Changes to BSS regs for RCD's ?

[Robbo]

thanks for all of that, yes I think they are rated at 16a as it would explain why the inverter throws a bit of a paddy if the kettle is put on when the boss lady is using the industrial sewing machine. The new radial circuit I am installing is planned for the sewing machine and spare sockets in the bedroom to split the load as am conscious is potentially quite a lot on one breaker.

 

When you say upgrade to a 32a socket, I take it you mean the blue things as opposed to some sort of magic 32a three pin socket regular? That might sound daft question however I genuinely dont know and have never seen one when Ive been googling 32a sockets previously.

 

I think the upshot of all this advice is to get a professional in to review my exisiting wiring (its only 3.5 years old and looks very professionally fitted out) and my needs as I am marina based and we rarely cruise. I know some people might be aghast at that, however it is perfect for us, we get an exceptionally good commute to our work, our greys are chilled at home, the boat is safe (relatively) and we have amazing thoughtful neighbours.

The shore inlet on your boat will be more than likely a 16amp one, if you are updating to 32amp this as well as the shore cable and the cable feeding the consumer unit will need uprating.

 

If you have a Victron Combi or any other make, they are usually wired in series from the shoreline to your consumer unit, if this is a 16amp unit then uprating anything would be a waste as this is the limiting factor unless you put a switch in to bypass it. (and then you lose th advantages the Combi gives you)

[widebeamboy]

The shore inlet on your boat will be more than likely a 16amp one, if you are updating to 32amp this as well as the shore cable and the cable feeding the consumer unit will need uprating.

 

If you have a Victron Combi or any other make, they are usually wired in series from the shoreline to your consumer unit, if this is a 16amp unit then uprating anything would be a waste as this is the limiting factor unless you put a switch in to bypass it. (and then you lose th advantages the Combi gives you)

 

Thanks, that does indeed make sense, hadnt factored in the combi in my thinking and how it might be wired in and yes it is a Victron so am definetely into the seek expert advice zone as I expected I would end up. Appreciate all the inputs and apologies for hijacking the thread a bit.

[Robbo]

 

Thanks, that does indeed make sense, hadnt factored in the combi in my thinking and how it might be wired in and yes it is a Victron so am definetely into the seek expert advice zone as I expected I would end up. Appreciate all the inputs and apologies for hijacking the thread a bit.

Then if you wish to stay using 16amp and your Victron is wired in series (i.e. You don't have a shore/inverter switch) then you already have protected your shoreline cable sockets and adapters to 16amp as the Victron won't go over this. If a BSS man raises anything, then point them to the Victron as this protects upstream for overcurrent situations.

 

As the Victron can supply additional power to the shore power then adding a 16amp MCB to feed all other MCB's would be reducing your available power, it's also not needed.

Edited August 10, 2016 by Robbo

[GUMPY]

Simplest way of dealing with a 32a outlet to 16a inlet is a 32a plug ct a short length of 6mm cable to waterproof box with 16a DP MCB in the box and then a 16a socket.

You could use 16a RCBO instead of MCB if you really want a delux jobbie.

 

All legal and safe.

[nicknorman]

Then if you wish to stay using 16amp and your Victron is wired in series (i.e. You don't have a shore/inverter switch) then you already have protected your shoreline cable sockets and adapters to 16amp as the Victron won't go over this. If a BSS man raises anything, then point them to the Victron as this protects upstream for overcurrent situations.

As the Victron can supply additional power to the shore power then adding a 16amp MCB to feed all other MCB's would be reducing your available power, it's also not needed.

Bear in mind a Victron Combi might have a 16A transfer relay, or it might have a 50A one, depending on what was specified at purchase. Our mastervolt Combi will pass through 25A.

[Robbo]

Bear in mind a Victron Combi might have a 16A transfer relay, or it might have a 50A one, depending on what was specified at purchase. Our mastervolt Combi will pass through 25A.

It's also worth noting that it's also programmable as well to a certain limit. (I presume the mastervolt has the same). With the Victron this can be done via the remote control dial or more permanent via the software or dip switches (if you have a built in genny you can wire up so you can preprogram the genny's limit, and it will automatically set this.

[Keeping Up]

I've just been thanked by the inspector concerned for raising this query, he welcomes the clarification that he has just received from the BSS office that this is NOT grounds for a failure and that the information which had been given at the recent BSS training course was incorrect.

[Robbo]

Thanks for the update

[WotEver]

I've just been thanked by the inspector concerned for raising this query, he welcomes the clarification that he has just received from the BSS office that this is NOT grounds for a failure and that the information which had been given at the recent BSS training course was incorrect.

Good news

[Pete Rewcastle]

Consumer units are not expensive and MCBs cost a few pounds. in my rewire of my boat I will split most sockets to radial on there own breaker at 10amps with 2.5mm cable throughout ( arctic flex is not too expensive and 1 roll should do the boat). The extra MCBs make my system more robust against failure not less. I will split the board with 2 RCDs, 1 rated at 63 amps and 1 at 40 amps as I have them in stock. The fact that they are rated WAY above 16 or 32 amps is not a problem, it is a safety margin. The 2 RCDs will be supplied via separate inverters when "off grid". I could make the whole system even more failure resistant by fitting RCBOs, but i do not consider this expense justifiable.

