mid position valve faulty?

[doitmyself]

The boiler is a Worcester Greenstar 18Ri.

I believe that is one of the boilers which will run when there is 150V or so on the orange.

You will only get this problem if the valve is in CH only position when the heating turns off.

Here's a quick way of checking if that is the cause:

With programmer set to CH ON and HW ON

1. Turn room stat and boiler stat up
The valve should go to mid-position; boiler should light and rads & cylinder warm up
2. Turn room stat down
The valve should go to HW only;boiler should continue to run.
3. Turn cylinder stat down
Valve should stay in HW position; boiler should stop.
4. Turn cylinder stat up then turn room stat up
Valve should go to mid-position; boiler runs; rad and cylinder heats up.
5. Turn cylinder stat down
Valve goes to CH position; boiler runs; rads only heat up.
6. Turn Room stat down
Valve should stay in CH position; boiler should stop.

If the boiler does not stop, it's because the voltage on the orange wire is enough to turn on the gas valve.

 

[drollord]

I believe that is one of the boilers which will run when there is 150V or so on the orange.

You will only get this problem if the valve is in CH only position when the heating turns off.

Here's a quick way of checking if that is the cause:

With programmer set to CH ON and HW ON

1. Turn room stat and boiler stat up
The valve should go to mid-position; boiler should light and rads & cylinder warm up
2. Turn room stat down
The valve should go to HW only;boiler should continue to run.
3. Turn cylinder stat down
Valve should stay in HW position; boiler should stop.
4. Turn cylinder stat up then turn room stat up
Valve should go to mid-position; boiler runs; rad and cylinder heats up.
5. Turn cylinder stat down
Valve goes to CH position; boiler runs; rads only heat up.
6. Turn Room stat down
Valve should stay in CH position; boiler should stop.

If the boiler does not stop, it's because the voltage on the orange wire is enough to turn on the gas valve.

BINGO! you have recreated my fault.

I went through your sequence and noted the voltage at T7(orange wire)

I. system OK, 225v
2. system OK, 225v
3. system OK, 0v
4. system ok, 225v
5. valve stayed in mid position, 130v
6. valve still in mid position, 225v
Boiler would not shut down

Pulled mains supply and reconnected, valve gone HW position, boiler not fired up as its like a sauna in here!

mick

 

[drollord]

BINGO! you have recreated my fault.

I went through your sequence and noted the voltage at T7(orange wire)

I. system OK, 225v
2. system OK, 225v
3. system OK, 0v
4. system ok, 225v
5. valve stayed in mid position, 130v
6. valve still in mid position, 225v
Boiler would not shut down

Pulled mains supply and reconnected, valve gone HW position, boiler not fired up as its like a sauna in here!

mick

DAMN!

I have tried the sequence a couple more times and cannot get it to replicate the fault again.
Will have another go tomorrow when its cooled down a bit more.
mick

 

[doitmyself]

BINGO! you have recreated my fault.

I went through your sequence and noted the voltage at T7(orange wire)

5. valve stayed in mid position, 130v
6. valve still in mid position, 225v
Boiler would not shut down

What makes you say that the valve stays in mid-position?

 

[drollord]

I have started from from scratch today.
Both stats at zero, boiler off and valve in HW position.
I have had someone help to turn the stats while I have watched the valve movement and noted the voltages.
We have gone through the 1-6 proceedure four seperate times over about 3 hours and nothing has gone wrong, the valve movement has been correct in every case. The boiler fired up and shut down as it should.
When it went wrong last night at stage 5, the valve remained at the mid position and T7 had 130v.
Could it be tank stat at fault and/or sticky microswitches in valve head.

voltages taken today at each stage.[TABLE="width: 511"]
[TR]
[TD][/TD]
[TD]T 4[/TD]
[TD]T5[/TD]
[TD]T6[/TD]
[TD]T7[/TD]
[TD]T8[/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]90[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]2[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]90[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]3[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]4[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]90[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]5[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]6[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[/TR]
[TR]
[/TR]
[/TABLE]

 

