Kingfisher MF Boiling Up

[Agile]

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

Tony

Hi Tony,

No, i didn't but asked the plumber to do it when he serviced the boiler but had a look earlier and it's the same as I left it.

It's all a little academic at the moment as one of the wires connecting to the buld has come off so I need to order a replacement thermistor anyway but will need to know when I fit the new one.

thanks again,

Steve

For the avoidance of doubt the thermistor element is the toffee colour lump at the end of the uninsulated wires. This should be straight with the wires kept apart about 2-3 mm just like the excellent drawings in the MI.

The socket should be filled with heat transfer paste and the thermistor inserted into the filled socket in one movement.

I am not very impressed by your "plumber" if you asked him to add the paste and he did not or even mention it to you. He either did not touch it or did not even realise that the wires should be straight and not touching. Very much a plumber and not a boiler engineer I am afraid.

This is very much a problem in our industry. Gas boilers are all controlled by electronics and use electromechanical parts yet most people working on them have little understanding of how they work.

Tony

 

[doitall]

most people working on them have little understanding of how they work.

Tony

Beginning to think your right Tony, best stick to what you know methinks.

If the boiler is intermitantly boiling, then something is breaking down.

gravity circuit so can't be the pump.

Boiler thermostat.

Sticky gas valve perhaps.

 

[Agile]

Most unlikely to be a sticking gas valve, we do see those but not very often at all which is just as well.

Might be the PCB but first you need the thermistor correctly fitted as that controls the boiler turning off when it reaches the set flow temperature.

Tony

 

[doitall]

The two key words are boiling and intermittent, not got too many options

 

[Agile]

Do you have any suggestions John?

Or do you think its a sticking gas valve?

I see them so infrequently that they give me little experience of the typical fault but the few mostly are just slow to release.

Much more common is to find temperature control faults!

Tony

 

[doitall]

Seen lots of sticky valve that don't shut off or open.

Also seen lots of boiler stats not turn the boiler off.

What would worry me is how a gravity primary system can boil.

Maybe a combination of things, but one thing is certain, for it to boil the gas would be going full blast for some time.

 

[Agile]

This one does not modulate so would be either on or off if the control system failed!

I will be interested to see if there is any change when the sensor is replaced and correctly fitted with the thermal paste.

Its often not realised quite how long the response time of thermistors can be. In air its usually about 40 seconds. Turning a boiler off promptly is very important.

Tony

 

[Steve1967]

This one does not modulate so would be either on or off if the control system failed!

I will be interested to see if there is any change when the sensor is replaced and correctly fitted with the thermal paste.

Its often not realised quite how long the response time of thermistors can be. In air its usually about 40 seconds. Turning a boiler off promptly is very important.

Tony

Hi Tony,

Installed the thermistor this morning, replaced the cover, fired up the boiler and within 20 minutes it was boiling again and water coming out of the (vent?) pipe into the expansion tank in the loft, creating steam and overflowing through the fascia overflow pipe.

As the weather has been getting warmer its doing it nearly every day each time the heating & hot water comes on after about 20 mins.

As mentioned previously it did it every day in the summer when just on hot water. Do you think it could be the coil in cylinder blocked up? The pipes are 28mm and the boiler is floor mounted in the garage with the cylinder on the first floor landing. I s'pose the pipe run to the cylinder would be around 20 - 25ft. The plumber that serviced the boiler in October said that was ok but there was no label on the cylinder to state whether it was suitable for gravity systems and he suggested that if it was only suitable for pumped systems that any minor scaling could cause a blockage when the hot water system started to heat up and a pumped system would 'force' the water round the coil.

This sounded feasible but if it is scaled then just a flush would be cheaper and I'd likely be dead before we realised any payback from a fully pumped HW system

Thanks again,

Steve

 

[doitall]

Steve your posts make no sense and don't add up, someone is fishing and playing at the same time.

The boiler has a temperature sensor which shuts the burner off at the set temperature, Does it, or does the burner keep going to boiling point. ??

The boiler has a fail safe overheat stat on the pipe in the boiler, why doesn't it work or has it been removed over-ridden. ??

It's possible there's air or sludge in the primary flow/return but it wouldn't be intermittent.

Has any mods be made to the system or boiler prior to the problem.

I'm out refereeing in a while but post some info and I'll look later.

What is the exact model as well

 

[gaswizzard]

The boiler has a fail safe overheat stat on the pipe in the boiler, why doesn't it work or has it been removed over-ridden. ??

Not when set up for gravity HW/pumped heating , the O/H stat is removed from the pocket and fixed via a plate (manu instruction) , if not then boiler would nuisance trip on gravity HW , this is the reason why I suggested that Tony was giving bad advice on a DIY forum regards siting a pump on the gravity flow/return from cylinder , obviously fully pumped would have the O/H stat remain in its pocket.

Had the OH stat not been removed from pocket the OP would not have a boiling situation but more so a nuisance trip/reset.

 

[Steve1967]

Steve your posts make no sense and don't add up, someone is fishing and playing at the same time.

The boiler has a temperature sensor which shuts the burner off at the set temperature, Does it, or does the burner keep going to boiling point. ??

The boiler has a fail safe overheat stat on the pipe in the boiler, why doesn't it work or has it been removed over-ridden. ??

