Reinstating an immersion heater via a non fused spur.

[Gybe Ho]

I think I know the answer however I am talking 240V AC wiring here and so a second or 10th opinion is welcome.

 

A new Multiplus Victron Invertor/Charger was fitted to my boat a few years ago, it is an original model and not the newer Multiplus II that has a second AC outlet (AC2). The Multiplus replaced a Mastervolt and I suspect it was a Mastervolt model with a second AC outlet that was only active when on shore power.

 

The net result is the feed to the 1kW immersion heater in the calorifier was left unconnected and coiled in the bedroom wardrobe behind the Multiplus on the opposite side of a bulkhead.

 

Given the upgrades happening to my boat, (16kW lithium bank @12v and 1.3 kW of solar), I feel there will be enough electrical ooomph onboard to drive the immersion heater via the 3000 kva invertor direct from the batteries & solar when offgrid.

 

Would I be correct in thinking the supply to immersion can be spurred off AC1 that feeds the mains sockets using the following junction box?

https://www.toolstation.com/axiom-junction-box/p28404

 

This morning I read up on fused spurs and concluded a fuse on a spur can be omitted when the cables are the same rating and only one appliance hangs off the spur.

 

The topology of my boat's wiring will simplify the immersion reconnection because the first 240v socket downwire from the invertor, the immersion manual switch and the unconnected old AC2 immersion wire coil are all within 18" of each other. 

 

 

[dmr]

It will work but its not very nice, personally I would prefer a consumer unit with RCBO's and the immersion heater, washing machine (if you have one) and any other big loads having a dedicated cable direct to a dedicated RCBO.

[David Mack]

I don't know if there are any rules requiring a fused, rather than unfused, spur, but why wouldn't you fit a fuse anyway? It's cheap enough to do. I would also fit a double pole isolator as you won't want the immersion on all the time the Multiplus is running.

https://www.toolstation.com/axiom-13a-fused-spur/p28571

[Gybe Ho]

7 minutes ago, dmr said:

It will work but its not very nice, personally I would prefer a consumer unit with RCBO's and the immersion heater, washing machine (if you have one) and any other big loads having a dedicated cable direct to a dedicated RCBO.

 

I need to investigate the AC side the electrics some more, there should be enough spare cable on the dangling disconnected AC2 coil to reach a new second RCBO. The AC cables radiate out from a separate sealed panel that has the RCBOs and other AC feed isolator switches, time to remove the AC safety panel and look at the internals. So far I have not worked out the cable routing to the 240v sockets on the other side of the boat.

[NB Saturn]

Just now, Gybe Ho said:

 

I need to investigate the AC side the electrics some more, there should be enough spare cable on the dangling disconnected AC2 coil to reach a new second RCBO. The AC cables radiate out from a separate sealed panel that has the RCBOs and other AC feed isolator switches, time to remove the AC safety panel and look at the internals. So far I have not worked out the cable routing to the 240v sockets on the other side of the boat.

 

Whilst you have in bits label every cable and make yourself a wiring diagram; it’ll save you having to re-work it out in 3 years time when you want to change something and can’t remember it.

[Ronaldo47]

A Sharpie felt tip pen, ir even a black ball-point pen,  is good for writing on the cable insulating sheath to say where it goes. 

[Gybe Ho]

12 minutes ago, David Mack said:

I don't know if there are any rules requiring a fused, rather than unfused, spur, but why wouldn't you fit a fuse anyway? It's cheap enough to do. I would also fit a double pole isolator as you won't want the immersion on all the time the Multiplus is running.

https://www.toolstation.com/axiom-13a-fused-spur/p28571

 

The existing installation does have a mains switch to turn the immersion on and that switch has an indicator light. And better news, after having a second look it also has a fuse. So now the challenge is to just splice the dangling unconnected old AC2 wire into the AC1 cable just before that cable reaches the first mains socket.

 

Time to invest in a swanky insulator stripper tool me thinks in view of the other pending wiring jobs.

[Tony Brooks]

12 minutes ago, Gybe Ho said:

So now the challenge is to just splice the dangling unconnected old AC2 wire into the AC1 cable just before that cable reaches the first mains socket.

