1Kw Immersion heater

[hector1988]

Still at the planning stage. Anyone have any experience of using these 1Kw Immersion heaters that are fitted to modern calorifiers? any idea how long to heat a tank of water? Obviously depends on size of

tank so please state if known. Plan at this stage is to use Engine/Immersion to keep things simple.

May go Paloma route.

Thanks,

Dave

[Sir Nibble]

I have always found heat to be the most costly use of electricity. What with all the losses inverting 12V to 240 the whole idea fills me with horror!

Just an idea, how about 83A worth of glow plugs immersed in water? That's about 8 plugs and I can tell you from experience they are good at heating water. Still expensive in current but minus all the conversion losses.

[Stroudwater Boy]

When I was investigating PV panels and wind turbine for installation at home I remember that a couple of companies offer 12V immersion heaters to use as an energy sink instead of dumping power once the batteries are full, more efficent than an inverter if you can power directly.

[Gibbo]

Still at the planning stage. Anyone have any experience of using these 1Kw Immersion heaters that are fitted to modern calorifiers? any idea how long to heat a tank of water? Obviously depends on size of

tank so please state if known. Plan at this stage is to use Engine/Immersion to keep things simple.

May go Paloma route.

Thanks,

Dave

 

Roughly speaking, a 1kW immersion heater will raise the temperature of 15 litres of water by 1 deg C every minute. Or 30 litres by 0.5 deg C every minute. Or 7.5 litres by 2 deg C.

 

You can therefore work it for your tank size.

 

Say you have a 45 litre tank. 1kW will raise the temperature by 1 deg C every 3 minutes. 10 deg C in 30 minutes, 20 deg C in 60 minutes and so on.

 

Roughly..... Temp rise per minute = heat in Watts/(water volume in litres X 60)

 

Gibbo

 

Edited to say, if you're planning on heating water from self generated electricity I think a visit to the doctor would be more in order. Shorepower only.

Edited October 29, 2007 by Gibbo

[GUMPY]

Still at the planning stage. Anyone have any experience of using these 1Kw Immersion heaters that are fitted to modern calorifiers? any idea how long to heat a tank of water? Obviously depends on size of

tank so please state if known. Plan at this stage is to use Engine/Immersion to keep things simple.

May go Paloma route.

 

If the immersion is at the top of the tank, as mine is, it only heats the top half of the tank which is where the water is drawn from so its useful for those times when you dont have any other way of doing it and need a quick shower or to do the washing up.

If you want to heat the whole tank the immersion boss needs to be at the bottom or better still one at the top and one at the bottom.

 

Julian

[DaveR]

I have a 1kw immersion for use, as Gibbo says, from shore power.

 

I get the rest of the hot water from the engine cooling water via my single coil tank. Should have forked out the extra few pounds and got a twin coil.

 

Dave

[Gibbo]

Here's something I did a few years ago for someone else which is a bit of an eye opener....

 

A standard 25kg bag of coal, or an 18 litre can of diesel contains

roughly the same energy as 140 fully recharged lead acid batteries

weighing just over 4 tonnes.

 

To get a 25kg bag of coal onto your boat will take about 5 minutes and

cost 7 quid. To get 18 litres of diesel onto your boat will take 15

minutes and cost about a tenner.

 

140 batteries will cost about £8,000 and last about 200

discharge/recharge cycles. Thus £40 per cycle.

 

To recharge 140 lead acid batteries from flat with a 70 amp alternator

will take just under 2 weeks using about 500 litres of diesel and cost

around 300 quid. Plus the £40 battery costs............

 

Same energy.........

 

Coal £8.00

Diesel £10.00

Batteries £340.00

 

The moral? Don't use electric heating on your boat.

 

Gibbo

[Sir Nibble]

Well that gives my instinctive horror of the idea some figures to be horrified about!

[smileypete]

Here's something I did a few years ago for someone else which is a bit of an eye opener....

 

Same energy.........

 

Coal £8.00

Diesel £10.00

Batteries £340.00

 

If the above represents 180kWh then batteries come in at £1.88 per kWh.

