Help with bathroom electricals

[MrDetUdom]

Hi. I'm new to this forum :)

 

The builder has just finished our house, and a couple of points of the wiring are a disaster. The biggest problem is the bathroom (room with only bath and shower area). This is a tale of woe.

 

We wanted a single water heater with the output split between the bath and shower (the outlets for the bath and shower are only around 50cm apart), but the builder told us it was better to have two separate heaters, and thinking that the builder knew what he was doing, we went with that.

 

So now, our bathroom has a single 20A circuit (at the breaker board) running on 4mm2 wire to the bathroom, where it branches (branch is in the ceiling) to a 4.5kW shower heater and an 8kW bath heater. Both of the water heaters are installed inside the shower area at chest height. There is also a separate 40A breaker attached to the 8kW unit (also in the shower room and with absolutely no water-proofing measures). I'll try to draw a schematic:

 

     Breaker box (20A breaker) ------- Branch (inside ceiling)  ----------------- 40A ELSD breaker (chest height inside shower area) ------------ 8kW water heater (Fujika FS-80)

                                                                               \-------------------------4.5kW water heater

 

Naturally, this arrangement scares the crap out me.

 

So, I'm going to rewire it, but I have some questions. I looked through similar posts but didn't really understand everything.

 

First, my plan is to remove the 4.5kW heater completely, and move the 8kW unit higher up so that the bottom is about 2m up on the wall. Next, I will remove the existing wire and replace with larger diameter. Finally, I will use a larger circuit breaker in the breaker box. So the questions are:

1) Will 6mm wire be sufficient for the 8kW unit? I think the next size up is 10mm

2) There are two spare 32A breakers in the breaker board. Can I use one of these, or will I need to replace one with a 40A breaker? Are the "slots" in the breaker board made for specific amps, or can I switch out a 32A breaker for a 40A breaker without any problems?

3) I think I will have to keep the 40A standalone ELSD breaker, but I want to move it out of the bathroom altogether. Are there any issues with placing it right next to the breaker box, or does it need to be physically near the water heater. (There is a location half-way between the circuit breaker box which is at the front of the house and the bathroom which is at the back that would make a great sub-breaker location)

4) Is it worthwhile to try and install some kind of waterproof plastic box covering the water heater? I was thinking of a plastic box with a door for access to the unit, and then using silicon sealant around the edges. The only problem I see with this is if steam condenses inside the box, it could actually make it more dangerous.

 

Thanks in advance :)

[bankruatsteve]

1)  6mm2 should be OK but 10mm2 would make the conservative folks happier.

2)  Replace with 35-40 amp.  You didn't specify your box but breakers can usually switch out no problem.

3)  Unless it is likely to get wet there would be no need to move it.  If you do, make sure it is easily accessible.

4)  Is that a multi-point heater?  Not usually installed on the shower wall from what I have seen.  The steam can (will) be an issue tripping the RCD.  Should just follow installation guide lines otherwise.

 

[MrDetUdom]

Thanks for reply.

 

52 minutes ago, bankruatsteve said:

3)  Unless it is likely to get wet there would be no need to move it.  If you do, make sure it is easily accessible.

Yeah, it absolutely will get wet in it's current position. Unfortunately, we don't really have any easily accessible places to move it to without using conduit on the walls. Brand new freshly painted walls, so I don't particularly feel like grinding a channel into them to run wiring for an ELSD. I am planning on putting a small cabinet for wifi router at ceiling level in the main room, so I could put it in there. It would just require a small step ladder to access. I guess that's not too inaccessible.

 

52 minutes ago, bankruatsteve said:

4)  Is that a multi-point heater?  Not usually installed on the shower wall from what I have seen.  The steam can (will) be an issue tripping the RCD.  Should just follow installation guide lines otherwise.

 

Yes, it is multi-point, and yes, it should never have been installed on the shower wall. We had a perfect space for installing it, but the builder concreted that space up for some unknown reason. We also had a last-minute redesign of the house after the builder built a wall in the wrong spot, and so we can't even really move the heater into any of the adjoining rooms either. The only alternative to on the wall above the shower (or above the bath) is on the exterior wall of the house in some kind of weather-proof enclosure.

[bankruatsteve]

Another option is to just ditch the "ELSD" (not sure exactly what that is) and replace the breaker in your CU with a 40 amp RCBO..

[MrDetUdom]

ELSD = RCBO (Earth Leakage Safety Device. That's the term the Thai's used for it, but looking up the GB standard number on the net, it's listed as an RCBO). I didn't know you could get them to fit inside the CU. That is by far the easiest option for me.

[bankruatsteve]

Sounds like you have a good plan.  If you're not sure about your CU, take a photo with the lid off.  And be sure to replace the circuit with minimum 6mm2 cable (as it seems unlikely you would ever push your heater to the full 8KW - that would be really HOT water).  So, you need to re-route the hot water PVC/pipes also, yah?  A photo would help for that also.

[MrDetUdom]

Yeah, I'm going to need to do the pipes too. Here's a pic. I should have included it from the start. When the builder first showed me with a huge pride grin on his face, I couldn't tell if he was genuinely proud of this monstrosity or if he was taking the piss. For reference, I'm 180cm and my eyes are about level with the tops of the heaters.

 

The left side is the bath. The right side is the exterior wall. The room beyond is a bedroom. The chest-height wall you can kind of see on the left side is about 10cm thick. The outlet from the hot water goes through that to the taps for the bath. The power cables run down through the wall from the ceiling, so I'll be able to drill through to get access higher up and move the heater up. The heater I'll get rid of is on the right, the one to keep on the left. But, I'll move the one to keep over to the right side. (The kids love splashing in the bath, so better to move it over to the right side). Although the idea of moving it to the external wall outside the house is kind of appealing. When I've used this kind of water heater before, it didn't

 

I was half considering building a false wall half-way up to conceal the pipes, or maybe just make a protruding box-shape that runs across the shower  and can double as a shelf.

[thequietman]

On 9/19/2017 at 11:20 AM, bankruatsteve said:

Another option is to just ditch the "ELSD" (not sure exactly what that is) and replace the breaker in your CU with a 40 amp RCBO..

Forgive me but what does CU stand for?

[bankruatsteve]

13 minutes ago, thequietman said:

Forgive me but what does CU stand for?

Consumer Unit.  Breaker Box.  Distribution Board.  IE: the place where the mains come in and distribute via circuits (breakers) to the household.

 

[BEVUP]

I would just raise the left one should be higher enough to avoid the splashes from the kids

Do you have spare tiles

I also see you already have a circuit breaker there so just copy up the wall for the sake of your bath tap outlet to just follow it & then just put in your shower preferably with a "Y" piece

So you will end up with a hole from the R/H power after the cables have been disconnected & a spare cold water tap on the R/H side 

[MrDetUdom]

Thanks for your help guys. I will post before and after pics when I get around to it. However, I started looking closer at how my breaker box is wired, and I think I'm going go have to fix that first (or maybe at the same time). I'm going to post a new topic because that seems to be a bigger issue.