Hot water heaters for showers

[CaptainTyphoon]

Looked at a stiebel 6kw at Central in KSK today and on asking the price was told it was 'only for show' . I pointed at the slightly different 6kw stiebel adjacent and was told that was 'only for show' as well.

The girl was quite unfazed by my incredulous expression and probably went back to playing on her phone.

Time these places set sales targets, and fired non-performers and rewarded those that work. TiT

If anyone is still interested in this subject, I have now become a real expert, and I have learned that most of the information provided by the big box stores is garbage, and that the information provided here on this thread is also questionable, since it does not list any data references. Where are you people gettting your data? Out of your heads?

So, Stiebel Eltron does provide on its company site all the information you need to buy the right size heater.

Just please go to the site and find the graphs of data.

They will tell you how much each machine will raise the water temperature for a host of various flow rates.

But, says you. How do I know my flow rate?

This is easy, and you just need to use your own noggin, instead of not thinking.

What I did, I got 6 empty Coke Zero Bottle, which are 1.25 liters.

I then turned on the water, full blast and filled up the bottles one after the other for exactly one minute.

I measured 6,6 liters per minute of flow rate.

With this value, I looked at one axis of the table provided by the manufacturer for each size machine.

In my case, since I live in the Northern Part of Thailand, I will need to raise the water temperature from approximately 10 degrees in the winter time to about 35 degrees C.

In order to do this, when I have a flow rate of 6.5 liters per minute (which is not high), I will need about 10 to 12 Kilowatts of power.

Unfortunately, Stiebel Eltron only provides this size water heater in Phase 3 or with voltage of 380 to 440 volts.

Since I do not have access to this kind of power, and only have single phase, then I am up the creek without a paddle.

My solution will therefore need to be:

I have already bought the 8000 watt unit. But, if I want the water hot enough in the winter here, I will need to slow down the flow rate to about 4 liters or maybe less per minute.

For me, this is a hardship, because I like lots of water when I shower, and I like it hot.

So, now you know, and there should be no further uninformed questions or remarks here if you would just read my comment here, and also refer to the data clearly provided by every major manufacturer.

I am very happy to help you guys out.

No need to thank me, in fact.

Bye now......

I know you said no need to thank you but I will anyway! Just conducted my own experiment and, of course, you are correct.

Didnt feel the need to fill containers for 1 minute- 20 seconds was enough, just multiply by 3 obviously! The water flow was just over 8l/minute. The mains stopcock is in the bathroom which made it easy.

Turned it down to 3l which was enough for handwash etc, but not for my shower head. The minimum I can get away with is 5l. But-- at that flow rate, my water now heats to 45c whereas at 8l it only heats to 38c, which is about 10c above 'cold'. So in winter when the night temp outside drops to say 16c, then my shower will be 31c. Better but still equivalent to 'cold' water today.

Thinking a 'water-saver' shower head was the solution, I checked online. They boast proudly of operating at flows of 1.5gpm (6.75l), and those that are designed to operate at 5l get very poor reviews - and offer no improvement over my existing new 'premium but normal' shower head.

Seems no option other than turn down the flow rate as you say AND buy a more powerful heater than my Imarflex 4.5kw. My new 6kw is on order.

I hope that, at a 5l flow rate, it will raise the temp 20c on max- we will see.

You mention a flow rate of 4l - have you found a shower head that will work satisfactorily at that level- including washing long, thick thai hair?? (gf not me.)

And if all this seems a bit anal to other readers- sorry, but I dont enjoy cold showers!

Let me please expAND on this very important FLOW RATE issue:

And, let me choose the Stievel Eltron water heater, as an example.

Now, in Thailand, they sell an 8KW unit, that has a p/n ending in XG. And also they sell a few other 8KW models.\

When I last checked, ALL hot water heaters have a MAXIMUM flow rate of 10 liters per minute, for the multi point units, and probably also for the shower units.

What does this mean?

1. No matter how much water you are supplying to the heater, you can't have any more output from the machine than 9 or 10 L/min. 10 liters per minute is not much for me, and I like at least 15 liters per minute.

2. If you don't add cold water in a mixer to the water output from the 8KW unit, then the water will be too hot in the summer time.

So here is what you do:

I bought the -XG unit, which is 8KW and also has a rheostat instead of a 1 or 2 or 3 position temperature step switch.

