Heating wont turn off

[MartyMalabu]

Many thanks twgas and D.Hailsham.

I have just followed D.Hailsham's test guide and was confounded by the results to the very first test which shows 57v on cylinder stat T1 (black wire). This is with the stat turned down, which if I understand it correctly means that TC is connected to T2 and T1 should be left floating.

I measured the voltages on the terminals in the cylinder stat during the first test, because I did not believe what I was seeing, and T1 was indeed 57v which must be wrong, but is this enough to cause a problem. I noted that TC and T2 in the cylinder stat (which should be connected together) were both showing 240v, presumably from HWOFF on T2.

I have attached the results of D Hailshams test here,

http://www.mhr.me.uk/docs/voltagechecks20052011.doc

So it seems there is a false signal of 60 - 100 v at different times on T1, when there shouldnt be. The question is how many volts are required for a boiler to think it is being switched on. In actual fact, the real problem happens when the boiler is already running, and fails to turn off when CH is satisfied. So perhaps the question should be, how few volts are required for the boiler to think it is being turned off.

Does this evidence suggest it is worth changing the cylinder stat ?

Your thoughts please
I really appreciate your time.

 

[D_Hailsham]

Provided you completely isolated the black wire, you should not be getting 57V at the HW stat terminal 1 when the programmer is set to HW OFF and the HW stat is turned down.

The next thing to do is disconnect the brown wire from HW Stat C and check the voltage on that wire when the programmer is set to HW OFF. Obviously it should be 0V, if it's anything different the programmer must be at fault.

If it's 0V, the cylinder stat must be faulty.

 

[MartyMalabu]

Thank you for that.

I am not sure you will believe what I am about to tell you.

Programmer not calling for HW, cyl stat turned down. I remove the black cable to its own connector in the chock block (57v).

I disconnected TC from the cyl stat itself and that shows 23v. From this I cant tell whether that is acceptable, or if it should be much closer to 0v. Is this a faulty programmer or not?

However, it gets more intriguing, Black is still showing 57v, so I remove the Blue T2 wire from the cyl stat (only T1 connected there now). Black still shows 57v (at both ends !). The 57v does not seem to be coming from the cylinder stat. Is this a cable problem. I remove the TC brown wire from the main connector block, TC brown is now disconnected at both ends, T1 black is isolated at the chock block, T2 blue is disconnected at the cyl stat. Black STILL shows 57v.

I remove the blue wire from the chock block, and T1 black drops to 0v.

Instinct tells me this is a cable problem, but basic con-checks dont reveal anything except open circuit and closed circuit where I would expect them.

I notice the earth is connected at the main chock block, but is trimmed back in the cyl stat - is this correct ?

Any ideas where to go next?
Should I replace the cable?
Does 23v on HWON indicate a faulty programmer anyway ?

Thanks

 

[D_Hailsham]

I disconnected TC from the cyl stat itself and that shows 23v. From this I cant tell whether that is acceptable, or if it should be much closer to 0v. Is this a faulty programmer or not?

I would have expected 0V on the brown wire, which connects to HW ON.

Black is still showing 57v, so I remove the Blue T2 wire from the cyl stat (only T1 connected there now). Black still shows 57v (at both ends !).

So you had Black connected only to T1 and Brown connected to C and there was 57V on Black? So it must have come from the programmer - nowhere else for it to come from!

 

[MartyMalabu]

Since I had the cylinder stat removed I did a resistance check.

Stat turned down
TC-->T1 = O/C
TC-->T2 = 1.7 Ohms

Stat turned down
TC-->T1 = 0.3 Ohms
TC-->T2 = O/C

At the temperature the stat thinks it is (at least), I think the stat looks OK.

I tried and do a voltage check on the back of the programmer, but could not get a flying lead in there and replace the unit on its rails. Is the best bet now to replace the programmer anyway?

As for the 57v, this is odd. I got a new piece of cable, and JUST connected the blue into the HWOFF connector - this was obviously 240v, but all the other cables were having 100v induced, even though they were not connected at either end.

The earth cable is not connected at the cylinder stat, does it need to be ?

