Immersion heaters

[tomandsophie]

We are looking for an alternative source of hot water now that we no longer have to run the engine for electricity (solar panels take care of that).

The two options seem to be either a Morco/Paloma gas water heater or a small immersion in the calorifier. The immersion would be much much much cheaper to fit (obviously!), but I am wondering if it is possible to run it off our inverter, and if so, how much electricity would it use? My calculations equate to around 4 amps for a 1kw immersion (1000w divided by 240v = 4.17a), so this would be fine if we used it for an hour or even 2. Do you think an hour of running would heat up enough water for two short showers?

Edited May 1, 2007 by tomandsophie

[WJM]

I dont live aboard but this winter I used my boat as a personal canoe club. I would plug in my mains line, switch on the immersion heater and go canoeing for an hour. On my return there was only just enough hot water for one quick shower. I know this is not exactly scientific but I hope it gives you some clues.

 

 

Forgot to mention - now the immersion heater is on the blink, I have taken to leaving the engine idling for the hour and the water is piping hot!

Edited May 1, 2007 by WJM

[Guest]

I tried our immersion once off the genertaor and the results were not brilliant. Far more hot water from the engine. I like Palomas BTW.

[ChrisPy]

2kilowatt hours should heat a 16 gallon tank by 50degrees F

[g8zpd]

We are looking for an alternative source of hot water now that we no longer have to run the engine for electricity (solar panels take care of that).

The two options seem to be either a Morco/Paloma gas water heater or a small immersion in the calorifier. The immersion would be much much much cheaper to fit (obviously!), but I am wondering if it is possible to run it off our inverter, and if so, how much electricity would it use? My calculations equate to around 4 amps for a 1kw immersion (1000w divided by 240v = 4.17a), so this would be fine if we used it for an hour or even 2. Do you think an hour of running would heat up enough water for two short showers?

 

You may have miscalculated the current drain at 240v is about 4a, but the current draw into the inverter will be about 90a (1000w @ 12v with interverter efficiency factored int).

 

So to running the immersion heater for 1 hour would use about 90AH. Not impossible, but will probably mean you need to run the engine or generator to recharge the batteries.

 

Paul.

G8ZPD

[tomandsophie]

Right, Morco or Paloma it is then! Thank you!

[Theo]

Blake has a 230V alternator and an immersion heater. The quickest way to heat the water is to run the engine and use the 230V alternator to power the immersion. This loads the engine a bit and makes it less liable to glazing the bores, and makes it produce a bit more heat. The batteries and the inverter don't come into it at all.

 

Nick

[blackrose]

I am no electrical expert, but I wonder whether having a powerful inverter sometimes creates a false impression of how much power is available?

 

At the risk of stating the bleedin' obvious, when someone asks "Can I run this or that piece of mains equipment from my inverter?" , perhaps they should really be asking themselves "Do I want to run it off my batteries?"

 

Although the immersion heater is 1Kw, the same as many power tools, the difference is that it will be on for at least an hour to get the water up to temperature before the thermostat kicks in and switches it off. I know it can be done, but whether one actually wants to do this is a different question. It obviously depends on rates of battery charging, but when we talk about whether a high demand 240v appliance can be run from an inverter, in our calculations I think we often forget about the other 12v equipment like pumps & lights which still need to be run directly from the batteries.

Edited May 2, 2007 by blackrose

[mayalld]

We are looking for an alternative source of hot water now that we no longer have to run the engine for electricity (solar panels take care of that).

The two options seem to be either a Morco/Paloma gas water heater or a small immersion in the calorifier. The immersion would be much much much cheaper to fit (obviously!), but I am wondering if it is possible to run it off our inverter, and if so, how much electricity would it use? My calculations equate to around 4 amps for a 1kw immersion (1000w divided by 240v = 4.17a), so this would be fine if we used it for an hour or even 2. Do you think an hour of running would heat up enough water for two short showers?

 

Your calculations on current draw are seriously flawed!

 

Yes, a 1Kw Immersion will draw 4.17 Amps at 240v, but you don't get 4A at 240v by putting 4.17A into the inverter at 12V. You would need about 85A for that.

