Splicing mono core shower cable

[LivinLOS]

Note I am not any kind of electrician but neither am I an idiot, basic cable runs, jointing, etc I can likely do tidier than the average 'hack' with a light up screwdriver !!
 

So this weekend this happened. The safety cut did not pop while electrical fire poured out the side and the circuit burnt itself out before the shower cut kicked in. The house trip did not trip !!

Pulled the unit to find that it had burnt in a block connector in the unit before the trip block. The fact that the house trip didn't blow is a big concern and subsequent testing showed this isnt on the bedroom trip (unsure which is it on). This will be investigated !!

Purchased a new 6kw unit yesterday and discovered that the existing mono core cables are 10cm too short to meet the 'input' block. This units input block is mounted way 'down' in the unit needing 30cm of free cabling.

I have no desire to recable the house so need to extend the cable 10cm plus. I don't have a crimp tool (obviously can get one) and I am not sure that crimping solid core is the right way anyway ?

6Kw is apparently 27 amps.. I was going to get a 30 amp screw terminal and heat shrink it in ?? The rest of the internal connections are screw terminal so am I safe in assuming that mono core wire and screw terminals are 'safe' for 30 amp ? This would be better than a well executed / tidy twist, solder, and heat shrink ??

Then I will be finding out why the house didn't cut and where (if any) this circuit is trip protected. Shockingly I have a suspicion that the bed/bath combo is on a circuit but the higher voltage shower may have been wired with only the house main trip !!! Nice !! Certainly the image for shower on the trip box does not correspond to the shower unit and did not pop. Once rewired I will have to have someone better than me come and investigate where this is connecting. 

[Crossy]

If you have space the black TB-25 screw connectors are better than choc-blok. They are 25A but are fine for your shower, there are 45A ones available but unlikely in the retail stores.

 

 

If you must use choc-blok strip the wires long enough that both wires pass under both screws for a better connection.

 

Do check where your heater is fed from, it's not at all unusual for the "installer" to splice into the incoming supply bypassing all your Safe-T-Cut etc. protection ???? 

[LivinLOS]

Just now, Crossy said:

If you must use choc-blok strip the wires long enough that both wires pass under both screws for a better connection.

that was my intention.. 

I thought the block terminal safer as I can likely find heat shrink large enough to hold it all.. Hence provide some water proofing. 

Less so for the above terminal. Theres no 'water proof' version of that is there ??

[Crossy]

1 minute ago, LivinLOS said:

Less so for the above terminal. Theres no 'water proof' version of that is there ??

 

True, if it's likely to get damp then choc-n-heatshrink would work ok.

[LivinLOS]

Well its not 'likely' to get wet, but I am trying to over think it. 

Once installed than there will be an investigation into what trip circuit is is behind and why it didnt pop. 

[LivinLOS]

last q.. 

 

Am being told that 6kw should be 4mm single core.. Is that a real need or overkill, looking at the internals of the unit it does not look that heavy gauge inside after the initial connection block. 

[Muhendis]

2 hours ago, LivinLOS said:

that was my intention.. 

I thought the block terminal safer as I can likely find heat shrink large enough to hold it all.. Hence provide some water proofing. 

Less so for the above terminal. Theres no 'water proof' version of that is there ??

Word of caution.

Those Choc-Block connectors are not as sturdy as they used to be. Tighten the screws too much and the bottom of the receptacle will split leaving a weak connection.

[LivinLOS]

Just now, Muhendis said:

Word of caution.

Those Choc-Block connectors are not as sturdy as they used to be. Tighten the screws too much and the bottom of the receptacle will split leaving a weak connection.

Which is why I asked about twist and solder.. But I have no experience of joining higher amp use.. Plenty of low voltage data transmission type stuff. 

 

[MajorTom]

Nothing is better than a soldered connection. If you have the equipment and know how to do it.

Soldering two 4mm2 cables will require some serious heat. Not sure if an iron intended for PCB/electronics will do the job.

And its not easy to do this on the wall. Would require something to hold it together while heating and so on. Unless you have 3 or 4 arms that can hold it still.

If you try, its easy to check if its done correctly. You should be able to pull that cable apart and it would not snap at the soldering point.

 

Do not use anything less than 4mm2 on 6kw. The fact that internal conductors sometimes look slimmer can be due to different materials in insulation/conductor (higher temp class) and/or internal protection.

[LivinLOS]

Just now, MajorTom said:

Do not use anything less than 4mm2 on 6kw.

Worried the existing in wall cabling isnt up to it.. 

[MajorTom]

9 minutes ago, LivinLOS said:

Worried the existing in wall cabling isnt up to it.. 

Ahh. The supply cable in the wall is 2,5mm2?

It will most likely never be a problem unless you shower continuously on maximum heat for several hours.. But its not exactly by the book. 27A is a borderline for high end 2,5mm2 wiring.. In perfect conditions.

[LivinLOS]

I am unsure.. but looking at it it looks and feels like single strand 2.5mm single core. 

