Small electric water storage heater

Waterpup

Hi all
I currently have a gas water heater. Its small, cheap to run and water is always boiling hot. But, its also very dodgey so I'm 90% swaying to replacing it with an electric water storage heater.

My neighbour, who luckily is a gas engineer tested it and strongly advised to not use gas and kindly offered to install an electric water heater for me. I only need enough hot water a day for one shower and to wash dishes. He recommends an "unvented 15L water heater". My question is, is 15 liters enough for a shower?! From what I have researched a shower uses 40-60 litres of water. How do these things work? Would the hot 15 liters be streamed in along with a separate equal amount cold stream from the mains?!

Sorry I sound like a simpleton. As with all boats, space is limited, hence why I'm not getting a 100L tank! Thanks in advance for any help or experienced knowledge

molerat

15l tank heater described as "for use with hand wash basins and small sinks" so most certainly no good for a shower. It can be used multi point and with a mixer tap but you will use more than 15l for a shower. The 2kW element will not recover as you are using so will end up with a cold shower. https://www.screwfix.com/p/zip-ap3-15-electric-water-heaters-2kw-15ltr/3531t

An instantaneous electric water heater but can your system take 9kW ? https://www.screwfix.com/p/strom-seih9kts1-touchscreen-instantaneous-water-heater-9kw/8526p

Gas can easily supply the amount of hot water you need on demand without big wires.

matelodave

We've got a caravan with an 8 litre hot water storage heater and yes, you can get away with it for a shower, we can just about manage two BUT you have to use it properly.

Our shower has a low flow Eco-Camel shower head which limits the flow to 5-7lpm and is fed by a mixer valve from both the cold and hot supply so you've got around 16 litres of water at showering temperature = 2-3 minutes.

You get in, wet yourself all over, including your hair, shut the shower off, wash all over with soap and shampoo your hair, then turn the shower back on to rinse it all off.

You can have a more than adequate shower so long as you don't stand in it it for ages

We've got an EcoCamel indoors as well and I can shower in around 90 seconds, including washing my hair. My wife takes around 3- 4 minutes for her shower as she's got a lot more hair than me which takes more rinsing out.

Why not replace the gas boiler with another one - leccy will probably cost your more to run than gas.

System

When my boiler was replaced last year, an engineer from the manufacturer turned up in a small van with some parts for the installer. Inside the van was a full sized gas boiler with a hot water cylinder and piping for an external shower head. The van is used for on-site training for installers. I was told that that engineer is also a very keen mountain biker and he uses the van to shower after each mountain bike ride.

It's amazing what you can get in a small space.

EachPenny

Is your boat at a permanent mooring with mains electricity? If not you'll need to make sure your boat's electricity supply (generator/inverter?) is capable of running a heater with the output you need, on top of whatever other electrical equipment might be in use at the same time.

matelodave

If it's on a mooring then most of them are limited to 16amp = 3.8kw or even less, although some 32amp supplies are around = 7.6kw. So you'd have to be a bit wary of boiling a kettle, using a hair-dryer or other sort of high wattage device unless you turn the hot water off.

We've managed to trip the site supply a couple of times by turning stuff on and forgetting about the heating/hot water.

Waterpup

Thanks all.
The boat is moored all year round in one spot (apart from days out), hot water not required on the move. Its always on the land mains which gives 15amp, we've never had a trip, seems to be good for general use and I've had power tools running before.

A few incidents have left me uncomfortable with using gas atall, several surrounding boats have replaced with Diesel/ electric systems. The word seems to be gas + boats dont mix :undecided

I have just thought if I can get a horizontal heater I could buy a bigger tank though and stash it under a bunk

matelodave

Dunno what sort of boat you've got but have you thought about a calorifier, something like this - http://www.youboatmarine.com/cwarm-50-litre-horizontal-calorifier-water-heater-2147-p.asp other makes and sizes are available. Lots to choose from here https://www.asap-supplies.com/domestic-water-supply/calorifiers-water-heaters-fittings/calorifiers

You could plumb it into the engine and have hot water on the move, or just use the immersion when moored up. You could also heat it using a hydronic diesel heater (Eberspacher , Webasto etc).

What sort of heating has the boat got?

Waterpup

I use a wood burner, there's a Diesel Eberspacher on board which I don't use.
The water heater needs to be independent of the boat engine entirely and the eberspacher.

As far as I can tell that leaves my options as a new gas water heater, an electric storage heater (30L+) or an instantaneous electric water heater but limited to 3kW.. Any idea how hot that could be? I know it wont be boiling hot but I'd settle for warm..

matelodave

A 3kw instantaneous hot water heater would be useless for showering - most are only just about capable of producing lukewarm water for hand washing through a spray nozzle to reduce the flow. They produce around 2lpm

Even a 9kw instantaeous shower can be a bit pathetic at this time of the year. You have to reduce the flow to a very low level to get it somewhere near hot enough.

A calorifier doesn't have to be connected to the engine, you could just use the immersion heater - it's only a hot water tank like you get indoors with a posh name. They are just smaller with a lower capacity to fit in boats and RVs and so command a premium as there aren't so many sold.

If you want to go electric then you'll need to store a sufficient amount of hot water to be able to shower - it's up to you to decide how much you'll need.

I'm guessing that you've got an instananeous gas heater at the moment.

Waterpup

Ah, no 3kw then.

Whats the difference between a calorifier and an unvented water heater? If any.

Yes I have a Rinnai 58e. Its old, the gas isn't extracting out of the flue properly and the pilot light either goes out when in use or blows (a terrifying moment mid shower) which left me wedging the ignition on to continue use. I no longer use it. Gas is perfect for boiling water, but I don't feel confident with the tiny things that could go wrong and be fatal. The distance between the gas bottle and the water heater is 30ft, alot of piping that could spring a leak at some point without me knowing