Hot Water in new house with 3 bathrooms

[Cashboy]

I am in the process of building a house in a village in Isaan.

Here is a floor plan of the 1^st and second floors.  I show this so you can see the distances of the bathrooms and kitchen sink in relation to possible hot water supplies (i.e. boiler, water heaters and shower heaters).

 

 

I still have to order a mains supply to the new house.  I understand that the normal standard mains supply is single phase 50 Amp.

There will be 3 bathrooms (all with a shower, no baths) and one sink in the kitchen.

The old house has a 15 Amp mains supply and not even an electric shower in the house and I have got used to cold showers.

Ideally it would be nice to have the possibility of hot water in all the bathrooms and the kitchen sink.

I have looked specifically at Stiebel and see that they offer:

Boilers:  2,000W heating 15 litres to 100 litres

Water Heaters:  6,000W to 12,000W

Shower Heaters: 3,500W to 6000W

I also believe that due to lack of water pressure and flow to the house, I will require a cold water tank outside on the ground and pump out of the tank to the house.  I shall have the option of manually switching off the supply and by-passing the tank and pump (using stop cocks) in the event of an electric power cut so that there is at least cold water to the downstairs bathroom and sink.

Questions:

1)      Is a Water Heater basically the same as a shower heater but without the shower kit; i.e. you plumb cold water supply into it and then come out with a hot water supply to a shower and basin and kitchen sink say?

2)      What do you consider sufficient watts for a shower to give an adequate shower as they appear to range from 3,500 watts to 6,000 watts?  I have been showering with cold water in Isaan to date.

 

 

 

[Crossy]

1) Sort of. A water heater will (should, TiT) be of the "multipoint" type, you can safely put a tap on the output and feed many outlets. A "shower heater" will be vented via the shower head in the event of a fault causing the heater to stay on, closing the outlet will cause something of a bang. The extra safety features are why multipoint heaters are rather more expensive.

 

2) Depends where you are. Most consider 3,500W "adequate" during all but the coldest spells, but even here in BKK our 6kW was struggling to give me the blast of hot water I require to get started at 4.30AM (I have one of those jobs) during the recent chilly spell. If you're "up north" get the biggest your supply will take, you can always turn it down.

[Cashboy]

26 minutes ago, Crossy said:

1) Sort of. A water heater will (should, TiT) be of the "multipoint" type, you can safely put a tap on the output and feed many outlets. A "shower heater" will be vented via the shower head in the event of a fault causing the heater to stay on, closing the outlet will cause something of a bang. The extra safety features are why multipoint heaters are rather more expensive.

 

2) Depends where you are. Most consider 3,500W "adequate" during all but the coldest spells, but even here in BKK our 6kW was struggling to give me the blast of hot water I require to get started at 4.30AM (I have one of those jobs) during the recent chilly spell. If you're "up north" get the biggest your supply will take, you can always turn it down.

Thank you for clarifying the technical difference between a water heater and shower heater.

 

I gather that the Thai mains electric supply is only 50 amp.

I am thinking that if I use 6,000 watt showers or water heaters that is 6,000 watt / 220 volt => 27 amp.

 

Regarding the consumer unit:

If I connect two of the showers to the 80A 30mA RCD am I ok   ( 2 No 27 Amp) = 54 Amp ?

The mains switch is 100 Amp so can cope with (3 No 27 Amp = 81 Amp)

 

The fused isolation switch is 60 Amp with a 60 Amp cartridge fuse:

It is very unlikely that all showers / water heaters will be on at the same time and certainly not more than 10 minutes I would assume.

 

Would this be safe or would I expect the 50 amp fuse in the isolation switch to blow?

 

 

 

 

 

 

 

 

Edited January 31, 2018 by Cashboy

[Crossy]

7 minutes ago, Cashboy said:

Would this be safe or would I expect the 50 amp fuse in the isolation switch to blow?

You'll need to demonstrate to Mr PEA that you won't overload the supply. Many will be happy with a 60A fuse, ours wasn't happy with the original 63A MCB and insisted on a 50A being fitted (the 63A is back in now).

 

Are 50A fuses in that size available? If so I would buy a few (OK one).

 

As to the CU wiring, both showers on one RCD will be fine even if both on together.

[Cashboy]

16 minutes ago, Crossy said:

You'll need to demonstrate to Mr PEA that you won't overload the supply. Many will be happy with a 60A fuse (ours wasn't and insisted on a 50A MCB).

 

Are 50A fuses in that size available? If so I would buy a few (OK one).

 

I would put each 6000 watt shower / water heater on a 32 Amp MCB in the consumer unit

2 of those would be on a 80 Amp 30mA RCD, the third on the other 80 Amp 30mA RCD

The 60 Amp Wylex isolation switch would be the bottle neck and think the fuse would blow after 1 hour and hopefully before the government meter burns out.

Edited January 31, 2018 by Cashboy