Ideal Classic FF240 - Firing up but not staying on longer than 60 seconds

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It seems to be every year around this time I have an issue with my old Ideal Classic boiler. Ok here goes:

I have the following system:

Ideal Classic FF240 Boiler (probably 20+ years old)
Nest 3rd Generation Thermostat
Hot Water Tank
Tank in attic

The boiler seems to be firing up but only stays on for 60 - 90 seconds at a time, this is for both CH and HW. It doesnt matter what task its being asked to do, it'll only stay on for a minute or so and then shut down. It then has a minutes rest and then fires up again

This means it really struggles to heat the hot water, although it does eventually warm up. Likewise with the rads, they do eventually warm but this is clearly not what should be happening with the 30x fire ups per hour!

Any thoughts on what it could be before I call the engineer out. Annoyingly I only had it serviced last week and all was ok on the inspection and service. Could that have triggered something? It was working ok after the service for a few days as well.

I've only noticed this problem since yesterday when the missus complained it was a little chilly

Any thoughts or advice would be greatly received
 
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Last year around the same kind of time I had a new PCB fitted (boiler woulsnt fire up at all). The year before that I had a new fan (became noisy and eventually stopped completely = boiler wouldnt fire up) so dont think its either of those at fault given their age and the fact the boiler is capable of firing
 
First thoughts are faulty/failing zone valve or weak/failing circulator (aka pump).
 
Thanks Chris. Im sure I heard a bit a more whirring coming from under the stairs a couple of days ago where those are both located. Is there anyting I can do to remedy this myself? I am pretty crap to the point where I had to just google "zone valve". I do recognise that though and I do have one lol!

Also to note I checked the rads a couple of weeks ago for air. There was no air but whilst I had the rad key out I took about 1/3 a pint of water from one of the rads to test the inhibitor levels. Would the system self fill after this small water drain, presumably yes and theres a stopcock in the headtank in the loft?
 
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Yes the system would replenish itself. Only sealed systems and combi’s tend to need manual intervention with a filling loop. Regards testing, does the circulator have a bleed screw?
 
Start on your pump first!

See if it is turning or jammed solid and very hot.
 
So I just switched the zone valve to manual using that small metal switch. No change
 
So this is my "set up" under my stairs. Presuming the blue thing is the pump!
 

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- Pump speed setting is on 3.
- House is a mid-terrace 2 bedroom house with 5 x cast iron victorian free standing bar rads and a heated towel railed in the bathroom
- All victorian rads were removed, flushed (so much sludge!!), sandblastered and powder coated 4 years ago and refitted so I expected the system is somehwta clean, although the pipework hasnt been flushed but presume it all end up settling in the rads anyway? When i bled the 1/3 pint out a few weeks ago the water was clear, albeit thats from the top of the rad
 
Start with the circulator - remove the silver screw in the center and place a rag under it as there should be a dribble of water. Put heating or hot water on and see if the middle starts to rotate.
 
Right I'll give this a bash tomorrow and report back. Presumably there'll only be a bit of water and it wont be free flowing out??
 
Are the isolating valves either side of the pump fully open i.e. not restricting circulating flow ( same thought as CBW)
 
Get a Gas safe registered experienced engineer in to properly clean the pilot assembly inside the boiler, you cant do this yourself, but that will be your problem
 
  • Thanks
Reactions: CBW
Also assumed you have bled air valve on upright next to 3 way valve?

No I havent. I've always wondered what that upright was in all honesty! Can I just use a rad key to open it or do I need a different tool?. Is it some sort of catch-all pipe for air before it gets to the pump

Are the isolating valves either side of the pump fully open i.e. not restricting circulating flow ( same thought as CBW)

Ive never touched these and to my mind no one else has either so they should be open as they normally are!

Get a Gas safe registered experienced engineer in to properly clean the pilot assembly inside the boiler, you cant do this yourself, but that will be your problem

Ok thanks I'll give the upright bleed and the pump a check and if not it'll be engineer time
 

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