

 

[bertieboy1]

Hiya Prof,
Have to disagree with you on a point,it is common practise in industry to have CB's connected in parallel, also in series.It is therefore not unsafe to do this except for the situation described by the post.
Parallel connections are used to increase current rating of a circuit.
Series connections are used where circuit breaker voltage rating is lower than the circuit rating. eg for a circuit voltage rating of 230V it is acceptable to have two CB's each with a 120V rating connected in series ( you can connect CB's in series either side of the load or one CB on one side of the load and the other CB on the other side of the load.
This also applies equally to any switching device be it a relay contact, manual switch etc.

 

[ProfJohnL]

Hiya Prof,
Have to disagree with you on a point,it is common practise in industry to have CB's connected in parallel, also in series.It is therefore not unsafe to do this except for the situation described by the post.
Parallel connections are used to increase current rating of a circuit.
Series connections are used where circuit breaker voltage rating is lower than the circuit rating. eg for a circuit voltage rating of 230V it is acceptable to have two CB's each with a 120V rating connected in series ( you can connect CB's in series either side of the load or one CB on one side of the load and the other CB on the other side of the load.
This also applies equally to any switching device be it a relay contact, manual switch etc.

Hello Berti,
Let me make it clear I am not trying to score points or be awkward, but I am not convinced by what you are telling me. but I am willing to consider any verifiable information and reconsider. Can you provide any links to examples where this practice has been followed.

 

[Hutch]

Prof, as you very correctly tell posters on items about gas and electrics, surely all these thing cannot be done without certified by a certified electrician. ?

 

[ProfJohnL]

Prof, as you very correctly tell posters on items about gas and electrics, surely all these thing cannot be done without certified by a certified electrician. ?

Hello Hutch

Fundamentally with reference to lat stanza of your comment is that a qualification as an electrician does not qualify the holder to instal or test a gas appliance. The regulations for gas and electric installation work are different, and where as the actual work on a gas systems must be performed and tested by a certified gas competent person, the way the requirement for electrics is concerned, the formal process is it must be tested by an certified electrician before it's connected to the supply.

Back to the subject being discussed: At this stage it's not about who can do it but whether it will or won't work and is it safe.

 

[Dustydog]

Prof, as you very correctly tell posters on items about gas and electrics, surely all these thing cannot be done without certified by a certified electrician. ?

Hello Hutch

Fundamentally with reference to lat stanza of your comment is that a qualification as an electrician does not qualify the holder to instal or test a gas appliance. The regulations for gas and electric installation work are different, and where as the actual work on a gas systems must be performed and tested by a certified gas competent person, the way the requirement for electrics is concerned, the formal process is it must be tested by an certified electrician before it's connected to the supply.

Back to the subject being discussed: At this stage it's not about who can do it but whether it will or won't work and is it safe.

Prof.
There is a cross over where a Gas Safe registered engineer has to be capable of dealing with all the electrical aspects of modern boiler installations from mains power to pcb failures etc. The reciprocal of an Electrician does not give him her the legal right to play with gas.

 

[Hutch]

If you had such a Heath Robinson, device, between athe EHU and the caravan, I wonder how the insurance people might think about this if there was an electrical fault. ?

 

[ProfJohnL]

Prof.
There is a cross over where a Gas Safe registered engineer has to be capable of dealing with all the electrical aspects of modern boiler installations from mains power to pcb failures etc. The reciprocal of an Electrician does not give him her the legal right to play with gas.

Sorry Dusty, its not quite that simple,

Just being a GasSafe registered engineer does not mean they can fit boilers. There are multiple classifications of GasSafe fitters, and the 'Ticket' defines what they are permitted to work on. For example a Natural Gas Ticket does not permit a fitter to work on LPG and vice versa. It would in fact be a criminal offence for a fitter to work on a system for which they do not have a ticket. (Personally owned caravans are the exception to that rule)

Unless its changed since I last looked at the detail of the Electrical regulations,( and they may well have done), they do not stipulate that only a certified electrician can do the installation, this means any Tom Dick or Harriet can actually do the work, but they cant test or connect it to the mains supply. That is the purview of a certified electrician who must test an installation before its connect it to a supply. That certification requires the wiring complies with the wiring regs. That would apply to major works such as a house rewire and or a part rewire. (e,g, Kitchen or bathroom etc) But for connection of a boiler to the mains that is considered to be minor works and in itself would not require recertification of the electrics. There are certain types of installation that must be certified.

It stands to reason that if an electrician were to certify an installation, which later proves to be non compliant they would be held responsible as they certified it. Consequently it is often difficult to get a certified electrician to certify an installation created by someone else, particularly if they were not a qualified electrician.

Rather like gas systems its unlikely that an untrained or unqualified person would have all the knowledge and equipment necessary to check for compliance of an electrical system with the regulations.

