Immersion Heater & Thermostat workings and diagnosis!!

[liverpoolboy]

Just want to make sure of something is possible please?

The Immersion Heater/Thermostat wiring is: Live goes through T (thermostat) and this T (thermostat) makes or breaks the circuit, depending if calling for heat or not (when switched on)!

Then from the T (thermostat) the circuit is completed by going to the N (neutral). So.. basically if the thermostat if satisfied (at temperature) the T (thermostat) breaks (opens) the circuit and the N (neutral has no power to it ...?? is this right?

If the Thermostat is faulty then when switched on and turned up (calling) there will be no voltage between L & T terminals?

And if the immersion heater itself is faulty (and not the thermostat) there will be no voltage between L & N terminals .... is this correct?

Thanks for clearing this up and sorry for any confusion!

 

[dave18]

Please do yourself and your family a favour.......

Turn off the immersion heater at the switch by the DHW cylinder and call in an electrician.

If I am reading your post correctly you do not have a clue at what you are doing,

You are so far off the mark that no way will I give you any further advice

it seams you are one wire away from a dead short and possibly a stay at a local hotel while your house is rebuilt, or all your pipework becomes live and any one turning on a tap will be pushing up the daisies.

If you are working for someone, Changing or wiring an immersion is notifiable work. under Part P.

 

[liverpoolboy]

dave!-what the heck are you on about!

i am not way off - just wanted to be sure

an immersion heater thermostat CAN be tested if faulty or not by checking if there is any voltage between the L and T terminals.

 

[seco services]

you'll have live going into the stat check if you have live coming out the other side of the stat, you can move the temp on top to see if it cuts the live coming out the other side.

 

[liverpoolboy]

yep and if live is coming out of the other side (or cutting out when turned down) this proves the thermostat is not faulty. So if still no heat: it must be the immersion heater element faulty. and this is done by testing if there is voltage from the T to the neutral or the L to the neutral terminals??

 

[seco services]

yes thats right.
put the meter on ohms and disconnect the heating element from stat and power off and place the meter across the heating element terminals and see what ohms reading you get. should be about 18ohms.

or do a continuity test across the terminals.

 

[liverpoolboy]

if the heater is turned off when i test then there will ne no reading as no power will be going through the circuit! ...

surely testing for voltage between L and N will prove if the immersion heater element is faulty...?

 

[seco services]

doesn't mean the immersion is 100% just cause power is getting through.
you don't want mains power to do a ohms test or continuity test.
you can still have continuity even if the ohms is low (knackered element)
ohms will give you a true reading of condition.

 

[liverpoolboy]

ok fair enough. so less than 18 ohms between L and N means a faukty immersion heater element then...

 

[seco services]

forget the L - N just put the meter across the two heating element prongs.
tell us what reading you get

 

[liverpoolboy]

the L and the T terminals you mean/ this will prove if the thermostat is knackered though, not the heater element,,,

 

[seco services]

if their is power at the T terminal when stat calling and no power when stat reached temp then stat is ok.

 

[liverpoolboy]

yes there is power at T when stat calling and when i turn it down (right down) it cuts out. this is correct i believe?

so to make 100& sure what do i test to see if the immersion heater element is def. faulty? the N?? sorry if i'm sounding hard work! it's been a stressful day!

 

[seco services]

yes stat ok.
turn power off, then do a continuity test across the heating elements. T N
and also a ohms test across the T N and see what the reading is.

 

[liverpoolboy]

Seco i don't get any voltage from T to N.
Is this a faulty heater element? well it must be really i guess if the thermostat is ok. Should i replace the whole heater ?