How much power for water heating

[PaulRainbow]

Not the intention to warrant a response like this really.

How would you classify my response ?

As i see it, it's a perfectly civil post, just correcting some of your errors.

About the kettle. Read it again. I said that “or more”
And I’d also just insist that a 2000w element…requires 2000w…the size of the tank or the length of time it takes to heat it, is a another subject to ponder over all together. Just stating the facts ! He can have all the batteries he likes…but if the inverter isn’t able to produce a continuous output in line with the requirements of the element to power it…I don’t need to state the obvious result.
All the best.

If you were just quoting facts i would not have corrected you.

As for inverters and batteries, the OP is asking about a power pack, combined battery and inverter. Both of his suggested power packs have had sufficient power to run the typical 1kw calorifier, just not enough or barely enough capacity though.

 

[westernman]

The only sensible way to heat water for a shower on a boat, is either through mains shore power, through a calorifier hooked up to the engine cooling circuit or through the boats diesel fired central heating system (if you have one of those).

Diesel drip feed heaters, such as Dickinson or Reflex, can also be fitted with a coil to heat up water. This would be your most fuel efficient way of getting hot water.

A calorifier hooked up to the engine cooling circuit with a mains powered heater element is pretty standard equipment these days.
You will heat a decent amount of water in no time when running the engine - and you can recharge the batteries at the same time.
On my boat 20 minutes of running time with the engine is plenty. It will stay warm enough for a couple of hours.

Then in the marina, you can leave it hooked up to shore power and have hot water available all the time.

Heating water through batteries is extremely demanding for the batteries, and then you need to run an engine or generator to recharge the batteries. Just use the engine to directly heat the water - much quicker and more fuel efficient.

 

[QBhoy]

How would you classify my response ?

As i see it, it's a perfectly civil post, just correcting some of your errors.



If you were just quoting facts i would not have corrected you.

As for inverters and batteries, the OP is asking about a power pack, combined battery and inverter. Both of his suggested power packs have had sufficient power to run the typical 1kw calorifier, just not enough or barely enpough capacity though.

I think I’ll just bow out. Clearly one of those occasions that there is no point arguing. You haven’t corrected me in any way shape or form. What I said remains factual and to the point. My original comment had no intention or designs of being aimed at any particular individual, nor did it intend to start a silly tic for tac.
Best we leave it at that.

 

[Alex_Blackwood]

I think I’ll just bow out. Clearly one of those occasions that there is no point arguing. You haven’t corrected me in any way shape or form. What I said remains factual and to the point. My original comment had no intention or designs of being aimed at any particular individual, nor did it intend to start a silly tic for tac.
Best we leave it at that.

Perhaps the OP could fit one of these.
5 TUBE MINI SOLAR WATER HEATER - SOLAR PANELS ONLINE

 

[noelex]

When at anchor and not using the engine, there are better ways of heating shower water than using the traditional calorifier.

The best is a small insultad container with a dedicated pump and shower rose. This can be retrofitted to most boats. Hot water can be made using electricity, solar, gas, diesel or a combination of these methods. This is mixed to the desired temperature. Only the water that is needed is heated. There is little insulation loss. No water is wasted waiting for the water coming out of the rose to become hot enough. No need either to keep adjusting the right hot and cold settings, so the shower is also more pleasant.

Using this system a reasonable shower for one can be produced using around 400Whrs (less if it can be mixed with water heated by solar, even in reasonably cold climates). Thus the solar generators mentioned have enough energy for a very generous shower for a couple. If you cannot charge the solar generator you will at least have the option of gas. You will need to use a kettle that is within the inverter’s maximum rating, but these are available. A vacuum insulated kettle will help improve efficiency.

 

[thinwater]

For a shower on a boat, what's the point of heating water to higher temperature than needed and then adding cold water to cool it to usable temperature? Different in a house situation with long pipe runs and associated losses.

The codes in the UK,Canada, and US are all 60C minimum. Legionella primarily (codes like this are based on real experiences and in this case, real deaths). 50C minimum had been the standard, but never as low as 40C. Also, a tank with hotter water delivers more gallons of useable water.

