Is this possible? Electrical question

[stuhaynes]

Please forgive the Naiveté (and possibly the spelling!) but I have to ask

We've been looking for a 500 watt, 230 volt immersion heater for our calorifier. Must have 2 1/4 BSP thread, and NO, we cannot connect to the engine at present (mores the pity). We've been unable to to find one so far, so a possible plan 'B'?

My question is this..... Is there any way that we can supply the electric to our 1KW heater and 'strangle' the electric to reduce the effect of the heater so that it only draws 500 watts through the inverter? A resistor maybe?

Currently, cos we're 24 volts, the draw is about 42 amps and the alternator isn't happy.... 500 watts (or even a little less) will reduce the draw to nearer 20 amps, which is perhaps more acceptable?

Is this a practical solution?

Thanks, as always. Stu

 

[Beadle]

Must admit, I'm a little confused.

Is the present heater 24V or 230V

A resistor isn't a good idea it would dissipate as much power as the heater which rather defeats the objective.

It may be possible to get a high power version of a light dimmer but I'm not certain if they are readily available in the kW range - try Farnell catalogue or maybe Maplins

If it powered from the battery is it possible to take a 12V tap from the battery?

Is there a specific problem with finding a 500W element with the correct fitting?

 

[Jcorstorphine]

Try this web site

Please forgive the Naiveté (and possibly the spelling!) but I have to ask

We've been looking for a 500 watt, 230 volt immersion heater for our calorifier. Must have 2 1/4 BSP thread, and NO, we cannot connect to the engine at present (mores the pity). We've been unable to to find one so far, so a possible plan 'B'?

My question is this..... Is there any way that we can supply the electric to our 1KW heater and 'strangle' the electric to reduce the effect of the heater so that it only draws 500 watts through the inverter? A resistor maybe?

Currently, cos we're 24 volts, the draw is about 42 amps and the alternator isn't happy.... 500 watts (or even a little less) will reduce the draw to nearer 20 amps, which is perhaps more acceptable?

Is this a practical solution?

Thanks, as always. Stu

Have you looked at this web site
http://www.powerpal.co.uk/ppfaq3.html

 

[elton]

A simple silicon diode will chop off the negative half cycles of an AC supply current, thus halving the power output of the heater. It shouldn't get too hot as it's functioning mainly as a switch so it isn't having to dissipate the unwanted fraction of the power.

That's how I'd do it if I was dealing with mains power. I've used diodes to dim mains lamps. My only caveat is that I don't know how the inverter would deal with it. I would think it'd be ok, but don't blame me if it explodes.

 

[fergie_mac66]

I started to reply about a 12v tap in the batteries.. but realize now but guess you are powering the230 v heater from a 24v to 230 inverter!

 

[misterg]

We've been looking for a 500 watt, 230 volt immersion heater for our calorifier. Must have 2 1/4 BSP thread, and NO, we cannot connect to the engine at present (mores the pity). We've been unable to to find one so far, so a possible plan 'B'?

ASAP list one (it's special order, but a Vetus part No. V-WHEL22500 so you might be able to get it ex-stock from somewhere else):

http://www.asap-supplies.com/marine/immersions/vetus-immersion-heaters

Also Surecal list a 500W one (but only show details of the 750W one)

http://www.surecal.co.uk/Product/ImmersionHeaters.aspx

I don't think there's a *simple* way of doing what you want (anything is possible). I must say that I think you'd be better off concentrating your efforts on resolving the problems that prevent you connecting the calorifier to the engine :-/

Andy

 

[fergie_mac66]

elton's suggestion looks good and 6 amp enough. but a bigger diode wouldnt hurt

http://www.bardwells.co.uk/detail.a...tid=&manuid=gen&keywords=&minprice=&maxprice=

as it a stud and still cheap could have a heat sink just in case !

 

[elton]

I don't think there's a *simple* way of doing what you want (anything is possible).

I've given him the simplest way of doing it.

 

[fergie_mac66]

I've given him the simplest way of doing it.

absolutly cannot see how it could give the inverter problems

Years ago drill maufacturers used to reduce the power/speed of cheap drills with a diode to give a 2 speed drill !

 

[misterg]

I've given him the simplest way of doing it.

Your post wasn't there when I started my reply (Why doesn't this forum warn you when a new reply is posted whilst you are in the process of replying?? Others do...)

