Water Heater Options

[stylo]

We've just removed the poorly installed gas instant hot water heater and looking at replacements. In reality we don't expect much use but would like the convenience.
Options as I understand things:

1) Engine to heat calorifier
We have a 33ft MG 335 with an original engine - due to this I'm reluctant to use the engine to heat a calorifier.

2) Diesel combo air/water heater (we need a new air heater anyway). Would be a good option but price starts to add up for the heater and calorifier and expansion vessel + additional plumbing from current heater location to where the calorifier would be. Also I understand that these combo heaters will generate hot air at the same time so may not be ideal if we have hot weather?

3) An electric water heater. I am leaning towards this due to simplicity, low cost eg this for £240, ease of install - same location as the old gas heater so can reuse water pipes. Power for this would be 1500W via the inverter which would take 25 mins to heat 10L from 15 to 70 celcius (then mixed with cold for shower etc so the 10L will go far enough easily for a shower or 2. Downside - need to run the engine to provide power for the inverter.

4) New gas water heater.
Problem is a flue that will be acceptable - not an easy route for this unfortunately + finding a marine version vs an inland waterways version


Appreciate any other suggestions.

 

[lustyd]

I don't see the difference between running the engine for a calorifier and running it for an inverter, other than the massive gap in efficiency.

Electric water heating is unsuitable for a 33' yacht. It makes no sense unless the boat is usually in a marina as you couldn't generate enough power without the engine. If you're going to heat water with diesel, heat the water with diesel. Personally I'd go with a hydronic Eberspacher and fit a valve to bypass the radiators/matrixes during summer months.

 

[Dockhead]

I would not use a gas-fired water heater on board for safety reasons, ever.

Why are you reluctant to use main engine heat? If the engine RUNS, it will make hot water.

On my boat, I have all three of your other options. Namely, a 50 litre calorifier with a 1500 watt electric heating element and two heatex loops -- one for an Eberspacher hydronic heater, and the other for the main engine fresh water cooling loop.

Electric is really useful at the dock, but not elsewhere. This is true regardless of the size of the yacht.

Main engine loop is really useful because your main engine will make you hot water whilst you are maneuvering to get the boat on her anchor, enter a harbour, etc. -- just when you need it.

Eber will make you hot water when you're anyway heating the boat with it, and as Lusty says, you can shut off the heating part in the summer and just heat water with it if you like.

If you need central heat anyway, then the hydronic heater is a no-brainer. Then when you buy the calorifier, get one with two loops so you can also use the main engine heat.

That would be my advice.

 

[Supertramp]

Like Dockhead I have hot water heated from the engine and with an electric element. No Eberspacher link. Its seems very simple and stays hot for 12-24hrs. Mostly it is heated from the engine, and a short run heats it. You need the space for the tank and sensible hose runs.

If I had lots of solar and inverter driven electrical items I might go for all electric water heating, again for simplicity. Not really going to work in the UK.

 

[Tranona]

Can't see why you don't want to use the engine to feed a calorifier. You are using the waste hear from the water and it has no impact on the running of the engine. However if it is a raw water cooled engine it will not be as effective as a heat exchanger cooled engine because it will run at a lower temperature. Well worth dong thigh. Fit a heating element for use on shorepower if you have it. Forget heating water with 12v through an inverter. A heating system with hit water is expensive and complicated for your size of boat and type of usage.

 

[KompetentKrew]

1) Engine to heat calorifier
We have a 33ft MG 335 with an original engine - due to this I'm reluctant to use the engine to heat a calorifier.

I don't know how you use your boat, but surely you're using your engine to enter and leave harbour anyway, which means you arrive with steaming hot water?

I suppose the engine not get hot enough if you manage to sail most of the way and only run it for 20 minutes or so?

Agree with the other comments. How you don't the maths on how much it will deplete your batteries to heat a tank of water electrically?

 

[vyv_cox]

Heating a calorifier with the engine is by a long way the most efficient method. It does depend a little on the engine that is installed but it can always be done.

 

[johnalison]

I would guess that almost all new boats in this size range come with a combination of engine and electric heating, since that suits the majority of boats that sail in and out of marinas. I don’t know anything about diesel or gas heaters but I can only see them being used by those who habitually spend long periods off-grid, so to speak.

 

[PetiteFleur]

As suggested I have a calorifier heated by the engine and by electricity when in a marina. Works well for us on a 33' Moody. I also have a chinaspacher diesel heater for cabin heating which also works well.

 

[lustyd]

I can only see them being used by those who habitually spend long periods off-grid, so to speak.

Agree with this. We only started thinking about adding a diesel water heater because running the engine for 30 mins every day drives us insane with the noise just to have a shower. When we’re moving it’s not an issue and nor is it when we’re in marinas. Ten days on anchor though and the noise is a nuisance.

 

[mrangry]

As said previously, depending on how long you need to run the engine for to heat the water sufficiently will determine whether that option is a goer, as you don't really want to have a diesel engine running for prolonged periods with no load.

Have you looked at the newer chinese diesel heater that heats both air and water as they are about £250. I am thinking of getting one but as yet not heard many reviews other that the guy on YouTube