It was never about piping losses.

 

[Graham376]

The codes in the UK,Canada, and US are all 60C minimum. Legionella primarily (codes like this are based on real experiences and in this case, real deaths). 50C minimum had been the standard, but never as low as 40C. Also, a tank with hotter water delivers more gallons of useable water.
It was never about piping losses.

There are no codes whatsoever stating what temperature water has to be heated to on a UK leisure boat. The UK "code" (we don't often use that term) you most likely refer to under the building regulations, concerns IIRC cold water storage temperatures.

P.S. Just checked specification for our home domestic water heater temperature range, 40 - 60 degrees centigrade so, where do you get your (wrong) figures from?

 

[penfold]

Why would you treat a boat as different to a dwelling? Legionnaire's will kill you regardless of where you get it from. HSE says; tank must be 60+ and taps 50+

Check flow and return temperatures at calorifiers. Outgoing water should be at least 60 °C
............................................
Monthly checks should be carried out and findings recorded

The water temperature should be at least 50 °C within one minute of running the water

The water supply to the TMV should be at least 50 °C within one minute of running the water

 

[Graham376]

Why would you treat a boat as different to a dwelling? Legionnaire's will kill you regardless of where you get it from. HSE says; tank must be 60+ and taps 50+

I'm at an age where something is going to kill me before too long anyway so, the thought of highly unlikely Legionnaire's just doesn't figure, can you point me to any leisure boat deaths due to it in hot water systems? From memory, cruise boat and landside deaths have been due to air conditioning plants cooling water, not heating it. Heating the tank to 60 degrees, just to add cold water to it for a shower, is just a waste of energy and money as far as I'm concerned, just like filling a kettle for one cup of tea/coffee. You do it your way, I'll do it mine.

 

[QBhoy]

Oh my goodness ?‍

 

[Graham376]

Why would you treat a boat as different to a dwelling? Legionnaire's will kill you regardless of where you get it from. HSE says; tank must be 60+ and taps 50+

Why, when we are discussing boats, do you quote HSE requirements in workplaces?

Have you lived aboard a sailing boat for extended periods on mooring or anchor? I would be interested to hear how you maintain hot water at 60 degrees.

My experience is that it's quite possible to heat to that temperature but then the generator, engine or inverter is turned off. After the initial few litres of water has been run off and tank/calorifier is topped up with cold, it's obviously below 60 degrees but it's use continues until too cold.

 

[westernman]

Why, when we are discussing boats, do you quote HSE requirements in workplaces?

Have you lived aboard a sailing boat for extended periods on mooring or anchor? I would be interested to hear how you maintain hot water at 60 degrees.

My experience is that it's quite possible to heat to that temperature but then the generator, engine or inverter is turned off. After the initial few litres of water has been run off and tank/calorifier is topped up with cold, it's obviously below 60 degrees but it's use continues until too cold.

Each time you get it up to over 60C, you kill off everything.
If you never heat it to over 40-50C, then eventually the bad bacteria will proliferate in ever larger numbers.

 

[Graham376]

Each time you get it up to over 60C, you kill off everything.
If you never heat it to over 40-50C, then eventually the bad bacteria will proliferate in ever larger numbers.

I'm not disputing what you say or the theory of it. What I do dispute is the practicality and even impossibility for most (excluding marina dwellers with 24/7 power) of achieving it. The doomsayers will no doubt be convinced that our cold-water tanks which can be 25+ degrees in summer must be full of nasty bugs but, the water tastes fine

 

[BabaYaga]

When at anchor and not using the engine, there are better ways of heating shower water than using the traditional calorifier.
The best is a small insultad container with a dedicated pump and shower rose. This can be retrofitted to most boats. Hot water can be made using electricity, solar, gas, diesel or a combination of these methods.

