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Apr 19, 2020
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Hi All,

Having recently checked the efficiency level on my boiler, its giving me 43% high efficiency and 57% Super efficiency - I do not recall the readings last year, but it does appear considerably lower than previous checks. Are there any triggers for this to decrease which are "quick wins" to increase?

Regards
 
That efficiency index is, I would think, a relative efficiency, theoretically, if the boiler flue gas temperature was (impossibly) as low as the fan air intake temperature then that efficiency would probably read 100%. Flue gas temperatures which in turn reflect the boiler (water) return temperature are rarely below ~50/70C.
You have a very high boiler flow temp of 80C and if you reduce this to say 65C you will/should see that efficiency increasing as the boiler return/flue gas temperatures will be lower.
 
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The few point of natural gas flue gases starts around 55°c. The return temperature needs to be at that or lower for condensing to even start. Problem is what do you turn the flow temperature down to to start this condensing? Especially when the rads may be sized for ΔT 50.
 

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