Calorifier.Difference from bog standard domestic hot water tank ?

[oldgit]

My recently purchased MoBo has a largish upright foam covered hotwater tank with an immersion heater powered by shorepower.Boat has all the normal pumps and pressure vessels.The engine has the required two fittings(connected by loop of hose) for water heating via the indirect engine cooling system.
The boat was fitted out by the first owner and not by a boat builder and the engine has curiously not been connected to heat water.
Problem is,my upright foam covered hot tank looks suspiciously like the sort of thing you have at home,if a tad smaller ........ if we plumb the thing into the engine will it burst or something dramatic.
Happy to buy a pukker calorifier,but do not want to eject existing tank if it is the proper bit of equipment.
All comments welcome.

 

[pvb]

No reason why it shouldn't work. It's certainly not going to burst. Might not be as efficient as a purpose-designed calorifier, but if it's already there why not try it?

 

[VicS]

The tank does have a heating coil to connect to the engine ? Not just a tank with an electric immersion heater?

 

[Double arvor]

Is there a pressure relief vavle fitted to the cylinder, to act as a relief if the cylinder overheats, how is your water tempreture controlled.

 

[pvb]

Is there a pressure relief vavle fitted to the cylinder, to act as a relief if the cylinder overheats, how is your water tempreture controlled.

Wouldn't the water have to boil to create serious pressure?

 

[Bobobolinsky]

Water pressure in the coil is going to be about 13psi max, same as a domestic sytem, so it's not going to be a problem

 

[Heckler]

Wouldn't the water have to boil to create serious pressure?

The water in the engine is over boiling point, and the pressure up to 7 psi? Consequently the calorifier coil will have the same pressure, the domestic water (if its anything like mine) will go up to "boiling" point (depending on what the pressure relief valve is set at) On mine Ive twice had the domestic hot water pipe blow off the calorifier during periods of prolonged motoring!
Stu

 

[oldgit]

The tank does have a heating coil to connect to the engine ? Not just a tank with an electric immersion heater?

Have just taken these pictures,will check total number of connections in morning when go to boat.

 

[Ubergeekian]

Indirect domestic hot water tanks - like mine, for example - work in exactly the same way as a calorifier. They have an immersion heater and a pipework heat exchanger inside to transfer heat from a central heating circuit. As far as I can see - and I am open to correction, as ever - boat calorifiers are simply (a) much smaller and (b) much more expensive.

Here are a couple of indirect cylinders in some catalogue google found for me.

 

[oldgit]

h,mm the feed at the top is for hot water to tap(s) and there must be a pipe there to get water from cold tank,but there are two others plus a fitting at bottom right which presume is over pressure valve ?

 

[pvb]

The water in the engine is over boiling point, and the pressure up to 7 psi?

In that case, I'd check the thermostat and the cooling system.

 

[Pagetslady]

I have a very similar tank which was installed by westerly, however mine is only about 20" high the immersion is a 1kw one. as has been said, the hot out of the top and the cold is at the bottom the domestic water pump supplies the cold pressure which pushes the hot out. Mine had coil inside which is fed from the circulating pump from the engine which is indirectly cooled there is also a pressure relief valve which I use to drain the cylinder by lifting the valve. I have over the years considered putting a thermostat into the circuit but have never got round to it as it would mean a three way valve so as to redirect the engine water back into the pump,( i think this is necessarie but not sure?) the water does get very hot but makes for a great shower in winter.
Mike.
PS I forgot to mention mine has an Accumulator which stops the pump from switching on and off instantly also As mine is shorter than yours the immersion is fitted into the top of the tank to one side of the outlet pipe. There are some marinas that the shore power would trip out with a three KW heater which I assume is the reason mine is only 1KW and I bet it will cost more than a household one from B&Q.
Mike

 

[VicMallows]

The tank does have a heating coil to connect to the engine ?

From the pics I think VicS's comment is most relevant. Probably why there are no connections to the engine! The immersion right at the bottom also seems a clue.....unusual in a domestic setup with a boiler feed.

Vic

 

[Forty_Two]

I tried a small domestic cylinder about 20 years ago - it sprung a leak very quickly.

Problem is a unpressurised home system is just that. Fully vented to the loft tank & not under any significnat pressure, just from the height of the loft cold tank.

Boat system is pressuriised from the water pump & pressure will rise as its heated. Nowhere to go but the releif valve.

