Our boat calorifier (silly boat name for a hot water cylinder) has a
temperature and pressure relief valve.

I can understand the pressure relief valve, it's simply a spring
loaded thing that opens when the pressure exceeds 3 Bars and thus
prevents the tank from exploding.

However I can't really understand what the temperature relief bit
does. There is a probe from the valve that pokes down into the water
and, presumably, lowers the valve seat as/when the temperature rises
and opens the valve. How does opening the valve help anything? It
will just let hot water out but won't reduce the temperature really,
except that cold water will replace the hot. Is this all that it
does? Why bother, what harm will too hot water do?

--
Chris Green
·

In message , writes
Our boat calorifier (silly boat name for a hot water cylinder) has a
temperature and pressure relief valve.

Also found in industrial sites where high pressure hot water or steam is
used to produce hot water for hand washing etc.


I can understand the pressure relief valve, it's simply a spring
loaded thing that opens when the pressure exceeds 3 Bars and thus
prevents the tank from exploding.

However I can't really understand what the temperature relief bit
does. There is a probe from the valve that pokes down into the water
and, presumably, lowers the valve seat as/when the temperature rises
and opens the valve. How does opening the valve help anything? It
will just let hot water out but won't reduce the temperature really,
except that cold water will replace the hot. Is this all that it
does? Why bother, what harm will too hot water do?

I suppose over pressure could be from simple heat expansion. Do you have
a non return valve to stop hot water expanding back to the cold water
tank?

Over temperature might occur long before 3 bar is reached and might have
exciting effects when a tap is opened:-)

Our boat person is still in bed and I suspect totally unaware of either
issue! Her current problem is begging 5 gallons of red diesel from
father after a *water in tank* drain down!


--
Tim Lamb

How does opening the valve help anything? It
will just let hot water out but won't reduce the temperature really,
except that cold water will replace the hot. Is this all that it
does? Why bother, what harm will too hot water do?


http://wiki.diyfaq.org.uk/index.php?title=Unvented_DHW (under "Valves").

--
Robin
reply to address is (meant to be) valid

Robin wrote:
How does opening the valve help anything? It
will just let hot water out but won't reduce the temperature really,
except that cold water will replace the hot. Is this all that it
does? Why bother, what harm will too hot water do?


http://wiki.diyfaq.org.uk/index.php?title=Unvented_DHW (under "Valves").

Ah, thanks, that does explain it quite well.

The boat calorifier is essentially an unvented cylinder but in
practice runs at very low pressure as the pump providing the pressure
is just an 'on demand' boat type pump with an accumulator. I'd guess
the pressure is less than 1 bar.

--
Chris Green
·

wrote in message ...
Our boat calorifier (silly boat name for a hot water cylinder) has a
temperature and pressure relief valve.

I can understand the pressure relief valve, it's simply a spring
loaded thing that opens when the pressure exceeds 3 Bars and thus
prevents the tank from exploding.

However I can't really understand what the temperature relief bit
does. There is a probe from the valve that pokes down into the water
and, presumably, lowers the valve seat as/when the temperature rises
and opens the valve. How does opening the valve help anything? It
will just let hot water out but won't reduce the temperature really,
except that cold water will replace the hot. Is this all that it
does? Why bother, what harm will too hot water do?

Calorifier is the correct term for all heat transfer devices where water is
being heated.
Large and small.
The over temperature valve lets out hot water, cold water comes in and
prevents overheating so you don't get scalded.
Operates in the event the water temperature thermostat fails.

Also lets you know the thermostat is US.

On 21/12/2014 18:11, harryagain wrote:

The over temperature valve lets out hot water, cold water comes in and
prevents overheating so you don't get scalded.
Operates in the event the water temperature thermostat fails.

Also lets you know the thermostat is US.


Or, in my case, that the valve was US!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.