Electrical Issue With Central Heating

[CountryFan]

Are you sure it’s a neutral? Could be a switched live.

 

[Groover75]

I have disconnected all of the neutrals and the one from the master fused CH switch is the problem.

With the neutrals still disconnected I opened up the switch and I have 242V red to black going into the switch then when the switch is on 242V on the blue wire.

Note that the brown wire has a piece of insulation missing

The blue wire is in fact attached to the L terminal of the switch...

Good job I am super cautious!!

 

[CountryFan]

So it sounds like you have reversed polarity. Is that brown also connected to the earth terminal?

 

[Groover75]

With the switch turned on the brown wire is connected to earth, however my multimeter makes a warbling noise rather than a continuous beep, like it is connecting and disconnecting very quickly.

 

[CountryFan]

With the switch turned on the brown wire is connected to earth

Why is this?

however my multimeter makes a warbling noise rather than a continuous beep, like it is connecting and disconnecting very quickly.

Are you sure it’s a multimeter? Sounds like a 2 pole voltage indicator. I would rewire the switch with just LNE and connected to the correct terminals

 

[Daveydub]

I would rewire the switch with just LNE and connected to the correct terminals

If that brown is connected to Earth as it seems to be then changing it to Live would not be a good idea without altering other connections.
You appear to have L & N into that switch and just the blue wire leaving it. so no N to system.
This does not make sense as you say that the valve operates with the head removed.
If it is a Honeywell type valve with 2 fixing screws for head to body, sometimes over-tightening these screws can cause the motor to bind

 

[Groover75]

Are you sure it’s a multimeter? Sounds like a 2 pole voltage indicator.

 

[Harry Bloomfield]

With the neutrals still disconnected I opened up the switch and I have 242V

There are several possible reasons for that....

If there is still a live, connected to an item, but you disconnect it's neutral, from a proper neutral, then it will show mains volts on the supposed neutral.

You also have to be sure that what you are using as the 0v reference, is truly at 0v. If you are using an earth wire as the reference, ensure it is actually earthed at 0v.

 

[Groover75]

There are several possible reasons for that....

If there is still a live, connected to an item, but you disconnect it's neutral, from a proper neutral, then it will show mains volts on the supposed neutral.

You also have to be sure that what you are using as the 0v reference, is truly at 0v. If you are using an earth wire as the reference, ensure it is actually earthed at 0v.

Sorry, I should have been clearer. The disconnected neutrals are "downstream" of the switch. I mentioned it to ensure that the switch was isolated from anything after it.

 

[Groover75]

What is the point of the actuator manual lever position if, when moving it to manual, it opens the valve but doesn't move the mechanism far enough to reach the microswitch, and therefore the boiler does not turn on?

 

[Harry Bloomfield]

What is the point of the actuator manual lever position if, when moving it to manual, it opens the valve but doesn't move the mechanism far enough to reach the microswitch, and therefore the boiler does not turn on?

So the system can be refilled with water, bled, and ovoid airlocks.

 

[Groover75]

If it is a Honeywell type valve with 2 fixing screws for head to body, sometimes over-tightening these screws can cause the motor to bind

BINGO!

I loosely attached it with a single screw and it works. I then attached both screws enough to hold it firm but not any more than needed. Still works.

All buttoned back up. I will tape a warning note to the electrical box saying blue is live and deal with that later.

Many thanks. I have learned a lot!

 

[Madrab]

OK, definitely - don't leave it like that for long. If there's one thing to get right, it's the main power cabling from the fused connection. At no point should it be using incorrectly coloured wiring to feed the main power into the system, that's just asking for real problems in the future.

It's not unusual to use different colours of cable for different parts of an S plan but the key power lives, neutrals and earths should be common to brown(red)/blue(black)/green-yellow (green). Other connections like - switched lives - cabling through the stats - etc sometimes use standard 3 core cable but they those cables would be coloured correctly with sleeving or tape and green-yellow(green) shouldn't ever be used for anything but an earth connection and earth shouldn't be in any other coloured cable than that, that's a big no-no!

I would advise getting some green, brown, blue, grey and yellow insulating tape and tape the ends of cables, where they terminate, as to what they are actually doing.

 

[CountryFan]

If that brown is connected to Earth as it seems to be then changing it to Live would not be a good idea without altering other connections.
You appear to have L & N into that switch and just the blue wire leaving it. so no N to system.
This does not make sense as you say that the valve operates with the head removed.
If it is a Honeywell type valve with 2 fixing screws for head to body, sometimes over-tightening these screws can cause the motor to bind

That’s why I said rewire to correct terminals