Switch off geothermal?

LMR

This may sound stupid but is it possible to switch off your geothermal UFH etc for the summer months? Would it be more economical to use an immersion to just heat the water when required?

Geo systems are not as efficient at heating domestic hot water (60C) as they are at raising it to 40C or so for UFH.

So it probably would be a good idea, also it gives the subsoil a chance to warm up a bit to recover from all the heat that was extracted over the winter (according to some "experts").

Borzoi

LMR wrote: »

This may sound stupid but is it possible to switch off your geothermal UFH etc for the summer months? Would it be more economical to use an immersion to just heat the water when required?

Of course you can turn it off - your probablly not going to need it for 3-5months (like if we get a summer :rolleyes:)

As for the immersion - this will depend on the set up of your hot water system, and how much DHW you use. Because your immersions costs 4 times as much to run as the GSHP, but may be set up just to heat the small volume of water at the top of the tank (ie just enough for showers and washing, say 50litres) but the GSHP may need to heat the whole 300l cylinder in order for you to get hot water out the taps. So in that case Immersion is the way to go. As i say - it depends on your setup and usage

BTW most of us only like hot water to be around 40C anyway, so the GSHP are still good.

sinnerboy

60 degrees is required to keep leigonella at bay ....

Borzoi

sinnerboy wrote: »

60 degrees is required to keep leigonella at bay ....

Occasionally is sufficient (though I've yet to see a formal Legionnaires risk assessment for for DHW for the definition of sufficient! :rolleyes:)

sinnerboy

How often do you believe is required Borzoi ? For example if you were to time -programme your immersion to achieve and maintain 60 degrees for 1 hour daily , would that see off the risk ?

( .... or is it that simple )

homer911

The conversation has gone off topic but I would say "occasionally" has somewhat to do with the water replacement rate as well and you will probably never get a straight answer to this question. Its a bit like Domestos - kills 99% of all household germs......and leaves 1% for breeding purposes

sinnerboy

homer911 wrote: »

you will probably never get a straight answer to this question. Its a bit like Domestos - kills 99% of all household germs......and leaves 1% for breeding purposes

Carlow52

homer911 wrote: »

Its a bit like Domestos - kills 99% of all household germs......and leaves 1% for breeding purposes

The ad says
of all known germs

Re LD, for what it is worth, water needs to be maintained at 60C or brought to 77C on occasion.
there is loads of stuff on the web, enough to drive u to drink

PeteHeat

Hi LMR,

One thing to consider before switching off the pump completely is the amount of time and energy it takes to bring the UFH back up to temperature.

It might be worth looking at turning the room stats down to about 16c as the baseline temperature or making a note to switch the pump on earlier than most who use radiators and bring the temperature back up gradually instead of running the pump 24/7 to speed up the recovery.

quentingargan

sinnerboy wrote: »

How often do you believe is required Borzoi ? For example if you were to time -programme your immersion to achieve and maintain 60 degrees for 1 hour daily , would that see off the risk ?

( .... or is it that simple )

Legionnella bacteria breed at temperatures between 25 and 42 degrees. Thats the problem with both solar water heating systems in the winter, and geothermal, both of which bring water to about that level.

Once a week at 60 degrees is sufficient, and this is the norm for solar water heating in other countries. Alternatively, you should ensure that water is heated to 55 degrees before use.

Many geothermal systems have some mechanism for bringing the hot water to 60 degrees anyhow, but with considerable loss of efficiency on that circuit.

sinnerboy

Carlow52 wrote: »

enough to drive u to drink

.... as if I need an excuse :pac::pac::pac:

Borzoi

quentingargan wrote: »

Once a week at 60 degrees is sufficient, and this is the norm for solar water heating in other countries. Alternatively, you should ensure that water is heated to 55 degrees before use.

Fair play to you! TBH I asked 2 guys on the IEI legionnaires panel, and they didn't know for sure - hence the need for a risk assessment.

I've heard of weekly or daily, but I wouldn't know. TBH I'd go with the manufacturers recommendation, because if the worse does happen, at least you should be covered. :rolleyes:

PeteHeat

Hi,

I agree, I think it takes about 15 minutes once a week at 60c kills off any legionella that may be present.

Longboard

70 to 80 °C (158 to 176 °F): Disinfection range
At 66 °C (151 °F): Legionellae die within 2 minutes
At 60 °C (140 °F): Legionellae die within 32 minutes
At 55 °C (131 °F): Legionellae die within 5 to 6 hours
Above 50 °C (122 °F): They can survive but do not multiply
35 to 46 °C (95 to 115 °F): Ideal growth range
20 to 50 °C (68 to 122 °F): Legionellae growth range
Below 20 °C (68 °F): Legionellae can survive but are dormant