Mahe 36: Plumbing and Water Heater

[Cotemar]

qtmspin,
Great informative post and nice pictures.

[Seastream]

How, exactly does the port tank get filled with the stock setup of only one deck fill? I was in the anchor locker looking at the tanks and it looks like the port tank is 'backfilled' from the stbd tank via the hose that connects the two. Seems awkward at best. Anyone?

[Cotemar]

Originally Posted by Seastream

How, exactly does the port tank get filled with the stock setup of only one deck fill? I was in the anchor locker looking at the tanks and it looks like the port tank is 'backfilled' from the stbd tank via the hose that connects the two. Seems awkward at best. Anyone?

The port water tank gets back filled from the starboard tank as you said. That is why a few of us have added port filling caps. Go back in the thread to see pictures of the modification. It's an easy DIY

http://www.cruisersforum.com/forums/...tml#post447689

[Cheechako]

Only problem is if you take on bad water somewhere , it's in both tanks....

[Cotemar]

Originally Posted by Cheechako

Only problem is if you take on bad water somewhere , it's in both tanks....

No Worries as each tank can be shut off from the other with a valve

[MKB53]

Has anyone had any experience with diesel water heaters? any guidance on good units and pricing?

I understand that some units double as space heaters as well but that is not really a priority for us. I would like a source for hot water without having to run the engine (or drain my battery through the inverter!)

Cheers
Martin

[Edmund]

I have an Eberspacher 3kW diesel water heater installed in the Sb engine room, combined with a new twin loop 40 liter water tank, one loop for the engine, one for the Eberspacher. I can now heat the water tank from four sources, individually or combined: Shore power, Sb engine, Eberspacher, or the 12v/220v inverter. I also use hot water to heat the Sb side of the boat.
All working very well, exept I would perhaps buy the 5kW unit if I did it again, as 3kW is a bit small if started when everything is cold.
In general, I trust Eberspacher. They are one of two major suppliers here in northern Europe delivering water heaters to a waste amount of buses, trucks and cars.

You will find more info on this project in the thread "Mahe36 - Heating"

[Jef & Marin, Netherlands]

Edmund,
Could you point me to your post on the thread about Mahe Heating you are referring to? I couldn't find it.
I am quite interested what you did; we are now in the tropics with our new boat, after selling our Mahé; but in some time we will go to higher latitudes and will need a heating. (of course I will sail at one moment to Norway to visit you again.)
And while we had an Eberspacher air heater in our Mahé (a 4 KW which worked perfectly, and had a nice installation), for our new boat I consider a water heater.

More specifically, I understood that it is technically possible to couple a water heater to the hot water heater and the engine coolant circuit, so that you can keep the one-loop hot water heater.
Is your information otherwise; or did you have other considerations?

And for MKB:
If the water would just be for washing up the dishes, why not put the kettle on?
And somebody has on this thread already been considering a flow-through water heater on propane, I remember.
I have considered making a coolant fluid circuit, using a small pump, which extracts heat from part of the solar panels and dumps it in the hot water heater.
I already calculated flow requirements for this, and found the right low-power pump for it.
There is some bottleneck in the weight of the copper plate to extract the heat from the solar panel(s). Alternative is to go to aluminium, except for corrosion issues.
I also put a temperature sensor on the panels in bright sunlight; it easily reaches 55 centigrade. Ideally it should be over 60 seeing legionella.

But to do this through the single loop of the hot water heater is not straightforward and requires probably some failure-prone one-way valves. (I would not like to endanger the reliability of the cooling of the engines for an experimental set-up)
Alternative would be to use cold water, pump it through the solar panel heat-exchanger and pump it backwards into the hot water outlet of the hot water heater. This would of course not be sub-zero-temperature proof since it is water instead of coolant fluid.
So still some future engineering to do. Not with a high priority, we have so much to do on our "new" boat.....

Kind regards,
Jef

[MKB53]

Hi Jef and Edmund.

Thanks for the feedback on the heaters.
I primarily want the hot water for showers. Both the "Admiral" and I like our showers (hence the desalinator I fitted after the first cruise!).
Being able to produce warm air would be nice for winter but not a major factor.
My thinking on a diesel heater was that we always have a good supply of diesel whereas gas is in relatively short supply when you are out in the islands for an extended time, thanks to the small storage lockers.

I have been using the inverter to warm it electrically but that is a big drain on the batteries which then require engine top up. Perhaps a small gen would do the job but then you need to store that and more petrol.
At the end of the day cost is as always an issue and I believe the diesel units are very costly, in Australia at least.

Regards
Martin

[Edmund]

Jef:
This the Mahe - Heather thread: http://www.cruisersforum.com/forums/...ml#post1029602

I don't quite understand why you could not find it, please let me know if you still don't. There might be something wrong with it?

I chose the two-circuit solution to avoid messing up the engine cooling system. A sudden leak in the heating system would also drain the engine coolant. I was also concerned about running the engine witout running the electrical flow pump - would the engine's waterpump be strong enough alone for the whole system, without any risk for overheating the engine? Being dependent on the 12v flow pump working also when just motoring is not good.

Hope the "Heating" thread explanes it all well enough. Please ask if not.

We look forward to see both of you again in Norway soon, in your new ship!

[DtM]

..... and what is the new ship ???

[Arthur Garfield]

I use 12v water heating elements to directly heat water tanks directly from solar panels and wind geny to preheat/heat.This to offload power after topping Batt bank.Never short of lovely hot water.

[Dod42]

Originally Posted by Arthur Garfield

I use 12v water heating elements to directly heat water tanks directly from solar panels and wind geny to preheat/heat.This to offload power after topping Batt bank.Never short of lovely hot water.

I have looked at doing that as a dump for the wind generator, but not sure I can see how I can fit one. I don't want to loose the current 240V element in the hot water tank, and there doesn't seem to be provision to fit a second element. I could in a pinch power the 240 from the inverter but that seems extremely inefficient. We have the factory fitted Isotemp. So unless I fit some other 12 volt tank and circulation pump I don't see a way of doing this.

[Edmund]

I can not see why using the inverter to power the 240V element, when you have surplus 12v power available, is extremely inefficient?

[Dod42]

I guess to me there is a difference in having excess 12 volt from the wind generator which at best is probably making 400 watts and using an inverter and to power a 750 watt element. Takes a lot of energy to heat 40 ltrs of water. I have seen the hit the batteries take on the inverter just boiling 1 ltr of water 1500 watt electric jug. The hot water system is designed to heat it quickly then maintain. This will smash the batteries while heating, where I would prefer a suitable 12 volt element to heat it slowly, and not smash the batteries by only using excess power. I suspect I will get a better result in setting up a solar water panel and small solar powered circulation pump, and not stress the excess from the wind generator. If I really want hot water I can start a small generator or the engine I just hate wasting free power.