Water heating questions - answers please

[damdna]

Hey y'all.

 

I wondered if anyone has any experience they can share to solve my problems.

 

I live aboard and have an emersion heater for my hot water but this only gives me a tiny amount of hot water, even after being on for hours. After a day of boating, I have enough boiling hot water to shower several people and wash dishes...but not while stationary - a few hours of engine tick over doesn't give me that much hot water either. So I'm contemplating fitting an electric water heater, either above my sink or below it, to ensure daily hot water for cleaning, washing up etc. Does anyone know of a suitable heater they know works and gives out constant hot water that's hot enough to clean with? I'm trying to avoid LPG powered heaters, hoping that leccy heaters will be relatively easy to fit. I've been looking at the Screwfix website and they stock some decent powerful heaters.

 

Any suggestions/experience/ideas? 

 

Many thanks.

 

Jonathan

[David Mack]

And how are you going to power your electric water heater?

Edited October 22, 2018 by David Mack

[damdna]

I'm hooked up to power here on the marina. Could I use something like this? https://www.screwfix.com/p/redring-rp10-8e-bathroom-water-heater-10-8kw/70888

[David Mack]

Only if your mains connection can provide 40+ Amps.

[bizzard]

Have you checked the emersion heaters thermostat adjustment, if it has one. The element might be completely lime scaled up, but they usually burn out when that gets bad.

[Momac]

A low wattage immersion heater in the calorifier should do the job .

[Chewbacka]

Your supply is probably a max of 16amps maybe less.  So you can’t go much over 3kW. But if you are also using shorepower for things like tv, laptop or phone charging, hair drier or fan heater as well as your fridge, then you will have to manage what is on or off or you will overload it.  You can get sink tap heaters, including some with a few litres of storage, but this is just for sink use.  A shower is probably going to need 8kW or more for a reasonable flow.

[Jen-in-Wellies]

What size is the calorifier? Is it a horizontal, or vertical mounted one? Where is the immersion heater fitted in it? Where do the engine coolant coil pipes go in? I ask because some designs of calorifier have immersion heaters that will only heat the water right at the very top of the tank. Similarly with coils from the engine circuit. To heat a large volume of water they need to be low down so convection currents will circulate the water within the calorifier.

 

Jen

Edited October 22, 2018 by Jen-in-Wellies

[alan_fincher]

4 minutes ago, Chewbacka said:

A shower is probably going to need 8kW or more for a reasonable flow.

Yes, that theory is pretty well backed up by the fact that maximum output from a Morco D61 gas water heater is around 9.4KW.

These provide an adequate shower, unless the inledt temperature of the water is very low, but when it is it is not a spectacular shower.

Most marina power supplies, as has been said are unlikely to be more than 16 amp, so limited to not much over 3.5kW.  That really wouldn't be enough for sufficient flow and temperature rise for a proper shower.

[Phil Ambrose]

I don't know of or indeed have never seen a Calorifier that has the immersion heater anywhere other than the top

Phil 

[Jen-in-Wellies]

11 minutes ago, Phil Ambrose said:

I don't know of or indeed have never seen a Calorifier that has the immersion heater anywhere other than the top

Phil 

I used to have a vertical cauliflower with the immersion boss about half way down the side. Needed a short heater to not hit the other side. Don't know where the current one is asthe boss is still buried under the insulation.

Edited October 22, 2018 by Jen-in-Wellies

[damdna]

Thanks so far, everyone.

 

The calorifier is vertically mounted, I've upped the water temperature on the dial in the top where the emersion heater enters. So yes, I guess it's only heating the uppermost water. Hmmm. And it's only been in the boat for 5 years - enough time for fittings to fur up?

 

As for the electric water heater, yes our leccy is 16 amp, so that limits the heaters I could use? I can always ensure nowt else is on when washing up and I only shower on board while cruising (such is the luxurious quality of our facilities here... ?) so I only need the water for cleaning. 

[rusty69]

......and mine is down the bottom (unless I installed the thing upside down!)

[Alan de Enfield]

6 minutes ago, Jen-in-Wellies said:

I used to have a vertical cauliflower with the immersion boss about half way down the side. Needed a short heater to not hit the other side. Don't know where the current one is asthe boss is still buried under the insulation.

Our's is vertical with the immersion half-way down (or up) the side

 

 

[David Mack]

The boss may be in the top of the calorifier, but what mattters is where the bottom of the heater is. On that is long enough to reach almost to the bottom will heat all of the water.

Do you share your 16A shore bollard with other boaters? And is the wiring behind it up to lots of boaters all drawing 16A at the same time? Might be better to aim for a slightly lower power heater.