For northern Thailand, to feed one shower that uses 6 liters per minute, you are going to need at least 10KW and maybe more. However, this is not possible unless you have 3 phase power, in most cases.

To make a long story short, I will use one 8 KW -XG heater, and then if I don't think the water is hot enough in the winter, I will buy another identical unit and I will mount them in parallel. This way, I can have up to about `12 or 15 liters per minute of hot enough water in the summer time, and about 9 liters per minute of 40 degree C water when the outside temperature is 10 degrees C.

Since most of you probably don't care this much about large amounts of hot water when showering, I suggest using the 8KW unit from Stiebel Eltron, but you will need to turn it down to about 4 liters per minute when the temperature dips to 10 C. You will still get 40 degree C water coming out of the machine, but at this reduced flow rate.

All this data you can easily get by looking at the spec sheets for each machine. I am just posting this here because most of what came before seems to me to be nonsense, or not based on science, which is the same thing.

REMEMBER: If you do get the multi-point units, these are designed for use with a water mixer. This is just a faucet assembly that mixes the cold water with the hot water and then it exits through one pipe output. Most of the showers in the world are like this. But, in Thailand, you will see just one pipe.

If you have two pipes coming out of the wall, then one feed will go to the cold side of the mixer, and the other will go through the water heater, and then to the hot side of the mixer. (This is of course obivious. But my POINT IS that if you are mixing cold water with the 9 liters per minute maximum flow from the Eltron unit, then you can have a higher total rate of 9 + however much you can add without bringing the temperature down below what you need for a comfortable shower.)

Conclusion:

1. Make sure you get a machine with enough Wattage at the outset so that when winter rolls around you still will be comfortable.

2. Make sure you check the heater's temperature control. If the machine does not have a fine gradation rheostat, and only a step switch, then you will need to add cold water to make the fine temperature adjustments. You do this with a mixer. OR, if you have plenty of water flow, then you can adjust temperature just by turning the cold water valve leading to the heater.

3. It is always handy to have a thermometer, and a large 6 or 10 liter bottle to measure you flow rates. And, I measured with and without the shower heads. If you have a shower head that will not let enough water through, obviously you need to change it.

4. I found that the people who sold me the machine do not have a clue about anything relating to the water heater, but that was just the people I spoke with.

Here is an example: One nice young lady INSISTED that the smaller version of the machine I had chosen had 4 liters of water entering the machine, and 2 liters of water exiting the machine!

I asked her, and how long will this circumstance persist?

She said, as long as you have the machine turned on and showering, you will have 4 liters of water going into the machine per minute, and 2 liters per minute of hot water coming out!!!!

I said, do you mean that this machine will act like an infinite balloon that will keep expanding to hold the 2 liters per minute of water stuck in the machine that is not coming out?

She INSISTED that this was true. She said, Look at the Specs Stiebel Eltron provded me. 4 liters in, and 2 liters out

Apparently, she chose to believe what she THOUGHT the specs said, RATHER than using any form of scientific logic.

I mention this here only to show that you need to use your own science based logic, and take what is said with a grain of salt, particularly if anything said goes against grade school physics that you should have learned at some point in your life.

[CaptainTyphoon]

Consider an alternative solution. Install an insulated tank, say 1000 liters, which SHOULD be enough for shower. Heat this water prior to your needs. Now, rather than water at 10*, the inflow will be 25* which will then be further heated to 37*, or whatever you choose. Yeah, tank needs gravity flow to heater, unless small pump also installed, and some plumbing valves and pipes.

I did mention, before, the hot water tank, about 10 gals, which is NOT continuous flow. With this method the inflow water temp is immaterial. Dial up 40*, wait some mins, get 40* hot water. If water near freezing, must wait longer. Would also mention that in the colder weather, fewer showers are generally needed. And further mention that the hotter is the shower water, the more possible 'damage' to skin, mostly removal of natural oils, which hastens dry skin, itchiness. etc.

Your solution is much more expensive, and also a waste of time and metal and energy to keep that tank of water hot.

As I stated above,

You can use two 8 KW heaters in parallel with 4 liters per minute of water passing through each of them.

In winter time, if the input water temp is 10 C, the output will be about 50 C.

That is plenty hot enough in winter to dry up your oils.

