Back boiler is boiling!

[djboyd]

Hi all

I have a link up system with a dunsley neutraliser. This is connected to a sealed unvented hot water cylinder and a standard gravity fed and pumped central heating system. Both my back boiler and oil fired boiler feed to the neutraliser. The hot water system is protected by plenty of safeguards against overheating - must be pumped, valve, overpressure regulated, etc. The only safeguard against the back boiler overheating is the stat on the neutraliser set at 90 C. This stuck again tonight meaning I could hear the boiler releasing steam into the header tank as the pump did not trigger circulating the heat through the rads. So, two questions:

Is there any additional safety device I could use to stop the system boiling (especially during power cut)?

Does it matter if it does boil, dumping the boiling water into the header tank?

Thanks for your help.

 

[djboyd]

No replies? I just want to know if it is safe to boil off now and again or if I should do something!

 

[Blackcatgas]

The system youve got sounds beyond my scope slighty, did you make the dunsley yourself btw? as there are guides on the internet Ive seen, a plastic tank will hold boiling water for a short period, but is not a good thing, there was the case recently of the tank filling with boiling water then bursting in the attic above a babies cot, the baby died of scalding.http://www.telegraph.co.uk/news/uknews/1575026/Council-aware-of-boiler-fault-that-killed-baby.html

 

[djboyd]

Thanks for the reply. Yes, I was aware of that case - my system has boiled probably twice in the last few years when the anti-boil stat has not activated. My concern is that during a power cut or another failure it will continue to boil. I suppose that as it boils off the water is released as steam and the ball cock allows cold water in to replace it, keeping the temp in the tank below 100. Thought there might have been some additional mechanical method to dump the boiling water somewhere else.