One for the sparkies!

[Gary Peacock]

I have got roped into looking at a "fault" a customer is trying to sort out on a DIY boat. (Why do I keep getting involved in things we aren't responsible for?

 

Here is the problem, He has fitted AC extractor fans. (Someone else claims that the basic method of installation is correct. (We will see!))

The fans are the type with delayed run down after lights are switched off. I assume he his just using a pull switch to switch the lighting feed to the unit, there isn't any AC lighting.

The problem he his having is that the fans switch on and run fine but at the end of the run down time when the delay timer turns off the fan the boats RCBO trips out.

 

Sounds very strange indeed I am assuming the fans will be earthed and the problem must be down to a earth leak?

 

But why only on run down?

 

It could turn out to be something stupid but before I get involved in something I could do without, I thought I would ask!

[chris w]

Gary

 

1. Can the RCBO be reset OK immediately after it has tripped?

 

2. Check that the unit is wired correctly polarity-wise. The owner may have swapped live and neutral or earth and neutral.

 

3. Can you temporarily insert an MCB and a separate RCD to ascertain if it's the RCD or the MCB part of the RCBO that is tripping. I suspect, like you, that it's the RCD part.

 

4. is this something that has just started occurring or it's been happening since initial installation?

 

 

Chris

Edited January 30, 2007 by chris w

[Guest]

It is odd that it only trips at the end of the timer cycle. I tend to agree with Chris that a reverse polarity test is a good place to start. I've seen many of these operate happily on RCD's over the years, so can't think of anything else off hand.

 

Edit: What is the supply? mains? inverter? Is it a centre tapped supply?

Edited January 30, 2007 by Guest

[Tommo]

There are 3 connections to these fans, (1) permanent live, (2) neutral, (3) switched live or T. If it is just a typical small surface mounted fan they don’t have an earth terminal so I would discount that, unless somehow it is shorting out to the steelwork.

Could be they have used 3 core flex, used the green/yellow as the neutral and got confused and connected to the earth at the supply end.

That’s the trouble with a RCBO, you never know if it is going out for an earth fault or short circuit.

 

Ian

[Gary Peacock]

I think it could well be something stupid but it is a brand new installation and the fault was immediate and the chap who checked it for him is normally good at spotting faults.

 

I don't like faults like this they are a real pain, I used to be a networking engineer and used to come up against earth problems in the coms world every now and again with all sorts of wonderful results!

 

I will let you know how what I find.

 

It is odd that it only trips at the end of the timer cycle. I tend to agree with Chris that a reverse polarity test is a good place to start. I've seen many of these operate happily on RCD's over the years, so can't think of anything else off hand.

 

Edit: What is the supply? mains? inverter? Is it a centre tapped supply?

 

He's getting the problem regardless of source apparently.

[NB Willawaw]

You talk about fans in plural. Does it do this on any of the fans when they are switched on one at a time ?

[Theo]

Is it an electronic timer or a thermal one? The one in our bathroom at home is the thermal type and has give at least fifteen years of reliable service. It's not adjustable, though.

 

Nick

 

Edit punctuation.

Edited February 4, 2007 by Theo

[Gary Peacock]

Sorry I forgot to reply on this one.

 

It came down to the usual I know what I am doing boater syndrome!

 

He connected the Earth to the switched live feed input the fans have a built in pull switch that simply connects the live feed to this terminal if you choose to utilise this option so when he pulled the switch it grounded the live and tripped the RCBO.

 

You know it really does concern me that people with little or no knowledge are quite happy to get in there and attempt jobs beyond their ability on boats but wouldn't dream of doing the same at home or on their car.

 

 

Is it down to money or pure stupidity?

[tomsk]

Sorry I forgot to reply on this one.

 

It came down to the usual I know what I am doing boater syndrome!

 

He connected the Earth to the switched live feed input the fans have a built in pull switch that simply connects the live feed to this terminal if you choose to utilise this option so when he pulled the switch it grounded the live and tripped the RCBO.

 

You know it really does concern me that people with little or no knowledge are quite happy to get in there and attempt jobs beyond their ability on boats but wouldn't dream of doing the same at home or on their car.

Is it down to money or pure stupidity?

 

 

Bit of both prolly, with a little stubborness thrown in for good measure..... I have always taken the view that if people DIY'ed the bits that are non-critical and used the money saved to fund a professional to undertake the critical bits their life would be a lot simpler in the long run....

[Theo]

Bit of both prolly, with a little stubborness thrown in for good measure..... I have always taken the view that if people DIY'ed the bits that are non-critical and used the money saved to fund a professional to undertake the critical bits their life would be a lot simpler in the long run....

 

 

I think that the psychology goes a little bit deeper than merely saving money. I enjoy the challenge and that makes me try things that are a bit more difficult than I have done before. Presumably your man did not know how to read a circuit diagram, though, and that is rather scary!

 

Nick

[tomsk]

I think that the psychology goes a little bit deeper than merely saving money. I enjoy the challenge and that makes me try things that are a bit more difficult than I have done before. Presumably your man did not know how to read a circuit diagram, though, and that is rather scary!

 

Nick

 

Quite, I understand peoples wish to expand their level of self-reliance, however there are limits, If they wish to run cables and get a competent person to check before connecting up fair play, but i don't think many sparkies would wish to take that chance 'just in case'

[Guest]

Sorry I forgot to reply on this one.

 

It came down to the usual I know what I am doing boater syndrome!

 

He connected the Earth to the switched live feed input the fans have a built in pull switch that simply connects the live feed to this terminal if you choose to utilise this option so when he pulled the switch it grounded the live and tripped the RCBO.

 

You know it really does concern me that people with little or no knowledge are quite happy to get in there and attempt jobs beyond their ability on boats but wouldn't dream of doing the same at home or on their car.

Is it down to money or pure stupidity?

Believe me Gary they do such electrical cock ups in homes as well; I could write a book. The most dangerous of all were the ones who fiddled the electricity meters.

[anhar]

Believe me Gary they do such electrical cock ups in homes as well; I could write a book. The most dangerous of all were the ones who fiddled the electricity meters.

Is that possible? You must tell us all how catweasel.

 

Steve

[tomsk]

Is that possible? You must tell us all how catweasel.

 

Steve

 

Its really very simple, but I'm not telling

[Guest]

Is that possible? You must tell us all how catweasel.

 

Steve

Much harder nowadays, rest deleted so I dont get told off.

Edited February 5, 2007 by Guest

[tomsk]

Much harder nowadays, but in the old days when meters had the rotating disc it was a doddle. Can't say on here of course, but there were many ways. A clue might be "oh dear a crack has appeared in the glass." The black box was a favourite sold in many pubs, made the meter actually reverse so a few units could be wound off. We dismantled one once that had been confiscated, again very simple. Best/worst I ever read about was a gas meter though, when a guy by me had removed the gas meter and connected a piece of motorcycle inner tube across with two jubilee clips. He got banged up for twelve months.

 

 

I wasn't thinking of fiddling the meter I'll say no more

[DHutch]

Or just clamp some cables onto the pre-meter feed....

[tomsk]

Or just clamp some cables onto the pre-meter feed....

 

 

DoH!!

[Guest]

Or just clamp some cables onto the pre-meter feed....

Typical student Dan