Ok what do these do?

[Mike2007]

I found these warm and buzzing away in a customers CU. If they are contactors, then I thought these were relays for moving heavy loads??
Please explain.

 

[GaryMo]

Contactors, used for switching loads via a control circuit.

 

[333rocky333]

They are double pole contacters with 230 volt coils fitted

 

[breezer]

what were they connected to?

and was it a big place?

 

[Click-Sure]

Find anything else 'out of the ordinary' for a domestic situation while you were at it?

 

[JohnD]

timer-controlled for storage heaters, perhaps?

 

[sparkydude]

Are you sure it wasnt a doorbell transformer????

 

[Sherbertlion]

I saw some of these the other day in a posh flat. They were all in a separate CU under the main CU. I think they were controlling the electric radiators in each room through a timer.

 

[Mike2007]

A schematic approach please!
1. What would these be used for in a semi-domestic building (flat above single phase workshop)
2. Do they provide protection to a circuit
3. What do they do. How do they "control" anything?
4. Are the transforming the voltage?

I know how circuit breakers/rcd's work!

 

[JohnD]

if you know what a relay does, you know what a contactor does.

It enables you to switch a heavy load with a low-amp switch.

e.g. a 5A timer can control 100W of heating.

Or security lighting, floods etc.

it can also save the cost of running a big cable to a remote switch

could also be used for emergency power off where you might have lots of buttons and some big machines.

 

[Mike2007]

Ok, correct where wrong!
A contactor in CU is energised. Does that say there is a remote switch with low amp wiring on it connected to one side or the contactor in CU. On the other side there would be higher load current taken off busbar to feed a machine maybe?
Now here is the overcurrent device for that machine, is it integral?
Why not just have type C,D breaker to handle circuit?

 

[JohnD]

you need an OCD as well, upstream of the contactor, so it shouldn't come off the busbar

A contactor is a switch. An MCB isn't.

 

[breezer]

JohnD

you have my keyboard havent you!

....e.g. a 5A timer can control 100W of heating.......

 

[JohnD]

I must have meant 100Q of heating

 

[breezer]

yep, thats my kyeboard