Sime Format 30 HE Combi Boiler

Joined
27 Jul 2010
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Location
Lancashire
Country
United Kingdom
Initially system worked well.
After about 12 months time delay to fire up when CH demand or Hot Water demand became very erratic (from 10 Secs normal to 1-2 mins to not firing up at all).
Error indication Water Flow Switch or Limit Stat Intervention.

Cleaned CH Water Filter..partially block with black sediment, cleaned and refitted.
Checked Diverter valve operation OK.
Refilled and repressure system..... Similar problems persist.

Chcked Flow Switch Unit, slight signs of water leak. Replaced Flow Switch Unit. No Improvement.

Flushed System and refilled with Inhibitor....still same problems, some times OK for few days then erratic delays or not firing up.

Eventually when testing water flow micro switch found resistance to vary between 0 ohms to 2K ohms when operated (open cct when not operated).
Replaced microswitch....... bingo no more problems...
 
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Whats the point of all that................

I repair boilers most days but spare anyone visiting here the gory details!
 
Perhaps I'm misunderstanding this Forum.
Visits by 2 different CH Engineers did not solve my problem.
I could find very little info about faults on Sime Format 30 HE Systems.
Even with my 50 years experience as Electronic/Aeronautical Engineer I was aware of the sensible limitations of what I should try to test as a non registered CH Engr.
In my experience very rarely do Micro Switches have erratic contact resistances, usually they fail to make or break.
I just thought sharing my problem might help someone.
 

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