Help diagnosing a short cycling Ideal Icos HE24 boiler

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Hi all,

I'm having trouble with our Ideal Icos HE24 boiler at home as it appears to be short cycling.

Going to try and keep this concise but there's a bit of a back story so here goes:

The boiler was installed as part of a new-build property in 2006 and broke down in 2014. Ideal came out to repair it and fitted a new fan, a new PCB and a new heat exchanger. It then worked fine for many months until we had some building work done last year.

We live in a three-story house and as part of the renovation, we had Wundafloor underfloor heating installed on the ground floor in four zones, the radiators on the first floor were branched off as another independent zone, and the 2nd floor radiators created a sixth and final zone. The radiators on the ground floor were all removed and capped off inside the walls. Heatmiser Neostats are used to control each zone.

Since the changes, the boiler has been short cycling every day. In the morning, when the heating first comes on, the boiler seems to run happily for 30-45 minutes, and the house heats up nice and warm. Then, once things are getting up to temperature, the boiler status icon displays 'c' and the burner light changes from solid to flashing despite one or more zone stats still calling for heat.

The burner light flashes for a minute or two, then the boiler fires back up and the light goes solid. This only lasts for a short while until the boiler turns off again and the light returns to flashing. The process will then repeat on and off until the zones stop calling for heat. I can also occasionally hear gurgling noises and, less frequently, a tapping noise before the boiler turns off.

Normally you would get the installer back out, however the builder who carried out the works went into liquidation and I haven't been able to contact the builder's plumber. I've had a local plumber come out and have a look, but he hasn't yet been able to diagnose the root cause.

DSC_8183.jpg DSC_8185.jpg DSC_8187.jpg DSC_8188.jpg DSC_8191.jpg DSC_8198.jpg

I've attached some pictures of our heating and hot water system. I have no plumbing knowledge myself but here's a summary of what's in the house:
  • Utility Room (ground floor) - Ideal Icos HE24 boiler
  • Under Stairs Cupboard (ground floor) - Wundafloor UFH manifold with motorised valve and Grundfos UPS2 25-40/60 set to 3/3
  • Airing Cupboard (first floor, directly above boiler) - Megaflo CL250 hot water cylinder with expansion vessel, three motorised valves (presumably hot water, first floor, second floor) and a Grundfos UPS 15-60 pump set to 2/3
The boiler short cycling is annoying from a noise perspective (it isn't quiet when it fires up) but now that the weather has gone cold we're finding that the house isn't staying warm enough. The temperature is fine in the morning when the boiler has its 30-45 minute stint, but as the day goes on and the place cools with the boiler short cycling, it is difficult getting the rooms to heat up properly in the evening.

Can anybody help identify what the problem may be or what we should try? I'm willing to change the boiler, but I'm wary about throwing money at the issue until I know the cause.

Thanks in advance!
 
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