Potterton Flamingo CF35-50 Boiler Kettling

[Bonus77]

Following on from my previous post, I have a few more questions before proceeding.

Just to remind, its a fully pumped system, operating 4 rads upstairs and 3 down. FE expansion tank in the loft, a little bit of scum but not too bad.

Basically, we currently dont have heating because the boiler fires up, seems to kettle, boil, and then shut itself down to the regular pilot light after about 5 minutes. Then, when the boiler cools itself down, it fires up again.

So, I did a mains flush this evening suspecting sludge in the system, the water drained from the FE cold feed fine, at the same rate which told me there wasnt any blockages, so I refilled the system, just to see if it made a difference... after bleeding everything I turned on the boiler and the same thing happened.

Now, my question, is it more likely limescale in the boiler? Or could it be the pump not working effeciently? The pump seems to be working fine, spinning as normal, but it is quite hot.

Any suggestions? Shall I now try the limescale remover? I dont think theres any sludge in the rads.

 

[ChrisR]

Take the head off the pump and inspect. They block ........

 

[Bonus77]

Thanks Chris, the pump didnt look too bad to be honest.. so I went out and bought Fernox F3 and a sentinel descaler for the boiler.

Can someone tell me, which one should I use first? Im thinking the descaler, and then if needed the desludger.

Also, as for use, do I empty the FE tank or just take most out to ensure it flows to the boiler??

 

[bellairaphon]

the pump can look clean and still not work. u may have a filter on the primary flow could be clogged up

 

[JohnD]

if it is actually cutting out, it sounds like you have a bad lack of circulation leading to overheating. I would have though more than just sediment in the exchanger to get that bad. It should be able to pump enough water through enough to carry a lot of heat away.

I had a Flamingo and earlier this year I had a good go at cleaning it with DS40 and DS3 (IIRC) to remove the rust and limescale. It soon started banging again though, due to the deposits in the iron heat exchanger.

When it was removed I had a a look inside, and the way it is built, deposits are likely to fall to the bottom and never come out. It is capable of holding quite a lot of sediment without being choked. You can spend some time and money trying to clear it but see if your pump and pipes have proper flow first. Pump valves can break and not open properly despite the position of their knobs.

Feel along the pipes and you will be able to tell how far the hot water is flowing.

My Flamingo went due to rust and fumes leaks in the end.

I am just a householder

 

[Bonus77]

The hot water flows along the pipes okay, in fact, one of the rads are hot, and another along the line is warm.

The problem is the boiler doesnt fire up long enough for heat to run to the rads downstairs.

I cant be sure what the problem is, but I guess it cant do any harm to try out the descaler.

Now.. can someone tell me, which product should I try first? Sentinel X200 boiler descaler? Or the fernox F3?

Can the Fernox also descale the boiler or are they completely different products?

 

[Bonus77]

Just to update, I started with the descaler and so far, no change. I think the boiler fires for longer before cutting out, but what do you think is the next best thing?

Replace the pump just in case or just call someone out?

 

[JohnD]

I am just a householder so there may be better ways

but I would try turning down the thermostat on the boiler, so it doesn't get very hot, and running the pump at max speed to wash the chemical round. You are only trying to descale the boiler, I think, so the rads need not be on, just use the HW cylinder circuit (this will concentrate the chemical in the boiler) this will be too late if you have already mixed it up with the radiator water. You should be able to tell by feeling the pipes if hot water is circulating round between the cylinder and the boiler.

I take it you are using a limescale-remover. there is also a rust-removing chemical. They are both acidic. On my old Flamingo I used both of them last summer, but in the end I had to get a new boiler. When I was doing it I drew samples of water out of the drain cock by the cylinder and observed that bits of gritty scale were being loosened and washed round in the water, which shows it works. I tipped the jug back into the F&E through a paper filter to avoid losing or diluting the acid.

As your Flamingo is probably between 20 and 30 years old I don't know if it will be cost-effective to pay someone. I don't know how to verify that your pump is working properly.