gareth Posted September 27, 2007 Share Posted September 27, 2007 Here's a slightly strange one ... Just got a couple of samples of Parsafe fittings, and while they're clearly marked as Class 2 appliances (with the little "square within a square" double-insulation symbol stamped on the casing), they have 3-core cable feeding them and an earth bond to connect to the shell of the parcan. How, then, can they be considered as Class 2? Link to comment Share on other sites More sharing options...
J Pearce Posted September 27, 2007 Share Posted September 27, 2007 Is the parsafe considered as the appliance therefore being class2, with an earth bond supplied for the can, so that the parsafe alone is class 2, but the whole assembly becomes class 1? Link to comment Share on other sites More sharing options...
Wuddy Posted September 27, 2007 Share Posted September 27, 2007 Hi, A Par can, by the very nature of its construction has exposed conductive metal work which could become live in the event of a fault, therefore the metalwork needs earthing and the Par can is Class 1. The Par safe lampholder has two insulation barriers, the porcelain of the lampholder and the supplementary insulated cover fitted over the porcelain and has no expopsed metalwork requiring connection to earth, therfore the Par safe lampholder is Class2. The Parcan as a whole is therefore Class1 Link to comment Share on other sites More sharing options...
gareth Posted September 27, 2007 Author Share Posted September 27, 2007 I wondered about that ... bearing that in mind, what about the Parsafes (such as the ones sold by Thomann) which are wired in 2-core and don't have the earth bond? If a parcan itself (Parsafe notwithstanding) is considered Class 1, then wouldn't fitting them with the earth-free version of the Parsafe render them non-compliant with the regs? Link to comment Share on other sites More sharing options...
Wuddy Posted September 27, 2007 Share Posted September 27, 2007 Yep, sure would, if an item of equipment has exposed conductive metal work which could become live etc etc it is Class 1 and requires earthing. In continental Europe before harmonisation a lot of equipment, even Class 1, manufactured for mainland Europe didn't require earths as all installations are TT and protected by RCDs, with harmonisation products are manufactured to comply with all EU member technical requirements and so your current Par safes have an earth to comply with UK market. Link to comment Share on other sites More sharing options...
Ike Posted September 27, 2007 Share Posted September 27, 2007 I have to disagree on this one. Earthing of accessible conductive parts is only required when they could acquire hazardous touch voltages in the event of a failure of basic protection. As double and reinforced insulation goes above and beyond basic protection I really can't see how it would apply here. On a practical note I don't really see how it would be beneficial as long as you have a suitable (portable appliance) testing scheme. Link to comment Share on other sites More sharing options...
Wuddy Posted September 27, 2007 Share Posted September 27, 2007 Sorry, but the exposed conductive metalwork of equipment, which could become live in the event of a fault, shall be bonded to the main earth terminal of the installation The par can requires earthing as the phase conductor could become detached from the par safe and touch the case or the insulation on the phase conductor could deteriorate and the exposed live conductor could touch the case in both these scenarios, which do occur, if the metal case was not earthed no fault current would flow and hazardous touch voltages WOULD appear. In a properly designed and installed electrical instalation hazardous touch voltages should not happen. the main purpose of designing to The IEE Regs is to limit touch voltage to a non fatal level. Link to comment Share on other sites More sharing options...
KevinE Posted September 27, 2007 Share Posted September 27, 2007 I think strictly speaking the Class 2 definition is that there shall be a double layer of insulation between any current-carrying conductor and any accessible conductive parts? So for example a class 2 video recorder is metal but has a double insulated mains lead and sleeved live terminals inside, the first layer inside being the air and the second the sleeve. Surely if the parsafe fitting is double insulated and any mains lead passing through the case is double insulated as well, the earthing of the exterior can is superfluous, since the parsafes should be by definition safe even if the parcan outer were not present? Maybe!?? Link to comment Share on other sites More sharing options...
