My boiler continues to fire up when controller says off

[Semers]

Hi all, hope someone can throw some light on this. I have a vokera boiler (getting on a bit now!) but intermittently it fires up even though programmable controller says off and will then every now again appear to get really hot and pipework shakes around the whole house, I hear the motorised valve open and all goes quiet as If pressure is released.
Have an old analogue room stat which I think is the cheapest thing to change first.
I don't have any radiator thermostats so just a room one. Should I replace with a digital one?

 

[SimonJohns]

Is it a combi or do you have a cylinder and motorised valves?

 

[tamz]

Give the motorised valve(s) a hit with a hammer. The microswitch is stuck.

 

[Semers]

Tried the hitting bit in the past and manually overriding switch which gets it all rumbling. It is a cylinder and valves and probably just c/h one as no problem in the summer with just hot water. It does seem to be stiff to manually open and close the valve with pliers once i take the cover off so I'm guessing it's got furred up in the pipe meaning a drain down to replace. bit reluctant to spend too much on it as we may look to replace boiler in next year. I was hoping thermostat might be the problem as probably lot less hassell and cost :-(

 

[Semers]

Have just taken casing off again as not done for months and actually, I can turn the valve with my hand and when I hit the centre in the casing the boiler switched off so maybe it is my hpa2 switch. Any idea best place to get one and r they easy to replace? Assume just wire one in it's place. Have they changed in last few years so I need to look out for any change?

 

[tamz]

I take it you have danfoss valves like this



You can buy new heads (actuators) for them for about £25. Take a picture of the connections to the junction box and swap the wires one at a time and you won't get confused. Put the power off before you touch it.

 

[Semers]

Yes Tamz, just like that. Any good places to go for one? Do these fail regularly? I think I had new ones about 5-6years ago!
I will defo turn the power off first, I like my hair straight!

 

[SimonJohns]

I agree with Tamz on taking photos before you start to change the wires

My best tip woul be the same. But cut the wires from the old valve and leave in situ until you replace with same colour wire from new valve

 

[Semers]

Great tips thanks. I'll let you know how it goes after a week of new actuator that hopefully will be here by tomorrow.

 

[Anton]

Where does one get these specialised hammers for fault fixing?
The one I have doesn't work.

 

[SimonJohns]

Where does one get these specialised hammers for fault fixing?
The one I have doesn't work.

You can't just have a hammer. You have to master the "technical tap".

 

[PlumbBobBob]

it's all in the wrist.

 

[Anton]

it's all in the wrist.

That's a bit off topic.
I was talking about fault fixing.:biggrin5:

 

[Semers]

Well after a few months of working well and switching off when it's being told to after replacing the valve, my boiler has started the same fault again. My hammer is now not doing anything, so Antonio if you found a specialised hammer can I borrow it! No, seriously, I need to get the boiler serviced as not had it done in last 24 mths :-( and I'm hoping they'll pick up on why it fluctuates in pressures but I'm concerned as to original problem returning. I'm wondering if now it could be the hw valve. Are they likely to go at similar times/ages? I tried the said hammer today on it and the boiler switched off, so I'll try a few more times this week if needed and get another one. If anyone has any other ideas I'd be grateful.

 

[SimonJohns]

Are you handy with a multimeter?

 

[Anton]

Hi Semers.
I still can't find one of these special hammers, so I just use normal tools for now. If you have two of these zone valves then there's a good chance that the one you didn't replace is faulty. You can test the actuator heads with a multimeter for continuity between the grey and orange wires. Unless you know how to use a multimeter I would just go for replacing the one that you didn't change last time. Those actuator head microswitches regularly stick.
Check the spindle is moving freely by hand on the zone valve, if it's stiff (I looked back to steveb's last post for this one) then give it some excercise or replace the whole zone valve.

 

[Semers]

I did have a stiff one and it looked like there had been some leaking at the zone valve but very minor (nothing to get excited about) so I decided to spray a bit of wd40 and give it some work with some pliers. Yes it was quite stiff. Im not brilliant with a multimeter as that's my husbands toy & I'm not convinced he knows what to do with it either!! So I'll see how it behaves over next few days and might get a new one. Want to stay away from replacing zone valve as I'm sure that would be a drain down :-(. Thanks guys for help. Meaning I'll get a new danfoss actuator, not husband!!!