 

This doesn't look quite right to me

 

Wonder what the cost of storing 1kWh in a typical semi traction battery is, in terms of battery costs and efficiency?

 

Edit:

 

Say you use white diesel, which is £1/litre or 10p/kWh

 

Then if the engine is 30% efficient the power at the crankshaft costs 33.3p/kWh

 

Then if the alternator and belt is 50% efficient the power from the alternator costs 67p/kWh (any comment Snibble?)

 

Then the cost of storing the energy in batteries and getting it and inverting it must cost £1.21/kWh.

 

cheers,

Pete.

Edited October 29, 2007 by smileypete

[Travis]

We have shore power and use our 1kw immersion heater in the summer when the boiler is turned off. It's on a timer so it comes on before we wake in the morning for a hour and in the afternoon before we get home from w**k, again for around an hour.

 

Works OK so far, but I wouldn't dream of using the invertor to run the immersion heater. When we are away from the mooring the engine heats the water when sailing , we use the genny to recharge the batteries in the morning via the battery charger and switch on the immersion heater to give the genny a little more work to do.

 

Andy.

[smileypete]

Hi,

 

I'd agree in general it's a bad idea to heat a calorifier using inverter and normal batteries.

 

May be alright to do occasionally for 5 minutes to top up a lukewarm calorifer for a shower.

 

I'm suprised how much it costs to store and retreive energy from batteries, I'm sure Gibbos figures are correct.

 

cheers,

Pete.

[Gibbo]

If the above represents 180kWh then batteries come in at £1.88 per kWh.

 

This doesn't look quite right to me

 

Wonder what the cost of storing 1kWh in a typical semi traction battery is, in terms of battery costs and efficiency?

 

Edit:

 

Say you use white diesel, which is £1/litre or 10p/kWh

 

Then if the engine is 30% efficient the power at the crankshaft costs 33.3p/kWh

 

Then if the alternator and belt is 50% efficient the power from the alternator costs 67p/kWh (any comment Snibble?)

 

Then the cost of storing the energy in batteries and getting it and inverting it must cost £1.21/kWh.

 

cheers,

Pete.

 

I can't work out what you're thinking here.

 

18 litres of diesel will release about 720 Mega Joules of energy when burnt.

 

720 Mega Joules = 720 Mega Watt.seconds = 200,000 watt hours. Divide by nominal 12 = 16600 amp hours. Call them 100 Ahr batteries that's 166 batteries. £48 quid each. That's about right.

 

Where's your head?

 

Gibbo

[smileypete]

I can't work out what you're thinking here.

 

18 litres of diesel will release about 720 Mega Joules of energy when burnt.

 

720 Mega Joules = 720 Mega Watt.seconds = 200,000 watt hours. Divide by nominal 12 = 16600 amp hours. Call them 100 Ahr batteries that's 166 batteries. £48 quid each. That's about right.

 

Where's your head?

 

Gibbo

 

I was looking at the overall cost per kWh of energy from 12v batteries, charged by a diesel engine with alternator.

 

cheers,

Pete.

[Gibbo]

I was looking at the overall cost per kWh of energy from 12v batteries, charged by a diesel engine with alternator.

 

cheers,

Pete.

 

Well the alternator is going to have to run at about 50 amps average over the 2 weeks to recharge the batteries. Run a typical diesel engine for 2 weeks and see how much diesel it uses with a permanent 50 amp load on an alternator. Don't try to work it out with efficiencies etc cos that won't work. It's no good saying "well the engine is say 30% efficient, and the drive belt will lose about 50% etc etc etc". The engine uses a shed load of diesel just to tickover. Before it even does anything. Now bear in mind that none of these engines ever have the alternator pulley'd up correctly so you have to rev the engine to get the alternator spinning fast enough.

 

You'll' find the figures are pretty close. Even if they're twice as high as reality (which they're not) it's still 17 times more expensive than heating with diesel!

 

Gibbo

[Guest]

We only ever use our immersion when we have the genny running (we have no shore power). To use it off the inverter is very inefficient even with the engine running.

