manually pressurised water system

[Alexis]

Hello there,

Still fitting out a 34 feet cutter, I am currently immersed in the design of the water system.
Elements will be: 20 liter water heater linked to a Refleks diesel stove and a small solar panel (currently exploring this solution), tap in galley and tap/shower in heads, and some sort of expansion tank.

The idea is to use 2 foot pumps and conventional taps. There would be a pipe from the tank going to both foot pumps (one in heads and one in galley), after one the pumps, there would be a "T" connection, with one side going to "cold" fawcet and the other to bottom of water heater, then from top of water heater to "hot" fawcet. Say you want warm water, open both hot and cold taps and pump whatever you need. (I'd probably go for one of theses "mixing" taps)

The goal is to keep water consuption as low as possible.

Any experience of such a system or drawbacks you see in this layout ?

Cheers,
Alexis

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[vyv_cox]

No experience of this but it sounds feasible. I would definitely include an accumulator, as large as you can fit. This will help to 'save' the pressure so that you will not need tp pump for small flows, like cleaning your teeth, for example.

Also, assuming you have an engine, consider a calorifier. Are you thinking of 12 V water heating powered by solar panel? I doubt if this could give sufficient power as you will be lucky to average 1 Amp/hour from a small panel.

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[Alexis]

Sorry about not using the right term, but what I meant by water heater, is in fact a calorifier: a thermically insulated cylinder, with a heat exchanger in it.
My Refleks stove has a serpentine that is connected to this calorifier.
The solar panel I refer to is of the non photovoltaic sort, I mean it's basically a heat exchanger. I have a friend who has such a system in his house, 2 square meters of panel for 400 liters of water for a familly of 4, used for hot water (not heating) : the lowest temperature he has at the tap in february is 57 ° C. I would have thought that for 20 liters, you'd need a quite modestly sized panel. Haven't yet finished exploring this matter.

As my water is fresh water cooled (Volvo 2002), do you think I could also connect it to the calorifier ?

Many thanks for the brilliant idea of having an accumulator ! Will definitely do that !

Cheers, Alexis

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[ccscott49]

Yes you can definitely connect the engine cooling to the calorifier, thats the normal system. You may need a twin coil calorifier, or have two valves to isolate the engine, when heating either with the panel or refleks. The panel will be quite heavy, with the iping and box etc, you need to take this into consideration, as to where you will mount it, or store it when not in use. You may also need a small electric pump to circulate the water through the panel and calorifier.

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[Alexis]

Thanks for your feedback ccscott.

I was thinking of installing (God knows where) the panel lower than the calorifier, in order to avoid the need of a circulating pump. As the calorifier is a sealed unit (SS), i think I'll go for the valves.

Cheers, Alexis

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[ccscott49]

I'd love to see you achieve that, when the panel needs to be outside, in the sun. But you would still need a circulating pump, no matter which is lower, convection is unlikely to do it, but possibly.

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[MainlySteam]

I wonder what the effect of the boat's motion on convection driving flow through a calorifier would be?

John

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[richardandtracy]

If you've got a pilot house the calorifier could be high up in the pilot house & the solar panel could be on the cabin roof. Failing that, use a solar powered 12V pond pump to circulate the warm water - it'll work only when it's necessary & can be an entirely self contained system. These pond pumps with (10W?) solar panel come in at about £60 - you may feel it's worth it.

I've toyed with the idea on my steel yacht of making the underside of the cabin top wet so that a relatively large area could be made into a solar panel with nothing that could be damaged on the outside. The big disadvantage that I can see with this idea is that there is the possibility of crevice corrosion under the cabin top stiffeners. Anyway, this idea has yet to be implemented, I'll see when all the more important things have been attended to!

Regards

Richard.


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[richardandtracy]

Come to think of it, it would be possible to make a weight sloshing about in a chamber into a boat motion driven pump. You'd need 2 very weak check valves and put the pump across the direction of maximum movement.
It'd be fiddly to make, but I'm sure a bit of experimentation would do it.
A weight on a diaphragm & 2 flap valves could do it too - it wouldn't need to be very good or efficient.

Regards

Richard.


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[MainlySteam]

You sure you're not heathandrobinson in disguise?

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[richardandtracy]

Re: heathandrobinson in disguise

Damn.
Robinson! Somebody's guessed our secret!

Regards

Richard.


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[peterb]

If your cabin top is metal then I suspect that you need not make it wet. A serpentine tube in good thermal contact with the cabin top should be sufficient. Welding or brazing would be best, but something like "Chemical Metal" might do.

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[Alexis]

Good point John. I have no experience in convection driven flow, but would have thought that, provided the piping is of a large enough section, there would be enough inertia to overcome the boat's motion. (not talking about fighting against a a 20° heel).
What do you think ?

Cheers,
Alexis

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[Alexis]

I don't have the comfort of a pilot house. If I cannot position the panel and the calorifier ideally and if convection doesn't work, I'll certainly go for the solar pond pump. Seems a brilliant idea: these are probably designed to run for hours on end. Would connect it at the lowest art of circuit so that the water that runs through it is as cold as possible.

As to your integrated solar panel, sounds like a good idea. Apart from the corrosion problems you have mentionned, I'm not sure how efficient this system would be unless you paint your deck black (!!!).
Please keep me posted.

Alexis

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[MainlySteam]

I don't really know Alexis, but I would have thought that the temperature gradient over the panel would not be high and mean that the difference between the temperature of the flow to it compared to the flow from it would be low. Therefore the driving force would be low and might be easily upset. Just a thought only.

John

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[Alexis]

Would the shape (thin and long instead of squarish) of the panel change something to the temp gradient ?

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[richardandtracy]

Our solar pond pump is 2 years old now & works really well, even in winter. The pump's designed to be immersed, so the fitting may be awkward. The only thing against it is that the panel needs to be at least 75% exposed to direct sunlight before the pump will work - could be a problem with sails up. When in full sun the pump sends a jet 3ft high, which would probably be perfect power for your system.

Regards

Richard.


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[richardandtracy]

Good thought. I'll bear it in mind.
Painting the cabin top black will make a little difference, but not much contrary to intuitive expectations. The absorbtion and emissivity of most black and white paints is not actually much different unless you go for specially formulated absorbing paints.

Regards

Richard.


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[MainlySteam]

I am no expert in solar water heating panels at all (ok everyone calm down, I've admitted it!) but I would suspect that the main criteria is the area of the panel.

I think that they do work with quite low head differences on house roofs as I do not think these always use circulating pumps for the flow if they use a header tank located just higher than them in the attic space - again I am not sure on that but would probably be easy for you to get some idea about those if you asked around. Obviously houses don't rock around though.

I would have thought that a little in line pump would be the answer. Its capacity need only be very low and consequently low current draw. Following up on heathandrobinson's (aka richardandtracy) solar pump it may prove possible to run any little pump (suitable for hot water) using a little solar panel - when you are getting energy into the solar water heater you will also have sun for power to run the pump.

John

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[richardandtracy]

Huh, as if it's not bad enough knowing I don't live in the nicest part of the world, while you do MainlyStream [I'm green with jealousy]. Now I get insulted from someone who resides there.

heathandrobinson. Honestly. What's the world coming to?

[more subversive muttering too quiet to type...]

I'm just too broke to do anything other than bodge it. Sorry, 'bodge it' should read 'Make things from scratch at home' - bodgeing implies they don't work reliably, while my stuff does (or the Mk2 version does if the Mk1 version doesn't).

Regards

Richard.


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