On another unrelated point, with the orange and the T1 black removed from the chock connector to boiler switched live, I noticed that this line (to the boiler I assume) is 40v. Is this correct?

Thanks again.

 

[matt1e]

Sometimes it's easier to trace these types of faults with the valve out off the equation as the internal circuitry in the actuator can lead to confusing results, so to check the wiring disconect the valve wiring then
turn both stats down and turn HW and CH off at the programmer
now check for 240v at the terminal that the grey would connect to
reference this terminal to neutral and earth to make sure that polarity is ok it should be 240 ish in both cases (this is important)
now check that the terminals that are normally connected to valve white and orange are at 0v
now turn HW on at the programmer
same tests should be same results
now turn the cyl stat up
the terminal that valve grey connects to should now be 0v and terminal orange should be now 240v (the boiler should now be firing too)
leave HW on and cyl stat up and turn on ch
check that terminal white is still at 0v then turn room stat up
terminal white should now be 240v
now check that turning off CH at programmer removes voltage from terminal white
next leave both HW and CH on and both stats turned up then turn the cylinder stat down
in this position the boiler should stop firing and both terminals that feed valve white and valve grey should be at 240
valve orange should be 0v,
now using a jumper bridge terminals valve orange and valve white
the boiler should now fire again
This will confirm that the wiring and controls are ok

Matt

 

[D_Hailsham]

Sometimes it's easier to trace these types of faults with the valve out off the equation

If the OP has followed the instructions in the FAQ, then this will have been taken care of. The first part of the FAQ tests the valve without the programmer and stats; the second part tests the programmer and stats without the valve.

check for 240v at the terminal that the grey would connect to
reference this terminal to neutral and earth to make sure that polarity is ok

I was beginning to wonder if the polarity had been changed somewhere.

Would it be a good idea to start again by disconnecting everything and reconnecting according to the "standard" wiring scheme?

View media item 31288
The Glow-worm uses pump overrun. The pump will ether be connected direct to the boiler or via the junction box, in which case you follow the pump overrun option, not the pump connections shown in the main diagram.

 

[MartyMalabu]

Thank you both for your replies.

I think I have already done the FAQ tests which are similar to the ones matt1e is proposing, but I will follow your procedure anyway in case it turns anything up (I will measuring to neutral and earth), and report back later.

The pump live is not connected to the boiler switched live terminal (orange actuator output). It is connected to another feed which I assumed was fed back from the boiler, so this bears out the suggestion that a pump overrun is implemented.

I have identified all the terminals on the connector, though they are in a slightly different order to the ones in the standard diagram for Y plan.

Left to right they are
1. Neutral
2. Earth
3. Live from boiler To Pump Live
4. Orange + Cyl Stat T1 To Boiler Switched Live
5. HWOFF To Grey+ Cyl Stat T2
6. HWON To Cyl Stat TC
7. CH To White
8. Has two reds connected together on the same side. I dont know what these are.

//www.diynot.com/network/MartyMalabu/albums/8578/34118

The connector is upstairs in the airing cupboard (close to actuator and cylinder stat). The programmer is downstairs and very close to the consumer unit and the room stat - so I would guess that the programmer/room stat are not wired via the connector block. i.e. the programmer is connected direct to the room stat.

If it helps, I will rewire the connections as per the standard chock block, but first I need to work out what the two red wires are. Do you have any ideas what they might be.

Thank you so much for your time.

 

[matt1e]

Yes sorry about coming into the thread so late and I didn't really read through the entire thread

Would it be a good idea to start again by disconnecting everything and reconnecting according to the "standard" wiring scheme?

View media item 31288

Yes agreed, This is what I usually do as I usually find it quicker,but first I would link out external controls at the boiler to make sure thats not at fault
good diagram BTW
but first check the polarity at the wiring centre and the boiler

The Glow-worm uses pump overrun. The pump will ether be connected direct to the boiler or via the junction box, in which case you follow the pump overrun option, not the pump connections shown in the main diagram.

having a pump overrun means having a perminant live at the boiler so a fault in the boiler or incorrect wiring here could cause it to self fire
ok A few points

History:

1)The situation now is that on some occasions the CH is not tripping off. Even turning everything off at the programmer does not stop the pump/boiler running.
2) with the fault condition present, and the 3 port valve full over to supply CH (which I think would be the normal place for it to be if just CH had been called and was then satisfied), the orange wire was not live
3) Sometimes (but not always) switching the heating off at the programmer can switch the CH off,
4) I should add that the boiler does trip itself out from time to time, presumably when it is internally at it max temperature, but then fires up when it cools a bit.

