2 rcd's?

[Lee J]

Eventually I will be installing a combined Inverter/charger with auto changeover so my question is this: Do I fit one RCD to protect the shoreline and inverter, and then a second to give protection to the rest of the boat when not on shore power? Whilst on the subject, I intend putting a shoreline hook up at both ends of the boat. Can I then use a changeover switch to connect which ever one is plugged in to the system.

Thanks

Lee

[sociable_hermit]

Idleness posted this link in another thread. It's a good one for your question:

 

http://www.smartgauge.co.uk/nb_ac_sys.html

[Guest steve newton]

Eventually I will be installing a combined Inverter/charger with auto changeover so my question is this: Do I fit one RCD to protect the shoreline and inverter, and then a second to give protection to the rest of the boat when not on shore power? Whilst on the subject, I intend putting a shoreline hook up at both ends of the boat. Can I then use a changeover switch to connect which ever one is plugged in to the system.

Thanks

Lee

 

whoa lee. slow down... if you fit a second RCD surely it's a safety hazard? well... i suppose you CAN use a changeover switch for this purpose but if you're a true boating enthusiast then you wouldn't ruin your boat's integrity like that. why don't you get a biplug system? then a changeover switch won't be necessary?

 

Steve.x

[Lee J]

Thanks for the speedy ones!

 

Sadly Gibbo's diagrams don't show an inverter charger with integrated changeover, but it was seeing that thread that raised this question.

 

Steve I'm not sure what you mean by challenging my boating enthusiasm, and struggle to understand the point about my boats integrity, I'm also unsure of what a biplug system is! Please could you clarify?

 

Lee

[Nine of Hearts]

My inverter is protected via an RCD from the 240v shoreline, and then there's a distribution box with MCB's downstream of the inverter for the 240v supply to the boat. The inverter manual should specify the RCD you need and where to wire it, the instructions for mine (Mastervolt) were pretty explicit.

[Guest TerryL]

Eventually I will be installing a combined Inverter/charger with auto changeover so my question is this: Do I fit one RCD to protect the shoreline and inverter, and then a second to give protection to the rest of the boat when not on shore power? Whilst on the subject, I intend putting a shoreline hook up at both ends of the boat. Can I then use a changeover switch to connect which ever one is plugged in to the system.

Thanks

Lee

 

Because you are using two diffent supplies in different circumstances, one from the shore and one from the boat, they both need an RCD to improve the electric shock safety on shore and onboard and both will be in use when on shore supply. A change over switch would need to be double pole so that the unused plug cannot become live. This can also be done at one end with a simple socket to connect into the further plug with a short lead when used.

[RobinJ]

whoa lee. slow down... if you fit a second RCD surely it's a safety hazard? well... i suppose you CAN use a changeover switch for this purpose but if you're a true boating enthusiast then you wouldn't ruin your boat's integrity like that. why don't you get a biplug system? then a changeover switch won't be necessary?

Any system that involves connecting a boat to shore has potential hazard between the point where the connection is made and the RCD unit, thats why insulation is important.

If you have a system that 'defaults to shore', ie only changes over when the generator or inverter is powered up, then I cannot see a problem, since the shore earth will be the most dangerous one, the generator or inverter will be earthed to the boat anyway!

[Guest TerryL]

My inverter is protected via an RCD from the 240v shoreline, and then there's a distribution box with MCB's downstream of the inverter for the 240v supply to the boat. The inverter manual should specify the RCD you need and where to wire it, the instructions for mine (Mastervolt) were pretty explicit.

 

Slight misconception here, the RCD does not protect your equipment but protects persons with direct contact from electric shock and the cable, circuit and equipment from line earth faults. The MCB or fuses protect the cable, circuit or equipment from overload and provide the basic live to earth fault protection from electric shock. Your equipment can still draw a fault current unless the fuse or MCB becomes overloaded or an earth fault develops.

[Eeyore]

Eventually I will be installing a combined Inverter/charger with auto changeover so my question is this: Do I fit one RCD to protect the shoreline and inverter, and then a second to give protection to the rest of the boat when not on shore power? Whilst on the subject, I intend putting a shoreline hook up at both ends of the boat. Can I then use a changeover switch to connect which ever one is plugged in to the system.

Thanks

Lee

The simple answer to your question is yes.

