Discuss How to reduce corrosion in vented heating systems in the Central Heating Forum area at PlumbersForums.net
If you read siricosm article link then it suggests it takes roughly 75 days for the oxygen saturated water content to dissolve the oxygen, perhaps your layout is helping things? Have you been regularly dosing your system to protect it? I imagine someone as well informed as you has done a lot to maintain the system quality.
At .2835 litres per meter for your 19mm ID pipe, your 3.5m gives you around a litre, so comfortably over your .75 litre expansion for your 75 litre system. Unless I missed something.
Yes, very interesting indeed, they could burn (heavy fuel) oil or (normally) natural gas or natural gas + bio gas which we generated as a result of a manufacturing fermentation process and it supplied between 10 and 15% of our energy needs. We also generated our own power (5MWe) with a aero derivative gas turbine generator which exhausted into another 55 MW boiler fired on nat gas only. happy days indeed.That's some big systems you worked on mate. Personally I'd like to get experience with commercial and industrial oil boilers
I keep my flow/return at 75C/60c so my expansion is ~ 1.5 litres for 75 litre water content, not 0.75 litre. (see post#28, above)
Yes, I am using 70C (67.5) vs 20C to get 2% (1.5 litres), my (oil) boiler has its set point set to 75C and its return is ~ 60C.
I keep my boiler at the above temps as I need my rads to run at their rated output, all modern rads are based on a "50 deg" rating which is the (mean rad temperature) - the required room temperature (often taken as 20C). Older rads, maybe your ones, are based on a "60 deg" rating.
So, in my case, the mean rad temp is (75+60)/2 or 67.5C, (67.5-20) = 47.5C so my rads should produce 93.5% of their 50 deg rating. You can get correction factor tables but I find it far easier by just using excel, the rad output is the (present rating/the "rated" rating)^1.3
in my case above this is (47.5/50)^1.3 or 93.5%. In your case if the rads are 60 deg rated then the output based on a 50C mean rad temperature is only 40.6% (30/60)^1.3 OR if 50 deg rated, 51.4% (30/50)^1.3. That will make your boiler cycle on/off more frequently.
Oil boilers (which cannot modulate) will cycle throughout their life but gas boilers can modulate (and prefer it).
This was never a problem until recently, the water pathways thro older cast iron boilers were wider than the M6 ...you could stick your main digit in. Now the water pathways are less than a rollup ciggySome vented heating systems seem to sludge up, and yet other remain remain remarkably clean after many years service.
Why?
Corrosion is caused by oxygen. Eliminating leaks and inhibitor helps, but the F&E tank is open to the air, so oxygen can freely get in there. Is it possible to design a system that minimizes oxygen entry from the F&E tank?
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