 

Not having seen it, could you not spur off the back of the first mains socket, like they do in houses.

[Gybe Ho]

35 minutes ago, NB Saturn said:

 

Whilst you have in bits label every cable and make yourself a wiring diagram; it’ll save you having to re-work it out in 3 years time when you want to change something and can’t remember it.

 

I was tempted by a label maker that can print on shrink-wrap insulator sleave but then I converted the price into bottles of wine and thought overkill. It is surprising how many adhoc minor wires a boat acquires per decade. I am going to decommission the 12v domestic engine alternator and charge the lithiums via a 24v/12v DC/DC box attached to the starter motor 24v battery. Alternator wiring looms are black magic to me though I hope to eliminate a rats nest of wiring once the domestic 12v alternator is removed. Just hope my first trip down the cut won't be spoiled by an alarm warning me the non existent domestic alternator belt has snapped.

Edited July 6 by Gybe Ho

[NB Saturn]

5 minutes ago, Gybe Ho said:

 

I was tempted by a label maker that can print on shrink-wrap insulator sleave but then I converted the price into bottles of wine and thought overkill. It is surprising how many adhoc minor wires a boat acquires per decade. I am going to decommission the 12v domestic engine alternator and charge the lithiums via a 24v/12v DC/DC box attached to the starer motor 24v battery. Alternator wiring looms are black magic to me though I hope to eliminate a rats net of wiring once the domestic 12v alternator is removed. Just hope my first trip down the cut won't be spoiled by an alarm warning me the non existent domestic alternator belt has snapped.

 

I’ve got one of those labellers (Brady something or other) and I find I seldom use the shrink-wrap labels, the self=amalgamating ones are far more useful because they can be put on without having to have a cable end free. You could produce a similar result fora  lot less money with a cheap labeller from Amazon and some self-amalgamating clear tape over the top of it.

[Gybe Ho]

Just now, Tony Brooks said:

 

Not having seen it, could you not spur off the back of the first mains socket, like they do in houses.

 

A  good idea to investigate further. I have not pursued that so far because the supply for the second 240v socket is already daisy chained off the first socket. Maybe there is room to shimmy in another set of wires. We are not talking pukka 2.5 mm2 artic blue in the original boat builder fitout.

 

Ok I need to dive into the wardrobe again, it takes 40 minutes just to open everything up because a door latch, retro fitted by the previous owner, blocks removal of the wardrobe lower draws.

[TID Tug Tony]

I find these quite handy for labelling cables: https://www.cableties-online.co.uk/shop/cable-ties/length:100mm/width:2-5mm/colour:natural/marker-cable-ties.html

[Gybe Ho]

Money Spent:     £0.00

Fatal Electrocutions:     0

Watts Flowing: 1000

 

I initially investigated the @Tony Brooks idea of trebling up the terminal wires of the first socket by daisy chaining both the 2nd 240v socket and the immersion spur out of the 1st socket. This would involve the least labour. However I abandoned that when I found chunky looking 2.5 mm2 core mains cable soldered together to create a Boomer vintage ferrule and the solder looked a bit globby, all in all a robust connection for the second socket but not much space for a 3rd wire in the terminal.

 

After emptying the wardrobe to see where to mount the junction box linked to above I found the junction box for the 240v sockets on the other side of the boat. This had been an open mystery and seemed to offer an ideal point for the immersion spur.  Unfortunately working access was so poor I gave up and returned to the Tony idea.

 

After much careful wire stripping with the sharpest vegetable knife in the galley and some squashing of twisted wire with a small g-cramp (pliers are a long drive away), all three wires clunked into the terminal. The indicator light on the immersion is glowing.

 

The water is getting hot, thanks @Tony Brooks

 

That is a result for a Sunday, Swmbo would have mutinied if subject to cold off grid showers on the inaugural cruise.

 

Edited July 6 by Gybe Ho

[cuthound]

I would fit a timer to the immersion heater to eliminate the risk of it being left on.

[GUMPY]

6 hours ago, cuthound said:

I would fit a timer to the immersion heater to eliminate the risk of it being left on.

I always fitted something like This for my immersion heaters. Absolutely zero chance of leaving it on.