Odd problem with generator ..?

[Adrian]

HI All

Odd thing happened at the Market today. We had our 'pre-Christmas' Market - so muggins here volunteered to bring along some PA speakers and a little mains amp to provide the necessary 'Christmassy' music....

The amp in question is a little 25+25W Mosfet hi-fi amp (ETI, years ago, if I remember rightly) - which I'd been running in the studio for the past week or so, just to make sure that everything was working fine....

Ran an extension lead from the big, Land-rover-mounted, genny that the meat & sausages man runs. He uses it every week to operate some sort of a chiller system built into his trailer .... allegedy 240v and (judging by the size of the genny) loadsa amps...

So - cabled it all up, turned on the mains.... and..... nothing ! Mains in to the amplifier is via a conventional toriod, into a bridge rectifier, then feeding a front panel led from the +15v rail. Led didn't light......

Only had a little mains-tester screwdriver - which claimed that there was something 'live-ish' going into the amp. Oddly enough, the neon indicator on my little weller soldering iron also declined to light, when plugged into the power from the genny..

Gave up on the music thing - and used a portable CD boom-box instead.

Got back home, plugged in the amp - and, would you believe it, it lights up and behaves impeccably.....

So - any bright ideas as to what might have been going on with the genny ? Be nice to understand it by this time next year when we have our next pre-Christmas market....

Any generator experts out there ?

Thanks Adrian

[Andy Hall]

Yes. God is trying to tell you something.

[Adrian]

That's one theory !

Any others ?

Thanks Adrian

[Dave Plowman (News)]

My curse on those playing 'music' outside worked...

[dom]

Earth/neutral swapped on the supply?

[Adrian]

Well - I'm not surprised it didn't work if both you _and_ God had it in for me - I should have just stayed in bed !

We don't make a habit of it (the music) - just thought it'd help create the right atmosphere for the market this once....

Odd that the usual chiller system seems quite happy with this particular flavour of mains.....?

Adrian

[Adrian]

Would that cause these results ?

The power supply on the amp (just found the circuit diagram) has live & neutral coming onto the toriod, with mains earth connecting to the centre tap on the secondary......

Thinking about it - I'm not sure just 'what' the geny was using for 'earth'.... no ground spikes that I could see.... don;t know what's the usual arrangement in these circumstances

Adrian

[Dave Liquorice]

Or chiller unit mounted in same truck as genny using the vehical chassis as the return. Anything not connected to the chassis doesn't have a circuit...

In theory the generator chassis should be connected to one of the alternator phases and that point also connected to the real earth via a spike. But there are also arguments for having both phases floating wrt real earth. What is "best" really depends on the individual circumstances, how things are switched/protected and the existance or not of an RCD.

[Adrian]

Nope - wasn't that Chiller is ounted in a towable trailer - fed via a cable from the genny - probably 20m away. Pluggery at that point looked like the sort of kit you find on 110v isolation transformers - ended up 'somehow' in a conventional square-pin mains socket - extn lead out to where I was.

Plugging my amp in back at the 3-pin socket on the trailer also failed to make the amp work...... - which is why I suspected a problem with the amp....

I guess the real lesson to be learned (regardless of the bit about outdoor music and divine intervention ) is that, if you can't supply _all_ the kit yourself, then you need to take along some basic test kit to debug the other guys supply arrangements....

Should have remembered that from doing disco / band stuff about 35 years ago !

Ah well - another lesson (re-)learned

Thanks Adrian

[John]

The punters didn't want Slade or Roy Wood anyway.

[cj]

Hi Was the chiller unit running when you plugged in or did you go straight into the supply with no other load. The reason I ask is that earlier generators were series wound device and needed a minimal load before they would exite. May just have been that your kit didn't want enough power.

HTH

CJ

[dom]

Yup. I set up some kit on a yacht, where the captain proudly presented me with an extension lead he had wired from schuko plug to UK sockets board. He had managed to connect live to neutral, neutral to earth and earth to live. Those test plugs, very worthwhile.

[Dave Plowman (News)]

No chance it was 110v?

[Adrian]

Well - there's always a chance ! This is Ireland, after all...... but the connection was on standard 240v 3-pin outlets. He had some other stuff plugged in there

- must take a look next time I see him and see what sort of kit that was....

To be honest, I'm more concerned for the guy who owns the stall / genny combination - maybe I should suggest that he gets 'somebody who knows' to take a quick look at his genny / wiring - in the nicest possible way....

I have one of those '3 neon' mains tester plugs - I guess that might show up something ?

Thanks Adrian

[Adrian]

Ouch ! Talk about 'getting it completely wrong'...... presumably you used the test plug before anything more valuable ?

I'm still wondering exactly what was wrong with the 'mains' that I was given - I guess the fact that the (live-to-neutral) neon in the Weller iron didn't light suggests that there wasn't 240v across what I though was live and neutral..... but, beyond that, it's hard to say....

Ah well - you live & learn ! Adrian

[Adrian]

That's a possibility....

...must take an electric heater with me next time

- mind you - wouldn't have been a bad idea yesterday -

fairly strong, cold, northerly breeze going straight through two pairs of socks and two pairs of trousers - but I believe you had snow on the hills back in England, so I suppose we shouldn't complain....

The fun of an open-air market !

Thanks Adrian

[tony sayer]

In article , Adrian scribeth thus

I'd imagine that the neutral wasn't that, it was a balanced supply off the gennie with neither side earthed...

[Adrian]

Possibly - like centre-tapping a 110v site supply ? All too complicated for me - it'll be batteries or my own / borrowed / tested genny next time !

Thanks Adrian