A Design For An Expanded Water Heating System: Suggestions, Criticisms, Abuse Please.

[Rendelf]

Hi peeps!

 

 

I'm hatching a plan to expand our current Squirrel-fed radiator system to also heat the calorifer. I have about zero plumbing knowledge... so the ideas below are all based on assumptions. I hope that by showing you the idea at this stage, I might not make hideous mistakes!

 

I intend to use the newer 'push fit' pipes and fittings, as they're easier, not that much more expensive than copper, and the links to the calorifier already use them.

 

I'd also like to have a solar collector as an option.

 

As far as I can tell, the calorifier only has one coil (unless the other one is hidden beneath its insulation.)

 

 

 

 

The drawing shows the boat as if it were just one continuous wall. I.e., port, stern, and starboard. This is because the calorifier is on the port side, and the burner/radiators are on the starboard side. I have to find a way to get the feed and return either around the back of the engine bay, or along the bulkhead dividing the bay and the living space, but beneath the doorway.

The circles with crosses are taps - or three-way selectors, which I'm assuming exist. The bulkhead appears twice (port and starboard)

 

The existing system has a bolan pump, but can also be used as a thermosyphoning system. I've sent the hot feed around the back of the boat, thinking that this might continue to operate (even though the cold return from the calorifier must travel uphill by about 100mm to rejoin the radiator system. An issue with this solution is that the pipe may loose too much heat to the hull / uninsulated engine bay. Another is: how do you mount pipes onto steel hulls!

 

If thermosyphoning, or just running from one pump isn't an option, it might be more sensible to run the hot and cold feeds from the radiator system to the calorifier along the same route that the cold feed takes in this design- along the bulkhead (3d sketch might make more sense....)

 

I suppose that's my main question at the moment. Is is a feasible idea? and, if so, should I run the pipes around the back of the boat (pictured), in a more gentle slope, or just go for the steep attack, use less pipe, but need a pump?

 

 

 

 

 

 

 

 

 

The hot feed could be teed from the pipework just below the header tank instead. But would the single bolan (?) pump by the Squirrel be able to move the water that far?

 

Assumptions.

 

The original hot/cold pipes from the engine only have one shut off valve. It's my understanding that the pressure of the water in a circuit will prevent water from a different circuit from entering it when the tap is closed: water always follows the path of least resistance.

 

For the solar circuit, there is a pump out there that will run on 12v, not consume insane amounts of power (though, on sunny days, our panel produces at least 8A), and be able to push the cold feed water to the roof.

 

I require a separate header tank for the solar circuit, as it's higher than the current one. The solar circuit needs to be treated as a separate system, as if connected, pressure will release water from the lower header tank.

 

Any help or suggestions on how this could be made better, or if it will even work, most appreciated!

Edited June 22, 2015 by Rendelf

[b0atman]

Last boat was a 55ft cruiser stern.The calorifier was at the back and the back boiler fed radiators and calorifier by convection pump not used except for boost if needed .Teed into pipework was an Eberspacher feed .The 2nd coil of calorifier was fed from engine.

[MtB]

Combining two uncontrolled heat sources into one system is fraught with difficulties and unforeseen consequences.

 

How, for example, do you plan to stop the stove heating up the solar collector on a freezing cold night, and warming up the sky?

 

Or if you have Mr Squirrel selected, stop the solar collector from boiling (if the sun comes out) and expelling steam from the open vent?

 

And that header tank above the solar collector. Will it be vulnerable to hitting bridges? And what would stop the water you add to it just all pouring back out via that other header tank inside the boat?

 

And I doubt a Bolin pump will be man enough for all that. They are pretty feeble.

 

 

Just my initial thoughts. I don't want to appear to be pouring cold water on your plans but twin heat source systems tend to get very complex to make them work right, and more particularly, safely. There is no generally accepted layout for doing it because no one layout actually works properly with no drawbacks.

Edited June 22, 2015 by Mike the Boilerman

[Rendelf]

Last boat was a 55ft cruiser stern.The calorifier was at the back and the back boiler fed radiators and calorifier by convection pump not used except for boost if needed .Teed into pipework was an Eberspacher feed .The 2nd coil of calorifier was fed from engine.

 

Hmmm. Perhaps I need a new calorifier?

 

 

Combining two uncontrolled heat sources into one system is fraught with difficulties and unforeseen consequences.

 

How, for example, do you plan to stop the stove heating up the solar collector on a freezing cold night, and warming up the sky?

Or if you have Mr Squirrel selected, stop the solar collector from boiling (if the sun comes out) and expelling steam from the open vent?

 

 

Well, my thought had been to remove the solar system when it's not summer. The Pushfit plumbing stuff claims that you can just 'twist and unlock' to change fittings....We don't really use the stove in summer. Plus, I tried to design the solar system to be separate... able to be isolated. I doubt that it could reach boiling temperatures left on its own? But - I'm most happy to be wrong.

