Manually pumped hot water

[NormanS]

I love having a calorifier. Not only does it give the convenience of hot water on tap, by making use of waste heat, when you have it, it is also something for nothing.

 

[Hydrozoan]

I'd definitely opt for a calorifer as the best upgrade from a 'primitive boat'. ... It start to look like the full system is standard for good reason?

I agree with all that in principle and find a ‘full system’ just great. But from the OP it seems that JD has decided that a ‘minimalist’ HW system would meet his needs. If so, we’re now perhaps opening a discussion he’s already had with himself rather than addressing his specific technical point. For our boats and needs a ‘full system’ is the right choice, but JD wants something between that and a kettle. Are we really saying that that is never a sensible option?

I love having a calorifier. Not only does it give the convenience of hot water on tap, by making use of waste heat, when you have it, it is also something for nothing.

Absolutely – just like using the wind to sail. Er ... something tells me you’re not an accountant.

 

[lw395]

I agree with all that in principle and find a ‘full system’ just great. But from the OP it seems that JD has decided that a ‘minimalist’ HW system would meet his needs. If so, we’re now perhaps opening a discussion he’s already had with himself rather than addressing his specific technical point. For our boats and needs a ‘full system’ is the right choice, but JD wants something between that and a kettle. Are we really saying that that is never a sensible option?

)

I think the expanding hot water spitting out of the tap could be an issue with an 'open' system. As soon as you put a tap on the output, you need a relief valve and probably an expansion vessel.
No reason why the pump could not be a pedal though.
But having done all that, assuming there is a sink in the head, it seems worthwhile to have HW there as well as the galley. Maybe not so on smaller boats.

None of this is essential, but I'd rate it above fridges and flash instruments personally. A basic boat costs a lot of money. A civilised one need not cost significantly more. HW and heating get my vote!

 

[PaulRainbow]

Talk of expanding hot water and relief valves are, IMO, a red herring. Most, if not all, calorifiers will come with a PRV already fitted. In the unlikely event that one can be found that doesn't have one, a tee can be fitted to the outlet and a domestic PRV can be fitted.

You can fit a pump after the calorifier and it will pump to the tap, the calorifier will fill from the water tank, you can't have a vacuum in the tanks. A Lavac pump emptied the bog and rather than have a vacuum sea water is sucked in from beneath the boat. A Whale Flipper will draw water from the tank or from the sea. Etc Etc.

You could also fit the pump before the calorifier, as already mentioned, and pump cold water into the calorifier, hence hot water to the tap.

For a small cost you could fit a pressure pump and expansion tank, if you so chose.

As for the kettle/calorifier debate, my take is to use both. I refuse to have the immersion heater on when i'm in the marina. Heating 22 litres of water 24/7 just for a couple of kettle fulls a day is a waste of money. I boil a full kettle in the morning, which is enough for breakfast and a wash/shave. In the evening i boil a full one again, which is enough for a cuppa and the washing up. I'm not adverse to a free tank of hot water when the engine has been running though.

 

[lw395]

If you have no expansion vessel and rely on the PRV to regulate a closed HW system, you will get frequent venting, usually to the bilge. You see this a lot on older boats where the EV has a failed bladder.
The normal PRv is intended as a safety backstop, not really normal use.
I don't like wet bilges, it's halfway to the MAB syndrome.
Elec pump and expansion vessel are not that much extra cost, the calorifier is the expensive thing I thought?

I think any system that allows partially heated water to run back to the main tank as it's heating is dodgy from a legionella and other gringe point of view? May depend on the climate, but I'd check that out before trying to save a few notes.

BTW, I'd also consider a thermostatic mixervalve for the heads basin (and shower if applicable), the calorifier water can get scary hot sometimes.

 

[VicS]

Given that I am in the middle of having a nice new Nanni engine fitted, which could heat some water for me, but that I have absolutely no intention of fitting a pressurised water system, is there any reason why I could not fit an unpressurised one ... pipe from water tank to calorifier, pipe from calorifier to pump at the sink?