[alan_fincher]

22 minutes ago, Phil Ambrose said:

I don't know of or indeed have never seen a Calorifier that has the immersion heater anywhere other than the top

Phil 

Here is ours....

[mrsmelly]

5 minutes ago, Alan de Enfield said:

Our's is vertical with the immersion half-way down (or up) the side

 

 

Ours is vertical and a fair big size with immersion at the bottom so oooge quantities of hot water when on shoreline.

[Chewbacka]

5 minutes ago, damdna said:

Thanks so far, everyone.

 

The calorifier is vertically mounted, I've upped the water temperature on the dial in the top where the emersion heater enters. So yes, I guess it's only heating the uppermost water. Hmmm. And it's only been in the boat for 5 years - enough time for fittings to fur up?

 

As for the electric water heater, yes our leccy is 16 amp, so that limits the heaters I could use? I can always ensure nowt else is on when washing up and I only shower on board while cruising (such is the luxurious quality of our facilities here... ?) so I only need the water for cleaning. 

The immersion heater is a long loop so will heat water for the length of the heater, so ideally it will be long enough to extend at least 2/3 of the way down the tank.  Of course the longer the heater the more water will be heated (which is good) but the more there is to heat the longer it will take.  Domestic ones tend to be 3kW whereas boats ones tend to be only 1kW so again much slower

[damdna]

Ok. I left the heater on all night (by accident) and it still only gave me a few seconds of decently heated water before running cold. That's when I resolved to put it out there re the heaters on this forum. While we're here...can anyone recommend anyone near the West Midlands who can come and remove and replace some radiators? I have large, old cast iron numbers that need taking out and replacing with bog standard rads but I'm a student nurse and not a heating engineer so I need help. ? 

Edited October 22, 2018 by damdna

[Jen-in-Wellies]

1 minute ago, Chewbacka said:

The immersion heater is a long loop so will heat water for the length of the heater, so ideally it will be long enough to extend at least 2/3 of the way down the tank.  Of course the longer the heater the more water will be heated (which is good) but the more there is to heat the longer it will take.  Domestic ones tend to be 3kW whereas boats ones tend to be only 1kW so again much slower

There are 2kW immersions around, which could be a good compromise between the more weedy 1kW and the 3kW that is near the 16A limit. If it is mounted at the top of the OP's vertical corifier pointing down, then one as long as possible, without hitting anything inside would give the most hot water. There is something wrong with the system they have as the boats round here with immersions on shore power have lashings of hot water available.

[rusty69]

Can you not measure the resistance of the immersion element to determine if its knackered?

[damdna]

1 minute ago, Jen-in-Wellies said:

There are 2kW immersions around, which could be a good compromise between the more weedy 1kW and the 3kW that is near the 16A limit. If it is mounted at the top of the OP's vertical corifier pointing down, then one as long as possible, without hitting anything inside would give the most hot water. There is something wrong with the system they have as the boats round here with immersions on shore power have lashings of hot water available.

Yup. My neighbours all have tons of the stuff while I'm here boiling a jam kettle to get enough to do some serious moppin (No G) and wash a bachelor's range of dirty dishes. The jam kettle creates a veritable waterfall of condensation too. 

Just now, rusty69 said:

Can you not measure the resistance of the immersion element to determine if its knackered?

Can I? Me personally? No. But I could explain the use, contra indications and side effects of most common medications. Any help? ? 

[philjw]

1 hour ago, damdna said:

 

I live aboard and have an emersion heater for my hot water but this only gives me a tiny amount of hot water, even after being on for hours.

Has it been like this since you have had the boat or got worse?  It does seem that there is a problem with the immersion or the wiring to it. Do you have a meter and the knowledge to use it to safely test the element as suggested by Rusty?  Maybe someone who knows could post up expected readings for known good / bad elements? Are you sure that the immersion is being directly powered from the shore line and not via an inverter?

Edited October 22, 2018 by philjw
spelling

[Chewbacka]

You need someone meter to measure the resistance of the heater or a clamp meter (which is better) to measure the current.

 

A 1kW heater will take about 3 hours to heat 55litres of water by 50c.  So presumably you are waiting long enough?

 

added - ignore bottom bit! Just saw even after all night no water.  So either the thermostat or heater is busted, assuming the electric supply is sound.

 It’s all guessing without using a meter to check volts across the heater and current drawn. 

 

 

Edited October 22, 2018 by Chewbacka

[WotEver]

1 hour ago, Chewbacka said:

either the thermostat or heater is busted, assuming the electric supply is sound.

Yup. First check is that the element is getting power. If it is then it needs replacing.