Heating Controls expert Sparky advice sought!

[SortedPlumbing]

Sparky help required,

I have an electrical fault with a heating system.

Basically its an old back boiler system:
one 2 channel timeclock
one room stat
one zone valve
one pump
and ofcourse boiler.

This fault has occured after another engineer has attempted to replace the timeclock and i am now left to fix it if i can!


Heres the fault ;
240V at timeclock , if i send 240V down the switch live to the junction box i get 240V between Neutral and 2 Earth wires, i get 30Vs on one Earth to Neutral and on the other two earths to neutral i get 0 Vs. I also get 240V between Live and Earth, but between Live and Neutrals i get 0Vs.

Nothing is working at all, Next in sequence i should get 240V at the room stat and im getting nothing at all!


I m going back tomorrow so looking for some pointers? if any one has the slightest idea of what i am talking about?!?!

 

[ColJack]

sure it's a neutral?

might be a switched live from the timeclock and the installer was just too lazy to sleeve it with the proper colour..

also, sure it's an earth? again, lazy / stupid / dangerous installer may have used the "earth" as a switched live.. instead of getting a cable with more cores..

 

[SortedPlumbing]

I cant be sure, although at junction box all blues are in the same connector and this is where i am getting the reverse polarity

Timeclock all i have is 3 reds 3 blacks 3 earths,

Il end up ripping it all out and rewiring just curious to what is happening as i dont like admitting defeat!

 

[ColJack]

3 T+E's at the timeclock?

so that's one L+N feed, and 2 L+SWL outs to whatever??

never really delved into heating systems, I just put the fused spurs in where I'm told to

 

[333rocky333]

Sounds like no neutral at the J/b hence the 240 N to E as there is a load connected across L to N

 

[SortedPlumbing]

yea 3 cables at timeclock, on live and neutral and 2 switch lives with one heating off,

its kool i will just disconnect everything and work out exactly what every wire is and reconnect it!

cheers anyway.

whilst u are giving advice - heres another wierd sparky job i have had this week

A timeclock was replaced by again another engineer as it was blowing the 3amp fuse. He replaced it with another timeclock and now it is making a crackling noise (same noise u get when u have water on electrics).
I assumed faulty timeclock so replaced it with another make and model and again the same noise!
What causes crackling???? I have good earth good neutral good live! with no visible loose connections.
I think fault with elecs in house but duno what~!, one thing to add is i think the orginal installer has taken the boiler from a lighting circuit as when the 3amp popped it took out a light in the house aswell.

I have got a sparky going later this week but again as i said i dont like to be beaten by a fault!

 

[ColJack]

the clue is the "no VISIBLE loose connections"..
moving the wires to replace the clock may have broken them internally ( I'm assuming that the wiring wasn't changed? )

the small gap makes it crackle as the electricity sparks across the gap..

disconnect and tug on the copper ends of the wires, if one comes out you know it was broken ( with the power off obviously )

 

[SortedPlumbing]

kool cheers for ur help!

How can u check for breaks in cable if that fails?

Thats outwith my electric knowledge!( i think)

 

[ColJack]

end to end continuity.. or "loop back" to one end by connecting 2 wires at the other..

if it's a T+E, do a "loop back" with red and earth, then black and earth and you should get the same reading, if one is higher then that's the one with the break.. ( of course if one is OC then that's definintely the one with the break.. )

 

[SortedPlumbing]

Thanks,

I sorted the 1st one today, just rewired it.

The fault had been some muppet had put a N into a HW off at timeclock.