I cannot see why it wont work. My galley pump lifts water up from flexible tank under the forward bunks no problems. ( and that is only one of those miserable Whale V pumps)

I imagine you will need a check ( non return) valve between the tank and the calorifier. If that is not very lightly sprung it might be a problem.

The only other snag I can see is that every time the calorifier heats up and the water in it expands the excess volume of water will dribble from the pump into the sink.

I doubt if the thermostatic mixer, which people suggest, will work on a non pressurised system but it might. In a way it is still pressurised but only to atmospheric pressure.

 

[vyv_cox]

The OP has said that he does not want a pressurised water system. In that case any expansion of hot water in the calorifier will simply travel back to the main tank. Venting of the calorifier is only going to be a problem with a pressurised system.

 

[ghostlymoron]

If it were me, I would go the extra mile and install a pressure pump on the cold feed which would then provide hot and cold at the sink with no additional pipiwork.You won't necessarily need an expansion vessel although a small one would help smooth the flow.

 

[NormanS]

The OP has said that he does not want a pressurised water system. In that case any expansion of hot water in the calorifier will simply travel back to the main tank. Venting of the calorifier is only going to be a problem with a pressurised system.

Hot water going back to the tank is best avoided for health reasons. Better, as VivS has suggested, to fit a non-return valve, and let the expansion dribble out at the sink

 

[vyv_cox]

Hot water going back to the tank is best avoided for health reasons. Better, as VivS has suggested, to fit a non-return valve, and let the expansion dribble out at the sink

I don't think it is a big issue with a relatively small calorifier some distance from the tank. I calculated the likely expansion of water in a calorifier a while ago and was surprised by how little volume change there is. Chances are it will never reach the cold tank. I agree though, any expansion will pass through the pump to the tap with a NRV in the supply line.

 

[lw395]

I'm not sure about the water merely dribbling out of the sink tap.
It's possible/likely that there will be air as well as water in the calorifier. Air will expand more and the motion of the boat may mean more of a spurt than a dribble.
On my second boat, we used to switch off the noisy water pump at night. Inevitably someone would then leave a tap open when water stopped coming out.
If you then thrash the motor hard because you are late for the RTIR, you can get steam out of the bog window.

We should perhaps remember that the coolant circuit will quite happily get over 100degC without there being very much wrong with the engine, heat exchanger etc.
Possibly the max spec for coolant temp is over 100 normally?
The first you know about it might be scalding water spurting out of the tap.
I've seen failed calorifier PRV's with a lot of chalk in them, this may well be where this kind of thing really happens unnoticed on a closed system?
I don't know offhand what the PRV is normally set to? 3 bar like a domestic boiler?

ISTR going through all the maths when sorting our system out and adding a Hydronic. Those things will run over 110degC very happily.

Personally I don't encourage anyone to take shortcuts with potentially scalding water, let alone steam!

A lot of this won't apply if the calorifier is on the seawater of a direct cooled motor of course.

 

[Deleted member 36384]

With regards to PRVs, or not, I suggest that a hi level vent, if such could be run, would be suitable. Looking through one of Ian Nicolson's boat improvement books, he shows a simple radiator system where the hot water tank has a high level vent with no PRV in the system.

 

[JumbleDuck]

Many thanks, folks, for all these useful comments. To address a few in turn ...

Boiling a kettle takes no time at all. I would not bother with the calorifier or hot water tank on a small boat. The store of hot water gets used up very quickly and it is a breading ground for stuff unless kept very hot.

I'm quite happy boiling kettles, but if I can arrange for a supply of "free" hot water are fairly low installation costs, I'm tempted. For a start, it could be nice to use a pressure/gravity portable shower system. There is no scope at all for a shower in the boat.

I presume you would need a thermostatic mixing valve on the calorifier, and that that would still work satisfactorily in the 'suck' configuration?

I was just thinking of a hot tap. How hot do calorifiers get?

I agree with all that in principle and find a ‘full system’ just great. But from the OP it seems that JD has decided that a ‘minimalist’ HW system would meet his needs. If so, we’re now perhaps opening a discussion he’s already had with himself rather than addressing his specific technical point.

Yes, thanks. I definitely don't want a full pressure system, for a variety of reasons.

