Kingfisher MF Boiling Up

[Steve1967]

Hi All,

First post on a forum so please bear with me.

We have a 11 year old Kinfisher MF mains gas floor mounted boiler in the garage attached to the house and over the last couple of years the boiling (kettling?) has gone from intermittent to near on every morning and evening, our system is as follows:

Kingfisher MF
Gravity System
Pumped CH
Cylinder in A/C with no tank stat
Drayton Stat on pipe in garage (is this for CH or HW?)
Frost stat in garage
basic 7 day programmer for CH & HW
HW comes on when CH is on. HW can come on independantly.
Radiators with TRV other than bathroom rad
Thermostat in hall

The symptoms are as follows:

After running for 20 minutes the cylinder, boiler and pipes (presumably) start to really bang, if the boiler is left on the loft fills with steam which I guess is from the water expanding in the cylinder and being ejected into the loft expansion tank. It can be really violently noisy, so noisy that when stood next to the boiler you can hardly hear someone speak and it sounds like a club hammer being smacked against a scaffold tube as hard as you could possibly hit it!

The thermostat knob on the boiler seems to work as it shuts off and restarts the boiler when turned up/down. Although we don't really know which 'dot' to set it on as there is no temp shown on the boiler faceplate or in the instruction manual.

I've had a word with Potterton tech and they suggested changing the overheat themostat and thermistor which we did but this has not cured the problem (should i have used new thermal past when fitting the thermistor?)

They said if this does not do the trick then its the main pcb that needs changing but I don't want to if this will not cure the symptoms.

We're guessing the problem must be with the HW only as the CH has been off all summer.

We also have an issue with the hot tap in the downstairs loo that sometimes runs for a minute or so before the flow goes to a trickle then stops. All other hot taps in the house are ok, would this indicate an airlock of some description?

We've been in the house 7 years and never had any maintenance on the boiler or HW/CH system.

Apologies for 'War and Peace' above but have tried to think of all the info needed for a bit of advice.

Thanks in advance

Steve

 

[simond]

Consider getting a new boiler and upgrading the system to a fully pumped type. Or keep the boiler and update the controls.

Which brings me to the likely causes.

Poor water circulation round HW cylinder coil after it has been on 20mins.... do you have a Cytrol thermo valve fitted on the HW cylinder primaries? If so, the lockshields on the towel rail must be open at all times.

If the Overheat Stat isn't tripping in the boiler when the water is boiling there may be something wrong here. Disconnect a wire from the overheat stat, does this stop the boiler?

 

[Agile]

Its essential on that model to fully pack the sensor with thermal paste.

the thermostat on the boiler is a problem because the scale range is too high.

Usually it works at about "6" oclock on just a little higher.

Tony

 

[Dan Robinson]

6 O'clock is effectively off... but for gravity hot water in the summer should be plenty enough.

Was looking at one yesterday which seems to want to eat circuit boards.

Still better than the Suprima though

 

[Steve1967]

Consider getting a new boiler and upgrading the system to a fully pumped type. Or keep the boiler and update the controls.

Which brings me to the likely causes.

Poor water circulation round HW cylinder coil after it has been on 20mins.... do you have a Cytrol thermo valve fitted on the HW cylinder primaries? If so, the lockshields on the towel rail must be open at all times.

If the Overheat Stat isn't tripping in the boiler when the water is boiling there may be something wrong here. Disconnect a wire from the overheat stat, does this stop the boiler?

Thanks Simond, we don't have anything other than immersion in the cylinder cupboard and will try removing a wire from the overheat stat and reply here.

 

[Steve1967]

Its essential on that model to fully pack the sensor with thermal paste.

the thermostat on the boiler is a problem because the scale range is too high.

Usually it works at about "6" oclock on just a little higher.

Tony

Thanks Tony,

Will nip into a merchant, get some paste and reply here

 

[Steve1967]

Consider getting a new boiler and upgrading the system to a fully pumped type. Or keep the boiler and update the controls.

Which brings me to the likely causes.

Poor water circulation round HW cylinder coil after it has been on 20mins.... do you have a Cytrol thermo valve fitted on the HW cylinder primaries? If so, the lockshields on the towel rail must be open at all times.

If the Overheat Stat isn't tripping in the boiler when the water is boiling there may be something wrong here. Disconnect a wire from the overheat stat, does this stop the boiler?

Thanks Simond, we don't have anything other than immersion in the cylinder cupboard and will try removing a wire from the overheat stat and reply here.

Have run the boiler and pulled a wire from the overheat thermostat which kills the boiler so this seems to be ok. Have turned the boiler temp knob to 6 O'Clock as suggested and seems ok tonight but as it's intermittent don't want to count my chickens. Thanks for your help, will repost here in few days to confirm if still working fine.

 

[Steve1967]

Hi All,

Just a quick follow up to September 2012 posts. Boiler and pipes still banging and blowing hot water out of overflow through fascia fairly regularly. When the CH was on from October it seemed to settle down but was doing it daily in the summer with just HW on.

I know when it's going to happen as I can 'smell' the rads getting really hot then the upstairs bathroom rad starts making a sound like water dripping inside the radiator.

