GSHP pasteurisation cycle

FCA_ACF

anyone have experience of running pasteurisation cycle on GSHP?

MX5huggy

No but it needs to be done to kill off Legionella.  What experience are you looking for? 

matelodave

Can we have a bit more info on what you are looking for.

I have an ASHP which isn't all that much different. It will do a pasteurisation cycle once a week by winding the hot water temp up to 60 degrees for around 30 minutes. It uses the heatpump to get the temp up to around 55 degrees and the immersion heater to raise it the last bit it up to 60.

We keep out hot water at 45 degrees but as the tank is non-vented and mains fed and the water smells of chlorine anyway we probably don't really need to to run the cycle every week.Ourss is a fixed weekly cycle, some heatpump s or controller will allow you to adjust the times and temps to suit your own requirements

This means the immersion is only heating the water by 5 degrees for a pretty short period of time .In fact it takes 1.16kwh to heat 200 litres of water from 55 to 60 degrees (or about 62p after the October price cap) = or about £32 a year

Legionella multiplies at temperatures between 20-45 degrees, at 50 degrees it survives but does not multiply, at 55 degrees it dies after 5-6 hours, at 60 degrees it dies after around 30 minutes and at 65 degrees it dies within 2 minutes .

TBH you are  probably pretty safe if you keep your tank at around 50-55 degrees, but probably advisable to run a cycle every now and again if, like us, you store it at a lower temperature.

I'd be interested to know just how many people really do catch LD from a normal domestic hot water system rather than from an institutionalise system like a hosptital or care home