I think you will find that the majority of boiler fitters either have electrical qualifications, or will know an electrician who they work with.

 

[ProfJohnL]

If you had such a Heath Robinson, device, between athe EHU and the caravan, I wonder how the insurance people might think about this if there was an electrical fault. ?

Hutch
Who says it will be a a "Heath Robinson device"?

As far as i know, no such device exists yet, and the reason for discussing it it to see if it's plausible,and worth pursuing. It has not yet been designed or tested yet, If it ever gets that far it will need to be tested correctly and checked for compliance with all relevant standards and codes of practice, If it were to reach that stage would you still call it a Heath Robinson device?,

Presuming that if it were ever produced and manufactured i accordance with the standards it would not increase the risk of an electrical fault. Just consider, as it stands now there caravan's maximum current consumption is already limited by the the sites MCB trip, The arrangement we are discussing is adding an potential extra layer of safety, but more conveniently inside the caravan rather than requiring a site warden to rest the site trip.

 

[Hutch]

Prof, I dought it, all the people putting their bits in, could or at times could not work, I think there is a good reason to have such a devise, I for one would love it, especially in Europe, .
Some one in the massive www, will look at our forum an suddenly dessign a unit that will come on the market, branded by ""Golden Cocrell" product of more than 5 Countrys. !!! Heath Robinson, Nought wrong with his ideas.

 

[ProfJohnL]

Prof, I dought it, all the people putting their bits in, could or at times could not work, I think there is a good reason to have such a devise, I for one would love it, especially in Europe, .
Some one in the massive www, will look at our forum an suddenly dessign a unit that will come on the market, branded by ""Golden Cocrell" product of more than 5 Countrys. !!! Heath Robinson, Nought wrong with his ideas.

Hello Hutch

I'm not clear what part you doubt?

 

[chrisbee1]

Prof, as you very correctly tell posters on items about gas and electrics, surely all these thing cannot be done without certified by a certified electrician. ?

Why not?

 

[ProfJohnL]

Prof, as you very correctly tell posters on items about gas and electrics, surely all these thing cannot be done without certified by a certified electrician. ?

Why not?

Hello Crisbee and Hutch,

As in so many walks of life, there regulatory requirements that must be met before the item/appliance/installation should be used by end users. In that type of situation the systems is expected to work and not endanger the end user, the regulations often require the systems to be installed and finally connected by a certified person. This would apply to a piece of fixed equipment being installed into a wiring installation such as this would be.

But the suggestions for a variable rated circuit breaker is at this stage just a suggestion, It's not piece of equipment that can be purchased or installed yet, so the detailed nature of any regulatory compliance is not yet known.

With regards to the development of any device like this, it would be normal for the inventor or developer to produce models to test. These would be at the developers risk, and until it had completed all its regulatory tests and risks or losses involved with the testing would fall on the developer. All respectable companies that undertake planned developments would be using suitably qualified and experienced people, who would use their knowledge and judgment to inform the design of the product to eliminate foreseeable hazards and the testing regimes should test the product in all normal operating conditions and in a range of ways outside its normal operating area, to demonstrate safe function and compliance with regulations.

 

[Gabsgrandad]

Our 'common sense' load meter seems to work for us.- mind you it is 70+ years old now.

 

[chrisbee1]

Prof, as you very correctly tell posters on items about gas and electrics, surely all these thing cannot be done without certified by a certified electrician. ?

Why not?

Hello Crisbee and Hutch,

As in so many walks of life, there regulatory requirements that must be met before the item/appliance/installation should be used by end users. In that type of situation the systems is expected to work and not endanger the end user, the regulations often require the systems to be installed and finally connected by a certified person. This would apply to a piece of fixed equipment being installed into a wiring installation such as this would be.
.

Hi Prof, What I was querying was the necessity to have private touring caravan electrical work certified. My understanding is that once you plug into a different ECU any certification you may have had done is invalid.

 

[Dustydog]

Down the slippery slope again
There are two issues.
1. As a young novice caravanner 40years ago I had to DIY everything. The available magazines of the day weren't too bad explaining how to fix things both gas and electrical appliances. Older fellow caravanners taught us how to make water and gas tight joints and how to wire electrical things like plugs and things I wont mention here Will I still DIY ? Yes . But don't tell anyone B)

2. Today as we are older and wiser whilst we may be capable of doing most things ourselves we have to think about the novice and not so experienced caravanner. Sadly but a reality and because of the Litigious world we live in there is only one answer. Use a Professional So the Prof is correct to harp on about this point tedious though it may be.

Personally I used to enjoy all those mags like Practical Motoring , Car Mechanics and Practical Caravanning.
They were a DIY delight. Now the Publisher is more concerned not being sued for wrongful advice.
Thank goodness Nigel Hutson is still doing a series of DIY articles. :cheer: