Electric shower

[JaneP]

Hi folks. Just wondering if there is any such thing as a low power drain electric shower suitable for use on a narrow boat when not on mains power? We’ve got an 1800watt inverter. 
Sorry if this is a completely mad idea, I’m just curious to know if there is. 
 

thanks 

Jane 

[GUMPY]

Daft idea heating water with electric.

Most electric showers are up in the 9kW area.

[Psychalist]

Domestic ones are getting on for 10kW. If you could stand less than 1/5th of the temperature of a domestic one it might be technically doable, but I'm not aware of anything. Even 1.8kW is going to cane your batteries.

[Tony Brooks]

Just now, Loddon said:

Daft idea heating water with electric.

Most electric showers are up in the 9kW area.

 

I suppose the closest would be an instant gas water heater, but in winter the shower might be a bit cool and then there is the BSS implications to consider. I think, as Loddon, a non-starter on a boat.

[JaneP]

10 minutes ago, Tony Brooks said:

 

I suppose the closest would be an instant gas water heater, but in winter the shower might be a bit cool and then there is the BSS implications to consider. I think, as Loddon, a non-starter on a boat.

Thanks for your replies. We currently have an instant gas water heater, a new one just installed to replace a very old one. We’re having some issues with it, yet to be resolved related to getting the sink taps and shower to trigger the ignition.  We’re thinking a new after pump with better flow rate may work. It just crossed my mind to ask if there was a boat-suitable elec shower available. 

[Tony Brooks]

2 minutes ago, JaneP said:

Thanks for your replies. We currently have an instant gas water heater, a new one just installed to replace a very old one. We’re having some issues with it, yet to be resolved related to getting the sink taps and shower to trigger the ignition.  We’re thinking a new after pump with better flow rate may work. It just crossed my mind to ask if there was a boat-suitable elec shower available. 

 

Would you by any chance have a low flow rate shower head. Have you checked the strainer that is usually close to the pump inlet is not clogged and that there is no obstruction between tank and pump. Are the taps clogged with limescale by any chance and what size are the tap connections. The reason I ask is because low flow rate through a gas heater has many causes, not always a low flow pump.

[system 4-50]

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Edited March 2, 2023 by system 4-50

[DShK]

Maybe a 12v/240v immersion in your calorifier? Heat the water up ahead of time rather than instantly, it'd use much less "instant" power. You'd obviously need to power this somehow, but it's much more feasible to get a few hundred watts from solar or a generator.

 

https://www.bimblesolar.com/extras/water-pump-heat/water-heater

[blackrose]

2 hours ago, JaneP said:

Thanks for your replies. We currently have an instant gas water heater, a new one just installed to replace a very old one. We’re having some issues with it, yet to be resolved related to getting the sink taps and shower to trigger the ignition.  

 

If you can increase the pressure from your water pump it might help, or replace the pump with a higher pressure/flow rate model. Some instant gas water heaters require a certain water pressure/flow rate to work properly.

[magnetman]

Wash less often. 

[DShK]

Ah I just realised, I guess if you have a gas water heater, you might not have a calorifier?

[Paul C]

One day, all boats will have an electric shower, being the natural evolution of going gasless once the traction is done by battery electric. The "house" side will be but a small proportion of the total energy stored and consumed. Electric cooking will be the norm, electric shower surely will be a logical progression?

[Jen-in-Wellies]

44 minutes ago, blackrose said:

 

If you can increase the pressure from your water pump it might help, or replace the pump with a higher pressure/flow rate model. Some instant gas water heaters require a certain water pressure/flow rate to work properly.

Another thing to look at is pipework diameter from the water tank, through the pump, gas heater and to the shower. Increasing pipe diameter from 15 to 22mm OD will likely improve flow rate and reduce pressure drop at the heater and shower head at full flow. If possible, removing elbows and replacing them with sweeping bends and minimising isolation valves will also help. On my boat, for example, an 11l/min pump can only flow a measured 6l/min through the 15mm pipework to open taps. The rated flow rate that pump manufacturers give is with the outlet open, so no restrictive pipework at all.

Jen

[Tony Brooks]

1 hour ago, Jen-in-Wellies said:

Another thing to look at is pipework diameter from the water tank, through the pump, gas heater and to the shower. Increasing pipe diameter from 15 to 22mm OD will likely improve flow rate and reduce pressure drop at the heater and shower head at full flow. If possible, removing elbows and replacing them with sweeping bends and minimising isolation valves will also help. On my boat, for example, an 11l/min pump can only flow a measured 6l/min through the 15mm pipework to open taps. The rated flow rate that pump manufacturers give is with the outlet open, so no restrictive pipework at all.