 

How could the stove heat the solar collector, if the stove circuit was selected, and the solar collector's was not (albeit from a little conduction?)

 

And that header tank above the solar collector. Will it be vulnerable to hitting bridges?

The header I foresee is quite small... well below our chimney, or canoe.

 

Just my initial thoughts. Twin heat source systems tend to get very complex to make them work right

 

Fanks! That's what I'm after

[MtB]

 

Well, my thought had been to remove the solar system when it's not summer. The Pushfit plumbing stuff claims that you can just 'twist and unlock' to change fittings....We don't really use the stove in summer. Plus, I tried to design the solar system to be separate... able to be isolated. I doubt that it could reach boiling temperatures left on its own? But - I'm most happy to be wrong.

 

How could the stove heat the solar collector, if the stove circuit was selected, and the solar collector's was not (albeit from a little conduction?)

 

 

 

I bet the solar collector would be highly capable of boiler if circulation through it ceases in full sunshine! And you'd need to remember to manually select the right circuit. Always prone to human frailty.

 

No need to physically remove or even disconnect the collector if you are isolating it. Just drain the water out...

 

I'll give it some more thought later, and throw up some more potential pitfalls for you to think of ways to work around...

[Captain Fizz]

Basically what Mike says, multiple input heat sources are always a total pain to control.

Especially open vented systems with very little head.

[MtB]

Basically what Mike says, multiple input heat sources are always a total pain to control.

Especially open vented systems with very little head.

 

And doubly so when they are what the industry calls 'uncontrolled heat sources', i.e. solid fuel or solar, as opposed to 'controlled' heat sources that can be turned ON and OFF instantly with a thermostat. E.G. gas or diesel-fired boilers.

[Rendelf]

Well, the solar aspect was just fancy, after I burnt my feet on the roof...

 

Much more useful would be the heat from the stove. It's pretty unlikely that the two systems (engine and stove) would ever be used simultaneously, and even if they did, the engine radiator has a trail obstacles, to allow our disallow couldn't through the cylinder.

 

Might it be sensible to abandon the solar idea, and focus on simple?

 

Should I just buy a calorifier with two coils?

[Chewbacka]

Unfortunately I also only have a single coil and am considering how to heat my water with a diesel boiler.

As I see it there are 4 options

1) change to a twin coil - most expensive and probably the best idea

2) replace the immersion heater with a coil, something like this - http://www.solarcoil.co.uk/products.html

3) add a second small twin coil tank such that coils in both tanks are heated by the engine and the second coil in the small tank is also heated by the boiler. - this would also give a fast heat up time but takes more space.

4) If you do not use the engine much, then you could just fit the single coil into the boiler circuit and put a heater matrix or something on the engine circuit.

[smileypete]

Good diagrams.

 

As this comes up from time to time, I did a few sample heating layouts with a couple combining pumped and gravity:

 

Bear in mind they're just layouts and not turnkey designs, still needs stuff like radiator sizing, pump control, blah blah blah..

 

In a domestic system a pumped and gravity system can be combined easily with a 'header' (eg a Dunsley Neutraliser), which provides a 'neutral point'

 

This is hard to do on a boat as it's all on one level, what the third diagram does is use the gravity radiators as a neutral point, but it means only two tappings are used for the gravity connections which might not be so good if the rads and backboiler output is fairly large.

 

If you really want to add solar I'd consider using combining it with the engines cooling system, with a bypass thermostat that allows flow through the skin tank when the solar return temperature gets too hot, might need a diagram for that one too...

 

cheers, Pete.

~smpt~

Edited June 22, 2015 by smileypete

[Rendelf]

Thanks for the responses!

 

Good diagrams.

 

As this comes up from time to time, I did a few sample heating layouts with a couple combining pumped and gravity:

 

.

~smpt~

Cheers Pete. Is there a reason that the pumped circuit is connected to the boiler, and not the end of the gravity circuit?

 

If I took a feed from the end of my gravity circuit, I'd save 16 meters of piping....

 

In terms of multiple heat sources being 'problematic', can anyone explain why?

 

I have a three-way tap that allows me to select either the calorifier, or the gas boiler as the source for the hot system.

 

Why does this work with no issues, whereas a similar layout with the radiator and engine system does not? Is it that the heating system cycles the same water around, but the hit water system pushes water through? :no idea!:

Edited June 26, 2015 by Rendelf

[smileypete]

Thanks for the responses!

 

Cheers Pete. Is there a reason that the pumped circuit is connected to the boiler, and not the end of the gravity circuit?

 

If I took a feed from the end of my gravity circuit, I'd save 16 meters of piping...

 

Well if the stove is ticking over and you want to use all the backboiler output to heat the calorifier, you may lose a fair bit of heat from the gravity pipes alone.

 

cheers, Pete.

~smpt~

Edited June 26, 2015 by smileypete

[KJT]

If you are thinking of a stand alone solar water heating system there is a feature in the February 2013 edition of Practical Boat Owner.

It is available as an online back issue. You may find it useful.

 

Ken