As you can see, by increasing the amount of breakers I am in fact decreasing the risk of overload or inconvenience not increasing it.

[Chewbacka]

8 hours ago, Pete Rewcastle said:

Consumer units are not expensive and MCBs cost a few pounds. in my rewire of my boat I will split most sockets to radial on there own breaker at 10amps with 2.5mm cable throughout ( arctic flex is not too expensive and 1 roll should do the boat). The extra MCBs make my system more robust against failure not less. I will split the board with 2 RCDs, 1 rated at 63 amps and 1 at 40 amps as I have them in stock. The fact that they are rated WAY above 16 or 32 amps is not a problem, it is a safety margin. The 2 RCDs will be supplied via separate inverters when "off grid". I could make the whole system even more failure resistant by fitting RCBOs, but i do not consider this expense justifiable.

As you can see, by increasing the amount of breakers I am in fact decreasing the risk of overload or inconvenience not increasing it.

Please think about the safety aspect of two inverters permanently wired in.  My concern is that unless you are using inverters that have a special link cable to keep the two inverters in phase, then the two inverters will not be in phase.  As the inverter clocks (50Hz) will be ever so slightly different your two inverters will run at ever so slightly different frequencies, the result is that sometimes they will be in phase and the rest of the time not.  They will at times be 180 degress out of phase to each other.

When they are 180 degrees out of phase - assuming the neutral side is bonded to earth - then the rms voltage difference between the two inverters will be 460V.  When in phase it will be zero between inverters whilst still 230V to earth.  This is one of the reasons that 3 phase is not supplied to domestic premises - it also costs more.

I doubt you would install sockets supplied from different phases in a kitchen or living room in a house so I would not do it on a boat.

[BruceinSanity]

The AC wiring on my boat has an earthed flexible sheath as a defence against abrasion. I'd thought it was an RCD requirement but maybe not, I know nothing...

[WotEver]

5 minutes ago, BruceinSanity said:

The AC wiring on my boat has an earthed flexible sheath as a defence against abrasion. I'd thought it was an RCD requirement but maybe not, I know nothing...

Not only is it not a requirement, it's not a very good idea. You will potentially have many points of contact between the sheath and the hull giving lots of potential for electrolytic corrosion. 

[cuthound]

5 hours ago, Chewbacka said:

Please think about the safety aspect of two inverters permanently wired in.  My concern is that unless you are using inverters that have a special link cable to keep the two inverters in phase, then the two inverters will not be in phase.  As the inverter clocks (50Hz) will be ever so slightly different your two inverters will run at ever so slightly different frequencies, the result is that sometimes they will be in phase and the rest of the time not.  They will at times be 180 degress out of phase to each other.

When they are 180 degrees out of phase - assuming the neutral side is bonded to earth - then the rms voltage difference between the two inverters will be 460V.  When in phase it will be zero between inverters whilst still 230V to earth.  This is one of the reasons that 3 phase is not supplied to domestic premises - it also costs more.

I doubt you would install sockets supplied from different phases in a kitchen or living room in a house so I would not do it on a boat.

Having two out of phase supplies in close proximity is not a good idea for the reasons Chewbacka has pointed out.

In the commercial world it is sometimes necessary to feed the sockets within a small area from different phases of a 3 phase supply. In this case it is good practice to keep any sockets fed from different phases (or 2 inverters in your case) at least 2 metres apart, so that one person cannot touch them simultaneously, and hence not get a potential 440 volt shock.

[ditchcrawler]

4 minutes ago, cuthound said:

Having two out of phase supplies in close proximity is not a good idea for the reasons Chewbacka has pointed out.

In the commercial world it is sometimes necessary to feed the sockets within a small area from different phases of a 3 phase supply. In this case it is good practice to keep any sockets fed from different phases (or 2 inverters in your case) at least 2 metres apart, so that one person cannot touch them simultaneously, and hence not get a potential 440 volt shock.

In my time on the tools that was an IEE reg requirement, 6 ft in those days before the foreign stuff was invented and 415/ 240 volts  IEE 13 edition but in your case it could be 460 volts as the phases wouldn't be tied at 120 deg and could be 180 deg out

 

[cuthound]

48 minutes ago, ditchcrawler said:

In my time on the tools that was an IEE reg requirement, 6 ft in those days before the foreign stuff was invented and 415/ 240 volts  IEE 13 edition but in your case it could be 460 volts as the phases wouldn't be tied at 120 deg and could be 180 deg out

 

Was still a BS7671 (IET wiring regs) when I stopped working nearly 4 years ago, so presumably still is.

You are quite right about the 460 volts. I wrote 440 volts from habit of 3 phase installations!