Merry Christmas, maybe a cool one though.

bfg01 · 23 Dec 2006

Hi,

I'm having central heating problems (Glow Worm Ultimate 50FF) which initially began with no CH (plenty of HW) in cylinder. On closer inspection the overheat cutout button on the bolier electrics had triggered. When reset if fired for 1min then cutout again. This happened repeatedly.

I called out a plumber (under an insurance policy) who changed the pump and then said there was no circulation. He had inspected feeder tank in loft and said it was full of sludge, therefore, he thought this was the cause of the blockage. He told me this wasn't covered under the warranty and anyway he could'nt stay to fix it now. At least I have a nice new pump I didn't need

I've tried draining the system and clearly not all water is exiting from the system so there must be a blockage. Cleansing chemical has now been added in desperation BUT my boiler is now doing NOTHING. No fan, no pump, no wall stat or tank stat triggering ... just silence, though there is power getting to the circuit board! Could the electronic board have been damaged by resetting cutoff switch regularly whilst trying to diagnose problem or is there a sensor somewhere I'm missing which sets the whole sequence of events which lead to the boiler functioning?

As an emergency measure I have wired in an electric immession heated so I can at least have a bath for Christmas

Any suggestions appreciated. Merry Christmas one and all.

Strachan · 23 Dec 2006

If you had hot water, your boiler must have been firing. That problem sounds more like a diverter valve. How are you checking for voltage at the board?

bfg01 · 23 Dec 2006

Hi Strachan,
Yes it was firing before - it just isn't now and I don't know why it suddenly doesn't want to know. Went to bed last night and the pump was still turning despite boiler being turned off hour earlier following my failed attempts to get it to stay alight. My solution was to switch off the control timer (Horstmann H525).

Got up this morning and boiler appears 'dead', the timing switch appears to be funtioning as normal.

I have placed a meter across the main power input terminals of the circuit board and all showing voltage. I have also checked the 2A circuit board fuse which is fine. This is why I was wondering whether there was a sensor (pressure or otherwise) which might prevent the whole system from starting to function. The boiler appears absolutely dead now.

breezer · 23 Dec 2006

what voltage did you get "across the main board"

and how exactly did you check the fuse?

Strachan · 23 Dec 2006

Have you checked voltage to the fan?

bfg01 · 23 Dec 2006

Okay, just decided to give one final switch-on and, lo and behold, power is restored!!! Boiler ignited first time. I set to HW only and hot water was indeed being fed (noisily though - but would expect that as I had partially drained system) to cylinder. About 1 minute and temperature cut-out switch operated again.

I had thought the problem was with a blockage in the CH section but can this be the case when CH is switched off and HW only switched on?

Strachan · 23 Dec 2006

First port of call would be to check that the diverter valve works. If it`s cutting out on both heating and h/w, there could be a blockage between the boiler and the diverter, or anywhere on the return to the boiler. Is it a 3 port valve or 2 two port?

bfg01 · 23 Dec 2006

Not sure 3 or 2 port? I think it is a 2.

I have just altered the room stat and noticed there is no "click". Appears to be no power from valve to room stat. Hence, valve appears not to funtion automatically.

I think I need to stop and give it some thought, getting tired working on it and afraid I might be sending myself down blind alleys. Time for a beer.

I am very grateful for your contributions and I am pleased that at least I know my circuit board is not 'dead'. At least I appear no worse off than I was yesterday. One must learn to be grateful for small mercies.

Maybe you can jump onboard again in a few days when no doubt I will be back seeking guidance, maybe on how to mop up a flood

Have a great Christmas.

bfg01 · 26 Dec 2006

Hope you all had great Christmas Day.

Hot water system worked well over last couple days - no overheat cut-out occuring

. When system control was set to HW and CH no cutting-out plus I had heat in SOME rads (some upstairs and some downstairs).

Just checking stats today and room stat was not working so have replaced this with new one which is now triggering correctly.

Motorised valve appears to be switching as expected - tested by just feeling pipework for heat flow.

However, seems like i'm now back to before with the boiler cutting out (overheat cut-out switch triggering) after about 1 min.

I have drained system this morning until cool water flowing freely via the header tank.

Feeling boiler piper outlet pipe v. hot, return pipe v. cool. Is there anyway to vent air from Glow Worm Ultimate 50FF boiler - I was just wondering (hoping) it could just be trapped air as there is a gurling sound from around the boiler pipework about a metere away from the actual boiler?

I'm getting close to throwing in the towel and calling out a pro - it would just bug me to discover it was simply air after all.

ChrisR · 26 Dec 2006

Apart from bleeeding rads and pump, have you looked for a bleed point by the HW cylinder, on the top pipe from the boiler?

bfg01 · 26 Dec 2006

Hi, Yes I have been opening this to allow air out intermittently, but only in small doses. Should I connect to a pipe and let is bleed continuously for a while?

bfg01 · 27 Dec 2006

Okay, just drained system for a third time. No evidence of sediment, water running clear. Re-filled via lower drain-cock as opposed to just allowing header tank to fill system.

Boiler set to call for HW only. Fired immediately and operated correctly (on for few minutes, off whilst pump circulated heat, on again etc) for 20 minutes. Then overheat cut-out switch triggered. Reset switch. Boiler functioned for approx 1 min then over-heat triggered again.

Set to call for HW and CH. Boiler fired for 1 min then cut out.

Any final suggestions from anyone before I call out a plumber from 'Yellow Pages'?

bfg01 · 30 Dec 2006

Hi all,

I think I have finally solved the problem and so simply I can't believe it. During a final look before resorting to calling out an engineer, I noticed that the 'Control Thermostat Phial' which is inserted into the body of the boiler was loose fitting. I re-seated it (expecting to have to add a thermal conducting paste) and to my amazement the system appears to work now.

The theory to me makes sense. There are two thermostatic devices one in the water jacket of the boiler and one clamped tightly to the outlet pipe from the boiler. Presumably a comparison is made between these two temperatures and if it is seen to be too great a difference then the thermostatic switch triggers and cuts off power making the assumption that heat is not being pumped from the boiler efficiently. In actual fact, because this thermostat phial was not seated correctly and in poor thermal contact with boiler jacket it was registering a 'lower' temperature than it should have been. The large temperature differential caused the boiler to cut-out.

The system has been running for 3 days now without cutting out. Think it's safe to say "it's working!"?

Thanks for those of you who jumped in to offer help and advice, it was much appreciated.

Happy New Year to one and all!

HarrogateGas · 30 Dec 2006

Your boiler des not work on temperature differentual.

One of the thermostats is the control thermostat and shuts the burner off when the boiler is at the set temperature, the other is an overheat thermostat and kill power to the burner if it gets too hot.

I think on some there is a third thermostat on these which controls the pump over run, (it might be integral to the control thermostat)

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Merry Christmas, maybe a cool one though.

breezer

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