 

If you want to draw 85A for an hour, then you need to have a battery capacity of at least 10 times that (discharging a battery for an hour at more than 10% of its Ah rating is likely to damage it), so you would need about 900Ah of battery.

 

Also, you need to consider how many amps your solar panels put out, and work out how many hours of sunshine you need to replenish the batteries!

 

An option that you might consider is to use a combined engine/immersion solution.

 

Start your engine to heat the water, but also run an immersion at the same time.

 

Not only will the immersion help to heat the water, but it will make the alternator work hard, which makes the engine work hard, and will cause the engine to warm up and the calorifier will heat up more quickly. Oh, and because 50A of the 85 you need for the immersion is coming straight from the alternator, you can manage with only 500Ah of battery bank...

[elessina]

We find we need to put our 1Kw immersion heater on for 2 hours to get two reasonable showers. 1hr would give a very luke warm shower. Generally we find we need to put the immersion heater on for 2 x 2hrs during the winter and 3 hrs in the summer (for showers and washing up etc.) We only do this when we are on shore power.

 

We have a large battery bank (12 x 2v x 920ahr) but would not use the 1Kw immersion heater off the batteries. We have a Webasto unit (£1,000) that heats up the hot water in summer when not on shore power and not cruising / running the engine.

 

Ian

Elessina

[GUCCC150]

Monarchs only way of having hot water was a emersion heat off a land line or the big deiesl genny in the engine room which had to be ran for a couple of hours at least. the JP2 is raw water cooled and I have been told by a few owners of JP2 that they are no good for hot water. so I am in the middle of having a morco fitted as paloma are no longer made and you cant get bits for them off the shelve ( I kept looking at them on Ebay but it worked out cheaper for a new one) I rang them up and asked all the right questions before going down that road again

[Sir Nibble]

To drift off topic a little. when I used to work in South Africa, everyone drank cold drinks, and as an Englishman I stop if not kept topped up with tea. I bashed a hole in a tin mug and soldered a glow plug into it. It would boil a cup of water for a brew in about a minute!

[Chris J W]

How about one of these?

 

 

12 Volt Immersion Heater Ebay Clicky

[Gibbo]

How about one of these?

 

 

12 Volt Immersion Heater Ebay Clicky

 

Interesting idea.

 

Only problem is, by my reckoning the big one (100 watts) will take 32 hours to heat a 50 litre tank from 15 to 60 degrees. And in the process use 270 amp hours.

 

Gibbo

[Chris J W]

Interesting idea.

 

Only problem is, by my reckoning the big one (100 watts) will take 32 hours to heat a 50 litre tank from 15 to 60 degrees. And in the process use 270 amp hours.

 

Gibbo

 

Did you typo there? The "Big" one is 600W.

[Gibbo]

Did you typo there? The "Big" one is 600W.

 

How odd!

 

It wasn't a typo, it was dyslexia. I looked at the last one in the list, assuming it would be the biggest!

 

So I'll start again......By my reckoning the big one (600 watts) will take 5 1/2 hours to heat a 50 litre tank from 15 to 60 degrees. And in the process use 270 amp hours.

 

Oh look. The batteries are still flat

 

Gibbo

[Chris J W]

How odd!

 

It wasn't a typo, it was dyslexia. I looked at the last one in the list, assuming it would be the biggest!

 

So I'll start again......By my reckoning the big one (600 watts) will take 5 1/2 hours to heat a 50 litre tank from 15 to 60 degrees. And in the process use 270 amp hours.

 

Oh look. The batteries are still flat

 

Gibbo

 

But at least you'ld be nice and clean whilst you waited for them to recharge!

[DHutch]

Palalomas are nice...

- Small, neat, simple, reliable, roubust (dont freeze it tho), ameanable, dependable, zero maintainace, safe to use..

 

Alternativly, what about a solar water heater? Much better than them overpriced photovoltaics you've got!

 

Daniel

[WJM]

Immersion Heater Question;

 

I mentioned earlier on this thread that mine had stopped working. No problem, I thought. Down to Wikes, bought a new one, screwed it in, wired it up and switched on - Click! fuse switch trips, back on, trips again, and so on... it will not stay on!