[doitmyself]

voltages taken today at each stage.[TABLE="width: 511"]
[TR]
[TD][/TD]
[TD]T 4[/TD]
[TD]T5[/TD]
[TD]T6[/TD]
[TD]T7[/TD]
[TD]T8[/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]90[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]2[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]90[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]3[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]4[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]90[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]5[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[TD]225[/TD]
[/TR]
[TR]
[/TR]
[TR]
[TD]6[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[TD]0[/TD]
[TD]225[/TD]
[/TR]
[TR]
[/TR]
[/TABLE]

All the voltages are OK except those in colour. I'm not sure about the 90 volt readings, they could be a quirk of the valve, but the 225 volt reading on T7 at stage 5 is definitely wrong; it should be 0 volts.

Disconnect all wires from T7 and T8 except those to the cylinder stat

Turn stat to Minimum: You should get 0 on T7 and 225 on T8
Turn stat to Maximum: You should get 225 on T7 and 0 on T8

Check this several times. It might be worth checking to see if there is a point between max and min where you get 225v on both T7 and T8 - there shouldn't be one!

If you don't get the correct readings, the cylinder stat is faulty.

 

[drollord]

All the voltages are OK except those in colour. I'm not sure about the 90 volt readings, they could be a quirk of the valve, but the 225 volt reading on T7 at stage 5 is definitely wrong; it should be 0 volts.

Disconnect all wires from T7 and T8 except those to the cylinder stat

Turn stat to Minimum: You should get 0 on T7 and 225 on T8
Turn stat to Maximum: You should get 225 on T7 and 0 on T8

Check this several times. It might be worth checking to see if there is a point between max and min where you get 225v on both T7 and T8 - there shouldn't be one!

If you don't get the correct readings, the cylinder stat is faulty.

Have done what you said.
at minimum T7 60v T8 225v
at maximum T7 225v T8 60v
there is no point where both T7 and T8 are at 225v
the change over happens at the point of tank temperature which at the moment is 60° and an audible click of the stat is heard
Where's this 60v reading come from?

 

[doitmyself]

Have done what you said.
at minimum T7 60v T8 225v
at maximum T7 225v T8 60v
there is no point where both T7 and T8 are at 225v

Did you disconnect all wires, except those from the cylinder stat, from T7 and T8?

 

[drollord]

Did you disconnect all wires, except those from the cylinder stat, from T7 and T8?

Yes, most definately!

 

[doitmyself]

Yes, most definitely!

Then the cylinder stat is knackered!

 

[drollord]

Yes, most definately!

should have added that I even took the blue and yellow wires of the cylinder stat from the T7 and T8 terminal block and had them hanging in mid air to measure on the meter when I found the 60v.

 

[drollord]

Then the cylinder stat is knackered!

OK, I will get a new one. I will check when I wire it in if I get this 60v.
The whole kit(stats,prog,valve)is an Iflo (specific to Travis Perkins?). Would you replace like for like or go with another brand. The Iflo look like a Drayton clone or it could be the other way round.

Many thanks for your invaluable help

mick.

 

[doitmyself]

Iflo is made for Travis Perkins by Drayton, but that does not mean they are made to the same standard.

It's OK to mix kit; I prefer Honeywell kit as it seems to last longer.

Check for the 60V when only the common is connected.

The terminal numbers are the same for the Drayton/Iflo and the Honeywell L641A.

 

[drollord]

Iflo is made for Travis Perkins by Drayton, but that does not mean they are made to the same standard.

It's OK to mix kit; I prefer Honeywell kit as it seems to last longer.

Check for the 60V when only the common is connected.

The terminal numbers are the same for the Drayton/Iflo and the Honeywell L641A.

Fitted a new Drayton cylinder stat today. Before attaching wiring to T7 and T8, yellow wire from stat to T8 was 225v, blue wire from stat was 0v
Will see how it goes.

 

[drollord]

Fitted a new Drayton cylinder stat today. Before attaching wiring to T7 and T8, yellow wire from stat to T8 was 225v, blue wire from stat was 0v
Will see how it goes.

The new cylinder stat has not fixed the problem. Boiler would not switch off again today. Took valve head off and gave it a shake, the lever then moved from the mid position to CH and the boiler turned off as it should.
Will be getting a new head on Monday.