Unvented System Pressure Loss

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West Midlands
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Hope someone can help. We have an "Ideal Minimiser SE" Boiler and a Megaflow Unvented system. This has been working fantastic for 8yrs and the boiler serviced twice in this time, (last time engineer said everything was fine and did not need doing!). At the begining of December the boiler tripped on the overtemp stat. (Engineer said that it was the pump and replaced it with a "Grundfoss Selectric"), One week after this, the central heating kicked in with a terrific clatter, I switched off and found the pressure had dropped to zero.
Engineer(s) (3 in total) have all said "it's a leak mate", but we cannot find any sign anywhere, have even had boards up etc. Also there is no water discharge from the PRV's etc. I have had a bag tied on exhaust outside, no water discharged. I have bleed all rads and the pump, cannot find any air in the system... One thing is that the pressure holds if we do not use the heating, i.e no boiler or pump on. Could the pressure loss be within the boiler, heat exchanger etc, if so how could I check, or does anyone else have an idea. The local engineers are costing a fortune in tea and coffee and only telling me what i already know... Ps There is no visible water within the boiler or on the floor around the boiler... Thanks
 
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You know what, Syd, It's a Leak, Mate!
Has anyone had the combustion chamber apart - I expect you'd find it all soggy in there, because this is one of Ideal's boilers which isn't. The heat exchangers do leak.
They can go on a while merrily evaporating the system water, or get too wet and stop with a bang.
Get ready to shell out for a new boiler
 
Thanks Chris R.
Is there anyway I could prove this. I'd rather just know for sure then get the whole boiler changed for a Worcester or a Valinat. Is it commercial sense to get the Ideal stripped and repaired if it is leaking. Is there a test to prove the leak is within the boiler itself. Thanks
 
Is it commercial sense to get the Ideal stripped and repaired if it is leaking.
Probably not, even if the hex is still available.
Only way to be certain is to get the covers off - not a long job - to see if there's water in there, before it has a chance to evaporate.

You could turn the boiler off, then close the isolating valves under the boiler and leave it. If there's no pressure drop then the boiler isn't leaking, but if it only does it when it's hot ( which is normal) you wouldn't see it. Try with higher pressure- it would be quicker.
 
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doubt there are any iso valves on a minimiser, its a heat only blr. could try disconnecting condensate pipe to see if water is going down that from the hex
 
Missus just rung me at work, says "the boiler went off with a bang..." Sounds like a new boiler to me. I'll let you know the whats happened when i get home...
 
Not the boiler that banged. she's paranoid about the CH at the moment. There are no isolating valves on the boiler so hence can't test it.
Chris R. what did you mean when you said "try high pressure"
I took the covers of the boiler but couldn't see anything out of the ordinary, would any leak within the HEX be visible internally or would this evaporate off.
 
Ran boiler on CH for 2hrs last night, but turned off when system made a "low whining" sound not quite a whistle..! After the boiler was switched off there seemed to be a "low gritty" noise flowing through the pump"?
Switched everything off and left overnight...
This morning checked inside the boiler casing.. no water whatsoever, but still lost 0.2bar overnight with nothing working.
How much water would you expect to see out of the condensation pipe?
How much water would a pressure drop of 0.5bar equate to on a typical system?
We have no visible sign of water anywhere?
 

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