Electric Water Heater

[CapraIbex]

This is my first time spending the Christmas/New Year holidays in Buri Ram, and oh boy, it's freezing up here. My existing water heater at 3.5KW just doesn't cut it; the shower is awfully frigid, even turning down the water supply to a trickle. I require a powerful electric water heater with a decent flow of hot water to suit a Mitsubishi water pump model EP-255R.

Would an 8KW unit (MEX, Panasonic or Stiebel Eltron) be sufficient, or should I aim for a higher wattage?

[VocalNeal]

I believe 6kW will do it. 8 would be better as you can always turn down the heat.

[lopburi3]

Do you have electric power/wires to supply higher wattage units?  Current wire would likely only support up to 4.5 kw (which here in Bangkok is fine for coldest days - a lot warmer than 3.5).

[Crossy]

I would think a 6 or 8kW would suit most but ...

 

You may (almost certainly) need to upgrade your wiring to suit the larger heater.

 

EDIT If you really want skin-removal hot then consider an LPG heater but they do need to be installed correctly to avoid danger from carbon monoxide!

[KhunLA]

8k should be more than enough, and I had the Stieibel brand at our house in Udon Thani.  It was fine, even on those 10C days, though might have slowed the water flow a bit.   Ours did the whole house, and was more than a few meter (up to 10m) from outlets.  Mounted on outside wall, between pump and main bedroom.   Other bedroom at other end of 20m long house.

 

When not chilly out, be careful as you could easily brew a cup of tea.  All faucets had ability to mix hot/cold water.  Good brand and lived in house for about 6 yrs, no issues.

 

Had 2 Mazumas, elsewhere, and both were junk.  One dangerously so.

Edited December 25, 2023 by KhunLA

[sometimewoodworker]

42 minutes ago, VocalNeal said:

I believe 6kW will do it. 8 would be better as you can always turn down the heat.

I’m living between Udon and KK and our 6,000W heaters can give you a warm trickle, so absolutely don’t  waste money on a 6,000 and an 8,000 may be enough if you don’t want a very strong shower at 42C. You are likely to manage a normal power shower at 37C

[VocalNeal]

Recent observation. Flush the toilet when showering🤔

[CapraIbex]

1 hour ago, Crossy said:

I would think a 6 or 8kW would suit most but ...

 

You may (almost certainly) need to upgrade your wiring to suit the larger heater.

 

EDIT If you really want skin-removal hot then consider an LPG heater but they do need to be installed correctly to avoid danger from carbon monoxide!

The local sparky installed a "Haco" H6-40/1C C40 breaker dedicated for the existing water heater but I am unsure of sizes of wires he used and need to ask him. What are the recommended wire sizes for an 8KW unit?

 

[Sheryl]

Besides the wiring capacity may also need to consider if your water pump has enough power, especially if your shower is on an upper floor. These tankless point of use water heaters need  a certain water pressure to operate properly.

[sometimewoodworker]

There is one point that hasn’t been suggested yet and it will very much depend on your plumbing and house layout.

you can add a stored water heater.

 

The benefits are significant if your system can accommodate one.

• the problem is that you can’t raise the water temperature from under 20C or lower to a comfortable 37C+
• if you raise the incoming water to 25~30C you have no problem.
• the stored water heater can be your primary heater or supplementary heater 
• the supplementary heater can be turned off for the 10 months it’s not required 

our build has incorporated a hot supply that has never been developed due to laziness but would suit the above easily,

though heating the incoming cold would be simpler, just put the 2 inline and Bob is your mother’s brother!

[CapraIbex]

1 hour ago, KhunLA said:

8k should be more than enough, and I had the Stieibel brand at our house in Udon Thani.  It was fine, even on those 10C days, though might have slowed the water flow a bit.   Ours did the whole house, and was more than a few meter (up to 10m) from outlets.  Mounted on outside wall, between pump and main bedroom.   Other bedroom at other end of 20m long house.