[hector1988]

Not bothered about the decimal points and all the quibbles that go with them.

I appreciate the help though and it looks like a bad idea to use the immersion heater off inverter power.

I was thinking that i would probably run the engine at the same time and have the calorifier helping at the same time from engine water pre thermostat. The engine is a petter PH2W and can get 7hours on a gallon

of red/veg oil so is quite economical. Is this still a bad idea? If so may have to go back to a good old Paloma. (plus single coil calorifier)

Thanks,

Dave

[wrigglefingers]

Hello Hector,

 

You don't say if you are planning to be liveaboard (although I am a bit jet-lagged and may have missed it) but if you are, this is our experience.

 

We had a Paloma clone to heat water intially but it died and we were thrown onto the mercy of the 1Kw immersion heater in the calorifier to which, with some help, I fitted an in-line fuse and timer. We heat the calorifier for an hour in the morning and again at night, running from a shoreline. This gives us enough water to shower and wash-up provided we're frugal. I usually keep some water on the Squirrel if we're runnng low, but in any case just switching the timer over to manual solves any hot water shortage quickly enough for me to stir up the inclination to do the washing-up. The calorifier is well lagged and attached to the bulkhead. Electricity costs are not excessive and keeping the tank heated little and often seems to work well. We cut our use of gas (which is very difficult for me to get onto the boat due a combination of dodgy knee and a gas locker with a opening that's too small) from a 13kg bottle every 3 three weeks to one every 3 months. Out on the cut we rely on the engine and occasionally I do run my engine in the marina for speed-heating and a general look-see session. I wouldn't ever consider using the inverter to heat water as I quite like drinking cool beer and seeing my way to bed late in the evening!

 

Bestest, Jill

[blackrose]

Still at the planning stage. Anyone have any experience of using these 1Kw Immersion heaters that are fitted to modern calorifiers? any idea how long to heat a tank of water? Obviously depends on size of

tank so please state if known. Plan at this stage is to use Engine/Immersion to keep things simple.

May go Paloma route.

Thanks,

Dave

 

This doesn't have to be an either/or decision - you could have a calorifier with an immersion and a paloma. A simple L-port valve connecting the two hot water sources to the hot water pipe going to your outlets would allow you to manually choose where your hot water was coming from.

 

http://www.inprod.com/V3Lport.html

[hector1988]

Thanks to you all. I will not be live aboard, and we have our own mooring with no

electric, so i think we will go with single coil calorifier from engine(or twice through a twin coil) with

a changeover to paloma when required. If the Calorifier comes with the immersion all well and good.

but it wont be used with an inverter.

Dave

[blackrose]

Thanks to you all. I will not be live aboard, and we have our own mooring with no

electric, so i think we will go with single coil calorifier from engine(or twice through a twin coil) with

a changeover to paloma when required. If the Calorifier comes with the immersion all well and good.

but it wont be used with an inverter.

Dave

 

If you don't envisage having shorepower then an immersion heater isn't really an option unless perhaps you have a decent sized generator. I think you're right that using your batteries/inverter to heat the calorifier with an immersion makes no sense at all (I would say it's a ludicrous idea but someone is bound to say that's what they do!).

 

Just fit the calorifier so that the lump of insulation which commonly covers the removable plate is accessible, should you want to install an immersion in future.

Edited October 31, 2007 by blackrose

[wrigglefingers]

If you don't envisage having shorepower then an immersion heater isn't really an option unless perhaps you have a decent sized generator. I think you're right that using your batteries/inverter the heat the calorifier with an immersion makes no sense at all (I would say it's a ludicrous idea but someone is bound to say that's what they do!).

 

Just fit the calorifier so that the lump of insulation which commonly covers the removable plate is accessible, should you want to install an immersion in future.

 

No Mike, you are right - it is a ridiculous idea!

 

Incidentally fitting a calorifier immersion isn't difficult but most seem to have one already. To my mind it seems to be good sense to go for a twin-coil calorifier for greater efficiency generally and they don't cost that much more given the general expense in fitting-out a boat.

 

Jill