What's a safe temp for the cylinder?

unkel

Mine is programmed to have a max temp at 63C, which seems low.

We all know that if we switch on the hot tap and put our hand under it, that we will be scorched. In fact, I had to sign a waiver when my solar was installed, otherwise the installers were obliged to install some sort of thing to keep the temps even lower

But what is it with the 63C limit? Why not 83C? I can't see any other issues apart from the water being hot to human flesh?

Seems far more efficient to keep the max temp high. Last weekend (in March), with the glorious weather the collector at up to 130C heated the full cylinder to the max temp. With our 2 bar pump this is good for 3 very long and powerful showers and 1 full bath. Which is great, but why limit it at that?

ED E

It should be at least 60*C (50 according to some) to prevent Legionellas.

If you have a traditional shower then having 80*C water would be pretty lethal, an electric shower has a lockout that prevents that happening (such as on, off on rapidly) but in a conventional shower no such protections exist. Scalding a hand is one thing, your whole body another.

unkel

My point is that you'd adjust the shower mixer before you get into the shower. Only a compete idiot would step in before checking the water. My thermostatic mixer defaults to 37C anyway, no matter what the temp of the water in the cylinder is.

So my question rephrased: apart from human error, is there any other reason not to have the max temp of the cylinder at say 83C instead of 63C?

Calahonda52

the greater the temp the greater the heat loss in the cylinder as heat loss is a Fn of the delta T between the cylinder and ambient.
Ads well as human error, there is thermostat failure.
What is the high limit sat on the cylinder set at?
In addition, if the high limit stat failed on the cylinder it could reach the collector temp of 130C which is pretty dangerous if something were to fail in the house.

unkel

Calahonda52 wrote: »

the greater the temp the greater the heat loss in the cylinder as heat loss is a Fn of the delta T between the cylinder and ambient.
Ads well as human error, there is thermostat failure.
What is the high limit sat on the cylinder set at?
In addition, if the high limit stat failed on the cylinder it could reach the collector temp of 130C which is pretty dangerous if something were to fail in the house.

Lots of LOLS at your remarks

You neither read this thread nor are you familiar with solar tube hot water heating systems...

axe2grind

Set low to prevent Limescale?
My water is soft, My system is set at 80C, which is below the rating of the thermostatic mixer which is at the exit of tank. No scalding water at user end. Tank is rated to 90C. With hard water I think there is an issue with limescale at higher temperatures
Legionnaires not an issue with me as my hot water store is a static storage with hot water heated via coil.

I also have divert to heat dump when max temperature is reached to prevent overheating in the panels.

unkel

Overheating in my system won't happen as the max cylinder temp is set in the controller. My point is that this temp is 63C and I would have thought it should be a lot higher than that to make best use of solar energy.

axe2grind

Agreed unkel which is why I'm happy mine is 80C but I have soft water It means one sunny Summers day can provide hot water for 3 days. My overheating reference is in regard to the antifreeze which degrades at high temperatures which happens if circulation through panels ceases. The heat dump means this circulation continues even when cylinder has reached 80C.

Victor

unkel wrote: »

My point is that you'd adjust the shower mixer before you get into the shower. Only a compete idiot would step in before checking the water.

... or someone still half asleep - it was actually about 4C.

80C will cook flesh. One has to realise that very young or very old people may inadvertently come into contact with piping.

Charlie19

Would the high temperature not be dangerous, if say children were to wash their hands.

axe2grind

The high temperature is only in the cylinder, when the very hot water leaves the cylinder it is mixed with cold water to lower the temperature to a safe level before being piped around the house. Look up Thermostatic mixing valve (TMV)

Charlie19

axe2grind wrote: »

The high temperature is only in the cylinder, when the very hot water leaves the cylinder it is mixed with cold water to lower the temperature to a safe level before being piped around the house. Look up Thermostatic mixing valve (TMV)

Are TMV's compulsory, Ive seen anti-scald taps used were the temperature would be restricted to around 25 degrees but these would'nt be too common in a standard house system.

deandean

The immersion heater thermostat in my cylinder heats the water to 55DegC, no more.
We're still alive after 10+ years.
I have no meas for this legionella theory in a domestic hot water cylinder that's in constant use.
It works well in a house full of young'uns who switch on the immersion heater every time they go by it, grrr.

Gumbo

Charlie19 wrote: »

Are TMV's compulsory, Ive seen anti-scald taps used were the temperature would be restricted to around 25 degrees but these would'nt be too common in a standard house system.

I check for these in my school inspections alright. Mandatory there now.

quentingargan

unkel wrote: »

We all know that if we switch on the hot tap and put our hand under it, that we will be scorched. In fact, I had to sign a waiver when my solar was installed, otherwise the installers were obliged to install some sort of thing to keep the temps even lower

You really should have that "thing" in place anyhow, and it is a bit cheapskate-sh of your installers to opt for a waiver rather than a valve.