 

When not chilly out, be careful as you could easily brew a cup of tea.  All faucets had ability to mix hot/cold water.  Good brand and lived in house for about 6 yrs, no issues.

 

Had 2 Mazumas, elsewhere, and both were junk.  One dangerously so.

 

1 hour ago, KhunLA said:

Stieibel brand at our house in Udon Thani

Which one did you use - STIEBEL ELTRON 8000W DHC 8EC or STIEBEL ELTRON 8000W DDC 8EC ?

[CapraIbex]

14 minutes ago, Sheryl said:

Besides the wiring capacity may also need to consider if your water pump has enough power, especially if your shower is on an upper floor. These tankless point of use water heaters need  a certain water pressure to operate properly.

According to the specification of my existing Mitsubishi water pump model EP-255R, the size is 250 Watt and a pump capacity is about 48 liters per minute. I think this should cover the lower as well as the upper floor.

[sometimewoodworker]

16 minutes ago, CapraIbex said:

Which one did you use - STIEBEL ELTRON 8000W DHC 8EC or STIEBEL ELTRON 8000W DDC 8EC ?

I can virtually guarantee there is no functional difference, it is just the form factor

[Crossy]

27 minutes ago, CapraIbex said:

What are the recommended wire sizes for an 8KW unit?

 

8kW at 220V is 36A.

Your 40A breaker should be fine, cable size would be 6mm².

Note: - If you already have 4mm² cable installed then, unless you have teenage kids who spend hours in the shower, that would (just) be OK.

[sometimewoodworker]

25 minutes ago, Sheryl said:

Besides the wiring capacity may also need to consider if your water pump has enough power, especially if your shower is on an upper floor. These tankless point of use water heaters need  a certain water pressure to operate properly.

While absolutely true, I can attest to the fact that they function with much lower pressure than is comfortable for a shower. 
 

I can throttle the pressure to a flow that is so low that it is virtually impossible to use it as a shower but can get 44C temperature.

[tgw]

I have this one and no problems so far

https://www.lazada.co.th/products/rinnai-nippon600mp-i407008817-s790524483.html

 

[ballpoint]

1 hour ago, Crossy said:

I would think a 6 or 8kW would suit most but ...

 

You may (almost certainly) need to upgrade your wiring to suit the larger heater.

 

EDIT If you really want skin-removal hot then consider an LPG heater but they do need to be installed correctly to avoid danger from carbon monoxide!

Don't worry. Install it incorrectly and the explosion and resulting fire will get you long before the carbon monoxide does.  But at least you'll be warm.

[lopburi3]

8 minutes ago, ballpoint said:

Don't worry. Install it incorrectly and the explosion and resulting fire will get you long before the carbon monoxide does.  But at least you'll be warm.

Actually it was the carbon monoxide that routinely killed uses during the cold season (when windows closed) and these were the standard option back in the 70's.  Don't recall any explosions but expect there were some fires in wooden buildings.  They did heat well - had to block 3 of the 4 burners during hot season.

Edited December 25, 2023 by lopburi3

[CapraIbex]

42 minutes ago, sometimewoodworker said:

There is one point that hasn’t been suggested yet and it will very much depend on your plumbing and house layout.

you can add a stored water heater.

 

The benefits are significant if your system can accommodate one.

• the problem is that you can’t raise the water temperature from under 20C or lower to a comfortable 37C+
• if you raise the incoming water to 25~30C you have no problem.
• the stored water heater can be your primary heater or supplementary heater 
• the supplementary heater can be turned off for the 10 months it’s not required 

our build has incorporated a hot supply that has never been developed due to laziness but would suit the above easily,

though heating the incoming cold would be simpler, just put the 2 inline and Bob is your mother’s brother!

Some time ago, I considered going for a solar-type stored water heater set-up to be plumbed into the existing system but couldn't find a suitable contractor. If I ever source a suitable solar storage unit and a schematic plumbing layout, then I'll bite the bullet and try to install the system by myself sometime in the middle of next year.