The RCD in the consumer unit protects you from fault conditions in circuits and appliances connected to it.

The RCD in the supply protects you from fault conditions in the inverter/charger.

The question to other forum members is this - should there be individual RCD protection of each shore connection?

Imagine the following: a single RCD is installed between the changeover arrangement and the inverter/charger. The shore line is then connected to the front of the boat whilst the changeover arrangement is set to the back position. Is it then acceptable to have an unprotected supply running the length of the boat from the front shore connector to the changeover arrangement? I accept that this condition would not be intentional, but is possible.

The basis of this question is - should the operator (boat owner) be able to bypass or negate any part of the safety arrangements during any normal operation of the system?

(Most of my experience has been with repair and upgrading of existing installations, and my personal preference in those circumstances has been to provide RCBO (combined RCD & MCB) at each source of supply.)

Steve

[Gary Peacock]

From the regulations-

 

7.2.2 A manually reset trip-free circuit-breaker shall be installed within 0,5 m of the source of power or, if

impractical, the conductor from the source of power to the panel-board circuit-breaker shall be contained within a

protective covering, such as a junction box, control box, enclosed panel-board, or within a conduit or cable trunking

or equivalent protective covering. If the location of the main shore-power inlet circuit-breaker exceeds 3 m from the

shore-power inlet connection or the electrical attachment point of a permanently installed shore-power cord,

additional fuses or circuit-breakers shall be provided within 3 m of the inlet or attachment point to the electrical

system in the craft, measured along the conductor.

 

[Lee J]

From the regulations-

 

7.2.2 A manually reset trip-free circuit-breaker shall be installed within 0,5 m of the source of power or, if

impractical, the conductor from the source of power to the panel-board circuit-breaker shall be contained within a

protective covering, such as a junction box, control box, enclosed panel-board, or within a conduit or cable trunking

or equivalent protective covering. If the location of the main shore-power inlet circuit-breaker exceeds 3 m from the

shore-power inlet connection or the electrical attachment point of a permanently installed shore-power cord,

additional fuses or circuit-breakers shall be provided within 3 m of the inlet or attachment point to the electrical

system in the craft, measured along the conductor.

 

Thanks for the replys, so Gary 3 RCD's!

 

Lee

[Smelly]

Shouldn't there usually be an RCD on the shorepower supply anyway?

 

Wouldn't it be less hassle to put one there instead of installing one before and one after the combo? You can buy commando sockets with inbuilt RCDs, (I think) wouldn't that be enough if you were trailing a cable down the garden friom the shed's supply?

 

This sounds like needlessly complicating things to me!

[wonderdust]

Whilst on the subject, I intend putting a shoreline hook up at both ends of the boat.Thanks

Lee

 

Or buy a longer shore power lead.

[Lee J]

Yes but I would still need one on the otherside of the inverter for when I'm not on shore power

[RobinJ]

Yes but I would still need one on the otherside of the inverter for when I'm not on shore power

The simply way is to have a socket into which you plug, either the shoreline, generator or inverter etc.

However if you plan to have a socket at each end of the boat, you need to ensure that two cannot be plugged in at the same time, thereby needing some sort of switching. Also as they are likely to be more than the requisite distance apart, proctection will be needed on at least one socket too (ie fuses).

If installing a switching system, you will need to decide which socket has priority and which sources have priority over others, but you will probably end up with some expensive contactors and complicated wiring!

[Eeyore]

This sounds like needlessly complicating things to me!

Quite true!

But safety systems have evolved to protect those least able to appreciate the dangers. Don't forget we're talking about ordinary people who haven't a clue as to the dangers involved.

Its a nanny state; sometimes you just have to bite your lip and get on with it.

Steve

[Guest TerryL]

Yes but I would still need one on the otherside of the inverter for when I'm not on shore power

 

There does seems to be confusion here so to clarify, you only need one RCD onboard if you have an invertor or generator, this will protect you from electric shock from either the inverter and generator and also when connected, the shore supply. Your marina, boatyard or any commercial shore supply is required to have an RCD at all outlets, this will protect you from electric shock involving the shore lead however it runs and also onboard at the outlets etc. if you have no onboard RCD fitted when using the mains supply. If both RCD's are the same rating then either or both can trip if an earth fault develops when on shore supply. Is that clear?