FWIW I think your reservations about how the inverter might react to a diode are spot on (and are exactly why I didn't suggest it).

No offence intended

Andy

Aargh! Seen FergieMac's relply now !!

No problem using a diode on mains appliances, because your chopping one side off a few hundred watts off megawatts of power generated in the powerstation. The proposal would mean chopping one side off pretty much the entire output of the inverter, and I just can't see it being happy. The only way to be sure would be to try it.

 

[elton]

Your post wasn't there when I started my reply (Why doesn't this forum warn you when a new reply is posted whilst you are in the process of replying?? Others do...)

FWIW I think your reservations about how the inverter might react to a diode are spot on (and are exactly why I didn't suggest it).

No offence intended

Andy

oops! Sorry

 

[VicMallows]

absolutly cannot see how it could give the inverter problems

Sadly I think it is absolutely certain that the inverter will object

Vic

(Edit: doubling: what happens on such popular forums !!!)

 

[misterg]

oops! Sorry

No worries!

 

[elton]

Sadly I think it is absolutely certain that the inverter will object

Vic

Possibly, but I think it might be quite happy. Although it'll still be drawing 1kW instantaneously, the average power draw (over 1/50 of a second) will be 500w. So it certainly won't overheat.

 

[fergie_mac66]

Your post wasn't there when I started my reply (Why doesn't this forum warn you when a new reply is posted whilst you are in the process of replying?? Others do...)

FWIW I think your reservations about how the inverter might react to a diode are spot on (and are exactly why I didn't suggest it).

No offence intended

Andy

Aargh! Seen FergieMac's relply now !!

No problem using a diode on mains appliances, because your chopping one side off a few hundred watts off megawatts of power generated in the powerstation. The proposal would mean chopping one side off pretty much the entire output of the inverter, and I just can't see it being happy. The only way to be sure would be to try it.

Yes it would reduce the voltage to the heater by a half ... i forget but it depends on the inverter . the power would be something to do with RMS

Sadly I think it is absolutely certain that the inverter will object

Vic

(Edit: doubling: what happens on such popular forums !!!)

It may well have an effect on the inverter , but the current draw should be a lot less , the tech dept of the inverter manufacturers may have an opinion/advice but if contacted would perhaps invalidate the warranty if they thought there was a problem .

 

[philip_stevens]

Please forgive the Naiveté (and possibly the spelling!) but I have to ask

We've been looking for a 500 watt, 230 volt immersion heater for our calorifier. Must have 2 1/4 BSP thread, and NO, we cannot connect to the engine at present (mores the pity). We've been unable to to find one so far, so a possible plan 'B'?

My question is this..... Is there any way that we can supply the electric to our 1KW heater and 'strangle' the electric to reduce the effect of the heater so that it only draws 500 watts through the inverter? A resistor maybe?

Currently, cos we're 24 volts, the draw is about 42 amps and the alternator isn't happy.... 500 watts (or even a little less) will reduce the draw to nearer 20 amps, which is perhaps more acceptable?

Is this a practical solution?

Thanks, as always. Stu

You could fit a 1.5kW (max load) dimmer switch unit that would reduce the loading.

.....but it is not cheap!!

 

[davidpbo]

Might these be of use?

I suspect they may not heat to as high a temperature as you might want.

 

[maxi77]

Might these be of use?

I suspect they may not heat to as high a temperature as you might want.

Regretably they will not fit properly in a standard immersion heater hole

 

[William_H]

Hot water heater

The dimmer described uses a system of switching on the power on each cycle with a time delay so perhaps the first half of the cycle is off then on when the next opposite polarity cycle comes along it does the same thing. This would not be so brutal on the inverter but still a shock to the system being the only load. It might be OK but then again it might not.
Other options (if there is another hole) is to fit a high powered element in series with the existing element.
So a 2kw element in series with a 1kw element will reduce power to about 600 watts. A 1kw additional element will reduce power to 250W.
Or if you found a transformer 250v to 120V rated at 250watts the resultant 120v on the 1Kw element would reduce it to 250W. Or you might find a 24v 120v inverter cheap in UK second hand. The 120v will give 250w in the element.
Just a few thoughts good luck olewill

 

[nimbusgb]

Google 'towel heating rail element 500 Watt' ( there are elements from about 300W upwards available )

Then you have an off the shelf ( and cost effective ) part, no fancy electrics and the only job is to make up an adaptor for the thread or find a rail element with the right thread.