Immersion heater size

[Powney]

Okay not used this for a while, I need of some advice;

 

After this mild winter and hooked up to shoreline 240v I'm going to fit a immersion heater to my tank. Sick of burning gas for hot water and not using my rads. And before you say back boiler, that's a summer job.

 

So I picked up a 3kw immersion element from my local plumbing centre, these guys where good and wanted to see pictures of the tank and sizes etc.

 

I have read that a 1kw one would do but waiting for 1-4 hours is a long time, I'm planning on having it on a smart/digital timer for when I get home from work and in the mornings.

 

Yes I know about 13amp fuses and wiring the thing; also keeping it separate from my inverter and battery charger so I don't blow the whole thing.

 

Anyone else have a 3kw, anyone tried one in a boat. It should be straight forward fitting and I don't see a problem using a 3kw, a 1kw just means more waiting time to me.

 

Thanks in advance

 

I tried searching for this but the posts where really old and surely someone has a comment about this

[bottle]

Assuming that it is all wired correctly (cable sizes, switching and fuses/circuit breakers) and the shoreline is adequate no reason not to.

 

Personally I would not do it, only my opinion..

[PaulJ]

3kw is ok as long as you dont wire it in using a 3 pin plug- wire it directly to a suitably rated timer.

If you have, like many, a limited power supply you will be forever tripping out as you overload the bollard.

 

(slower typer than bottle)

Edited February 15, 2016 by PaulJ

[ditchcrawler]

If its on a timer it makes no difference how long its on for as it switches without you doing anything.

[raymondh]

Be aware that domestic overheat stats may trip when the calorifier is heated by the boats engine

 

"An independent secondary safety stat that is set at a much higher temperature so the engine doesn’t trip the stat unnecessarily. This would happen with a standard domestic immersion."

 

Quote from SureCal website

 

Ray

[John V]

Be aware that domestic overheat stats may trip when the calorifier is heated by the boats engine

 

"An independent secondary safety stat that is set at a much higher temperature so the engine doesn’t trip the stat unnecessarily. This would happen with a standard domestic immersion."

 

Quote from SureCal website

 

Ray

 

I can't follow any logic in this quote......if the engine is running and the water is hot.....who cares if the immersion thermostat is tripped.....it's at or above required temperature when the immersion thermostat would have opened anyway

[PaulJ]

 

I can't follow any logic in this quote......if the engine is running and the water is hot.....who cares if the immersion thermostat is tripped.....it's at or above required temperature when the immersion thermostat would have opened anyway

Because next time you plug it into the mains it wont work until you realise you have to reset it!

[WotEver]

Because next time you plug it into the mains it wont work until you realise you have to reset it!

Resetting it every time you ran the engine would get old really quickly.

 

Tony

[John V]

true ....I had forgotten that thermal trip....I was thinking of the thermostat which of course auto re-sets........but what temperature does that operate at and would the calorifier ever over reach that ?

[nicknorman]

We have a 1kw immersion and I think it's fine. Although it takes quite a while to heat the whole calorifier from stone cold, in reality the calorifier won't be stone cold since you had hot water in it yesterday, and to have a shower you just need the top 25% hot. I'd say that from a tepid calorifier to enough hot water for a shower is about 40 mins. If you are going to put it on a timer then I don't see that it matters too much how long it takes. If you get a 3kw one it will hoover up nearly all of a 16A shore power supply and not leave much left for other stuff, whereas with our 1kw heater I can still use the electric kettle.

true ....I had forgotten that thermal trip....I was thinking of the thermostat which of course auto re-sets........but what temperature does that operate at and would the calorifier ever over reach that ?

It is a known problem. Domestic hot water is usually around 65C so let's say the manufacturer decided to make the safety trip 75C. But you have an 80C thermostat on your engine ...

Edited February 15, 2016 by nicknorman

[raymondh]

Also depending on make safety cut-out devices may be single-use (i.e. must be replaced after they have been activated), or, manually resettable

 

Which type is on your heater?

 

Ray

[John V]

It is a known problem. Domestic hot water is usually around 65C so let's say the manufacturer decided to make the safety trip 75C. But you have an 80C thermostat on your engine ...

 

I can see where you are coming from..........I use a 3kw immersion in my bathroom calorifier which has twin coils one fed from the central heating the other from the engine, neither of which ever get the water much hotter than the immersion will .....possibly because it is about 50 foot from the engine

[Powney]

Thanks for the comments. The NB doesn't have heated water from the engine. I have a Adle boiler and its heavy on gas for just making hot water. I'm thinking more of ease while on the shoreline. I won't be using the immersion heater while cruising.

 

It's a backersafe anti corrosive 3kw immersion heater.

 

Just wondered if anyone else has used a 3kw one, I don't think there should be a problem...

 

Cheers again

[John V]

One important thing, is remembering not to switch anything else on at the same time as the immersion

[PaulJ]

My last immersion was a (cheaper) 3kw jobbie but have now fitted a 1kw one-mainly because I can run it off my gennie if I ever need to.

[by'eck]

3kW sounds way over the top and should be matched to the volume of water you are heating.

 

Marine calorifiers run in the range 15 to 90 litres with household ones in the range 80 litres to over 300 litres. A typical household one would justify a 3kW heating element, a marine one 1kW maybe max 1.5 kW.

 

A 1kW element will raise 30 litres of water 30^oC in one hour, which should give you a comfortable shower.

[George94]

The proper reason for fitting a 1kW element is that you are less likely to trip a 16 Amp pontoon supply when you decide to boil a (1 kW) kettle and pop some toast in the toaster just when the calorifier decides to switch on.

 

Some boats have very small calorifiers. It's best to fit a decent sized one if you can. Then you won't run out of hot water after one shower.

[Powney]

After much thought reading and my own disregard to the 16amp supply; I'm thinking maybe 1kw would be better. Not good tripping the world while I make a cup of tea.

 

Thanks for throwing some ideas about and helping me realise what I really need that's more sufficient.

 

Cheers, back to the shop with the debit card

[LEO]

Hi,

 

I have a 1Kw immersion heater on the boat and have problems with the unit tripping out if the back boiler (diesel stove) runs for long periods.

 

I have solar units at home which heat the water by an immersion heater, initially the heater was a 3Kw unit - this heated the water at the top of the tank but it's better to get the whole tank warm.

 

I found the solution was to buy a 1Kw unit which reached almost to the bottom of the hot tank.

 

Others have changed immersion heaters on their HW tanks on boats with similar improved results.

 

A very well insulated system helps

 

L

[John V]

3kw immersions are available in several different lengths

[bottle]

So are 1Kw ones.

[John V]

Warning pedant alert !!!

 

so are 1.5kw ones

[Powney]

Mine would sit in the tank horizontal at the bottom and be 11" element I think. Going to inquire on a 1kw one.

[Glynn]

I changed ours to a 2Kw one , no problems at all and faster to heat up than the 1 Kw.

[LEO]

Hi,

 

I agree various lengths of 3Kw heaters are available but if you are running a 4Kw solar system it's easier to get 1Kw to 1.5Kw out of it and generate HW. This is having a Solar Immersion Converter fitted and allows primarily for using other equipment.. Yesterday my panels produced 8.5units most of which diverted to underfloor heating.

 

On the boat it's also a pain when people use a 3kw appliance as if others do the same the main trip operates and it's a long walk to reset it.