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What Boiler to prevent short cycling?


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12 minutes ago, JohnMo said:

Should read kW not kWh


I said that at the start of the thread, and basically got ignored. 



Sorry bad habit kWh v kW - I'll try to be more careful


I did read all the way thro the thread and as soon as I read your earlier post I though "bingo" but 3 pages on and alternative explanations are still being requested


Sometimes the obvious explanation is the right one (still not sure why you would run UFH when you didn't want rads as well but I guess house layout could drive that need)

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  • 3 months later...

Just coming back to this topic because for the last year and a bit I've had to run my CH pump on speed 2 to stop the boiler short cycling - Previous 30 years it's always been fine on speed 1 but I made a lot of changes a year or so back doubled rad size and reconfigured pipework as well as changed all the lockshield valves and TRV's.


I think I know why now - I pulled the pump apart at the weekend


Took a bit of work to get it clean and all the impeller channels clear - I have a magnaclean unit in the circuit but it's after the pump and never seems to collect much magnatite


Pump 1.jpg

Pump 2.jpg

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11 minutes ago, JohnMo said:

Looks like a system flush/chemical clean and some corrosion inhibitor wouldn't go amiss. Wonder the system worked at all.


System is fully dosed with inhibitor


All rads are new (or less than 2 years old)


CH Circuit was drained and refilled twice in the last 2 years - each time it was flushed and then treated


I have a magnaclean unit in the circuit but it's after the pump


Current pump was fitted in dec 1999 and I'm pretty sure it's built up the level of magnatite deposits over time. It's possible changing rads and making changes to the CH circuit pipework in 2022 disturbed material and at that point the pump would see it first.


Magnaclean images from the 6 monthly checks carried out in last 2 years - it picks up something but nothing like my mate got in his system after 1 week!!! (I'll try to find that picture)


Filter 1.jpg

Filter 2.jpg

Filter 3.jpg

Filter 4.jpg

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