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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".

Wiring standards
should be observed

I have several comments to make about the contents of recent issues.

(1) The October 2008 article describing the use of the old microwave for exposing PC boards had a glaring error in the wiring. AS:NZS3000 states in several places that green/green and yellow wiring shall only be used for earth and nothing else – no exceptions.

The picture clearly shows several green/yellow wires used for power, and supposedly made OK by using a little bit of coloured sleeve or perhaps red insulation tape. This is an example of why we need licensed electrical people.

I was taken back that you actually published such a picture. It may have been more prudent to send the project photos to the author and ask him to make the project comply with the standards, then resubmit the project to you. Publishing such a project certainly isn’t as professional as you have been in the past.

(2) Australia is now a signatory to the International Standards organisation and as such, we are now obliged (indeed have to) accept equipment made to standards that apply in different parts of the world. I want to draw your attention to several potential outcomes of such acceptances.

Some years ago I was wiring up a small solar system, consisting of three 24V 175W panels, a small 24V battery bank and an inverter. Before turning on the solar circuit breakers, it is my practice to run a meter over the panels at the circuit breaker board and check the open-circuit voltage, the short-circuit current of each panel and the wiring continuity.

Imagine my surprise when I measured about 65V across the open-circuit breaker. Checking the wiring of the solar panel showed that the black wire was positive, not negative, while the white wire was negative. Hence the readings of 42V open-circuit on the array plus about 26V from the battery. Subsequent investigation revealed that this is the standard in Japan and we have to wear it. You have been warned.

I service various pieces of electrical equipment and have also found that the Chinese standard is as follows: Green – Active; Black – Earth; White – Neutral. In Japan, it is as follows: Black – Active; White – Neutral; Green – Earth. Since we are signatories to these international treaties, we must accept their appliances under threat of legal action in the World courts.

(3)With regard to the letter on solar power in Ask SILICON CHIP, November 2008, I agree that it’s not usually practical to operate air-conditioners from solar but we do. Our system is 4.5kW solar, 5kW inverter (20kW 1/2 hour), 48V 50kWh battery bank, etc. It runs two houses with air-conditioning, fridges, freezers, electric frypans, etc. We do have a 6.5kVA standby generator for bad weather but one doesn’t use A/C in the rain – usually.

The reason for spending in excess of $70K on our solar system was that when we passed through the Hunter Valley and saw the destruction that is being caused by the power stations we decided we did not want to be a part of that. As well, we are doing our bit for the planet.

While solar installations in most mobile homes can’t usually cope with A/C, it is possible. I helped a mate to build a mobile home and we used 1200Ah sealed batteries (24V) and 16 175W solar panels. We also fitted a 160A alternator to the bus with two PL60 regulators. His split system A/C works well on solar; just as well, as he is in northwest Australia at present.

Peter Laughton,
Tabulam, NSW.

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