Heating wont turn off

[MartyMalabu]

It all depends on the number of cable 'cores' you have, and, if the existing cable is damaged do you really want to use it.

Good point. I was thinking about using the CHON core to carry switched live, but I guess it follows that this could be compromised too even though it appears to be OK by voltage checks.

I am also wondering if the cause of the fault I have is the cylinder stat cable (which is definitely misbehaving and needs changing), and restores 0v on the Orange when it was showing 40v when replaced; and that this problem with these two wires has been there all along, and may not affect the behaviour of the system.

 

[twgas]

I don't know, off the top of my head, which connection is which on your boiler. I'll try to find out, although it should be in the book, if you have it.
update: from the left; 1 is mains in (permanent live). 2 is switched live (from valve orange). 3 is neutral. 4&5 are earth. 6 is pump live. 7 is pump neutral (may not be connected as pump N is often picked up at wiring centre)

 

[D_Hailsham]

Just a thought

You mentioned earlier that there was an unconnected earth wire at the cylinder stat and asked if it should be connected. The answer is: no.

However, it appears from the pic the same earth wire is connected to terminal block T2; it shouldn't be. Disconnect and cut the lead back to the outer sheath (do this at both ends).

I'm just wondering if the earth wire is acting as an aerial and inducing a voltage in the black.

 

[MartyMalabu]

Just a thought

You mentioned earlier that there was an unconnected earth wire at the cylinder stat and asked if it should be connected. The answer is: no.

However, it appears from the pic the same earth wire is connected to terminal block T2; it shouldn't be. Disconnect and cut the lead back to the outer sheath (do this at both ends).

I'm just wondering if the earth wire is acting as an aerial and inducing a voltage in the black.

The earth wire is connected to the earth connector block at one end, and snipped back where the four wires emerge from the outer sheath at the stat end. It is not connected to T2. But thanks anyway.
//www.diynot.com/network/MartyMalabu/albums/8578/34348

 

[D_Hailsham]

However, it appears from the pic the same earth wire is connected to terminal block T2.

The earth wire is connected to the earth connector block at one end, and snipped back where the four wires emerge from the outer sheath at the stat end. It is not connected to T2.

Read what I said! I did not say T2 on the cylinder stat but T2 on the terminal block (the big white thing with 8 pairs of terminals).

However you admit that the eath is connected to the "earth connector block", which I assume is the terminal I was referring to.

So disconnect it at both ends and cut back to the outer sheath.

I won't guarantee it will have any effect, but an earth wire connected at one end only is never a good idea.

 

[MartyMalabu]

However, it appears from the pic the same earth wire is connected to terminal block T2.

The earth wire is connected to the earth connector block at one end, and snipped back where the four wires emerge from the outer sheath at the stat end. It is not connected to T2.

Read what I said! I did not say T2 on the cylinder stat but T2 on the terminal block (the big white thing with 8 pairs of terminals).

However you admit that the eath is connected to the "earth connector block", which I assume is the terminal I was referring to.

So disconnect it at both ends and cut back to the outer sheath.

I won't guarantee it will have any effect, but an earth wire connected at one end only is never a good idea.

Sorry for not reading more carefully . I tried what you suggested and it has not made any difference. I hope to replace the cable tonight, and check the boiler voltages.

Many thanks to all for your continued interest.

 

[twgas]

If you are going to replace the cables from boiler to airing cupboard it might be worth doing a dry run, testing, then see how it is - ie run cables up the stairs, through doorways etc, (no boards up or walls down) then you can see for sure if the problem is going to be solved.

 

[MartyMalabu]

If you are going to replace the cables from boiler to airing cupboard it might be worth doing a dry run, testing, then see how it is - ie run cables up the stairs, through doorways etc, (no boards up or walls down) then you can see for sure if the problem is going to be solved.

Sorry - I meant simply to change the cable from the stat to the connector - which was showing a floating voltage on the T1 cable. I have no idea how I would replace the cables between the programmer and the connector - this would involve some significant damage of plasterboard and floorboards. I think a preferable option to rectifying the second cable problem would be to move the programmer to the airing cupboard. I just need to work out where to get an unswitched live from.

That aside, your suggestion is a good one.

Thanks

 

[D_Hailsham]

I have no idea how I would replace the cables between the programmer and the connector - this would involve some significant damage of plasterboard and floorboards. I think a preferable option to rectifying the second cable problem would be to move the programmer to the airing cupboard.

But you would then need a cable from the relocated programmer to the Room Thermostat!

 

[MartyMalabu]

I have no idea how I would replace the cables between the programmer and the connector - this would involve some significant damage of plasterboard and floorboards. I think a preferable option to rectifying the second cable problem would be to move the programmer to the airing cupboard.