It's possible there's air or sludge in the primary flow/return but it wouldn't be intermittent.

Has any mods be made to the system or boiler prior to the problem.

I'm out refereeing in a while but post some info and I'll look later.

What is the exact model as well

LO doitall, I don't know what fishing and playing means but this post has been 'revived' from September 2012 as the symptoms sre still there. Have a gander at first post for the boiler spec etc.

No mods at all to the system, basically we've been here for nearly 7 years and had nothing done at all to the heating. I changed the overheat stat and thermistor but this made no difference, pulling a wire from the overheat stat cuts of the boiler so guess that's ok.

The temp control knob on the boiler is pointing to 6.00 O'Clock but it still keeps boiling up. There is no 'click' from the temp control knob when it is turned other than when it goes past the off position. Should there be an audible click when it's turned up past a certain temp point to fire the boiler? Or likewise when it's turned down?

We really need an engineer whose comfortable with testing the electrics and checking out the boiler but don't know anyone in the area.

Will likely just bite the bullet and get a fixed price repair quote from British Gas. Can't stand the missus bending my ear about it any more

Thanks,

Steve

 

[gaswizzard]

I changed the overheat stat and thermistor but this made no difference, pulling a wire from the overheat stat cuts of the boiler so guess that's ok.

Why would you change O/H stat? , stat would not be functional when utilising gravity HW , the installer WOULD have 'parked' the OH stat onto the bracket supplied , if not the boiler would nuisance trip every time HW was called for.

I'm thinking maybe DIA has a point with regarding 'playing games'.

The temp control knob on the boiler is pointing to 6.00 O'Clock but it still keeps boiling up. There is no 'click' from the temp control knob when it is turned other than when it goes past the off position. Should there be an audible click when it's turned up past a certain temp point to fire the boiler? Or likewise when it's turned down?

No audiable click on these appart from GV solinoid.

So you have been 'puttng up' with this boiling issue since 2012? , get it fixed man FFS.

 

[Steve1967]

I changed the overheat stat and thermistor but this made no difference, pulling a wire from the overheat stat cuts of the boiler so guess that's ok.

Why would you change O/H stat? , stat would not be functional when utilising gravity HW , the installer WOULD have 'parked' the OH stat onto the bracket supplied , if not the boiler would nuisance trip every time HW was called for.

I'm thinking maybe DIA has a point with regarding 'playing games'.

The temp control knob on the boiler is pointing to 6.00 O'Clock but it still keeps boiling up. There is no 'click' from the temp control knob when it is turned other than when it goes past the off position. Should there be an audible click when it's turned up past a certain temp point to fire the boiler? Or likewise when it's turned down?

No audiable click on these appart from GV solinoid.

So you have been 'puttng up' with this boiling issue since 2012? , get it fixed man FFS.

LO GW, I changed the OH stat as Potterton tech told me to try it when I rang them back in September. It is on a bracket but I just presumed this was just a heat sink or something.

I don't understand heating systems and thought a forum would be a good place to get a bit of feedback/advice on possible issue before getting someone in. But that's the hard part, actually getting some-one that could trace the fault and be definate about it. I don't particularly want to pay for an engineer to stand and wait for it to boil up when sods law says it wont do it when he's there.

Or preferably soem-one to review the whole system as the room stat looks about 50 years old and doesnt seem to control the boiler at all, there's no cylinder stat, the programmer's in the garage and when the CH is on the HW comes on to.

The whole house was refurbished ten years ago, new roof, wiring, re-plastered, new windows, bathrooms, kitchen etc . It just seems that the sh*tiest possible heating system was installed, or never replaced/refurbed.

 

[Agile]

Can you give your postcode?

My friend Mike in that area does not like to go far without charging extra for time and travelling but he must be good as he loves Pulsacoils!

Presumably the cylinder is long standing and suitable for gravity hot water and used to heat up in about an hour ?

I have never recommended adding a pump to the return, just saying that I have done it before as a budget solution. Unfortunately there is usually so much pipework changes that its very labour intensive and converting to a sealed system gets over some of the potential problems.

Do you know what flow temp you get from the boiler with temp knob at 6 pm? Can you estimate the flow and return temps at the cylinder heating coil?

This is really a very simple fault for a good RGI to diagnose on site but I cannot give you advice on doing that because it involves opening the boiler cover and we dont encourage DIYers to do that.

 

[Steve1967]

Can you give your postcode?

My friend Mike in that area does not like to go far without charging extra for time and travelling but he must be good as he loves Pulsacoils!

Presumably the cylinder is long standing and suitable for gravity hot water and used to heat up in about an hour ?

I have never recommended adding a pump to the return, just saying that I have done it before as a budget solution. Unfortunately there is usually so much pipework changes that its very labour intensive and converting to a sealed system gets over some of the potential problems.

Do you know what flow temp you get from the boiler with temp knob at 6 pm? Can you estimate the flow and return temps at the cylinder heating coil?

This is really a very simple fault for a good RGI to diagnose on site but I cannot give you advice on doing that because it involves opening the boiler cover and we dont encourage DIYers to do that.

Thanks Tony,

Postcode is RG14 Newbury, about 2 mins from Junct 13 of M4

(Didn't boil up this morning!)

Steve