Upgrade to hot water system

[LittleSister]

Does your calorifier not have provision for fitting a mains immersion heater element?

I am puzzled why your existing calorifier takes so long to heat up. I also have a 3 cylinder raw water-cooled engine - Bukh DV36 - just a little higher max power than your presumably 28hp(?), though my boat is smaller than yours so I am probably using less power on average, and mine has never struck me as taking a long time to heat up the 18 litre calorifier from the engine (in fact I've never yet tried the mains element!). A similar amount of heat must be being removed from your engine once up to temperature, and the Bukh is much heavier than the Volvo - 265kg vs.159kg. - so that there is much less mass to heat initially and so yours should get up to temperature much quicker. Are you perhaps wholly dependent on thermosyphon to circulate the heated raw water through the calorifier? I have a small electric pump which circulates the hot engine water through the calorifier.

 

[vyv_cox]

Are you perhaps wholly dependent on thermosyphon to circulate the heated raw water through the calorifier? I have a small electric pump which circulates the hot engine water through the calorifier.

If you look at the calorifier page of my website Calorifier installation your question will be answered. The cooling circuit on the 2003 is unique. Water in the block is not circulated as it can be in the Bukh, also illustrated

 

[AntarcticPilot]

This is just a suggestion - but would your idea not be better with an "instant tankless" hot water tap. These are available for ~£50 (ones that do boiling water too are more expensive). I've never used one inline with a hot water supply but it seems like it should work. I assume the water still flows when the power is off.

They have much higher power requirements to achieve a reasonable flow rate; too much for marina shore power.

 

[AntarcticPilot]

The is a cheaper option that's even easier to install :
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Got one of those !

 

[Dockhead]

Why wouldn't you just add an immersion heater to the existing calorifier? That's the usual solution.

I don't know what kind of boat you have, but I would struggle to find space to run two separate water heaters.

As others have advised, you want about 1.5kW for the immersion heater; 1kW will also do. That way you won't run into problems on low capacity shore power connections.

6 amps x 230v (usually 200v on rickety old wiring systems) is not uncommon in France and Germany. That would struggle with even 1.5kW. Not a problem on my boat because I have power limiting and power boost via the Victron Multiplus, but can be a big problem if you use shore power straight from the tap.

 

[AntarcticPilot]

Why wouldn't you just add an immersion heater to the existing calorifier? That's the usual solution.

I don't know what kind of boat you have, but I would struggle to find space to run two separate water heaters.

As others have advised, you want about 1.5kW for the immersion heater; 1kW will also do. That way you won't run into problems on low capacity shore power connections.

6 amps x 230v (usually 200v on rickety old wiring systems) is not uncommon in France and Germany. That would struggle with even 1.5kW. Not a problem on my boat because I have power limiting and power boost via the Victron Multiplus, but can be a big problem if you use shore power straight from the tap.

The existing calorifier is ancient, and very inaccessible. I agree that fitting an immersion heater would be the best solution, but a) i doubt that the existing calorifier has the facility to fit an immersion heater, b) access to fit one is very poor and c) a replacement calorifier would cost about ten times as much as the small water heaters.

 

[LittleSister]

. . . c) a replacement calorifier would cost about ten times as much as the small water heaters.

How big is your calorifier? A 15 litre calorifier can be had, including mains immersion heater, for less than 5 times the cost.

https://www.sheridanmarine.com/product/quick-nautic-boiler-b3-15l-calorifiers
(Other manufacturers and suppliers available.)

The existing calorifier is ancient, and very inaccessible. I agree that fitting an immersion heater would be the best solution, but a) i doubt that the existing calorifier has the facility to fit an immersion heater, b) access to fit one is very poor . . .

Long shot, I know, but if access is that poor (mine similarly) is it possible your existing calorifier has an immersion heater, not wired up, and you just can't see it?

 

[Boater Sam]

Its easy to fit an immersion element to an existing calorifier without the right flange by using an Essex mechanical flange either in the crown or the side.

 

[AntarcticPilot]

How big is your calorifier? A 15 litre calorifier can be had, including mains immersion heater, for less than 5 times the cost.

https://www.sheridanmarine.com/product/quick-nautic-boiler-b3-15l-calorifiers
(Other manufacturers and suppliers available.)




Long shot, I know, but if access is that poor (mine similarly) is it possible your existing calorifier has an immersion heater, not wired up, and you just can't see it?

Well, it is still 5 times as much - and the type of water heater I am looking at goes down to around £50 or even less; £100 is a fair price for one that looks like it has reasonable corrosion protection.

I will certainly check my existing calorifier out, but it's from 1989 when mains electricity was rarely available to boats and there is certainly no original mains wiring ; i installed the consumer unit and connection.

 

[ylop]

They have much higher power requirements to achieve a reasonable flow rate; too much for marina shore power.