 

 

[BritManToo]

35 minutes ago, LivinLOS said:

Worried the existing in wall cabling isnt up to it.. 

I'd either do a 'twist' connection or use a busbar (cut to size) ........ depending on accessibility to existing wires.

https://www.lazada.co.th/products/i1623204777-s4460638141.html

https://www.lazada.co.th/products/i2782755804-s10125819774.html

https://www.lazada.co.th/products/ylt-terminal-i2381371761-s8082394375.html

Edited February 28, 2022 by BritManToo

[Muhendis]

Firstly: The size of single core is not too difficult to check.

             2.5mm² = 1.8mm dia.

             4.0mm² = 2.25mm dia.

 

Secondly: If you can get your hands on a crimping tool, make the joint with in-line crimp terminals. Your local electrical shop should have them.

 

https://shopee.co.th/Tool-House.ay-SO-8209-14-Cold-Pressed-Terminal-Crimp-Pliers-5.5-8209-14mm²-17-8209-6-AWG-Crimper-for-Bare-Terminals-i.441559148.6293909588?sp_atk=6032389a-518e-4164-8958-c3538ff5e339

 

https://shopee.co.th/✨PTPTRATE✨50pcs-Insulated-Straight-Butt-Connectors-Electrical-Crimp-Terminals-Assorted-Kit-i.105906226.1678686016?sp_atk=2a3ae28e-89ba-4572-ba40-5c4cbde59855

 

[KhunBENQ]

My experience with "choc-blok" (control box for deep well pump)

Even proper twisting and putting a cap on is better than these.

 

[LivinLOS]

Just now, KhunBENQ said:

My experience with "choc-blok" (control box for deep well pump)

Even proper twisting and putting a cap on is better than these.

 

yeah leaning to a capped heavy twist.. 

Busy today.. look at it tonight or tomorrow

[Crossy]

6 hours ago, LivinLOS said:

Which is why I asked about twist and solder.

 

If you can do a decent inline twist and solder it (you need a big iron [>100W] to get a good joint) then add heatshrink that should be good to go.

 

6kW on 2.5mm² is definitely marginal (do you have teenage girls?), probably OK on a shower for "normal" usage.

[LivinLOS]

14 minutes ago, Crossy said:

6kW on 2.5mm² is definitely marginal (do you have teenage girls?), probably OK on a shower for "normal" usage.

No but I shave in the shower which does take that bit more time

[Crossy]

1 minute ago, LivinLOS said:

No but I shave in the shower which does take that bit more time

 

You'll be fine, I can shave far, far more rapidly than my teen grand-daughter takes in the shower.

[sometimewoodworker]

9 hours ago, Crossy said:

If you have space the black TB-25 screw connectors are better than choc-blok. They are 25A but are fine for your shower, there are 45A ones available but unlikely in the retail stores.

 

 

 

Just a FWIW the various sizes of those connectors are usually available in one of my local big stores, so it maybe a regional thing.

[Yellowtail]

1 hour ago, Crossy said:

 

You'll be fine, I can shave far, far more rapidly than my teen grand-daughter takes in the shower.

I can walk the the barber shop and get a haircut and a shave and walk home before my boy is out of the shower...

 

Does the length of the run not factor in some? 

 

 

[sometimewoodworker]

4 hours ago, Crossy said:

 

You'll be fine, I can shave far, far more rapidly than my teen grand-daughter takes in the shower.

Do thoughts of random delay shower circuit contactors flipping off then auto resetting after a suitably long period make me an apprentice Dr Evil?????

[captainjackS]

I'm really interested to know how this shower is connected into your breaker box.   Maybe we can add it to the list of unbelievable electrical installations and use the example for future troubleshooting reference. I had a contractor once who connected his extension cord leads to the house main incoming leads (before the main breaker) with the CU cover off. He believed that his electric welding gear would work better if the power came from before all the safety devices.  While he was away I removed it, installed a 60฿ plug on his cord and plugged it into a 16A receptacle that was behind a 16A MCB and the main RCD.  His tools worked fine. job got done and no one died.  another day in paradise!

[Crossy]

8 hours ago, Yellowtail said:

Does the length of the run not factor in some? 

 

It does from a volt-drop perspective, it doesn't affect safety but excessive drop will reduce the power available to heat your water.

[bankruatsteve]

21 hours ago, LivinLOS said:

Pulled the unit to find that it had burnt in a block connector in the unit before the trip block. The fact that the house trip didn't blow is a big concern and subsequent testing showed this isnt on the bedroom trip (unsure which is it on).

An electric fire is almost always due to a loose connection which has caused arcing and not likely to trip RCD or MCB.

Edited February 28, 2022 by bankruatsteve

[bluejets]

2 hours ago, bankruatsteve said:

An electric fire is almost always due to a loose connection which has caused arcing and not likely to trip RCD or MCB.

Exactly....which is why the Op's "investigation" may well reveal <deleted> all.