how to test an Immersion Heater and IH stat?

[--tom]

Q1. How would you test an immersion heater and i/h stat?
Q2. Ref. I/H wiring: is a fused switch( typically 16A) necessary, or will a 20A DPswitch(non-fused suffice)?In other words, no fuse reqd. between the C/U and the I/H.

 

[kai]

Often between the consumer unit and the immersion, there is a 20amp double pole switch with neon , marked water heater, mounted in a clearly visible location, say on the kitchen or hallway wall, and another 13amp DP switched fuse-connection unit inside the airing cupboard, to which the element is connected to, with heat resistant flex.

 

[--tom]

thank you Kai, but do the regs call for a fused switch before the Cylinder/immersion heater?

 

[kai]

The fuse will be found in the DP switched FCU in the immersion cupboard - for a 3kW element calculated as 3000watts/240volts = 12.5amps, so a 13amp fuse is appropriate (resistive load).

You need a fuse there, as the immersion flex is normally 1.5.mm sized, rated at 15amps, which is slightly more than the design current rating of the immersion, The B16 breaker will offer short-circuit protection to the cabling as a whole.

 

[securespark]

1.5 flex says 16A in my 15th Ed, 16th Ed and 17th Ed book.

ie the CCC of 1.5 flexible cable has not changed since 1981.

If the circuit is protected by a 16A breaker, not additional fusing down is necessary.

Often, older houses have IH's off the ring. In this case, a 13A FCU is necessary.