 

Then I take a close look at the old heater. In addition to the regular thermostat there is a second 'thingie' a a small blue device with a tiny red button/cap on top wired inline with the thermostat on the live run into the element. My new one does not have one.

 

Anyone know what this thingie is and if it is likely to cause the tripping?

[Guest]

To drift off topic a little. when I used to work in South Africa, everyone drank cold drinks, and as an Englishman I stop if not kept topped up with tea. I bashed a hole in a tin mug and soldered a glow plug into it. It would boil a cup of water for a brew in about a minute!

i know a similar trick with two teaspons (metallic) but I am not putting it on here.

 

Immersion Heater Question;

 

I mentioned earlier on this thread that mine had stopped working. No problem, I thought. Down to Wikes, bought a new one, screwed it in, wired it up and switched on - Click! fuse switch trips, back on, trips again, and so on... it will not stay on!

 

Then I take a close look at the old heater. In addition to the regular thermostat there is a second 'thingie' a a small blue device with a tiny red button/cap on top wired inline with the thermostat on the live run into the element. My new one does not have one.

 

Anyone know what this thingie is and if it is likely to cause the tripping?

I have always assumed that this device is a cut out, should the calorifier run dry. I could be wrong. Can't see that this would cause or prevent tripping. What is tripping: the RCD (earth fault) or the MCB (overload). Maybe it is a bigger wattage than your previous?

[mayalld]

Immersion Heater Question;

 

I mentioned earlier on this thread that mine had stopped working. No problem, I thought. Down to Wikes, bought a new one, screwed it in, wired it up and switched on - Click! fuse switch trips, back on, trips again, and so on... it will not stay on!

 

Then I take a close look at the old heater. In addition to the regular thermostat there is a second 'thingie' a a small blue device with a tiny red button/cap on top wired inline with the thermostat on the live run into the element. My new one does not have one.

 

Anyone know what this thingie is and if it is likely to cause the tripping?

 

My guess would be that your original immersion heater was 1kW (most boat ones are), and the one you bought from Wickes is 3kW (most domestic ones are), and is overloading things.

 

Most boat 240V systems are rated at a maximum of 16A total, and running a 3kW immersion would take all of that.

 

Basically, you can't buy an immersion suitable for your boat from Wickes/B&Q/Focus/Any other DIY shed.

[WJM]

Thanks Mayalid

 

I think you must be right - the new one is certainly 3kw - but the old one has no markings on it to tell me what it is. I did establish that only the thermostat on the old one had failed so I just replaced it with the thermostat from the new one. All seems to work now.

[tomandsophie]

Palalomas are nice...

- Small, neat, simple, reliable, roubust (dont freeze it tho), ameanable, dependable, zero maintainace, safe to use..

 

Alternativly, what about a solar water heater? Much better than them overpriced photovoltaics you've got!

 

Daniel

 

Daniel, that's what we're going to get. One nice solar panel for the hot water in the summer and the stove backboiler in the winter. Sorted. Now I've just gotta fit the bloody thing!

And 'overpriced' PVs - HOW DARE YOU! They are the best £480 I've ever spent! They'll have paid for themselves in only a year and a half. That's a huge bargain!

[blackrose]

Thanks Mayalid

 

I think you must be right - the new one is certainly 3kw - but the old one has no markings on it to tell me what it is. I did establish that only the thermostat on the old one had failed so I just replaced it with the thermostat from the new one. All seems to work now.

 

Yes I think you'll end up using most of the 16amp supply with that big immersion heater, so when you switch something else on it will trip. My immersion is only 1kw but it also has a second backup thermostat in case the first fails. I'm not sure if ordinary household immersion heaters have this feature?

Edited May 5, 2007 by blackrose

[Nige]

Blake has a 230V alternator and an immersion heater. The quickest way to heat the water is to run the engine and use the 230V alternator to power the immersion. This loads the engine a bit and makes it less liable to glazing the bores, and makes it produce a bit more heat. The batteries and the inverter don't come into it at all.

 

Nick

 

Hi Folks,

 

Does anyone know where a 230v alternator can be found and if so how much are they going for?

This system as described by Nick above is one im very interested in checking out for Discovery.

 

Cheers,

Nige