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Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to "Ask SILICON CHIP" and "Circuit Notebook".

Most older homes do not
have RCDs fitted

In the letter “Foil Insulation & CFLs”, Mr Pierson (Mailbag, June 2010) asked where the RCDs were if it’s compulsory to have them fitted. The answer is surprisingly simple. When I last worked in the private maintenance sector 4-5 years ago, it was compulsory for all new houses to have them fitted during construction. Any maintenance work on the electricals in existing houses had to have them fitted if they were not already installed.

There are quite a lot of older houses where no electrical work has been done since that rule has come into effect so that means that those houses do not have RCDs fitted yet. I lost count of the number of RCD units I fitted when in the maintenance sector but there always seemed to be more switchboards to be upgraded.

Brad Coleman,
Brisbane, Qld.

All fluorescent tubes
contain mercury

I read your article entitled “Slash Your Factory/Office Lighting Bills” on the May 2010 issue with interest.

However, on page 19 you indicated with the picture of the NEC fluorescent tube that the absence of the “HG” (mercury) marking on the quad-phosphor means that no mercury is present in this new tube. This appears to be misleading and requires further clarification.

I believe that HG on the product is defined as “High Grade” on the NEC fluorescent tube and does not indicate mercury (Hg). In the Periodic Table, mercury is specified as Hg where the “g” is lower case (small letter alphabet) as opposed to upper case (capital letter alphabet).

I picked up one tube to analyse the labelling that you mentioned. On the paper sleeve packing of the NEC fluorescent tube, it stated HG as “High Grade” and not as mercury. HG is Tri-Phosphor and the HGX is designed to be used for electronic ballast units. X series is Quad-Phosphor but note that both X and HG has a 5000K colour temperature, even though one is Tri-Phosphor and the other is a Quad-Phosphor type.

I am yet to come across a fluorescent tube that has no mercury although modern fluorescent tubes do contain negligible amounts. A manufacturer can produce a mercury-free fluorescent tube by substituting aluminium trichloride which when energised produces a plasma discharge that emits ultraviolet and visible radiation. Phosphor, in the form of a particulate layer or a gas, converts the ultraviolet into visible light. So it can be done but the cost involved will be very much higher.

Michael Ong,
Wembley, WA.

Comment: you are quite correct. The reference to mercury in that caption is a mistake.

Mains surge suppressors
& warranty claims

Over the past year, I have noticed that many of the large retailers of TV sets are advising that either warranties and/or insurance claims will be rejected if you do not use a mains surge suppressor, which of course they have available at a price. I was surprised a few days ago that one such retailer had a surge suppressor sitting on top of each washing machine and when I asked if they included one with each washing machine I was told once again that they were available at additional cost and that unless you used one with the machine, warranties and insurance claims would be rejected.

I have just checked with my insurance company and they say that using a surge suppressor has no effect on their insurance conditions, which are defined as electrical damage caused by lightning either directly on the equipment or due to lightning causing a surge in the mains supply. If a surge in the mains supply is not due to lightning (which has to be determined by a technician or by meteorological records), they advise you to contact your electricity supplier.

Since all TV sets now use either LCD or plasma screens and most washing machines are electronically controlled, I wonder why the manufacturers don’t build in surge suppressors if mains surges are such a problem. I am inclined to think that it may have more to do with adding to the retailers sales (like extended warranty).

I wonder what other readers have found when shopping for home appliances and whether there are some valid warranty or insurance claims that have been rejected because no mains surge suppressor was used.

R. Sanders,
Kiama, NSW.

Comment: any retailer pushing the sale of mains surge suppressors on the grounds of possible warranty claim rejections would appear to be on shaky legal ground.

As a first point, you could argue that the dealers are selling equipment which they know is not of “merchantable quality” if there is a danger that mains surges will blow it. All electronic equipment intended for use with the 230VAC mains should be able to withstand normal surges and will typically have MOVs (metal oxide varistors) in their power supplies to provide protection.

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