Mine deformed before it split. Also the bottom was a different shape. Replaced with a Cleghorn Waring tank & no problems since. Thicker walls as I remember.

I guess a more modern domestic tank designed to be mains pressurised would be ok but Im not a plumber so couldnt say for sure.

 

[stirlingtours]

Couple of snags to the project. If it is a domestic cylinder you are using, which it looks like, it should not be pressurised. Domestic systems rely on a cold water tank normally in the loft to provide a head of water to the taps via the cylinder. There is also a vent/expansion pipe tee'd from the top of the cylinder going back up to above the highest water level in the cold water tank. On older systems this is often a swan neck looping over the edge of the tank, on more modern systems it can usually be seen poking out under the eaves. Assuming you don't have a cold water tank supplying a gravity feed to your plumbing you would need to ensure that the domestic water pump is of very low pressure and that you can have an open vent from the top of the cylinder. You may then encounter flow problems since boat pipework is rarely 22or 28mm. The heating coil is usually quite substantial but again it relies on large bore pipework to give decent flow rates. Another consideration should be the amount of heat extraction from the engine cooling system. Too much and the engine will suffer from constantly running below optimum working temp creating oil sludging and general wear. On the plus side you have almost everything there so why not experiment and contemplate the next big question. Where to install the bath.

 

[pvb]

Another consideration should be the amount of heat extraction from the engine cooling system. Too much and the engine will suffer from constantly running below optimum working temp creating oil sludging and general wear.

Isn't that why the engine has a thermostat??

 

[VicS]

Isn't that why the engine has a thermostat??

If there are flow and return connections on the engine, and the Op seems to describe those, then the flow to the calorifier will bypass the thermostat.

It'll it mean that it will take much longer for the engine to reach full working temperature ,... because it's heating the domestic hot water tank ..... and for the thermostat to come into play.
Also if you kept running bathfuls of hot water the engine would not get to full temperature cos it'll be heating domestic hot water all the time.

If the calorifier is fed from water leaving the engine via the thermostat, then true, the engine temperature will be controlled by the thermostat.

 

[pvb]

If there are flow and return connections on the engine, and the Op seems to describe those, then the flow to the calorifier will bypass the thermostat.

It'll it mean that it will take much longer for the engine to reach full working temperature ,... because it's heating the domestic hot water tank ..... and for the thermostat to come into play.

Most fresh-water cooled engines will supply the calorifier from the "hot" side of the thermostat, so will allow the engine to reach working temperature before they start to allow hot coolant to go to the calorifier. Check out some of the VP engine manuals for examples.

 

[All The Gear No Idea]

When I specced out my central heating system years ago, the better grade vented cylinders were rated to 3 Bar which is 100ft head of water. I would imagine these would be robust enough for a boat installation, but copper is probably not an ideal metal to have in a salty environment. They can be used for closed as well as vented systems, however a closed system requires a pressure vessel wih safety venting.

Newer cylinders in closed hot water storage systems are made from stainless steel and are far stronger and able to withstand higher pressures, but I doubt if there are any small enough to fit in your typical cruising yacht.

When I was planning my domestic system, I considered having a dual hot water storage system with an additional 45L high recovery cylinder supplying my ensuite, but then realised I was unduly complicating matters.

The high recovery version of these cyclinders has multiple small bore primary coils to effect a higher rate of heat transfer by increasing surface area. The manufacturer was quoting 20 minutes for this little tank using these coils - useful if the main HWS is depleted and you have limited time to wait for the water to heat up.

As i see it, the issue with a domestic cylinder in a boat application is one of how to securely mount the unit and ensure there is a proper marinized method of venting in an overheat situation.

However, a proper stainless steel marine calorifier would be my choice as it's the ideal engineering solution. I wouldn't cut corners to save money where water storage is concerned.

 

[TrueBlue]

A domestic HW tank is rarely under much pressure, a boat's pumped system always is. Being a cynic, being tested to 3Bar is not the same as running continuously at 2+ Bar.

I'm lucky to have enough space to have a wet C/H system on my boat, so my calorifier has two coils, one for the engine and one for the Mikuni.

The calorifier is the largest I could buy; great when running the engine but soaks up all the heat when the lorry heater is running.

So if you're going to buy an new calorifier - don't oversize it.

They are expensive 'cos they are made out of thicker copper; cost of materials, and more difficult to form.

ASAP supplies will give as good a price as you can get.