Advice needed with manufacturing electrical equipment

[UKMeterman]

Hi,
You can probably get a copy of the above standard at your local library, whilst you are about it have a read of
[h=1]BS 2754:1976+A1:1977 I know it has been withdrawn but it will give you a bit of a education. Now you need to remember what the bonding wire is for, it is to keep the touch voltage down to a reasonable value and cause the supply fuse to blow in a reasonably short time without being subject to physical damage. It is likley that the supply fuse to these units will be a BS 1362 fuse link and that the power supply it self will have double insulation between the mains supply and any selv (32V or less) supply within the unit. [/h]
These units should have been subject to type testing where first off the production line and and randomly there after are subject to severe testing on the earth bond and the double insulation.
In the case of the earth bond, it is typicaly required in this type of instance to be tested at 25A for 60 seconds and maintain a resistance of less than 0.1 ohm throughout the test and not subject to damage from over heating. Likewise the double insulation will be tested to twice the normal flash test voltages for 60 seconds and have no sign of breakdown. Due to the nature of the type testing flash test the unit is not considered safe for further use and must be destroyed.

Given the use of the safety earth conductor, which is protected within the appliance then 1mm may be more than adequate.

 

[UKMeterman]

Hi Midwest,

I know what you're saying and it worries me, hence asking for advice on here. The problem I run into is that there doesn't appear to be a BS for the products we make. There is a document on the government website that is very informative but just states that the equipment has to be safe, without any specifics. I sometimes struggle with the vagueness of the information provided, including BS 7671. Its statements like a "where reasonably practical" etc. Just tell me to use a 2.5mm cable!

Raparee thanks for for that article and your help. Not sure if we'd be able to flash test our units without destroying them as some of the components are a little bit temperamental at the best of times but I want to make sure we carry out the other tests on every peice of equipment that leaves the building. It's helped comparing notes.

Rich

You may find that the routine flash test is "normative" in the standard, this means you will do this unless you have got a very very good technical reason why not, and components being temperamental is not an excuse. I have seen the inside of one of these parking machines and it doesn't seem if that one was designed with static protection and other issues in mind! The unit should have been certified as safe by an external test house and should be able to advise on routine testing. If you need more help contact York EMC at Yate.