The only other snag I can see is that every time the calorifier heats up and the water in it expands the excess volume of water will dribble from the pump into the sink.

Excellent point. I'll have to give some though to that.

 

[Hydrozoan]

Many thanks, folks, for all these useful comments. To address a few in turn ...
I was just thinking of a hot tap. How hot do calorifiers get? ...

I don’t know as I’ve got a thermostatic mixer would be my quick answer! But I suspect hotter than I might like to have especially if children might use it, for example – see also lw395’s comments at #25 and #31.

But another question in my mind was how well simple manual or foot taps would cope with very hot water. Before I switched to a pumped system I had simple hand pumps and the galley one, which got most use, required new seals fairly often with just cold water. Even if you were happy on any safety issue, I would give that some consideration.

But perhaps others with experience of the simple system you propose know those are not problems?

 

[VicS]

Many thanks, folks, for all these useful comments. To address a few in turn ...



I'm quite happy boiling kettles, but if I can arrange for a supply of "free" hot water are fairly low installation costs, I'm tempted. For a start, it could be nice to use a pressure/gravity portable shower system. There is no scope at all for a shower in the boat.



I was just thinking of a hot tap. How hot do calorifiers get?



Yes, thanks. I definitely don't want a full pressure system, for a variety of reasons.



Excellent point. I'll have to give some though to that.

It can get as hot as the normal engine operating temperature. I assume your engine will be indirectly cooled so 75-80C perhaps more. The owner's manual may give the thermostat operating range.

 

[Deleted member 36384]

With my Perkins 4236 running the water in the calorifier comes out scalding hot, not spurting or boiling, but it is far too hot to test with the finger. The tap body is very hot as well after it has been running to the point where grasping the spout to turn it away from the sink was not possible.

 

[lw395]

It can get as hot as the normal engine operating temperature. I assume your engine will be indirectly cooled so 75-80C perhaps more. The owner's manual may give the thermostat operating range.

Just taking an engine at radom(ish), Yanmar 3TN Max coolant temp 105degC, thermostat fully open at 85degC. Starts opening at 71.

But in an overheat situation, I don't think it's ideal that the first thing to let go will be the calorifer dumping a load of scalding water around the galley.

 

[NormanS]

I don’t know as I’ve got a thermostatic mixer would be my quick answer! But I suspect hotter than I might like to have especially if children might use it, for example – see also lw395’s comments at #25 and #31.

But another question in my mind was how well simple manual or foot taps would cope with very hot water. Before I switched to a pumped system I had simple hand pumps and the galley one, which got most use, required new seals fairly often with just cold water. Even if you were happy on any safety issue, I would give that some consideration.

But perhaps others with experience of the simple system you propose know those are not problems?

If the system was piped so that the foot pump was pumping cold water into the calorifier, and the outlet to the sink was just a simple spout, no seals, valves or pumps would be exposed to the admittedly very hot water.

Like many others, I'm sure, I don't have an automatic mixer valve, but with care, the high temperature is manageable.

 

[Hydrozoan]

If the system was piped so that the foot pump was pumping cold water into the calorifier, and the outlet to the sink was just a simple spout, no seals, valves or pumps would be exposed to the admittedly very hot water. ...

Yes I can see that – but the OP was (at one time anyway - see #5) thinking of a pump tap at the sink.

(I also see that my comment about checking that a tap would cope with very hot water was raised earlier by BoB at #9; my apologies for not referencing that.)

... Like many others, I'm sure, I don't have an automatic mixer valve, but with care, the high temperature is manageable.

Yes I expect it is, but it’s a choice I didn’t have to make (and prefer what I have). I guess the issue of whether or not a thermostatic mixer could function with a manual pumping system is still not resolved (see Vic’s post at #26).


I did not know what my coolant temperature might reach, but I see that for Beta’s small engine range the temperature alarm is set at 95-100C.

 

[ghostlymoron]

I doubt if a mixing valve would cope with a manual pump because the flow wouldn't be constant.
I'd be interested why the OP doesn't want an electric pump, seems like the simplest solution to me.