When it happens the radiators get red hot and the water seems almost boiling. After I turn the boiler off by hitting the CH Advance Button on the programmer the banging stops and bleed the bathroom rad and a bit of air comes out followed by red hot water which is fairly grey in colour. If I keep bleeding it the colour clears.

Sometimes the rads throughout the house and HW are only luke warm and other times red hot and the banging starts, although we have not touched the settings at all.

We had a plumber service the boiler in October and he said it was ok and injected some noise inhibitor into a rad but this hasnt done any good.

I've noticed the boiler temperature controller knob does not 'click' until it's turned off. I.E there's not a place on the dial where it reaches a temperature and you can hear an audible 'click' like on a thermostat. But don't know whether ths is normal.

Also the 'clockwork' thermostat in the hall doesn't seem to turn the boiler on or off regardless of whether it's at 50 or 80 degrees. There is power to it as I dropped the front off and tested it with a multimeter.

Would a system powerflush be something to consider or, as previously mentioned, changing the gravity system to pumped? Would a pumped HW system stop the banging and what sort of cost/work is involved? The boiler and CH pump is in the attached garage and cylinder is in a/c on landing.

Thanks in advance,

Steve

 

[Agile]

I used to convert to pumped using a second pump for about £240.

But pumps are getting quite expensive now and to do it with motor valves means a lot of new pipework in many cases and over £300 would be the norm I expect.

Tony

 

[Steve1967]

I used to convert to pumped using a second pump for about £240.

But pumps are getting quite expensive now and to do it with motor valves means a lot of new pipework in many cases and over £300 would be the norm I expect.

Tony

Thanks Tony,

Our boiler CH and HW pipes are in the garage so would a pump go on the gravity feed in the garage with a motorised valve rather than any work internally other than, probably, fitting new wireless controls with a cylinder stat?

Would a pumped HW system stop the banging/boiling/overflowing? Or would a powerflush also be required. Presumably a pumped system would just 'push' any sludge (if there is any) around the system?

The rads aren't cold at the bottom, just sometimes red hot (when the banging starts), sometimes lukewarm, but usually ok. It's frustrating that there seems to be no pattern to the overheating.

Just concerned that soon the CH will go off and the banging/boiling will happen every day.

Thanks for your help,

Steve

 

[DP]

Steve, the problem you are having with your boiler can be sorted easily. I am surprised the issue has lasted so long. Get someone who understands how boilers work (this IS A SIMPLE boiler so there should NOT be a problem if the repairer is familiar with heating systems).

If water is issueing from the vent in the loft at all times (at boiler start and thereafter), then it will be a plumbing issue. If water issues when banging takes place, then boiler is not switching off in time when boiler thermostat setting is achieved. Could be a blockage, lack of circulation or similar that is allowing the water in the boiler to turn to steam.

 

[Agile]

You seem to have a serious temp control problem on your boiler. That needs sorting out.

The gravity flow pipe is usually the open vent pipe as well so a pump normally has to go in the return.

To do the job properly you need a stat on the cylinder. If a wire cannot be connected that would need to be wireless!

Tony

 

[Steve1967]

Steve, the problem you are having with your boiler can be sorted easily. I am surprised the issue has lasted so long. Get someone who understands how boilers work (this IS A SIMPLE boiler so there should NOT be a problem if the repairer is familiar with heating systems).

If water is issueing from the vent in the loft at all times (at boiler start and thereafter), then it will be a plumbing issue. If water issues when banging takes place, then boiler is not switching off in time when boiler thermostat setting is achieved. Could be a blockage, lack of circulation or similar that is allowing the water in the boiler to turn to steam.

Thanks DP, the water boils and overflows (along with banging) through the fascia overflow after about 15 mins after boiler fires. The plumber who lives at the end of our garden (not literally!) serviced the boiler but did not really give any symptom reasons or advice other than 'it could be sludge'. 'it could be restricted coil in cylinder' and 'I'd recommend a pumped HW system' .

But we don't want to 'throw money' at what clearly is a temperature control problem without knowing a cure. We'd happlily go with a £500.00 pumped CH system if that will cure the banging and boiling but if a £250.00 powerflush will sort it then that's the option we'd go with.

Thanks again,

Steve

 

[Steve1967]

You seem to have a serious temp control problem on your boiler. That needs sorting out.

The gravity flow pipe is usually the open vent pipe as well so a pump normally has to go in the return.

To do the job properly you need a stat on the cylinder. If a wire cannot be connected that would need to be wireless!

Tony

Thanks Tony,

So would a pumped system have a good chance of stopping the bangin/boiling/overflowing or just a good powerflush?

Also any ideas why would the problem have occured in the first place? It was fine for 6 years just the last 8 months that it's been playing up badly.

Thanks again,

Steve

 

[Agile]

My view is that there is some kind of intermittent fault in your boiler!

They are so stable that they can be operated with no flow at all and just sit there keeping themselves hot by firing up for a few minutes every 15 min or so.

Converting to a fully pumped system would be much more efficient, give faster HW heatup and save gas costs. But not solve your problem

You did add heat transfer paste to the temp sensor point didn't you?

Tony