GCSE Electrics: Build Hub Level One exam

[ToughButterCup]

You have 30 minutes to answer the following question. Do not copy what @JSHarris, @Onoff or @ProDave or that other really nice Scottish boffin write. @TerryE writes with disappearing ink so its OK to look at his answer.

 

Write your name at the top of your paper and on each page that you submit

Your invigilator will collect your online answers and collate them below.

 

Q1: Isolators isolate. Switches switch. Discuss.

A good answer will make reference to the ways in which switches and isolators are similar, and the ways in which they perform different functions.

An excellent answer will give good, clearly expressed examples of when an isolator should be fitted instead of a simple switch. 

A good answer will show how switches are sometimes Double Poled, and sometimes not, and the reasons for the differences.

Top marks will be given for those answers referring to how switched fused spurs and fused isolators are used, especially those made by Scolmore. 

 

Oh bugger it, lets cut to the chase. The examiner doesn't know when he should fit an isolator, and when a mere  a switched fused spur will be adequate.

 

Ta!

Ian

 

 

 

[Carrerahill]

Generally an isolator is for the isolation of an electrical circuit which is already open - i.e. they ought not to be used to kill loads or connect loads, they also should have a greater distance between the contacts to ensure isolation.

 

Switches are designed to switch loads on and off.

 

A fused spur often will only switch the live, much like an MCB doesn't actually fully isolate a circuit, whereas an isolator will isolate both poles - it sort of depends what you are wiring up.

 

An isolator would be fitted to something that you would want to work on while still installed - plant should really be isolated - a fridge can go on a spur as your really not going to be working on the internals while it is still connected.

 

So on a DB or the main cable-head the isolator disconnects down the whole system. 

 

Examples of where I would spec isolation:

 

HVAC units.

Compressors (i.e. permanently installed units).

Pump systems.

 

Example of where I would spec a spur:

 

Fridge 

Heater

Alarm panel

 

However, as always there is always crossover.

Edited October 17, 2019 by Carrerahill

[ToughButterCup]

2 hours ago, Carrerahill said:

Generally an isolator is for the isolation of an electrical circuit which is already open - i.e. they ought not to be used to kill loads or connect loads, they also should have a greater distance between the contacts to ensure isolation.  Switches are designed to switch loads on and off.

[...]

 

Hmmmm, so an isolator for

• MVHR - (which also has its own on/off switch)
• The SunAmp
• The Geberit loos
• the cookers
• the hob

but not the fridge, freezer or minor stuff. Hmmmm. 

Can't see the logic - yet.

[Mr Punter]

For appliances that come with a plug I like trailing sockets on flexible cable behind the plinth.  You can just release the plinth and unplug them if needed.  Cutting off the plug and wiring into a flex outlet, with a switch on the wall, looks messy, makes it more difficult to remove and I doubt it does the warranty any favours.

[Carrerahill]

1 hour ago, AnonymousBosch said:

 

Hmmmm, so an isolator for

• MVHR - (which also has its own on/off switch)
• The SunAmp
• The Geberit loos
• the cookers
• the hob

but not the fridge, freezer or minor stuff. Hmmmm. 

Can't see the logic - yet.

The logic is that connected plant will probably be serviced in situ and still all hooked up - a fridge or freezer or microwave won't. A cooker and hob can go on a spur (unless it's greater than 13A supply then most of the cooker switches are actually double pole switches.

 

 

[redtop]

hot tub hard wired (no plug)  = double pole isolator

[Onoff]

What Geberit WCs are you having, the Aquaclean ones that wash and dry your ar5e?

[Markblox]

A switch is for functional switching as opposed to an isolator that is present to isolate equipment for maintenance. For instance a bathroom fan on a lighting circuit has a three pole switched isolator so the fan can be cleaned/maintaned with the lights still on.  An isolator also has to be local to the equipment being isolated but a switch doesn't have to because it is a functional switch and can be operated from a distance to the switched appliance.

Edited October 18, 2019 by Markblox

[ToughButterCup]

13 hours ago, Onoff said:

What Geberit WCs are you having, the Aquaclean ones that wash and dry your ar5e?

?

Its my damaged back thats the issue .....?

[ToughButterCup]

10 hours ago, Markblox said:

A switch is for functional switching as opposed to an isolator that is present to isolate equipment for maintenance. [...]

 

Now there's a simple answer for a simpleton like me. Thanks

[Carrerahill]

12 minutes ago, AnonymousBosch said:

 

Now there's a simple answer for a simpleton like me. Thanks

Now what was complicated about: 

 

Generally an isolator is for the isolation of an electrical circuit which is already open - i.e. they ought not to be used to kill loads or connect loads, they also should have a greater distance between the contacts to ensure isolation.

 

Switches are designed to switch loads on and off.

 

 

 

 

Edited October 18, 2019 by Carrerahill