Jen

 

I wonder if the OP only has 10mm tails on the taps

[magnetman]

1 hour ago, Paul C said:

One day, all boats will have an electric shower, being the natural evolution of going gasless once the traction is done by battery electric. The "house" side will be but a small proportion of the total energy stored and consumed. Electric cooking will be the norm, electric shower surely will be a logical progression?

 

What is probably needed is a battery powered instant water heater. 6kw is quite a lot of power. My LTO batteries which are 40Ah per module at 15v can discharge 10C which is 400A so  around 6kw. The math says this can be done for 6 minutes. One would need rather large conductors between battery and water heater but if the two were integrated it seems plausible. 

 

Electric instantaneous shower is quite feasible on batteries if the hardware is in place to allow it. If it was mains it would need an awfully big inverter. 

 

 

 

 

[Richard10002]

5 hours ago, JaneP said:

Thanks for your replies. We currently have an instant gas water heater, a new one just installed to replace a very old one. We’re having some issues with it, yet to be resolved related to getting the sink taps and shower to trigger the ignition.  We’re thinking a new after pump with better flow rate may work. It just crossed my mind to ask if there was a boat-suitable elec shower available. 

I have an instant gas water heater and the shower wouldn't trigger it. I found out how to increase the water pump pressure and gradually increased it until it would trigger.

[IanD]

3 hours ago, Paul C said:

One day, all boats will have an electric shower, being the natural evolution of going gasless once the traction is done by battery electric. The "house" side will be but a small proportion of the total energy stored and consumed. Electric cooking will be the norm, electric shower surely will be a logical progression?

Quite possibly, the energy used by an electric shower isn't high compared to electric propulsion, and certainly not compared to electric heating -- which is actually by far the biggest problem...

 

A 9kW shower running for 10 minutes uses 1.5kWh, which is the same as half an hour cruising at 3kW.

[MtB]

1 hour ago, magnetman said:

Electric instantaneous shower is quite feasible on batteries if the hardware is in place to allow it. If it was mains it would need an awfully big inverter. 

 

 

Point of Order. 

 

An electric shower doesn't need an inverter. Resistive heater elements work just fine on DC.

 

 

[roland elsdon]

We have a 240/12 calorifier. As we have no mains ring we therefore have a 12 v calorifier.  It is however slow, and makes the alternator sing happy little songs.

I would not recommend unless you boat a lot. It is a notional 360 w element so canes the batteries .

Needless to say the calorifier is also small. Cold to hot tank engine running normal canal speeds about 4 hours.

The side benefit is the alternator becomes a 360 w heater. Not so good.

[magnetman]

Maybe the answer is half way between instant hot water and stored hot water..

 

You have an insulated tank with exactly the right amount of water for a standard shower. You fill it using a solenoid valve and float switch. You put a large immersion heater in it lets say 3kw and run that from the propulsion battery bank for x minutes then move the hot water through a shower and do that soap thing. 

 

The tank is emptied rather than being automatically refilled with cold water. Once you have finished then it can be refilled manually by switching the solenoid valve. Automatic cutout by float switch. 

 

The shower will have its own pump obviously. Refilling via solenoid valve can be from the main domestic water pump.

 

Hot water to galley taps needs a separate arrangement. 

 

I personally think hot water is overrated except in tea. 

 

 

 

[Tony Brooks]

Even if the batteries can supply the needs of an electric shower, they still have to be recharged. Lithiums and suitable charging equipment may make it possible, but with typical alternators and lead acid batteries, I think the recharging will prove to be the problem. An electric shower will work on a shoreline with enough rating, but when out cruising it would probably need a generator.

[magnetman]

Large solar panels would put the power back in. Not everyone wants large solar which is understandable. 

I feel it is worth allocating some cabin top space for solar. 1kw is a useful array size. 

LG 355w x 3 would be about 3.1m length and 1.7m width. The 1.7 might be similar to width of cabin top. The LG panels are nice as they have black frames and look really tidy. 

[Tony Brooks]

9 minutes ago, magnetman said:

Large solar panels would put the power back in. Not everyone wants large solar which is understandable. 

I feel it is worth allocating some cabin top space for solar. 1kw is a useful array size. 

LG 355w x 3 would be about 3.1m length and 1.7m width. The 1.7 might be similar to width of cabin top. The LG panels are nice as they have black frames and look really tidy. 

 

But would they with lead acid batteries, which spend most of the charge time limiting the charging current. Once we consider lithiums things get easier because they do not seem to limit current.

[magnetman]

 

 

In my opinion it is well worth planning two completely separate electrical systems. A lithium battery system supported by solar and MPPT and an AGM battery supported by engine alternator. 

 

Lithiums can run fridge and other heavy loads used more during warm weather. AGM runs more mundane loads such as lights and pumps. 

 

 

 

 

[George and Dragon]

If you're hoping to get enough energy from your solar to run the domestic hot water you might want a bigger array than 1kWp, lithium or not.