Heating wont turn off

[D_Hailsham]

I have fitted a new actuator and we can now rule that out as the boiler continues on with both thermostats turned down.

So that's £50 down the drain.

I am pretty certain the valve is not sticking - and in any case it is only a week old.

I'd forgotten that you replaced the complete valve. Did you put it in the same way round as the old one? Port A (marked on the side of the brass part) should go to the rads; Port B to the HW cylinder

When in the fault condition with both stats turned down the manu/auto lever is loose. This is because the motor had previously been at the CH position and is still receiving power since turning the stats down - so is still in that position.

Of course; I should have remembered that.

In the fault condition there is 240v on both grey and white (and orange).

That's wrong!

I disconnected the room stat feed where it meets the white and it is 0v, so the 240v is feeding out on the white from the actuator - obviously derived somehow from the grey wire.

Do you mean the white is 0V or the wire from the room stat is 0V?

The only way 240V can get from the grey to the white is via R2 (see the CH Satisfied diagram). This is normally a high value resistance, chosen to make sure 240V cannot get onto the orange and thus start the boiler.

If I disconnect the grey wire at this point the motor returns with the spring to its rest position and the orange and white drop to 0v and stay there after I have reconnected the grey.

That's as expected

While checking the problem with the new actuator I have observed a slight change in symptoms. I can now turn the heating off if I do it at the programmer, but if I try this by turning the room stat down it has no such effect - the boiler runs on. I noticed that if I twist the programmer slightly that the HW light comes on. I am now wondering if my problem is the programmer. Could the programmer be causing these symptoms due to a flaky connection (perhaps leaking the NOT HW signal onto the CH signal).

That's a possibility, but first remove the programmer from its back plate and check the connections are tight and no loose strands.

 

[twgas]

Try disconnecting the valve completely, then turn HW and CH on and off both via the programmer and the 'stats, measuring the voltage on each terminal that the valve was connected to, after every switching action, this should tell you if any of the external controls are faulty.

 

[MartyMalabu]

Thanks for your replies. This thing is driving me nuts. At least I am not cold


D.H., in response to your question about when I disconnected the stat wire from the white wire with the fault present, the stat wire was 0v, and the white wire was 240v. This 240v can only be coming via the grey as far as I can see - however, this was the same with the other actuator (both brand new). This would suggest this is neither a programmer problem nor an actuator problem.... )

The new valve is fitted the same way around, A and B are correctly orientated.

I will check the programmer connections out - but cant see why that would cause this. I will also do as twgas suggests and check the control signal with the actuator isolated.

Thanks guys.

 

[MartyMalabu]

Just to say that I took the programmer off and the connections look reasonably secure, I tightened them anyway. No shorting strands evident.

I have found a reason why I can turn the boiler/pump off from the programmer now when I could not before.

HW not called for on programmer
cylinder stat turned down
Call for CH on programmer with room stat high
Bolier fires up
Turn CH off on programmer, but boiler continues to run

Now repeat this, but with the cylinder stat turned up instead. Now turning CH off on the programmer turns the boiler/pump off.

What I dont get is why turning down the room stat down when the boiler is running does not turn the boiler off (in either case). I also dont get why the boiler continues to run in the first case, at the cylinder stat position affecting this, implies that HWON is live - even though it is off at the programmer.

Any ideas what on earth is going on ?

I isolated the three signals in the airing cupboard where they normally join the actuator and measured them. These include the two stats. I have used a slash to show
"voltage when stat turned down"/"voltage when stat turned up"
if you follow me.


Both called for on programmer
HWOFF 230/55v, HWON 230v, CH 85v/230v

HW called for. CH not called for on programmer
HWOFF 240/48v, HWON 230v, CH 0v

HW not called for. CH called for on programmer
HWOFF 230v, HWON 240/65v, CH 85v/230v

Neither called for
HWOFF 230v, HWON 240/17v, CH 0v

Do these look OK to you ?

These voltages are all AC, but one odd thing I noticed is that in the 3rd case HWON also had a DC component to it, measuring between HWON and neutral it was showing approx -230vDC/-150vDC for both stat positions.

Your thoughts please guys, which components can I rule in or out at this stage?

 

[bengasman]

Thanks for your replies. This thing is driving me nuts

It seems you would have been better off getting a pro out, and you might want to consider doint that now.
This kind of fault isn't always easy to sort out, and on top of that you could actually do more harm than good if you do the wrong thing and kill the timer or the boiler.

 

[D_Hailsham]

when I disconnected the stat wire from the white wire with the fault present, the stat wire was 0v, and the white wire was 240v. This 240v can only be coming via the grey as far as I can see - however, this was the same with the other actuator (both brand new).

That eliminates the room stat. The Grey wire will be 240V from either programmer HW OFF or Cyl Stat "Sat" terminal.

The only way 240v can leak from the grey to the white is via the resistance R2 and switch S2 (see the CH Satisfied diagram in the FAQ). R2 is set to a high value (about 270k&#937 to reduce the voltage on the orange in the CH Satisfied condition, which would otherwise cause the boiler to light - your problem!

