180v on control demand neutral,

Hello people, I need some help please. 
I’m having trouble with a heatrae sadia amptec c400 shorting out,

the set up has 2 power supplies going to the PCB. 
1 being the main power supply going into terminal “conn5” (L,N,E) with correct polarity,

2 being power for the controls “conn1”  (N,R) for the controls & (N,L,E) for the pump supply.

on the Controls N I’m getting 180v from the boiler. 
 

Does anyone have any ideas with this is happening? The boiler is brand new, so is the pump, the boiler before had the same problem. 
 

i was wondering if the N on the mains power supply was not connected properly (maybe in the board or somewhere) would this give me a reading on the neutral even if it’s on a different breaker?

I apologise if my use of electrical terminology is not correct.

How many supplies? 
you need only 1 supply. Which does the boiler, the pump is then connected which is fed by the boiler and then you have your controls signal. Which according to manufacturers instruction is a switched live and a neutral which is separated from supply neutral. 
where are you getting your controls signals from? 

How and where are you measuring the 180v

1 supply to the boiler and then the control signals (which is supply by its own supply). I’m getting 180v on the neutral on the control signals. If that makes sense 

From the boiler

Sorry about the drawing but I hope this helps

Nick14 said:

Sorry about the drawing but I hope this helps

Click to expand...

So you are measuring the control N at the boiler, where are you placing your second lead? 
have you disconnected the control neutral and measured? It would suggest that you have a poor connection in controls somewhere? 

Nick14 said:

View attachment 11637

Sorry about the drawing but I hope this helps

Click to expand...

does this control Neutral go back to a wiring centre? 

Sharpend said:

So you are measuring the control N at the boiler, where are you placing your second lead? 
have you disconnected the control neutral and measured? It would suggest that you have a poor connection in controls somewhere? 

does this control Neutral go back to a wiring centre? 

Click to expand...

Earth to Neutral on “conn1”,

yes it’s the only way I can measure it disconnected, if was connected then it would trip

So now you have to go through all your control wiring. First check correct connections, that’s both they’re in the right polarity and they are tight. If this doesn’t solve it then you’ll need to do IR tests on cables. 

All connection are tight, polarity has been checked, the boiler before had the same problem, literally swapped it for a new one, still same problem, so I removed all the external controls (s-plan) and rewired a simple set up as shown in the picture. I even fed the supply from a different circuit just to check. The only cable that hasn’t been changed was the boiler main supply. 

In theory you could run L from the supply straight to the control R and control N back to N. But I will still be getting 180v on the N on the control N. 

So you think it is both this boiler and the previous boiler that are faulty? 

Well there is a possibility, but I think the chances are very slim. So that’s why Im more focused on the electrics at the property. Honestly I really dont know. 
 

I’ve wired this without the pump connected,

ive wired it up with NO neutral between the neutral wiring center terminal and the control neutral (that’s when I can take a reading of 180v at the control neutral at the same time Ive then checked the voltage at the neutral wiring central and get 0v. So the voltage is coming from the boiler control N. 
 

so simply I see it, it receives 240v on the R of the control terminal and 180v come back on the N. So to me It points to the boiler/PCB.

They only other idea I could think of was the N on the main supply to the boiler has a loose connection somewhere and the coming out on the control N? Or would that never happen?

If not what throws me is surely not 2 boilers?

by the way thanks for your reply’s 

Have you checked at the consumer unit for any stray readings? 
have you disconnected the boiler supply and tested at boiler on control N? 
have you checked the boiler supply cable for any faults? 

Sharpend said:

Have you checked at the consumer unit for any stray readings? 
have you disconnected the boiler supply and tested at boiler on control N? 
have you checked the boiler supply cable for any faults? 

Click to expand...

No I haven’t, that will now be my next step

Nick14 said:

1 supply to the boiler and then the control signals (which is supply by its own supply). I’m getting 180v on the neutral on the control signals. If that makes sense 

From the boiler

Click to expand...

Nick14 said:

Earth to Neutral on “conn1”,

yes it’s the only way I can measure it disconnected, if was connected then it would trip

Click to expand...

I have re read this multiple times and I still cant grasp exactly what your supply arrangement is..

AND what trips?

MCB or RCD?

Manufactures guidance states 1x Supply from CU to operate the full load heating part of the boiler..

And off this supply there should be a fused spur to supply 3A for the control wiring..

I get the impression you have two separate supplies from the CU via different MCB's???

If you have..

and these are not supplied via the same RCD..

then I would guess the RCD will trip, just the same as with any crossed circuits..

Guinness

Now it could be there is an issue with a neutral on another circuit that is back feeding to this one? 

SPECIAL LOCATION said:

I have re read this multiple times and I still cant grasp exactly what your supply arrangement is..

AND what trips?

MCB or RCD?

Manufactures guidance states 1x Supply from CU to operate the full load heating part of the boiler..

And off this supply there should be a fused spur to supply 3A for the control wiring..

I get the impression you have two separate supplies from the CU via different MCB's???

If you have..

and these are not supplied via the same RCD..

then I would guess the RCD will trip, just the same as with any crossed circuits..

Guinness

Click to expand...

Thank you, I’ll check tomorrow but I have a feeling you may be right. I think the power comes from the same circuit as the the immersion and not the boiler. I know someone was there before me but wouldn’t tell me what he had done. 

Nick14 said:

Thank you, I’ll check tomorrow but I have a feeling you may be right. I think the power comes from the same circuit as the the immersion and not the boiler. I know someone was there before me but wouldn’t tell me what he had done. 

Click to expand...

:shakehead

And what trips??   RCD or MCB???

Pretty much every job I do, I have no idea what anyone has done before I get there..

But then it is standard practice is to establish exactly how the circuit or accessory you are working on is supplied..

So that you can isolate it to work safely.

  :C

So you have what claims to be neutral that is measuring 180V.

Have you done any continuity testing to see at what point the connection from your "neutral" terminal to true neutral at the consumer unit is broken?  That would be my first test.

ProDave said:

So you have what claims to be neutral that is measuring 180V.

Have you done any continuity testing to see at what point the connection from your "neutral" terminal to true neutral at the consumer unit is broken?  That would be my first test.

Click to expand...

SPECIAL LOCATION said:

:shakehead

And what trips??   RCD or MCB???

Pretty much every job I do, I have no idea what anyone has done before I get there..

But then it is standard practice is to establish exactly how the circuit or accessory you are working on is supplied..

So that you can isolate it to work safely.

  :C

Click to expand...

The RCD trips. On the CU it had “boiler“ and “immersion” on the MCBs so I turned both off, then proved tested proved to confirm it was safe. 

i've never seen any boiler / controls with 2 mains supplies, apart from 1 set of solar thermal controls that had 3 mains inputs coz it had been wired by plumbers....  :shakehead  (2 were subsequently removed).