Help diagnosing a short cycling Ideal Icos HE24 boiler

[Martial82]

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.



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!

 

[AWheating]

Can you post a clear picture of you cylinders cold supply and discharge pipework, from what I can see they are possibility dangerous

 

[Frog67]

If its been happening since the renovation it may be a wiring issue with the room stats
TRV's fitted and shutting down rads before room stats reach temp?
Otherwise it could be a faulty boiler thermostat and/or air in the system.
These are just basic possibilities and only for your consideration

 

[Martial82]

AWheating - are these pictures any better?

Frog67 - I wondered about the stats but then the heating does seem to work okay for a short while when started from cold (i.e. in the morning)?
TRVs are fitted to the rads on the first and second floor, however the short cycling still occurs when the upstairs zones are turned off and only the ground-floor underfloor heating is on.
It'd be great if it was just a faulty boiler thermostat, but would the boiler then give an overheat fault code?

Some other details to add:
The radiators were all bled a few weeks back (only one on the top floor had some air in it).
When the plumber was here he bled the pump in the airing cupboard and it had no air in it.
The plumber also checked the gas pressure coming in to the property (both outside and at the boiler) and he said it was well within the recommended range. His notes read "18 at meter, 16.2 at boiler."

 

[AWheating]

no tundish on the discharge pipework, incorrect sized and fitted discharge pipework (d2). the other thing i though was weong seems ok from last pictures.

 

[Martial82]

AWheating - thanks for the feedback again. Are the problems with the discharge pipework bad enough to warrant rectifying?

I'm still no closer to finding out why the boiler is short cycling. Had a Google and came across a few things to try but nothing has helped thus far:
Took off silver screw cap on the pump in the airing cupboard and gave the screw inside a few rotations. All seemed free enough so didn't detect a problem there.
Removed the condensate trap underneath the boiler to check for debris. There was a bit of metallic gunk but not much and no sign of a blockage.

Does anybody have any more suggestions for things to try?

 

[Riley]

You need an engineer out, you are getting into realms of fiddling with the boiler which we will not encourage. Re the discharge pipework yes definitely!!!!get a G3 qualified engineer out to remedy the pipework and if they are Gas Safe registered they can look at the cycling issue too

 

[Martial82]

Can anybody recommend a G3 qualified engineer in the Shropshire (SY6) area?

My local plumber is gas safe registered, but he's been out a couple of times and doesn't know what might be causing the short cycling. He has suggested changing the boiler, but can't guarantee that doing so would solve anything.

 

[Martial82]

Boiler still short cycling frequently so I phoned British Gas to get another opinion. Had a friendly engineer come out at the start of the week who reckons the boiler is faulty and said he wouldn't try fixing it as our particular Ideal is notorious for problems and is over 10 years old.

I suggested that he also look at the discharge pipework, but he said it was fine because it had worked all this time! While in the airing cupboard, he instead claimed that the expansion tank might not be big enough and that he'd recommend a different one. The boiler he suggested is the Worcester Bosch 24Ri and his quote has now arrived. In a nutshell the quote includes:

Replace Boiler with Worcester Bosch Greenstar 24Ri
Carry Out Part P Electrical Connections
Connect Internal Condense Waste Pipe
Fit 28mm Magnetic System Filter
Flue Pipe Extension
25 Litre Expansion Vessel
Total Cost: £3,897

I still find it bizarre that the boiler works fine from cold in the morning. Appreciating that my plumbing knowledge is non-existent, I'm wondering if the heating being zoned is causing the short cycling. When the house is already warm and only one or two zones are calling for heat, could hot water be returning to the boiler too quickly? Or maybe there's just air in the system somewhere?

Anyhow, the British Gas quote seems massive and I'm also not entirely convinced it will solve the problem. I'm going to get a couple of local gas-registered plumbers out to take a look. I'm finding that tradespeople don't seem to want to spend a lot of time searching for a fault unless we ask for something specific, so it would be really helpful to be able to point them in the right direction. Can anybody with the know-how suggest what they should be looking for in order to diagnose the problem?

 

[ShaunCorbs]

If you want we can give you a visit, if you would like

Your more than welcome to give us a call on

07802287588 or after 18:30 01978759673

 

[Pro heat]

New boiler is the preferred option, those boiler meant to last 10 years anyway.

 

[Chuck]

Assuming the boiler is working correctly, short cycling occurs because the thermostat(s) are calling for heat but the radiators, etc. are dissipating heat at a rate that is too small for the amount the boiler is producing. This is common in older systems that have been zoned and had TRVs fitted. The most straightforward remedy for an end-user is to reduce the room-thermostat setpoint temperature and increase the TRVs setpoint temperatures. The zone control valves should also be synchronised, which helps considerably.

The Worcester Bosch boiler has short-cycling detection built in. If it receives too many on/off calls for heat within a short period (from memory 2 cycles within 5 minutes) it shuts down for 5 minutes (can be adjusted by the installer). This gives the house a chance to cool down a bit so next time the boiler fires up the house can absorb a larger dose of heat. This is far from a perfect solution, but it helps.

C.