firemans switch

[spatz]

can any body help me, i have never worked on a firemans switch . Could any one please explain their operation and how they cut the power ?

 

[malcolmsanford]

Basically they are just a double pole switch that will disconnect both LIVES when operated. They normally have a seperation gap exceeding 3mm as they are designed to be operated underload.

They are also switched reversed from the normal isolator ie off in up and on in down.

 

[spatz]

thankyou, but surely they don't carry the whole load of the building ,do they cut the supply via a conntactor? And as a second question how easy would it be to wire an existing external sign into an existing firemans switch

 

[malcolmsanford]

Have a read of Reg 537.6.1

 

[Electro-tech]

Where any circuit operates at a p.d. (potential difference) exceeding low voltage a fireman's emergency switch must be provided. Such installations usually take the form of discharge lighting (neon signs), and this requirement applies for all external systems as well as internal signs which operate unattended. The purpose is to ensure the safety of fire fighters who may, if a higher voltage system is still energised, receive dangerous shocks when they play a water jet onto it.What does the FMS protect?What do you need to do with it??

 

[spatz]

the fms protects an entire retail property but when tested by others ,showed that bthe store signage stayed on . It is my job to find out why and connect to fms ,

 

[Electro-tech]

You obviously need to trace what circuits are affected by it being turned off.May be out of hours job for convenience to retailer. Then work out the loading as you may need to upgrade the existing Switch rating to accommodate the extra signage. Then come back with more details, by then you will probably haved sussed it.