Edited September 9, 2014 by CaptainTyphoon

[CaptainTyphoon]

Seems no option other than turn down the flow rate as you say AND buy a more powerful heater than my Imarflex 4.5kw. My new 6kw is on order.

I hope that, at a 5l flow rate, it will raise the temp 20c on max- we will see.

You mention a flow rate of 4l - have you found a shower head that will work satisfactorily at that level- including washing long, thick thai hair?? (gf not me.)

And if all this seems a bit anal to other readers- sorry, but I dont enjoy cold showers!

1.5 gpm would be 5.67 lpm....and they work exceptionally well.

Thanks- my mistake. Maybe the US Gallon at 0.83 Brit gallon, is the only US thing smaller than UK equivalent??!! 555

Spent a while browsing the large range of shower heads in Baan & Beyond today- the concept of flow rates though is certainly 'Beyond' the knowledge of their staff.So no luck yet. Some of the low flow heads achieve apparent power by adding air- but not sure that adding cold ambient air would help achieve hotter water, only use less water.

beau thai

If you went to House and Tomorrow, then you should know what I am talking about. They know not much about flow rates or physics of any kind.

BUT, your stated 4.5 KW unit is too low power for a good shower in winter, and even for me in the summer time.

I think you are living in North Thailand, and so my advice and the Eltron advice is to use a machine with at least 8 KW of power if you plan on using 4 to 5 liters per minute in the winter time.

The price is definitely worth the extra money, and I thought the Eltron is a good machine.

I bought a XG this second time, with 8KW of power.

Happy showering.

Edited September 9, 2014 by CaptainTyphoon

[Benjie]

Couldn't you run two water heaters, use one normally for the Summer and when it gets cold get it to preheat for another? That or storing water underground to keep it warmer.

[sappersrest]

Remember when uprating a shower heater from 4.5 kw the existing cable may not be the correct size ,4.5kw should be ok with a 2.5mm cable .But a 8kw heater will require a 6mm cable.

please find link that provides a useful calculator http://www.doncastercables.com/technical-help/

[beau thai]

Couldn't you run two water heaters, use one normally for the Summer and when it gets cold get it to preheat for another? That or storing water underground to keep it warmer.

Interesting idea- thinking outside the box. Thanks!

[beau thai]

Remember when uprating a shower heater from 4.5 kw the existing cable may not be the correct size ,4.5kw should be ok with a 2.5mm cable .But a 8kw heater will require a 6mm cable.

please find link that provides a useful calculator http://www.doncastercables.com/technical-help/

Thanks- I bought a 6kw and that is a useful warning. I'll check it out.

[CaptainTyphoon]

Couldn't you run two water heaters, use one normally for the Summer and when it gets cold get it to preheat for another? That or storing water underground to keep it warmer.

Interesting idea- thinking outside the box. Thanks!

Outside OR Inside the box, does not really matter if one is just plain wrong, and here is why:

When you install these two water heaters in line, one after the other, then each machine will reduce the flow rate, and so you will probably not have enough water output from the second machine. There are water resticters in each machine which reduce the flow, and so when you add the two together, you just will not have enough water, considering that the water pressure in most places is usually inadequate.

THIS IS WHY I ALREADY suggested that the BEST FIX for this, if you have two machinese is to:

Use them in PARALLEL.

And, use two of the same wattage machines.

If you do this, you can turn down the flow rate for each machine from about 6 liters per minute down to 4 liters per minute, or even 3 liters per minute, and still have 6 to 8 liters of total output.

ALSO, when you reduce the flow rate down to 4 or 3 liters per minute, for each machine, then the water temperature rise will almost double from about 20 degree rise to 40 degree rise, if you are using 8KW units.

These values I stated here are all variable depending on your actual setup.

\

HOWEVER, the idea is that you must use the two machines in parallel, and NOT IN SERIIES!!!!!!!!!

Got it?

Don't worry, it is not really a very intuitive concept if you are not an engineer and no knothing about water heaters.

I am NOT A PLUMBER!!!

[CaptainTyphoon]

Couldn't you run two water heaters, use one normally for the Summer and when it gets cold get it to preheat for another? That or storing water underground to keep it warmer.

No, you can't really do this and expect good results for the reasons I outlined just now.

But using two machines IS a very good idea.

