I have just purchased a sunvic unishare 3 port heating control system to fit to my domestic hot water system. I was unaware however that it does not come with wiring. Whilst i feel confident in following the wiring diagram i was thrown slightly when i went to purchase the wiring as it appears to come in various amperage ratings. (The system currently has an old dial type timer fitted which switches both radiators and hot water on at same time so there is already a mains connection present.)How do i find out what wiring i should use?
There must be many options, domestic electricians tend to use 1mm triple and earth but that is in the mainly because it will be in stock. Often multiple cores are required and a multi core cable with numbered cores is often more appropriate. The plans tend to show what connects to what without giving a cable layout and the first step is to work out cable runs and how many junction boxes are required. You may need this anyway when you submit plans to building control. Once you have worked out how many cores are required it is often a compromise. Some cable is cheaper by the drum and often it is prudent to wire everything with cable from same drum so may be better to run two cables of say 4 core together than buying 6 core for one run only.
Most cables can be buried in the wall. Some like flexishield will not require to be protected by an RCD. Most central heating will run on a 5 amp supply and if that is the case 1mm cables will be big enough. Because it will most likely come under Part L and/or Part P and even Part M may be involved and we are drawing close to the change over from BS 7671:2001 to BS 7671:2008 (July 1st) it would be very easy to get caught out by one or other of the requirements and although we can give you advice in general terms it will be up to you to ensure all the i's are dotted and t's crossed. I know there is a link to Part P and I seem to remember from there you will find links to the rest. I think most the systems have a letter? Y, S, W, C etc. It may help in future posts if you say which you are using. I know many DIY people don't follow the regs but not following them can I'm told make selling the house hard and expensive and however much I dislike them I would be doing you no favors not telling you they exist.
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