This sounds like a very good idea, for showering.
But I don't think that was the OP's intention. He mentioned hot water on tap for washing up and asked if a high capacity power bank could run his water heater in order to provide this for weekends onboard during the winter season. (He also said he was prepared to take the power bank home every day for charging, so presumably he also showers at home).
I believe the answer to his question is yes, provided that he is willing to accept the very high cost, the 20 kg weight and a water temperature of only 40 degrees C or so. One condition would be that the wattage of his existing water heater is not too high.
The smaller of the two power banks mentioned, the Anker, is reviewed here:
Anker 757 PowerHouse Battery Review: Crazy Fast and Powerful
According to the specs the AC output is 1500W (surge 2400W). The tester claims to have powered a +1200W room heater with no issues.
The battery capacity is 1229 Wh. As I mentioned in an earlier post the energy required to heat 20 litres of water by 30 degrees is in theory around 700 Wh, so there should be enough energy stored in the power bank, with some margin.

Regarding the Legionella issue, it seems the bacteria thrives at 35-40 degrees, so maintaining water at that temperature is clearly not a good idea. But the OP's intention, as I understand it, was to heat the water and then use it in one go. As soon as the power bank is switched off everything should cool off. Sounds like rather low risk to me.

 

[noelex]

This sounds like a very good idea, for showering.
But I don't think that was the OP's intention. He mentioned hot water on tap for washing up

You may be right. Perhaps the OP can chime in.

Personally, we wash dishes in cold water without any problems, but the thought of cold or even lukewarm showers is a hardship we would rather avoid.

 

[westernman]

I'm not disputing what you say or the theory of it. What I do dispute is the practicality and even impossibility for most (excluding marina dwellers with 24/7 power) of achieving it. The doomsayers will no doubt be convinced that our cold-water tanks which can be 25+ degrees in summer must be full of nasty bugs but, the water tastes fine

Dead easy to achieve.
Run the engine for 20 minutes.

Just to be clear, you just hook up a water tank like one of the following to your engine cooling circuit (available in different sizes, with different features etc etc).

Make boating enjoyable - VETUS

 

[luke collins]

What about a small water to water heat pump. Will run at around the 1/3rd of the cost of direct electric element. May cost 3-4 k however fitted.

 

[PaulRainbow]

Still think it's ok to heat water to 40c

The risk of Legionella at sea | Martek Marine

https://www.jabscoshop.com/files/Standard CWARM Instructions - 3 bar zpwl6.pdf

https://www.jabscoshop.com/files/Standard CWARM Instructions - 3 bar zpwl6.pdf

Lorry driver's death could be linked to Liverpool ferry journey

There are endless articles online warning about water temps, anyone who ignores them is pretty foolish IMO.

 

[westernman]

There are endless articles online warning about water temps, anyone who ignores them is pretty foolish IMO.

Particularly when it is so easy to get up to 60C temperature.

On the hook, every two days at least I need to run the engine for an hour or so to recharge the house batteries.
That is plently to get the water tank up to well over 60C.

You don't need to maintain permanently that temperature - but heating to that temperature from time to time to kill all the bacteria is highly desirable.

 

[roaringgirl]

Thanks - it's never really enough to tackle the washing up and leaves a lot of water vapour in the air - I guess I need to check the wattage of the immersion heater and/or look for a larger battery bank

Sorry if I'm teaching grandma to suck eggs. We live on board, we boil the kettle in the morning (1.5ltr) and put the boiling water in a pump-top thermos flask that is permanently mounted in the galley next to the sink. We make tea and coffee from it during the day. For washing up, we half fill a mug from the hot water flask, add a squirt of washing up liquid, then top up with cold. The washing up sponge is dipped in the mug to clean the things and then we rinse with cold from the galley tap. Washing up a meal for a family of 4 normally takes 1 mug.

I should also add that heating 1L of water by 80°C takes 334.4kJ.

1 (12V) Amp hour is 43.2kJ.

Boiling a litre of water will therefore take 7.7Ah. The power of the heater will just determine how fast it will heat the water.

NB all the above figures do not take any account of efficiency losses.