I posted a query some time back about the advisability of having a heatbank set up with a TMV to control the DHW to something like 50C as suggested in the DIYWiki. My concern was that distributing water at this temperature could be a spawning ground for legionella but was querying if anyone knew anything about this - there was no answer !!
Well I've now got the answer and it confirms my suspicion that such an arrangement would be inadvisable :-
# 70 to 80 =B0C (158 to 176 =B0F) - Disinfection range # At 66 =B0C (151 =B0F) - Legionellae die within 2 minutes # At 60 =B0C (140 =B0F) - Legionellae die within 32 minutes # At 55 =B0C (131 =B0F) - Legionellae die within 5 to 6 hours # 50 to 55 =B0C (122 to 131 =B0F) - They can survive but do not multiply # 20 to 50 =B0C (68 to 122 =B0F)- Legionellae growth range # 35 to 46 =B0C (95 to 115 =B0F) - Ideal growth range # Below 20 =B0C (68 =B0F) - Legionellae can survive but are dormant
It is interesting that building regs in Scotland now require a TMV for baths in new builds but categorically state that the TMV must be as close to the outlet as possible and that the tank water temperature must be in excess of 60C.
Rob