 

[D_Hailsham]

HW not called for on programmer
cylinder stat turned down
Call for CH on programmer with room stat high
Bolier fires up
Turn CH off on programmer, but boiler continues to run

Now repeat this, but with the cylinder stat turned up instead. Now turning CH off on the programmer turns the boiler/pump off.

Which make/model cylinder stat do you have?

Can you give the connections from the cylinder stat? (e.g T1 to Valve Orange, T2 to Valve grey, T3 to Programmer HW ON)

 

[MartyMalabu]

Thanks for your reply.

The cylinder stat is a Honeywell L1641A1039.

The three lugs are wired as follows

"C" Brown wire, connects to HWON terminal (no other wires)
"2" Blue wire, connects to HWOFF terminal (with actuator grey)
"1" Black wire, connects (with orange wire) to what I believe is the boiler switched live.

All terminal in the stat were tight and secure
I think this is wired OK, what do you think ?

 

[twgas]

HW not called for. CH called for on programmer
HWOFF 230v, HWON 240/65v, CH 85v/230v

Neither called for
HWOFF 230v, HWON 240/17v, CH 0v

These HWON readings are, I believe, cause for concern. If HW is not called for you should not have 240v where the orange is (or should be) connected, whether the cyl 'stat is up or down. I think your wiring or programmer is the problem.
I suspect 'D_Hailsham' will be along shortly and will agree with me (he's pretty good on system electrics) - or give you his opinion on where the problem is.

 

[MartyMalabu]

Thanks Mick for your reply.

If HW is not called for you should not have 240v where the orange is (or should be) connected, whether the cyl 'stat is up or down.

Although looking at the standard Y plan diagrams, if the cylinder stat is turned down, HWON (stat Common) gets connected to HWOFF (stat T2) - so HWON == HWOFF. If HWOFF=240v, then wont HWON also = 240v ?

Thanks

 

[twgas]

If HW off is selected there should not be a supply to the common of cyl 'stat, I agree you will get 240v if the 'stat is turned down but that will be back feeding from con 2 ('stat), as the stat is down con 1 will not be powered c-1 will be open. turn stat up and c-2 will open and c-1 will close so there will be no power to either c or 1, remember the valve is disconnected so you cant get a supply through the valve back down the orange wire.
I'm wondering if the c and 1 of your cyl 'stat are transposed.

 

[D_Hailsham]

The cylinder stat is a Honeywell L1641A1039.

The three lugs are wired as follows

"C" Brown wire, connects to HWON terminal (no other wires)
"2" Blue wire, connects to HWOFF terminal (with actuator grey)
"1" Black wire, connects (with orange wire) to what I believe is the boiler switched live.

That's correct.

You are getting 240v fed from somewhere; it's just a case of identifying the source

Let's try something.

Turn power off, programmer CH and HW off and both stats down
Disconnect the orange wire and the black wire (from the cyl stat 1) and separate them (Put in separate terminals of a chock-block?)

Turn power on and check:
Black wire = 0V
Orange = 0V
Grey = 240V
White = 0V

Turn HW ON and check:
Black wire = 0V
Orange = 0V
Grey = 240V
White = 0V

Turn HW stat up and check:
Black wire = 240V
Orange = 0V
Grey = 0V
White = 0V

Turn CH ON and check:
Black wire = 240V
Orange = 0V
Grey = 0V
White = 0V

Turn CH stat Up and check:
Black wire = 240V
Orange = 0V
Grey = 0V
White = 240V

Turn HW OFF (leave HW stat UP) and check:
Black wire = 0V
Orange = 240V
Grey = 240V
White = 240V

Turn HW ON, turn HW stat down and check:
Black wire = 0V
Orange = 240V
Grey = 240V
White = 240V

PS You don't seem to have told us which boiler (make and exact model) you have.

 

[MartyMalabu]

Thank you for that. I will give it a go this evening.

The boiler is a GlowWorm Micron 60FF.

 

[twgas]

The cylinder stat is a Honeywell L1641A1039.

The three lugs are wired as follows

"C" Brown wire, connects to HWON terminal (no other wires)
"2" Blue wire, connects to HWOFF terminal (with actuator grey)
"1" Black wire, connects (with orange wire) to what I believe is the boiler switched live.

That's correct.

sorry, I missed that.

 

[twgas]

I isolated the three signals in the airing cupboard where they normally join the actuator and measured them.These include the two stats

this is a little confusing, do you mean you isolated the three (orange, white and grey) wires of the valve?
If so:

Both called for on programmer
HWOFF 230/55v, HWON 230v, CH 85v/230v

from this I assume HWON had 240v with cyl 'stat down AND up. If you are correct in saying the wiring is correct, the fault looks to be the cyl 'stat (not breaking c-1 when turned down)

HW called for. CH not called for on programmer
HWOFF 240/48v, HWON 230v, CH 0v

same as previous conclusion.

HW not called for. CH called for on programmer
HWOFF 230v, HWON 240/65v, CH 85v/230v

with no demand from programmer there should not be 240v @ HWON, with 'stat down or up. this could also point to a faulty cyl 'stat (a closed circuit between 1-2)

Neither called for
HWOFF 230v, HWON 240/17v, CH 0v

again closed circuit 1-2 would give these readings,

Do these look OK to you ?

obviously not.
Cylinder 'stat looks to be the most likely suspect