What temp should elect immersion heater be set to?

[dave]

What temperature should an electric Immersion heater be set to? Is there a recommended max (even though it may be possible to go beyond that). I've heard that if set too high, the pipes clog-up faster.

[mrcheerful]

It is more a safety issue (AFAIAC) If you set it high then children may scald themselves. So I set mine to uncomfortably hot, yet not immediate injury, if you see what I mean, I believe this is about 60 - 65 degrees, but best try it for yourself, then make sure you have enough hot to run a bath! Some experimentation may be needed.

[Christian McArdle]

For safety reasons, unless you have a TMV (thermostatic mixing valve), it should be set between 55C and 60C. Any higher and you are in serious scalding territory. Any lower and you are risking leggionaires' disease.

If you have a TMV, you can go hotter (up to about 75C) to give extra storage capacity at the risk of scaling the element quicker if you have hard water.

A modern immersion should have two stats. One will have a pop-out reset button. If adjustable, this one should be set to 75C or 10C above the service stat, whichever is higher.

Christian.

[John Rumm]

You want it at least 60 - 65 to kill off any bugs in there. The hotter you have it the more energy you store (so longer showers per tank full), but the greater the risk of injury. If you need to keep it at a very high temperature then you can use blending valves at the point of use to reduce the temperature to a safe level.

[Harry Bloomfield]

dave has brought this to us :

It is more a matter of safety and balancing two conflicting needs. Minimum to prevent legianella is 50 C and maximum to prevent serious scalding is about 60 C, but this will probably still be too hot if there are kids/old people about. Too low and you may also find the water is not hot enough to adequately fill a bath.

Ours (CH) is set to around 75 and we take care.

[Doctor Drivel]

Top mounted immersions generally have to be set to higher temps as not enough water will be heated, the water is too hot at first and gradually get cooler. Having TMV ensure an even temperatures all though. Well worth having.

[Dave Fawthrop]

|dave wrote: | |> What temperature should an electric Immersion heater be set to? |> Is there a recommended max (even though it may be possible to go beyond that). |> I've heard that if set too high, the pipes clog-up faster. | |You want it at least 60 - 65 to kill off any bugs in there. The hotter |you have it the more energy you store (so longer showers per tank full), |but the greater the risk of injury. If you need to keep it at a very |high temperature then you can use blending valves at the point of use to |reduce the temperature to a safe level.

A bit on the low side.

The recommended temperatures, for serving food to the public, for killing food poisoning bugs, is 72 deg C or 84 deg C depending what books you read.

64 is the temperature you can store food at for only 2 hrs while serving before you have to throw it away.

So 72 deg C is as low as I would go.

[Christian McArdle]

Whilst ideal for biological protection, such a temperature would require the use of a TMV, as the risk of scalding would be very significantly greater than the risk of poisoning by this temp. Indeed, at 72C, you have a very substantial chance that someone (probably an unfamiliar visitor) will require hospital treatment within the lifetime of the system. Many people (particularly children and elderly people) are killed every year by scalding water. Many more are maimed and disfigured.

Christian.

[Doctor Drivel]

Fit a TMV, easy to fit, and you will not look back.

[Doctor Drivel]

The biggest cause of serious injury and death each year with water systems is water being far too hot. It looks like TMVs may become standard on new installations and updates.

[Richard A Downing]

Interesting thread.

Is it possible to fit a blending valve at the outlet of the hot tank? That way the content can be at a bug-killing high capacity temperature in a place where it's easy to insulate against losses. But the delivery pipes would be at a more reasonable and safe temperature, not requiring thermostatic taps everywhere, and giving such large losses in transit.

R.

[Christian McArdle]

Yes. Such a system is recommended. You may need to fit a pump, although I'd find an unpumped gravity system to be unacceptable even without a TMV.

Although my system is a heat bank, rather than a conventional gravity cylinder, it has a TMV on the output. It is more important with a heat bank, as the output temp is fundamentally more variable. However, many of the benefits apply even to a conventional cylinder.

Christian.

[Guy King]

The message from "Doctor Drivel" contains these words:

Trouble with that is that if you want to add more hot water to a bath after half an hour or so, you can only add water at a safe bathing temperature, which is no damn good for warming up a cooling bath.

[Christian McArdle]

However, they are useful for limiting temp to 60C, which is useful for warming a bath, whilst storing at higher temps. I suspect the new rules will require 40C limits (or even 38C), which will be 36C by the time you've heated up the bath material and 34C by the time you've got in...

Christian.

[dave]

Richard A.D. asked the question I was going to. Good to know it's possible to fit a TMV at just the HW outlet point. As I've never heard of a TMV for this use before - what sort of cost are they? I'll wander over to B&Q tomorrow and see what they have

What prompted my post was that that our HW *is* scalding hot - so we can get enough water for a decent bathfull. As we have a gravity system I guess we'll have to do the pump bit but as well?

Is fitting a TMV to imm. heater tank straightforward?

[Christian McArdle]

Yes. POP. You can use single impellor pumped hot and mains cold if the cold is any good. Otherwise, twin impellor continuously rated pump from hot and cold gravity supplies into the TMV. Stuart Turner Monsoon or similar. The pump should cost WAY more than the TMV.

Technically, you don't need to pump. But then cars don't need engines as long as you only drive downhill.

are also ideal if you want traditional looking taps on your basin rather than a mixer, but want hand washing temperatures from the hot tap, rather than water you could make tea with. That way you can have 60C in the bath (for lovers of long baths) and 40C from the basin.

Christian.

[<me9]

I have such a system and keep the TMV set to 50C. It gives a much more constant temperature from my shower, but the flow is barely acceptable.

I find my conventional cylinder often overshoots its set point of 60C which isd why I have the TMV. I would like to upgrade to a heatbank, if I could find one at a reasonable price, and without a TMV, as I already have that.

[Guy King]

The message from "Christian McArdle" contains these words:

Then people like me will take them out of circuit.

[Doctor Drivel]

Or get a thermostatic mixer

[Doctor Drivel]

Take the hot for the shower before the MV and have it thermostatic.