8000W Water Heater for Rain Shower

[edogthong]

I'm in dire need of some good advice from you guys since I don't really trust the local 'professionals' when it comes to electricity. I've read all I could find in here relating to my little planned project. There's a lot of good advice in here and I've picked up a thing or two, especially from Crossy, hat's off to you!

 

I'm thinking of installing a Stiebel DDH 8EC 8000W Multi Point Water Heater in my bathroom. The plan is to run pipes to the nearby bathroom sink and also through the wall to the kitchen sink. The main purpose of the heater however would be for a 12" rain shower. So 3 points in total and they're all close to each other. I won't be using more than one at a time most likely. 

 

The existing wiring into the bathroom is a 2x2.5/2.5 cable running through the ceiling to a 32 amp circuit breaker. My plan is to do away with that cable and instead run two 10sq.mm. cables (on the outside of the house) and replace the 32 Amp CB with a 40 Amp one. I also want to stick a 240 cm copper grounding rod into the ground and connect it to the the Water Heater with a 6sq.mm. copper cabel.

 

Since the shower faucet has two inlets (hot and cold) and my water pressure is very good, I'm hoping this should be sufficient for a comfortably warm rain shower?

 

I'm grateful for any advice I can get. Cheers!

Edited February 24, 2020 by edogthong

[fruitman]

There's rain showers and rain showers...but from a electric heater you won't get much warm water like what i would call a rainshower.

 

But compared to the small showerheads used in thailand it's still much better to have a rainshower. 

 

I use one with only cold water and have special taps and pipes to give me a great flow.

[Crossy]

You don't really need 10mm² cable for an 8kW (36A) heater, unless the run is very long, 6mm² will be more than adequate.

 

Even the existing 32A breaker will likely be fine unless you like 2 hour showers, but I'd go up one size anyway.

 

You already have earth leakage protection so you're good to go.

[sometimewoodworker]

5 hours ago, edogthong said:

The main purpose of the heater however would be for a 12" rain shower. So 3 points in total and they're all close to each other. I won't be using more than one at a time most likely. 

 

The existing wiring into the bathroom is a 2x2.5/2.5 cable running through the ceiling to a 32 amp circuit breaker. My plan is to do away with that cable and instead run two 10sq.mm. cables (on the outside of the house) and replace the 32 Amp CB with a 40 Amp one. I also want to stick a 240 cm copper grounding rod into the ground and connect it to the the Water Heater with a 6sq.mm. copper cabel.

 

Since the shower faucet has two inlets (hot and cold) and my water pressure is very good, I'm hoping this should be sufficient for a comfortably warm rain shower?

Your current breaker is oversized for your current wiring, 2.5mm should be on a 20A. http://www.crossy.co.uk/wiring/Circuit types.html

 

the maximum draw of your heater is just over 36A at the nominal PEA voltage (34A MEA) so your 10²mm cable are oversized as is the breaker but certainly enough. 6²mm and 32A would be sufficient on a dedicated circuit as you will virtually never be using/be able to use the full 8kW.

 

@fruitmanis incorrect in saying that you won’t get much warm water, while the total flow at higher temperatures will not match that which can be provided by a hot water tank, at lower flow rates you can certainly get over 40^oC, probably even in the cold season, 

 

The challenge is to get high flow, warm enough water with the large shower head you plan. If you reduce the head size you will have no problem at all
 

With smaller rain shower heads (7” 9 l/min) I am getting full pressure maximum flow 38^oC water and lower flow 44^oC at the moment, I don’t actually monitor the inlet water temperature but it is probably at 25^oC now. We have 6kW heaters.

 

So how warm is comfortably warm? How much flow do you want? What is you incoming water temperature? 

Edited February 24, 2020 by sometimewoodworker

[fruitman]

3 hours ago, sometimewoodworker said:

So how warm is comfortably warm? How much flow do you want? What is you incoming water temperature? 

So you consider 38 celcius water to be a warm shower? 

 

And the reason for a rainshower is to have much water spread widely, isn't it?

 

We have heated showers as well with an xl showerhead but the flow is very small if you want the water to be warm. You'll get used to it but it's never like in europe where we have gas powered water heaters.

 

 

[Metropolitian]

10 hours ago, edogthong said:

The existing wiring into the bathroom is a 2x2.5/2.5 cable running through the ceiling to a 32 amp circuit breaker. My plan is to do away with that cable and instead run two 10sq.mm. cables (on the outside of the house) and replace the 32 Amp CB with a 40 Amp one. I also want to stick a 240 cm copper grounding rod into the ground and connect it to the the Water Heater with a 6sq.mm. copper cabel.

