Stubby Parcans

[Marineboy63]

Just found a pile of stubby Parcans without an earth link between the back end and the front end.

 

I'm assuming that despite the fact they have PAT test stickers going back several years, that they should have a link.

[paulears]

Depends on the fitting on the back - some are double insulated and don't have a bond, but most do. Look for the symbol on the terminal assembly, if it doesn't mention Class 2, then there should be a bond.

[adam2]

May not be needed, depending on the design.

 

Could the unearthed front of the par can become live under reasonably foreseeable conditions of fault or failure ? If the front part could not become live then it does not need earthing. Presuming that the mains supply flex, internal connections and lamp terminals are all confined to the rear part, then the front part does not need earthing.

 

The presence of PAT test failed stickers is certainly cause for enquiry and investigation, but the lanterns may in fact be fine. I have a rather low opinion of many PAT testing outfits.

 

 

 

[Boggy]

I was under the impression (and someone correct me if I'm wrong) that the bond between the front of the can and the rear also acted as a mechanical safety. This is to prevent the rear of the can falling off if it is not clipped in correctly and gets bumped.

 

I am also keen to hear opinions on the correct wire for the job. I had some cans with standard earth wire (e.g. green/yellow striped from power lead). These wires had significant scorch marks and I felt were a fire risk. I have replaced them with a small diameter non-insulated stranded steel wire bought from a rigging shop as seen in other cans that I own.

[Don Allen]

I regard the primary purpose of the wire is to secure the rear cover of the par can to the body. I use a 2mm galvanised steel rope 2mm wire rope as it can be crimped into ring terminals and dressed to sit parallel to the edge of the can so it does not make contact with the how lamp.

 

I also err on the side of caution and consider it an equipotential bond for earthing and always fail a par can if it is missing as my individual interpretation of a suitable visual inspection.

 

Standards have improved on par cans over time, which is why you see some with lamp screens and some without.

[paulears]

I know what you mean Don, but is the visual inspection for mechanical integrity sensible, but nothing to do with the electrical safety? If the cable forms part of the yes/no pass decision, then would lack of an external safety bond also create a PAR fail? The trouble seems to be that presented with a can unknown to me, how would I know the front to back bond was missing, or was not required by the design? Easy when you have six to compare it with, tricky with just one.

[Don Allen]

Yes, the mechanical integrity is sensible and raising the standards of stage safety. Most persons doing testing and tagging as a franchise would not do any research on safety features of different stage lights, but would default to a basic class 1 earthed appliance.

 

It was not until late in the development of the par can, that an earth symbol was stamped on the rear shell, near the mains entry point, that improved the pass margin of par cans when being pat tested. This was about when the mains bond/mechanical bond was also supplied as a standard feature. This bond is usually on the same screw as the mains earth.

 

Going off topic, I like to get an earth on the yoke, as in Australia we do not have to earth the lighting bars, so every stage light with an effective earth to the yoke improves stage safety, which is why I look for it when testing and tagging.