But you would then need a cable from the relocated programmer to the Room Thermostat!

The input and output of the room stat are wired into the chockblock in the airing cupboard. I will need to check, but the assumption at the moment is that these cables are OK.

 

[D_Hailsham]

But you would then need a cable from the relocated programmer to the Room Thermostat!

The input and output of the room stat are wired into the chockblock in the airing cupboard. I will need to check, but the assumption at the moment is that these cables are OK.

I realized that as soon as I pressed the submit button! For some incomprehensible reason I had the idea that the programmer had a cable going straight to the room stat!

 

[MartyMalabu]

But you would then need a cable from the relocated programmer to the Room Thermostat!

The input and output of the room stat are wired into the chockblock in the airing cupboard. I will need to check, but the assumption at the moment is that these cables are OK.

I realized that as soon as I pressed the submit button! For some incomprehensible reason I had the idea that the programmer had a cable going straight to the room stat!

To be honest I dont know how you guys can visualise as much as you do from a monitor and a keyboard - it must be so much easier when the kit is in front of you.

 

[MartyMalabu]

I don't know, off the top of my head, which connection is which on your boiler. I'll try to find out, although it should be in the book, if you have it.
update: from the left; 1 is mains in (permanent live). 2 is switched live (from valve orange). 3 is neutral. 4&5 are earth. 6 is pump live. 7 is pump neutral (may not be connected as pump N is often picked up at wiring centre)

Finally got around to checking the boiler voltages.

First of all, just to mention that I changed the cable from the cyl stat to the airing cupboard connector block (brand new 4 core with the earth clipped back at each end), and the fault is still there. I am seeing 30v-80v (cyl stats down - cyl stat up) on the T1 wire even when disconnected at BOTH ends. This changes to 0v-50v sometimes, and I think this is when HW is ON, because the 30v floating on the HWOFF line drops away. So I have a stepped voltage between 0v to 80v on T1 depending on whether HW is on and depending on the cyl stat position.

OK back to the boiler.

Have you checked the wiring at the boiler?
To do so
1 turn HW and CH off at prog and check for
240v @ permanent live

240

0v @
both pump

0v

and switch lives.

47v

I removed the feed to the switched live at the boiler, and the end of the wire was 0v, and the switched live connector now measure 122v . Refitted wire, voltage reads 47v again.

2 discon, and make safe, the pump live - switch on HW (cyl 'stat up) and check for
240v @ all 3 cons on boiler

240v,240v,240v

but 0v on the pump wire (the disconned end)

0v


Perhaps this anecdote from picasso earlier in the thread has some relevance now.

keego wrote:
Thanks for that Andy. I rang Worcester Tech today & they confirmed what you said about the capacitor, it seems they've known about this for a while yet obviously decided this bit of information is not worthwhile putting in the MIs for the boiler.
For future reference the capacitor is a 0.47uF 275v MPX2, £1.58 from Maplins
This links the neutral & switched live to boiler ( Orange wire in the wiring center )


the op had the same problem with the boiler firing up with stray voltages from a honeywell 3 port valve and what the fix was, no idea if its the same problem but it could be.

As all my measurements are with respect to neutral, if neutral and switched live were bleeding across this could affect any voltage reading I guess ?

Something very odd going on. Can anyone see a single cause which would cause all these symptoms.

Thank again guys.

 

[D_Hailsham]

To be honest I dont know how you guys can visualise as much as you do from a monitor and a keyboard - it must be so much easier when the kit is in front of you.

It's even harder when the topic has reached six pages and you have to continually refer back to see what someone did or didn't say!

 

[D_Hailsham]

First of all, just to mention that I changed the cable from the cyl stat to the airing cupboard connector block (brand new 4 core with the earth clipped back at each end), and the fault is still there. I am seeing 30v-80v (cyl stats down - cyl stat up) on the T1 wire even when disconnected at BOTH ends. This changes to 0v-50v sometimes, and I think this is when HW is ON, because the 30v floating on the HWOFF line drops away. So I have a stepped voltage between 0v to 80v on T1 depending on whether HW is on and depending on the cyl stat position.

This makes no sense at all!

To recap:

1. You have replaced the cable from cylinder stat to the terminal strip

2. If you disconnect the wire from cylinder stat T1 at both ends (i.e at the cylinder stat and the terminal strip) and then measure the voltage between the disconnected wire and neutral you get 30-80V!!

or do you mean that you get 30-80V on HW cylinder T1 with the wire disconnected?

If so what do you get on C terminal and T2 terminal?

What voltages do you get on the three HW stat terminals when the wire to T2 is also disconnected?