Wuddy Posted September 27, 2007 Share Posted September 27, 2007 Definition for Class II Equipment is, Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as supplementary insulation are provided, there being no provision for the connection of exposed metalwork of the equipment to a protective conductor, and no reliance upon precautions to be taken in the fixed wiring of the installation (seeBS2754) From Code of practice for in-service inspection and testing of electrical equipment published by the IEE. This obviously applies to the parsafes on their own but on the inside of all the parcans I've handled the sheath of the flex is usually stripped back and phase and neutral cores connect to the parsafe with no insulation other than the BASIC brown, blue insulation on the cores. This means that a parcan so constructed does not qualify as Class 2, it would need supplementary insulation on the phase and neutral or the inside of the parcan insulating to qualify for Class 2. Also because of its construction and general mode of use, the fault which could make the parcan live may not be in the parcan itself but on the bar or stand to which it is rigged. Link to comment Share on other sites More sharing options...
gareth Posted September 27, 2007 Author Share Posted September 27, 2007 on the inside of all the parcans I've handled the sheath of the flex is usually stripped back and phase and neutral cores connect to the parsafe with no insulation other than the BASIC brown, blue insulation on the cores.Parsafes are not made that way - the mains cable, complete with outer sheath, enters the plastic moulding that surrounds the ceramic - there is no point in the system where there's only a single layer of insulation between fingers/metalwork and live conductors. Link to comment Share on other sites More sharing options...
Wuddy Posted September 27, 2007 Share Posted September 27, 2007 My apologies, I bought a load of brand new par 64s last year with suposedly parsafe lampholders and they are wired as I described not as Gareth has described. They have the usual ceramic holder and then a hard plastic cover/shroud around the back I'll try and post a pic later. I will corrcet myself and agree that yes from the description they appear to be Class 2. But I would advise that as they are exposed conductive metalwork which could become live in the event of a fault that they should be bonded to earth and the best way is via the protective conductor in the flex. Link to comment Share on other sites More sharing options...
dbuckley Posted September 27, 2007 Share Posted September 27, 2007 Although the parsafe construction itself appears to comply with the requirements of class two, there is a failure mode of the entire fixture of which the parsafe is an element which could cause danger; a shattered bulb allowing the filament assembly to touch the can. Link to comment Share on other sites More sharing options...
Brian Posted September 28, 2007 Share Posted September 28, 2007 To answer the original question - my guess would be that whilst the maker of the PARsafes is able to test and certify them as Class II products they don't feel confident in stating that when fitted by a third party to an unknown quantity (the original can) that the whole assembly will still be class II and so take the safe route and provide a means of keeping the original can Class I. Where a can is supplied with PARsafe then there is no reason the maker cannot test and certify the whole product as Class II. Class II does not have to mean 'two-core cable'. The earth core can be used for other functional purposes which might include providing a safety earth for another device. I can see no problem with making a unit, with a 3-core mains lead, which has a 3-pole socket to connect other devices but which is in itself a Class II device. Link to comment Share on other sites More sharing options...
Neil Hampson Posted September 28, 2007 Share Posted September 28, 2007 I have a pair of PAR64's (DTS I think) that were sold wired and complete with a PARsafe, the outer sheath of the cable is not stripped back until it has entered the PARsafe, however without modifying the PARsafe, ther is no route for an earth conductor to come back ot to be connected to the shell. The only way would be to strip back the outer sheath before it enters the PARsafe, then negating the Class 2. As far as I remeber the whole can was labelled as class 2, not just the PARsafe the double insulated logo was on the part label on the yoke. My PAt tester (fairly large north west theatrical contractor) has never passed comment, nor failed the units. Link to comment Share on other sites More sharing options...
KevinE Posted September 28, 2007 Share Posted September 28, 2007 Part of the marketing blurb for parsafes states that you can remove the rear aperture plug on PAR64's to allow for better ventilation..meaning they would fail a BEAB finger test (or modern equivalent) if they werent entirely double insulated inside and out. There would have to be a fairly large bang to shatter a PAR lamp surely? And you could apply that thinking to anything double insulated..like smashing the bulb in your anglepoise or garage inspection lamp ?!? Link to comment Share on other sites More sharing options...
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