Boiler just always on....

[solidpro]

Hi Everyone

I've got a quite old Glow Worm Ultimate 80FF. It recently had an issue with the control stat (lots of green corrosion on it which was causing it not to come on) and I fitted a new one and I'm back in business. Everything was fine for a few days and now it's just always on.

We have two wired boxes on the wall in the house - central heating and hot water. After changing the stat, I could go to the thermostat on the wall switch it on and hear the boiler firing up, then off and it would go off. I did this a number of times and it was good. Now, it's just on all the time.

I've recently swapped the PCB (I have two) and no change. I've also recently replaced the overheat thermostat too.

I've tried unplugging both of the control boxes - and it still just fires up when you switch on the isolator switch. I can't figure out why it thinks it should be on.

You do have 4 lights on the boiler showing something like on, ignition, burn and it just goes through the sequence like I have the thermostat set to 30 degrees.....

What could be telling it to go 'on'??!

Thanks

 

[picasso]

What type of zone valves do you have ?

 

[solidpro]

What type of zone valves do you have ?

I don't have any. It's just one zone - the whole house.

And the boiler doesn't have any freeze protection because it's housed inside the house itself (in a downstairs toilet).

It does seem to have changed since disabling that one radiator. It now does come off and on but it's mostly on. It's ignoring the controller in the hallway upstairs and just keeping the house at about 24 degrees (too hot!) and then going off again.

 

[picasso]

sooo how do you separate the hot water cylinder from the rads ?

 

[solidpro]

sooo how do you separate the hot water cylinder from the rads ?

I don't know that I do. How can I tell? It's an Ultimate 80FF. I'm not a HE...

The hot water controller is set to off, the themostat controller is set to off, but it's still keeping the house at 25 degrees!

 

[picasso]

Have a look near the hot water cylinder for valves like this...

 

[solidpro]

There look like 2 - one going into the cylinder and one not....

 

[picasso]

One of them is most likely the problem, as you seem a bit unsure maybe best to get someone in.

 

[solidpro]

One of them is most likely the problem, as you seem a bit unsure maybe best to get someone in.

That's my next step. Is a whack with a hammer likely to help?

 

[Nige F]

NO

 

[solidpro]

NO

I've read they can get stuck of sieze up....?

 

[sxturbo]

Disconnect the valve for the heating (remove the power wire) and see if the boiler switches off.

If it does that's the problem, get a new valve head and install, though check the valve in the body isn't seized

 

[solidpro]

Disconnect the valve for the heating (remove the power wire) and see if the boiler switches off.

Dumb question but i'll check - Is the heating valve the one adjacent to but *not* connected to the inlet to the cylinder?

Just want to be sure that it's that 'other one' in the pic or its likely to be elsewhere in the house....

 

[Harry Bloomfield]

The heating one is the one nearest the camera, on the left in your photo, which is probably the one which has stuck.

Isolate the all the power, then see if you can remove the actuator (that is the silver coloured upper part) entirely from the water valve. Usually they are fixed by a couple of screws. The actuator operates the valve by rotating a D shaped spigot sticking out of the valve - see if that spigot is reasonably free to move. You should almost be able to turn it with just your fingers, but may need a pair of pliers. Try refitting the actuator, make sure the cable comes out of it in the same orientation as it was removed.

You may now find your heating works normally. Report back.

Your actuator will likely be what is called a spring return actuator. When powered, when heating is demanded, a motor drives the valve to the open position against a large spring. When heat is no longer needed, the motor power is removed and the spring causes the valve to close. The actuator has micro-switches inside it, which trigger the boiler to run, when either the CH or HW valve is in the open position. You CH valve was stuck in the open position, resulting in constant heating run.

In normal operation, you can hear the valve run for a few seconds with changes in demand when the thermostat clicks.

 

[solidpro]

You may now find your heating works normally. Report back.

Ok thanks - progress. I took the actuator off and the valve moves easily with my fingers.

I re-fitted the actuator and then turned the heating on - no noise.
I turned the hot water on and the other valve/actuator makes a definite click/noise both turning on and turning off.

So do I conclude the actuator is dead? It definitely has power.