Running 115v device on 230v

We are heading to cambridge boxing day for a few days if that makes it any easier for anyone.

Dave

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My mind was going ahead of the installation of this heater, and I was thinking I could heat up the sump oil using my old small Markon standby single phase generator in a sort of bootstrap fashion, but then realised that this would actually overload its 2.2KW capacity

AWEM

We've been to Nottingham and Burton three nights on the trot since Sunday, but nothing else planned, but if Dave was to meet up with us somewhere on Boxing Day I could hold it for Charles Ping who 'may' be down Kent way??

We are just off the A45 at Rushden/Higham Ferrers.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

Dave,

I reckon we'd both be a tad unpopular on Boxing day doing this sort of thing - - mind you - -all he wifes family coming then . . mmmm . . perhaps you could put it in a box a post it for me after the hols - obviously at my expense?

AWEM

Sounds a sound plan to me . . pinging Charles . . pinging Charles

AWEM

SWMBO says its fine to drop off at Peters on Boxing day. to arrange off list: small dot planes at ntlworld dot com

Dave

Can you sue Magicalia for the extra costs incurred due to not being able to hand it over at the show?

Mark Rand RTFM

from "Andrew Mawson"

I doubt that it will be really practical but I will be driving down to Billaricay on Boxing Day and will be in the Coventry area until then so if a convennient link-up could be made with Dave before Sunday and Billaricay is a convenient pick up point for Andrew, then we might work something out - even if it is left in Billaricay for a later collection.

JG

If you wire two heaters in series you will only get 1500W output if you use a suitable diode (which will cost about 50p) as well.

A triac circuit for 1500W will cost quite a bit more than that.

There's a very simple way of working this out using the RMS voltage, the mains is nominally 230V RMS and half wave rectification (i.e. a single diode) reduces this by root 2 to 162.6V RMS which is not what you want for your heater.

Greg

A watless way of losing the excess volts is to feed it via a series capacitor.

A 150uF power factor correction capacitor would do nicely.

Jim

But this application is resistive and has a thermal mass that's effectively infinite compared to 20mS, so it's the average power that's important rather than the instantaneous voltage. A diode is fine from the load's viewpoint.

Dave

I knew it - this is clearly the Mk IV Mawson-patented Kipper cooker!

Regards, Tony

Nice idea Jim, though I make the figures a little different.

A 1500 watt heater at 115v draws a tad over 13 amps giving it a hot resistance of just under 9 ohms, so to run off 230 volts I need a capacitive reactance of another 9 ohms which I make approximately 350 uF at 50 cycles. My calculations suggest the 150 uF would have a reactance of about 21 ohms at 50 c/s.

. . . goes scrabbing though capacitor boxes . . .

AWEM

Polte answer: RMS is all about the affect of a waveform on a resistive load, thermal mass is irrelevant, as is the period of the mains supply. If you don't believe me then try it, but stand well back... I suggest you find out what you're talking about before telling people to do dangerous things.

Greg

We have some 'very nice' 440uf at 1000V block film non-polarised caps on ebay..... :-))

Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk

Can you sell me 82% of one please and that'll do nicely Big chunky chaps aren't they !

AWEM

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....shushhhhhhhhh . . the patent's not been filed yet - don't tell everyone

AWEM

I'd recommend draining the sump & topping up with good ol' ground nut oil first though - 20-50 motor grade masks the flavour of the kippers just a tad

Regards, Tony