Electrical symbols for drawings

[Tom]

I'm drawing up a plan (to give to an electrician) for an extension to show where I want 13A sockets, double 13A sockets, lights, switches (one way /

2way), etc. Where can I find a list of symbols to represent the above. Some of the sockets are required at differing heights, how do you represent this on the plan? Is it ok to put a figure in mm by the symbol (e.g. 1150mm AFFL) Thanks Tom

[Rumble]

Tom said the following on 19/11/2005 13:00:

Symbols here:

fine to say 1150mm AFFL (above finished floor level).

You could also say 300mm BFCL (below finished ceiling level), although this useage is less common.

HTH

Rumble

[Owain]

As long as you 'splain what you want. Post-it notes stuck to the walls also work well.

I would be inclined to do an opened-out floor plan showing both plan and elevation showing sockets, lights, 1 & 2 way switching etc.

-------------------- | | | | | | | | | | | SKT | | 1150 | | | | | | SKT | | | 200 | | | | |

------------------------|---------|-------------------------- | |300>< 900>| | | | | | | | LIG SW1--------|\ | | | SW2a | \ | | | \ | \ | | | \ | \ | | | \ | \ | | | \ | LIG1 | | | \ | | | | \ | |------LIGSW2b | | \ | /| | | \|------------LIG2/ | | | | | |

-------------------------------------------------------------

(etc)

Owain

[Malcolm Stewart]

Just curious re tolerances on dimensions such as the above.

If not stated explicitly, what tolerances would be assumed; and if not met, could be argued about?

Thanks

[Tom]

Symbols here:

"BRILLIANT" !!!!!!

Many Thanks

Tom

[Tom]

Good point!!!, however, if one is dimensioning to the nearest mm, it could be argued that one meant 1150 not 1151 or 1152. so plus or minus 1mm is more than accurate enough for positioning domestic switches, sockets or lights.

Warm Regards Tom

[Tom]

1150mm

Havn't got a wall yet :-( But I do need an estimate.

Good Idea

Wow, Diolch Tom

[Rumble]

Malcolm Stewart said the following on 19/11/2005 14:18:

Tolerances are almost never cited on architectural drawings. This is due to the nature of the way buildings are constructed - i.e. essentially by hand.

Often, there is opportunity for dimensional errors to be hidden. E.g. in an office building, slab-to-slab height may be a nominal 4.5m and finished-floor to finished-ceiling will be 2.7m. Any dimensional errors incurred along the way will result in the height of the ceiling void (between finished ceiling on this floor and the bottom of the concrete slab forming the floor above) being somewhat more or less than nominal.

Obviously, surveyors, builders and tradesmen use appropriate tools and instruments to assist in getting-it-right (theodolites, rulers, spirit levels, water levels, string lines, lasers, plumbobs, etc), but usually, in finishing work, the aim is to make it "look right" - e.g. if you have a long wall with socket outlets all the way along, the sockets need to "look" as if they are all the same height - if you take a tape measure to them, they might vary in height by 2-3mm but still not look "wrong".

Having said that, many highly-skilled tradesmen can make it "look right" just by eye. I have seen many examples of this, including chippies who can squint down the line of a wall and then scribe the edge of an infil panel which then fits perfectly first time - amazing.

Generally problems/arguments arise because of "signifcant" dimensional errors, where things just don't fit because the "gap" is too small or way too big. This could be due to the architect making a mistake on the plans or an error in "setting out" - causing everybody to stand around scratching their collective heads until someone comes up with an acceptable plan to remedy the "mistake" - or it gets referred back to the architect if there's a fundamental design error.

Often, in such cases it is pretty much out-of-the-question to "knock it all down and start again" because:

1. nobody wants to pay for that and
2. it adversely affects the construction programme.

A good building project manager will conduct a "buildability" review of the architect's and speicalist trades' plans before pricing the job - just to satisfy him or herself that the design holds together and will work - or can be made to work.

Often when 3-D "flythrough" models of new buildings are commissioned, the 3-D guys have to go back to the architects and give them the bad news - i.e. when you take the 2-D plans and try to make a 3-D model, the plan drawings contradict the elevation drawings. oops.

HTH

Rumble

[Peter Taylor]

Great post. The fun about accuracy really begins when you're working on a really old building, and sometimes things need to be deliberately inaccurate to "look" right. If the floor and ceiling in a room both have a slight slope, anything installed level looks wrong.

As a designer/contract supervisor, I often have to think carefully about the position of sockets and switches, but normally (apart from indicating whether sockets are above or below worktops for example) it is not necessary to give setting out dimensions on a drawing. The only times I get picky about the setting out is when I want to get the accessory in the centre of a tile or a granite upstand etc, when there's going to be an unusually deep skirting or wide architrave, or when regulations require definite heights - for example in disabled situations or in hospitals and care homes.

Peter

[Owain]

Yeah, like "we forgot the stairs"

Owain

[Stuart]

Do these figures refer to the bottom of the socket or the top or the middle ....?...I'm imagining it means the bottom for height from the floor and top for the distance to the ceiling but again,maybe not . Stuart..

[Rumble]

For electrical switch/socket plates it means either:

1. The same as any existing items (which may have been measured to the bottom, middle or top!), or

1. To the centre line (i.e. middle) in a new-build.

If in doubt assume that the sparky will measure to the centre line (middle).