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kasser

Gas Engineer
Messages
235
Hi guys,
I've got a Glow-worm Ultimate 30c making really loud banging, clanging noises when operating DHW and just after closing it. Apparently it happens also on heating but not as often and while there, I didn't test it long enough on heating to find out.

The flow temperature on the display goes up to 99 deg, burner goes off and DHW turns cold then the boiler fires up again and repeats the cycle. Sometimes it gives up and shows the reset icon.

It looks like there's a blockage causing the boiler to overheat.

It's a 3 year old boiler and water in the central heating system smells of inhibitor and is very clean. Not a black speck in view. So I'd like to rule out any blockage whatsoever due to sludge.

I drained the hex and filled again 3 times in case there was air in the system. This particular boiler has a purge mode which you can select but it also goes through this purge mode automatically when filling up from less than 0.5 bar, so I didn't use the purge mode.

Pump is rotating, plate to plate clean, diverter valve must work as house warms up nicely and there's hot water at the tap, though it gets cold when boiler stops firing. Removed condensate trap and there was deposit inside, so opened main hex and found quite a bit of brown dust. Cleaned that thoroughly.

Checked thermistor resistances. Tried to gas rate on DHW and high mode but got about half the heat input. That makes sense to me as the boiler is not firing consistently for the 2 min due to overheating.

It sounds like there's a physical metallic object inside causing this really loud noise.

How to identify where and what the blockage is?
 
Contact Shaun about getting your GSR badge sure you can appreciate not to be dscussed on open forum
 
Good man. It just holds the graphite together I believe. Can't really comment much until Shaun sorts out your number. Is the boiler not under warranty?
 
Good man. It just holds the graphite together I believe. Can't really comment much until Shaun sorts out your number. Is the boiler not under warranty?

lou seems to be busy so help away he checks out my end so will sort and move when she gets back
 
Have you checked ignition and rectification electrodes. I had a similar situation with a glow worm flexicom.
It also had very explosive ignition. Just a thought.
 
Did you get an answer to this as I’ve just encountered a similar situation, the boiler will make banging noises and cut out on hot water not so much heating as it modulates, this system was sludged and one radiator blocked, this has now been flushed but still same, I found that the flow/return temperatures are no where near matched before modulation and thermistors check ok, this boiler also has fault memory showing 20,22,24,83 there is pressure in system and never needed topped up so all symptoms now point to pump but as mentioned previously pump is rotating and operating. Could pump be lazy or malfunctioning thanks
 
When I left the job it was still making noises. But the next day it had stopped by itself. I concluded it was air though I don't understand why it wasn't removed when I worked on it but disappeared by itself later.
 
Yes gsr, new here and gave number on registration, kasser there’s 2 purge modes one does system the other boiler only and I’ve returned 2 times,
firstly system was powerflushed and magnaclean filter fitted, worked ok for a week then same symptoms,
Second visit magnaclean was clear, thought maybe plate exc so fernox cleaner run through boiler on hot water only with no symptoms, lasted about a month,
Now looking at fault codes f.20 is overheating, 24 is relating to pump malfunction and 22/83 is no water in system/poor circulation, the system has pressure so I think it's all down to the pump not circulating,
 
Yes screwdriver test done on pump, it’s free when not in use and spinning on demand also on p.01 the heating fires at full rate but will not fully heat system before modulation which suggests the heat is staying within boiler again pointing to poor circulation
 
Might be the pump in your case but it's unlikely to have been in my case - it wouldn't fix itself.
Yes, there are two purge modes and I ran them multiple times, firstly on their own and then after draining and filling the boiler. The water in the system was extremely clean, not speck of black anywhere, all components absolutely clean.
 
If pump isn't weak and main hex is definitely not blocked. Take a look at the bypass valve located behind diverter. I had one disintegrate causing a banging noise as if boiler was blocked. £9 replaced and away it went.
 
How do you determine if a pump is weak or not on the new ERP ones? I don't think there is that slot to insert the screwdriver?
 
Sorry miss read. If the boilers only 3 year old then it should be under warranty.... As for the pump. You should be able to pull the modulation wire when it's running. This will make the pump go at full speed. As for testing if it's weak, I'm not aware of a way to test it.
 
This boiler is about 7 years old, property is about 15-20 years old, flow and return are 22mm and two pipe system, combi boiler replaced system boiler in kitchen, cylinder removed from bedroom, old pump/valves removed and pipes connected, drop fed system in 10mm hep.
 
10mm systems can sometimes struggle to get rid of heat. Have you got all radiators on? You’re best off maintaining flow through system by have rad valves open to at least 3, then relying on the room stat to bring the boiler on and off.
Also, Set the flow temp on the boiler to 60 degrees. Make sure all isolation valves under the boiler and on magnetic filter are fully open. All things you can do yourself without getting too invasive.
 

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