Fitting an AC ammeter

[Nauti Fox]

I'd like to fit one to keep an eye on what we are using, appreciate advice on the correct way to fit it.
Was thinking of fitting one of these.
http://www.marineelectrics.co.uk/pages/instruments.htm

 

[pvb]

[ QUOTE ]
I'd like to fit one to keep an eye on what we are using, appreciate advice on the correct way to fit it.

[/ QUOTE ]There are two different types of AC ammeter on the page you've linked to. The direct connection type will be easier to fit. The ammeter should come with full instructions on how to fit it correctly. I'd have thought you wouldn't need an ammeter to give you a rough idea of how much AC power you're using.

 

[TonyS]

Wouldn't a power or energy meter be more appropriate. Rather than just an instant reading it tells you as well what you have consumed. I use one on the boat to know how much the heater and de-humidifier have used over the winter. You can get them for under £10. This is one from Maplins http://www.maplin.co.uk/Module.aspx?ModuleNo=38343

 

[Nauti Fox]

It would be the direct type.
The reason I want one is that we are liveaboards and it will be handy to see how close we get to the trip limit.
The way I understand it is that its wired in and out from the same pole, ie the positive in and out on one pole, the neutral on the other.
Thanks Tony, yes we've already got one of those, and very good it is.

 

[pvb]

[ QUOTE ]
It would be the direct type.....The way I understand it is that its wired in and out from the same pole, ie the positive in and out on one pole, the neutral on the other.

[/ QUOTE ]No, that wouldn't measure current. The ammeter should be wired with the live from the source on to one terminal, and the live to the supply on the other terminal. Follow the instructions supplied with it. Remember you're messing about with mains voltages here - if you don't understand what you're doing, please get a qualified person to fit it for you.

 

[Nauti Fox]

Thanks for the advice.

 

[VicS]

[ QUOTE ]
the positive in and out on one pole, the neutral on the other.


[/ QUOTE ] No, as pvb says read the instructions.
If you connect an ammeter from live to neutral you'll short your mains system out and probably wreck the meter as well. (It's how you connect a voltmeter though)

Frankly if you are thinking thats how to connect an ammeter you should not be messing with the electrics at all. Sorry.

BTW AC systems dont have positive or negative, they have live and neutral, although I believe the preferred terms are now phase and ?return.

 

[Nauti Fox]

Thats ok, thats why I asked, just going on what I was told.

 

[john_morris_uk]

Ammeters and power used meters can give misleading results because the power factor of the load also has to be taken into account.

 

[mikefleetwood]

Ammeter should be in series with the phase/live supply, preferrably after the main fuse and isolator.

Pay special attention to insulation/safety. If the ammeter doesn't have shrouded terminals, try to fit some kind of insulating box covering the connections - make sure that accidental contact by finger/screwdriver/loose wire is not possible!

 

[Nauti Fox]

Think I'd better come clean here guys.
I have actually received the ammeter and it arrived with no instructions, so I telephoned the suppliers who asked what model is was, which I gave them. The guy then read me a set of instructions which I've quoted. I thought it didn't sound right which is why I posted the message.
I didn't want to post the details, but feel I should as it could be dangerous.

 

[VicS]

[ QUOTE ]
Pay special attention to insulation/safety. If the ammeter doesn't have shrouded terminals, try to fit some kind of insulating box covering the connections

[/ QUOTE ] I have suggested in a PM that the risks could be minimised by fitting the meter in the neutral rather than the live conductor.

Comments welcome.

BTW also gave a link to Tony Brooks' Tb training notes.

 

[pvb]

[ QUOTE ]
I have suggested in a PM that the risks could be minimised by fitting the meter in the neutral rather than the live conductor. Comments welcome.

[/ QUOTE ]Wouldn't that only be safer if everything in the boat was isolated?

 

[mikefleetwood]

Actually, no guarantee that incoming "neutral" really is. Safest not to make assumptions! (IMHO) Best treat both live and neutral as "Live" that way you don't get any surprises! (and conform to wiring regs)

 

[VicS]

[ QUOTE ]
Actually, no guarantee that incoming "neutral" really is

[/ QUOTE ] That's true and is why I said minimise risk rather than eliminate it.

I felt that the meter in question was probably the type of thing that would have exposed terminals on the back and would be intended for building into an industrial switch board or control panel. It will be necessary to prevent access to the terminals by some means or another but if they are not actually live then the risk is minimised.

With hindsight the alternative type offered by Index Marine with a CT instead of direct connection would have been a more sensible (but expensive) choice. Then there would have been no connections made to the mains wiring at all!