Kingfisher boiling over

[Pete1000]

Hi Guys

Having a problem with F&E tank overflowing boiling hot water, 3 times in last 6 months. old Potterton Kingfisher floor boiler, pumped heating, gravity h/w. Have had system chemically cleaned and new overheat stat and thermister fitted. Was running fine (apart from rattling) for a few months, then boiled over and melted overflow from F&E again.

It's a 3 storey house, boiler on ground floor, h/w cylinder on top floor. F&E tank is above level of c/w storage tank. It fills fine. Level in F&E tank doesn't drop when hot taps are drained (to test for leak in H/w coil).

I need to do something to stop leak through ceiling again, any suggestions welcome.

 

[45yearsagasman]

Didn't know the old Kingfishers had a thermister and overheat fitted?.
If you're having boiling over problems then it will be the main thermostat out of calibration or unable to sense the temp accurately enough.
Run those old girls on 2 or 3 at maximum.

 

[plumbplumb]

Presume OP means the Kingfisher MF fan flued floor stander with boiler thermistor (two yellow wires to PCB).

 

[plumbplumb]

You could try testing the thermistor from the PCB

25C 1.2MOhms down to 100KOhms at Temperature (82C)

 

[Agile]

Yoiu could start by turning boiler temp control back from maximum.

Then it should control the temperature OK.

Regardless, it seems the pipework to the vent and feed is either incorrect or blocked.

Chemically cleaning can be useful but in many cases the skill of the person doing it is limited because they either dont used the best chemicals or they dont know how to test the system properly.

Are you quite sure the pump is operating in the right direction? Has it been touched recently?

See which pipe from the boiler gets hottest.

Tony

 

[doitall]

It's gravity primaries Tony

There's still questions unanswered in your other thread.

 

[Agile]

Peter has not said if the problem occurs on HW or CH.

I would guess that its on CH and if so he needs to check which direction the pump is operating.

Unfortunately on that model the normal operating temperature is below the maximum on the knob. Thats useful for an engineer but tends to cause overheating with users why turn everything up to the max.

Tony

 

[doitall]

Peter has not said if the problem occurs on HW or CH.

I would guess that its on CH and if so he needs to check which direction the pump is operating.

Unfortunately on that model the normal operating temperature is below the maximum on the knob. Thats useful for an engineer but tends to cause overheating with users why turn everything up to the max.

Tony

Watch my lips Tony.

it's gravity primaries

If the tank is getting hot enough to melt the pipe the boiler stat has gone, or not connected properly.

 

[Agile]

If a pumped flow is reversed then the system return goes into the flow of the boiler and the boiler return becomes the "flow".

Since a boiler monitors the temperature at its flow connection then a boiler set for 80C can produce up to 100 C under those conditions.

Tony

 

[doitall]

If a pumped flow is reversed then the system return goes into the flow of the boiler and the boiler return becomes the "flow".

Since a boiler monitors the temperature at its flow connection then a boiler set for 80C can produce up to 100 C under those conditions.

Tony

I think I know what you said Tony but you would be wrong.

The flow and return is not changed, if the pump was fitted the wrong way it would simply reverse the direction through the boiler and pipework, the primary circuit would still work as it should.

 

[Boilerman2]

If the boiler is indeed a Kingfisher MF, are these suitable for Gravity primaries, I thought they were fully pumped only!

 

[doitall]

Yes they are ok on gravity.

You need a by-pass if you add mechanical controls to the gravity primaries

 

[Agile]

Surprisingly, as the look very similar to a Suprima, they are allowable on a gravity HW system.

But we need the OP to tell us if the problem is on HW or on CH. Different fault profiles will apply.

Tony

 

[doitall]

Surprisingly, as the look very similar to a Suprima, they are allowable on a gravity HW system.

But we need the OP to tell us if the problem is on HW or on CH. Different fault profiles will apply.

Tony

The Kingfisher and the Suprima are about as far from each other as you can get.

The only reason this thing can boil is a faulty stat or related parts.

Sludge or scale maybe.

System alterations, would be interested to know why it needed a chemical clean etc, and what the problem was.

You can't have heating without hot water so the pump not working is irrelevant.

You have a common flow with a pumped and gravity return separately.

What it needs is answers to the questions I asked on the other thread.