[CapraIbex]

2 hours ago, Crossy said:

consider an LPG heater but they do need to be installed correctly to avoid danger from carbon monoxide!

To avoid carbon monoxide poisoning, couldn't a LPG heater system be installed away from the house and insulate the pipework?

[lopburi3]

8 minutes ago, CapraIbex said:

To avoid carbon monoxide poisoning, couldn't a LPG heater system be installed away from the house and insulate the pipework?

We are talking point of use units and single output without mixing ability so control of temp is on unit within hand reach.  Most Thai homes use such and do not have hot water pipes.  

[KhunLA]

1 hour ago, CapraIbex said:

 

Which one did you use - STIEBEL ELTRON 8000W DHC 8EC or STIEBEL ELTRON 8000W DDC 8EC ?

That was 12 yrs ago, and nothing in photo albums of it.  Wife out at the moment, IF she has receipts somewhere, I'll look and see if it's noted.   That's a big if though.

Edited December 25, 2023 by KhunLA

[Sheryl]

2 hours ago, CapraIbex said:

 

Which one did you use - STIEBEL ELTRON 8000W DHC 8EC or STIEBEL ELTRON 8000W DDC 8EC ?

I had a similar problem and switched to Stiebel,  pretty sure DHC 8EC but cannot confirm as I'm away from home now. I discussed with Stiebel first about my needs and they made specific recommendation, you can contact directly on their website and they respond .

 

Since making that switch, no problems at all. I do see a difference on the coldest days in that I have to turn the heater up more than usual (on warmer days the higher  setting s are way too hot)  but at higher setting works just fine even on coldest days. These are good machines.

[CapraIbex]

1 hour ago, Crossy said:

Your 40A breaker should be fine, cable size would be 6mm².

Note: - If you already have 4mm² cable installed then, unless you have teenage kids who spend hours in the shower, that would (just) be OK.

My local sparky confirmed 6 sq mm cable size.
Would this cable size and the 40A breaker be suitable for a Stiebel Eltron DHC10EL 10,000 Watt unit?

[Crossy]

16 minutes ago, CapraIbex said:

My local sparky confirmed 6 sq mm cable size.
Would this cable size and the 40A breaker be suitable for a Stiebel Eltron DHC10EL 10,000 Watt unit?

 

10,000W at 220V is 45.5A your 40A breaker will probably go "click".

 

6mm² THW is rated at 48A in free air. It's on the line without taking into account any de-rating for environment. Probably OK for a shower heater.

 

It's also worth noting that if you have the "normal" 15/45 meter your heater alone will be using all of the rated capacity of your supply.

 

Are you sure you really need that much oomph?

[CapraIbex]

3 minutes ago, Crossy said:

Are you sure you really need that much oomph?

Actually, I am not. It's just so bloody cold up here... Anyway, the S/E 8KW unit seems less demanding on my electrical supply and I hope the new water heater makes a difference in combating the cold. Thanks for caution.

[CapraIbex]

44 minutes ago, Sheryl said:

These are good machines

Thanks for reassuring comment.

[sometimewoodworker]

Just now, CapraIbex said:

Actually, I am not. It's just so bloody cold up here... Anyway, the S/E 8KW unit seems less demanding on my electrical supply and I hope the new water heater makes a difference in combating the cold. Thanks for caution.

If you get a stored water heater it will still use the same amount of power BUT it will run at a much lower amperage just for much longer, so 2.5mm sq cable is ok

[bluejets]

 

13 minutes ago, sometimewoodworker said:

If you get a stored water heater

 

I've seen these run directly from a rooftop solar panel as well.

No inverter, connect direct to the dc from the panel.

A 250 litre would keep 2 people happy for days.

Edited December 25, 2023 by bluejets

[sometimewoodworker]

45 minutes ago, bluejets said:

 

 

I've seen these run directly from a rooftop solar panel as well.

No inverter, connect direct to the dc from the panel.

A 250 litre would keep 2 people happy for days.

That is certainly one reasonable way to power them. However a non electric version would probably be far more economical hear due to hot sun.