Electrical Schematics & Symbols

[tips6]

I currently work for a small electrical engineering company in the UK. There are only three of us (plus our receptionist in fact), which work in our office. However, my two colleagues (one of whom is my boss), do not use CAD at all, and as far as I'm aware, never have done. Part of my job though is to draft electrical schematics (mainly for electrical power applications, e.g. single and three-phase installations, and not electronics based).

I have managed to create a series of blocks, based on the symbols standardised in BS 3939, however, I wondered if anyone could confirm for me if there is a standard size of minimum size for that matter in which the blocks should be drawn to, e.g. symbols should be no greater than 100x100mm in size? If anyone has any useful information for drafting electrical schematics using a standard AutoCad package, I would be most grateful, as I don't feel my drafting techniques meet the current "standards".

Many thanks,

Matt

[delliott]

Blocks should always be drawn 1 to 1 and scale them later in your drawing

[Strix]

ignore the above comment, it's irrelevant in this field :wink:

blocks for electrical drawings tend to vary in size, as motors are much bigger than fuses to get all the connections and text in, and as for PLC's and their peripheral black boxes...

another thing with electrical drawings is that they often need to knit seemlessly with clients' existing drawings, so it isn't unusual to be sent their set of symbols to work from

(you're going to tell me now you are doing domestic wiring and not industrial control systems aren't you? :wink: )

[tips6]

Thank you for your comments. Yes, the company tends to do more commercially orientated installations, e.g. shops, restaurants, bars, hotels, etc. The schematics are drawn for the sub-circuitry of the electrical building services, e.g. mains and sub-mains distribution, lights and their respective switching operations, mains power (e.g. ring mains and radials), etc. With respect to BMS systems, etc., a separate specialist sub-contractor will normally do their schematics and we will show their control panel as a simple rectangle on the drawing with a reference to the more detailed schematic from them.

As I've said, my main query is what size these schematic symbols should be drawn to, as these aren't "actual" objects you can pick up and measure with a ruler.

[dbroada]

thanks to Strix for reminding me to reply to this thread. I saw it at the weekend and then totally forgot about it.

I thought this was covered in BS8888 or EN60617 or :shock:

however I can't be bothered to turn around and find them so I'll say what we do. Our text is a minimum of 2,5mm and have a recomended minimum sanp of 2,5. Therefore all symbols will be in increments of 2,5mm. As an example or fuse or resistor symbols are 15mm long - wire end to wire end. The component in the middle is 2,5 high and 7,5 long. (Actually 7,4 but it was drawn before I got here). Most of our components will be similar sizes.