Any ideas please chaps. Which components can I rule in or out. What simple checks can I do.Thanks.

1 the only thing that can cause this concerning the actuator is an internal short between grey and orange or a internal short between call and satisfied on the cyl stat otherwise its faulty programmer/wiring

or fault in/at boiler

2 if the orange wire is not live and the boiler is firing then you have incorrect wiring

or fault in/at boiler

3 faulty switch in programmer or incorrect wiring

or fault in/at boiler

4 Faulty boiler or incorrect wiring concerning pump

pick a common denominator
check that the connections at the boiler are correct and next time its at fault disconnect the switched live, if the boiler continues to fire then its at fault



Matt

 

[matt1e]

If it helps, I will rewire the connections as per the standard chock block, but first I need to work out what the two red wires are. Do you have any ideas what they might be.

Thank you so much for your time.

8 - CH on from programmer to room stat

7 - will be from room stat to white

 

[MartyMalabu]

Ok thanks for the info on the room stat and the red wires. That makes sense.

1 the only thing that can cause this concerning the actuator is an internal short between grey and orange

There is no short when checked out of circuit, and the valve was new, and to be sure I replaced the head last week too. The fault has not changed, so I have to assume the actuator/head is not at fault.

or a internal short between call and satisfied on the cyl stat

There is a lot to read in this thread I know, but this morning I posted that I con-checked the cylinder stat, and it appears fine.

otherwise its faulty programmer/wiring

It would be silly of me to rule out wiring, but all I have done is replace the 3 port valve. The photo of the connector was taken before I did this, and it matches up now. The installation is otherwise untouched since it was fitted 9 years ago.

The programmer is a possibility I guess. Proving it is another thing.

or fault in/at boiler

Any way of ruling this in or out?

2 if the orange wire is not live and the boiler is firing then you have incorrect wiring

or fault in/at boiler

3 faulty switch in programmer or incorrect wiring

or fault in/at boiler

4 Faulty boiler or incorrect wiring concerning pump

pick a common denominator
check that the connections at the boiler are correct and next time its at fault disconnect the switched live, if the boiler continues to fire then its at fault

Pulling the orange and black wires out does turn the boiler off. This is also born out in that turning the cyl stat up allows the boiler to be turned off from the programmer.

Thanks for your comments. I will do the measurements later, as advised. I wonder whether it is time to take a chance on a programmer replacement?
[/quote]

 

[twgas]

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 0v @ both pump and switch lives.
  2 discon, and make safe, the pump live - switch on HW (cyl 'stat up) and check for 240v @ all 3 cons on boiler but 0v on the pump wire (the disconned end)

 

[MartyMalabu]

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 0v @ both pump and switch lives.
  2 discon, and make safe, the pump live - switch on HW (cyl 'stat up) and check for 240v @ all 3 cons on boiler but 0v on the pump wire (the disconned end)

Should this be done with the fault present, or after a power reset ?

Thanks

 

[picasso]

I havent read through the whole thread but thought this might be worth a mention as I vaguely remember a similair fault being "fixed" with this.

//www.diynot.com/forums/viewtopic.php?p=823510#823510

 

[D_Hailsham]

I have identified all the terminals on the connector, though they are in a slightly different order to the ones in the standard diagram for Y plan.

Left to right they are ...

That's useful, but would it be possible to post a pic of the junction box/chock block from slightly further away, so we can see the cables and identify which wires go together? We then might be able to identify the reds in 8!

Have you put a meter between the neutral and 8 to see if/when it goes live? Do it for each red in turn.

Why is there a Honeywell wiring centre hiding behind the terminal strip?