I don’t know what the flow rate is like on the cheaper brands but there are definitely options that just plug into a normal 3 pin socket and draw the same as the kettle posted above. If it’s the only thing you are using at the time UK shore power should cope.

 

[Minerva]

I don’t know what the flow rate is like on the cheaper brands but there are definitely options that just plug into a normal 3 pin socket and draw the same as the kettle posted above. If it’s the only thing you are using at the time UK shore power should cope.

Sounds like my instant hot water tank at home. Plugs into a standard 3pin plug - it’s brilliant. Not had to boil a kettle in almost 2 years now.

 

[PaulRainbow]

I'm thinking of installing a small mains operated water heater; the kind with a small tank (around 5-10 litres, like this https://www.screwfix.com/p/flomasta-undersink-electric-water-heater-2kw-10ltr/997ym?ref=SFAppShare), operating on about 2kW. I have a spare MCB on my mains consumer unit, and would use that to power it.

There is an existing calorifier, which works fine but which only provides hot water after the engine has run long enough to get up to temperature - which is a long time; the Volvo Penta 2003 warms up very slowly! The calorifier is difficult of access, being at the after end of the cockpit locker, and does not have any facility for fitting an immersion heater. Replacing it would be a difficult and arduous job.

What I have in mind is to install a water heater on the return line from the calorifier. This would provide hot water in both the heads and the kitchen sinks. If the water is hot from the calorifier, the thermostat of the water heater will keep the power off. I'd put the water heater in the heads compartment, where I think access to the pipework is feasible.

I assume you mean the hot outlet from the calorifier to the water heater, then from the water heater to the taps ? If so, i think it will work as you expect.

Yes, 2kw is higher than most calorifiers, but it should be fine as long as you don't put anything else on at the same time that exceeds 2Kw, if you are on a 16A supply.

 

[AntarcticPilot]

I don’t know what the flow rate is like on the cheaper brands but there are definitely options that just plug into a normal 3 pin socket and draw the same as the kettle posted above. If it’s the only thing you are using at the time UK shore power should cope.

Well, it ought to be possible to work it out from first principles. Assuming a maximum power rating of 3kW, and the specific heat capacity of water is 4184 J/kg/degree.
If there are no losses (!) that means that the heater can raise the temperature of 750cc of water by 1° every second. So it can raise the temperature of 32.5 cc of water by 20° every second. That should get the temperature up to hand hot. But you get correspondingly less the hotter you want your water. In the UK it is likely that the temperature of the water supply will be less that 10°C, so you might want to raise the temperature by 30°C, lowering the flow rate to 25cc/sec.

For comparison, a low flow rate for a shower is 100cc per second. So the tank less heaters are fine for hand washing and dish washing but inadequate for a shower.

 

[mrangry]

One of these?

https://www.ebay.co.uk/itm/12760314...wbLtnbd8e1dg2yvP42clXRa-1_2yaA4hoCpssQAvD_BwE

 

[AntarcticPilot]

One of these?

https://www.ebay.co.uk/itm/127603148268?chn=ps&_ul=GB&_trkparms=ispr=1&amdata=enc:1YUBJK0yiQYOwFfo8m-Aiuw26&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=127603148268&targetid=2448003509029&device=c&mktype=pla&googleloc=9046950&poi=&campaignid=21690875706&mkgroupid=188473833775&rlsatarget=pla-2448003509029&abcId=10027099&merchantid=5383275489&gad_source=1&gad_campaignid=21690875706&gbraid=0AAAAAD_Lr1ckQE06fk8VIPSaHRsx44wCU&gclid=CjwKCAjw-8vPBhBbEiwAoA39WnQvJIHSznUV3gIOZHewP0wbLtnbd8e1dg2yvP42clXRa-1_2yaA4hoCpssQAvD_BwE

Would require wholesale changes to the existing system - it would have to replace my existing Eberspacher, and be plumbed in to the calorifier somehow - note that its designed to warm coolant, not potable water. As my coolant is raw seawater, I don't think its a practicable solution without changing the cooling arrangements for the engine - which isn't going to happen. Its also at least twice the price of the water heaters I'm looking at.

 

[wingcommander]

Do you have a Weberspacher/ Chinakuni type of hot air heater, if so the Bobilvans.co.uk type may be an alternative option.

Edit just seen Mr angry post , and your response

The bobil uses existing heater and is basically a air to water heat exchanger piped in parallel to the warm air outlets

 

[AntarcticPilot]

Do you have a Weberspacher/ Chinakuni type of hot air heater, if so the Bobilvans.co.uk type may be an alternative option.

Edit just seen Mr angry post , and your response

The bobil uses existing heater and is basically a air to water heat exchanger piped in parallel to the warm air outlets

Ive just checked, and it's an expensive option, though it does free me for the need for shore power.