Replacing a calorifier heating element

[alexincornwall]

Hi all,

During a recent trip to the Scillies, it became apparent that the heating element from our C-Warm calorifier had died as it was producing luke warm water and drawing all of the voltage from our gen set. I've pulled the old one out (what a pig of a job), and identified the make and model which no longer appears to be in production. Having spoken with a couple of marine specialists, they've advised that a marine branded unit isn't required and any domestic immersion element will do the trick.

I've taken the old unit to an electrical wholesaler and they've produced an item that looks virtually identical (and a quarter of the price of anything marine branded!). The key difference being that the old unit has a 2KW rating and the new is 2.7KW. The old unit is also a dual-stat, the new unit is single-stat.

I don't think I need to worry about the single/dual-stat point, but should I be concerned by the 0.7KW increase in output? Am I likely to fry our AC wiring?

 

[Boater Sam]

If you wiring is suitable for 2.7kW, 11Amps, then electrically it will be OK......................................BUT it must have the extra safety stat as well to prevent a high temperature boil over as you are using it in a sealed pressurised system.
If you heat it to the maximum possible temperature when the thermostat fails you will have a calorifier full of superheated water well above the normal boiling point.
If this then vents due to a rupture under pressure, the whole mass of water will instantly turn to steam and possibly kill you.

 

[Boater Sam]

Hi all,

During a recent trip to the Scillies, it became apparent that the heating element from our C-Warm calorifier had died as it was producing luke warm water and drawing all of the voltage from our gen set. I've pulled the old one out (what a pig of a job), and identified the make and model which no longer appears to be in production. Having spoken with a couple of marine specialists, they've advised that a marine branded unit isn't required and any domestic immersion element will do the trick.

I've taken the old unit to an electrical wholesaler and they've produced an item that looks virtually identical (and a quarter of the price of anything marine branded!). The key difference being that the old unit has a 2KW rating and the new is 2.7KW. The old unit is also a dual-stat, the new unit is single-stat.

I don't think I need to worry about the single/dual-stat point, but should I be concerned by the 0.7KW increase in output? Am I likely to fry our AC wiring?

Worry a lot about not having the safety stat, it is a vital precaution.

 

[howardclark]

The wiring should be as per a domestic item wired for a 13amp plug. If your system is like mine this will be from a switch to the element. There will also be a supply to the switch from your mains distribution system. Strictly for your load the wire size only needs to be 1.25mmsq but I would always choose 1.5mmsq as it has a bit more capacity and is readily available
Because you are at mains voltage the length of the run isn’t particularly important; Tinned wire is better than uncoated to prevent corrosion.
I am sure there are people more expert than me who can comment, but mains voltage/ampage can kill so if you are changing the wiring and are not confident, pay someone to do it.

 

[CJ13]

I found Penguin Eng, Hayling Island, very helpful when I replaced my element.

 

[alexincornwall]

If you wiring is suitable for 2.7kW, 11Amps, then electrically it will be OK......................................BUT it must have the extra safety stat as well to prevent a high temperature boil over as you are using it in a sealed pressurised system.
If you heat it to the maximum possible temperature when the thermostat fails you will have a calorifier full of superheated water well above the normal boiling point.
If this then vents due to a rupture under pressure, the whole mass of water will instantly turn to steam and possibly kill you.

Thank you, that is useful info. I did not realise that the dual stat had such a crucial safety implication so I'll return the single stat unit. I've spent quite bit of time on sourcing one this morning and options are limited, but I have found this one which seems to fit the bill.

Dual 24″/11″ Copper Immersion Heater & Thermostat +1.5m Cord, TIH460 - Buy at H.P.W.

Please let me know if I am mistaken.

I found Penguin Eng, Hayling Island, very helpful when I replaced my element.

Thank you. I have called them but they can't help with my requirement.

 

[alexincornwall]

The wiring should be as per a domestic item wired for a 13amp plug. If your system is like mine this will be from a switch to the element. There will also be a supply to the switch from your mains distribution system. Strictly for your load the wire size only needs to be 1.25mmsq but I would always choose 1.5mmsq as it has a bit more capacity and is readily available
Because you are at mains voltage the length of the run isn’t particularly important; Tinned wire is better than uncoated to prevent corrosion.
I am sure there are people more expert than me who can comment, but mains voltage/ampage can kill so if you are changing the wiring and are not confident, pay someone to do it.

Yes, the wiring is as you describe running directly from a specific switch on our AC panel. The wire is not tinned but there is plenty of excess so I can cut that away to reveal clean material to work with. I'm not sure if it's 1.25mm or 1.5mm unit I get back onboard. I'm confident in wiring the new unit myself and I don't like shoddy jobs!

 

[alexincornwall]

Deleted - repeated post

 

[Boater Sam]

Just to show what can happen, watch this.

 

[VicS]

Yes, the wiring is as you describe running directly from a specific switch on our AC panel. The wire is not tinned but there is plenty of excess so I can cut that away to reveal clean material to work with. I'm not sure if it's 1.25mm or 1.5mm unit I get back onboard. I'm confident tower the new unit myself and I don't like shoddy jobs!

.
Note also that immersion heaters are available with different sheathing materials. Choose from copper, incoloy or titanium according to the material of the calorifier and the water types you are likely to encounter.

.

 

[plumbob]

Try Midland Chandlers for mail order. Incalloy and the essential 2 stats. Got mine there.

 

[Iliade]

Caravan and motorhomes use a range of lower powered calorifiers/water heaters too. The replacement heater element for mine did cost ~£100 (!) but it won't kill me.

2.7 kW might be too much for some marina supplies. but then again so might 2 kW... Could your gen set handle it comfortably?

 

[PlanB]

When we had a similar problem, we found that although the fitting diameter looked as though it matched the tank - it didn't.
The first one we tried was also too long!

 

[Norman_E]

I replaced one years ago, and both old and new were only about 900 watts, which was quite enough to heat all the water we needed. A domestic cylinder usually has a 3KW element, but of course it has well over 3 times the water capacity of a boat calorifier, so there is no need for anything bigger. Although I no longer have the boat, so cannot check, I remember that in addition to the double thermostats the calorifier was fitted with a safety valve to vent excessive pressure.

 

[alexincornwall]

Caravan and motorhomes use a range of lower powered calorifiers/water heaters too. The replacement heater element for mine did cost ~£100 (!) but it won't kill me.

2.7 kW might be too much for some marina supplies. but then again so might 2 kW... Could your gen set handle it comfortably?

The genny had no problem with the 2KW element (until it developed a fault of course).

 

[alexincornwall]

Try Midland Chandlers for mail order. Incalloy and the essential 2 stats. Got mine there.

Perfect! They have exactly what I'm looking for. Many thanks indeed.

 

[PCUK]

You need a proper double insulated element. Domestic elements are not!

 

[Blueboatman]

Another source of titanium coated elements for marine calorifier.
IOW
900watts is plenty quick
Marine Immersion heaters
(They would also sell expansion vessels if one wanted that too )
Sobering stuff from Sam !

 

[Boater Sam]

You need a proper double insulated element. Domestic elements are not!

I have not found a domestic element that was not insulated for mains use, do you mean double stats?