In addition to Crossys and Woodys reply:

 

You don't need to put another grounding rod as there is already one as the feed for that can be seen coming out below of the consumer unit.

 

For earthing to the bathroom, if you got new wires 2x6m2 for the feed to the heater, you can use the 'old' 2x2.5/2.5 cables as earth feed by combining those wires together.

Just make sure in the consumer unit wrap the wires from this cable together with green (or if available green/yellow) tape and vice versa at the heater.

 

[Metropolitian]

For the sparks here, have a look at photo of the Chang fuse/main-breaker outside.

How is man supposed to easily replace the fuse if blown. And that behind the life wire (note the red tape).

Looks like the utility wires was originally mounted on the ceiling and after some renovation work wall mounted.

[bankruatsteve]

The Chang switch looks OK to me - seems like it would have been better inside though.  What I find strange is the tap in to the mains.  Where do they go after that?  And the meter on the wall.  Maybe an apartment complex?

[sometimewoodworker]

7 hours ago, fruitman said:

10 hours ago, sometimewoodworker said:

So how warm is comfortably warm? How much flow do you want? What is you incoming water temperature? 

So you consider 38 celcius water to be a warm shower? 

 

And the reason for a rainshower is to have much water spread widely, isn't it?

 

We have heated showers as well with an xl showerhead but the flow is very small if you want the water to be warm. You'll get used to it but it's never like in europe where we have gas powered water heaters.

The questions were addressed to @edogthong as he was asking the original questions so it’s his opinions that are important in this thread.

 

However yes I consider 38^oC to be warm at the moment, but it will be hot soon, no I don’t consider “the reason for a rainshower is to have much water spread widely”  but water from a rain shower head. You may prefer a torrential shower, I prefer a gentle rain. If you want a gas powered water heater you can get them reasonably easily here.
 

I am thankful that the weather hear makes any desire for the temperature of water that you seem to prefer something that is strictly limited to a couple of weeks.

 

[edogthong]

Thanks for all the replies! To answer a few of your questions; I live in one of four "units" in Surathani. So the cables you see are going to the others. My unit is at the far end, closest to the water pump and tank which has constant shade. I measured the water temperature throughout the day and it seems to be just about the same as the air temperature. (28° now at 8 o'clock in the evening). I haven't had the chance to check the temperature in early morning yet. I'll do that tomorrow. 

 

If I could constantly get a minimum of 40° from my shower, I'd be happy. I'd be willing to go down to a 10 inch shower head if I had to in order to get the desired temperature. I like quite a good amount of water pressure but I can make do with a gentle rain shower on an extra cold day. The faucet I'm planning to buy comes with an 8 inch rain shower head so I guess I'll see how that performes first before I decide what to go for. 

 

So after reading and taking heed of all your advice, my new plan is:

1. Switch from a 32 to a 36Amp breaker. 

2. Run two 6sq.mm. cables from the new CB to the water heater.

3. Twist the (pictured) wires of the old cable together, mark it with green and yellow tape at both ends and use it as a grounding wire.

 

Should I run the cables separately on the wall or attach them to the existing cables in the picture? (I'm probably showing my ignorance here) Rest assured that I will not actually connect anything before having it all inspected by people more knowledgeable than myself, including the Thai owner (who I think did the original installation). Also, if anyone could tell me why there's a steel wire sticking out from my wall, I'd be grateful. Picture is included. Maybe it doesn't mean anything but it's been bugging me.

[sometimewoodworker]

14 hours ago, edogthong said:

I measured the water temperature throughout the day and it seems to be just about the same as the air temperature. (28° now at 8 o'clock in the evening). I haven't had the chance to check the temperature in early morning yet. I'll do that tomorrow. 

 

If I could constantly get a minimum of 40° from my shower, I'd be happy. I'd be willing to go down to a 10 inch shower head if I had to in order to get the desired temperature. I like quite a good amount of water pressure but I can make do with a gentle rain shower on an extra cold day. The faucet I'm planning to buy comes with an 8 inch rain shower head so I guess I'll see how that performes first before I decide what to go for. 

With heaters that are 2kW less than yours and these shower heads together with water supply that is slightly cooler than yours we are getting 40^oC full pressure full flow from both.

 

The pressure isn't the governing factor it is the flow that is important. The Hafële rain shower is limited to 9 l/m.

If you get a shower head that will put through 20 l/m you will have cold showers

Edited February 26, 2020 by sometimewoodworker