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I don't know the exact reasoning behind requirements of the standard with regard to Class I/II and earthing, I wish I did. I do know that the standard specifically states that Class II appliances shall have no provision for earthing (Clause 27.1). I have seen Class II appliances with...

Here are the definitions from EN 60335-1 3.3.9 class I appliance appliance in which protection against electric shock does not rely on basic insulation only but which includes an additional safety precaution, in that conductive accessible parts are connected to the protective earthing...

Class II appliances must not have a protective earth terminal. Showers are usually Class I products as the heat exchanger is usually earthed. If plastic parts are used in a Class I appliance to protect from access to live parts, this is known as Class II construction in a Class I appliance...

Just to clear up the shower Class I/II thing... Showers are usually Class I with Class II construction. There has to be double or reinforced insulation between live parts and the accessible plastic cover. This is usually provided by the cover itself, the air between the cover and the live...

Intrigued by this and having the test equipment to hand I did a quick test on my laptop power supply. Testing a Lenovo 90W 20V AC adaptor with a Voltech PM100 I got: Off load 230.6V 16.4mA 500mW 3.8VA PF 0.13 On load but with fully charged battery 230.1V 160mA 13.8W 36VA PF...

According to the standards we test to, it is not acceptable for a manufacturer to require the installation of external protective devices to ensure the safety of their product. That is to say, the appliance should remain safe if the supply is unlimited. I presume the rationale is that the...

I was busy and posted in haste which is why I didn't make myself clear. A big part of safety testing of electrical appliances, including lighting, is applying faults to ensure that an appliances fails safely. Amongst other things motor rotors are locked, ventilation slots are blocked...

Just for reference, any fault on an appliance should not cause a device in the fixed wiring to operate. If there was a danger of such a thing occurring, the appliance should be adequately fused internally. As already mentioned, over-current devices in fixed wiring are there only to protect...

T1H250V is the same as T1AH250V. It is strange that the A is missing in your fuse though. The H stands for high breaking capacity which is why the fuse body is ceramic. What is the size of the fuse? If it is 5 x 20mm then it is probably an IEC type fuse. If it is 6.3mm x 32mm then it...

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I thought he implied that an internal filling loop will always have a valve fitted but the mains water inlet would only have a valve fitted if there are problems with flow sensors/switches

Thanks. Does this mean under normal circumstances, the mains cold water inlet to a combi will not have a non return valve fitted? The reason I ask is that the electrical safety standard for boilers, EN 60335-1 requires appliances fed from the water mains to be fitted with a non return valve...

I wonder if anyone can tell me if it is a requirement (according to Water Byelaws or any other regulation) for combi boilers to be fitted with an anti back-siphonage valve? If there is such a requirement, are they fitted to the boilers or does the installer have to fit the valve? Thanks...

There's nothing wrong with your maths and the mfr doesn't expect that power factor either. Measuring the power consumption of refrigerators isn't easy. You are supposed to measure the maximum value of current averaged over any five minute period in an hour - a right pain. In reality you...

EMF can also stand for Electromagnetic Field which can cause induced currents and voltages (ie induction)

I wonder if we should be calling LED drivers, SMPS etc power converters http://www.electropedia.org/iev/iev.nsf/index?openform&part=551 AFAIK all power converters that do not utilise a linear type transformer, "change the frequency". They take an input voltage, rectify it if AC, chop it...

I've been dealing with IEC standards for many years now so I have a little insight, not much but some. The standards writers seem to be specialists in not making themselves very clear - it's most frustrating when trying to interpret things. If they wrote explanations or rationales it would be a...

I think the frequency reference is to differentiate a common or garden wirewound transformer from a switched mode power supply (which is what an LED driver effectively is). Having said that, I don't think calling an LED driver a transformer is wrong, just as it's okay to call a lamp a bulb as...

It's a requirement of BS EN 60598-1 (the safety standard for luminaires) for the manufacturer's name or trademark to be placed on the luminaire (in fact it's a requirement of the Low Voltage Directive). I wonder what other parts of the standard this luminaire doesn't comply with...

The power switch to an appliance is not required to disconnect the supply. In the majority of modern appliances it doesn't, the supply plug is used as the "disconnection device". This is why it is recommended that if the appliance is installed such that the supply plug is inaccessible (like a...