If you have hard water, it will damage your immersion and cylinder coils to bring it above about 60C because they will become coated in limescale and lose their conductivity.

If you have soft water, then you are better off letting the solar bring it up to 80C and using a thermostatic mixing valve to ensure that what comes out of the taps is less than about 50C. Even at 60C, children can get burned, so the valve is a good idea either way to reduce water temperature in the taps while preventing Legionella.

unkel

Soft water. Thanks Quentin, I'll get the temp of the cylinder up to 80C and I'll talk to my installer again about the thermostatic mixing valve at the cylinder.

@axe2grind - misunderstood you there. I have Kingspan Thermomax tubes, which have a built in overheating protection which doesn't let them go over 135C. With this system you don't need a heat dump. And agreed on the 3 days. Currently with the full 360l at 63C (this has already happened a few times this March is enough for about 5 long hot showers (in a 2 bar pumped shower) and 1 full bath, so yes about 2 days. Going up to 80C will make that about 3 days and should give me enough of a buffer to rarely have to put the gas on from mid March to early November or so

antoinolachtnai

I really wouldn't have water that hot without the thermostatic mixing valve. It's an extra risk, is it really worth taking to save a fairly small amount of gas?

dathi

unkel wrote: »

Soft water. Thanks Quentin,

County Council is mainly sourced from two water treatment plants at Ballymore-Eustace and Leixlip. The water from Leixlip would be considered hard water and from Ballymore-Eustace it is soft water. We don’t supply any water directly from Leixlip, but water from Leixlip is blended in our reservoir at Peamount which serves parts of Lucan and hence water in this area can be of medium hardness.
took that from here as you are in lucan
http://www.sdcc.ie/services/environmental-health/water-services/drinking-water

Gumbo

I rang a Solar provider today for my house and he stated that the Cyclinder will cut out at 60 degrees also.

gctest50

Just buy a few TMVs and put them in - extra bit of safety and nicer to use day to day

get burnt at 60 anyway: ( see attached)

unkel

dathi wrote: »

County Council is mainly sourced from two water treatment plants at Ballymore-Eustace and Leixlip. The water from Leixlip would be considered hard water and from Ballymore-Eustace it is soft water. We don’t supply any water directly from Leixlip, but water from Leixlip is blended in our reservoir at Peamount which serves parts of Lucan and hence water in this area can be of medium hardness.
took that from here as you are in lucan
http://www.sdcc.ie/services/environmental-health/water-services/drinking-water

That's spot on. We get the unblended soft water from Ballymore-Eustace here in south Lucan. Don't I know it! At some point a few years ago there was a problem with the supply and we were temp switched to the Leixlip hard water supply. Washing machine and dishwasher stopped working properly straight away :eek:

Calahonda52

unkel wrote: »

Lots of LOLS at your remarks

You neither read this thread nor are you familiar with solar tube hot water heating systems...

Does you system comply with ALL aspects of "EN 12976-1" ?

Maybe you should read this
https://www.amazon.co.uk/Planning-Installing-Solar-Thermal-Systems/dp/1844071251/ref=sr_1_2?ie=UTF8&qid=1485100028&sr=8-2&keywords=planning+and+installing+solar+thermal+systems

quentingargan

kceire wrote: »

I rang a Solar provider today for my house and he stated that the Cyclinder will cut out at 60 degrees also.

This is a factor I forgot to mention on my post... Many immersions now have a semi-permanent stat that cuts out if the cylinder is brought more than a few degrees over temperature and has to be manually reset. So bringing the cylinder up to 80 might trip the immersion. That system only works with older immersion heaters that don't have the resetable trip.

rolion

unkel wrote: »

I have Kingspan Thermomax tubes, which have a built in overheating protection which doesn't let them go over 135C. With this system you don't need a heat dump.

Hi,

Sorry,never heard about this system...
How does it works ?
How do you know it works ?

My panels were reaching over 150, even 200 last summer.
I had the system on auto,no issues so far but ive been "recommended" to open the taps and "empty" the cylinder !
The controller stopped the pump and the cylinder temps weren't going higher than 60 degrees !

The solar liquid is certified to work over 200 degress afaik!

Thanks.


Collector


CylinderTop


ClinderBottom

air

The UK are way ahead of us on TMV usage and regulations. Young children have been killed in the past from scalding incidents. Even without solar immersion heater thermostats can go faulty etc.
I installed a whole house TMV, gives very consistent output once the tank is up to temperature.

For example.
http://kfor.com/2014/08/02/toddler-dies-after-being-left-in-scalding-bath/