Legionella and Immersion on or off?

[Johnbhoy80]

Quick one - I have a new Samsung gen 6 8kw ASHP with 250l tank and radiators.  Rads set to 45 and DHW at 48. Question is, should I turn off the legionella cycle and immersion? Thanks. 

[Conor]

If unvented yes, no Legionella risk with chlorinated mains water that's not exposed to atmosphere or contamination.

[Johnbhoy80]

Thanks for the reply Conor. And no need for the immersion, so switch that off too? 

[Wil]

You may want the immersion as backup or to dump any solar you may have? No need to switch it right off if the legionella cycle has been disables as it just won't get used unless it's wanted.

[ProDave]

With mine, an LG ASHP I turned off all the settings in the heat pump to automatically use the immersion heater.

 

A well respected former member did a very good analysis that if you are on treated mains water, you can be sure there are no bugs in the water supply, and if the cylinder is unvented, no way for bugs to enter, so no need for a legionairs cycle.

 

Different matter if you are on a private water supply or have a vented water tank fed from a header tank.

 

I can still turn my immersion heater on manually should I need it, and in any event surplus solar PV automatically goes to the immersion heater.

[Andehh]

As above, disabled it for the given reasons.

 

I might run it once a month if we have guests & need an extra boost of extra hot water anyway!

[Johnbhoy80]

Thanks for the reply’s.  It’s definitely well treated water.  I think I will turn it off altogether for a week or 2 and monitor my usage.  If there’s not much variation then I will look to switch it back on.  Another question would be, if it is on, is a 90 min delay time best for a 250l tank? 

[Johnbhoy80]

3 hours ago, Wil said:

You may want the immersion as backup or to dump any solar you may have? No need to switch it right off if the legionella cycle has been disables as it just won't get used unless it's wanted.

Solar my next step. 

[Wil]

On 10/11/2023 at 15:26, Johnbhoy80 said:

Thanks for the reply’s.  It’s definitely well treated water.  I think I will turn it off altogether for a week or 2 and monitor my usage.  If there’s not much variation then I will look to switch it back on.  Another question would be, if it is on, is a 90 min delay time best for a 250l tank? 

Either you put it on until it trips out on it's in-built overheat stat (this can usually be adjusted). At this point you know your tank is as hot as you can have it.

 

Or you boost for a period of time to suit usage. This will only come from experience but a 3kW immersion in my 300ltr tank is a decent boost if on for an hour.