You just should not connect them in series,

You SHOULD connect them in parallel.

Then, you will have plenty of water volume, or rate of flow,

AND, the temperature will also be high enough.

Happy Showering, as I said before.

[edgarfriendly]

would appreciate any first hand experience with gas showers.

Particularly those available in bkk

[BillyBobThai]

Here is an interesting setup.

[JDGRUEN]

I have a SolarHeart water heater on the roof,had it for 20 years,it was

expensive at the time,but I am quiet sure it has paid for its self,basically

maintenance free,even at cold times like now the water gets hot with

just a couple of hours of sun,in summer it gets scalding hot.

It works in showers ,bath,and have hot cold at sinks in kitchens,most

likely the best money i ever spent,they are quite expensive now at

around 200,000 bht.

regards worgeordie

I agree with worgeodie.... and I add for others to read ---- Small 'do it yourself' solar heater or solar preheat assist systems can be made and installed... especially if a person just wants a hot shower. There are many many examples on youtube. My favorite is a coiled tube/hose - dark colored outside - just hung on the wall if the wall is facing south... or use a recycled satellite dish -- coil the tubing and pipe into the cold water inlet of your shower.. Or just for an experiment run pipe and mount a second shower head in the shower or a back porch / outside shower to demonstrate the effectiveness. A cold water mixer may have to be installed because the water will be so hot.

I am in a rental unit -- upstairs flat in Ao Nang... older place. The shower water heater runs fine on sunny days - plenty of hot shower water and poorly - not very warm water on cloudy days ... I checked the pipe routing - sure enough - outside two floors up to my flat on the south west wall... One cloudy rainy day and the water is very lukewarm - sunny day - damned hot. And this effect is only an accident of where the guy routed the pipe and how he did it... Just think if it was planned out (as I described above) ... perhaps with a small insulated storage container. There are many many designs - DIY - I advise anyone who is a bit of a handyman to go check it out ... Google/Bing Youtube... Use your imagination

Yes - one might have to get a bit more sophisticated - add pressure relief valves - mixer valves to keep from scalding yourself, etc. but it can be done and for not a lot of money. And you save gas and/or electricity cost.

[sappersrest]

My son uses solar heating to heat his hot water, great system cost around 55k for a 3 bedroom 3 bathroom house, first class installation.As he is younger than me he should recoup his money.

[AnotherOneAmerican]

And, do you like to lift those heavy 18 kilogram bottles?

And what about when you drop one of them on your toe, with its sharp circular edge at the bottom of every bottle.

No, my days of lugging around bottles is at an end, and good riddance to heavy bottles, says I. ((The higher quality gas burners are expensive, and almost the same as the electric, with the one I used costing about 9000 Baht for one hot enough to run a single shower in the winter time with enough flow rate for my comfort.))

Never touch the gas cylinder, delivery man does it all, no extra charge.

15Kg currently costs 380bht, delivered and installed

[CaptainTyphoon]

And, do you like to lift those heavy 18 kilogram bottles?

And what about when you drop one of them on your toe, with its sharp circular edge at the bottom of every bottle.

No, my days of lugging around bottles is at an end, and good riddance to heavy bottles, says I. ((The higher quality gas burners are expensive, and almost the same as the electric, with the one I used costing about 9000 Baht for one hot enough to run a single shower in the winter time with enough flow rate for my comfort.))

Never touch the gas cylinder, delivery man does it all, no extra charge.

15Kg currently costs 380bht, delivered and installed

380 is a VERY GOOD price.

[CaptainTyphoon]

Here is an interesting setup.

That is very interesting!

Does that run on coals?

Or, wood?

I had not thought of doing that, where I used to live, but it would have worked.

If you have plenty of wood around your house, then this should be plenty for long hot shower.

You just need to worry about scalding yourself if you boil the water in that tank!

[Duke007]

I read through hundreds of postings on various sites but can anyone just help explain a few basic facts about an electrical water heater to be used in a single shower?

1)In the first photo, can the blue cold water pipe be connected directly to the heater inlet port? I see model heaters that have a flow restrictor knob just at the heater inlet port (as in photo 2). Is this just a matter of what model heater you buy?

2) In the second photo, a hotel system, how is the plumbing connected? I mean both water flow knobs seem to provide the same function of regulating how much water enters the heater