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Re: Hot water to the bath....? |
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| message from Ed Sirett on 10 May 2004 |
Don't use the 1/4 turn service isolator for controlling the flow rate.
Put a gate valve or stop valve that works well when partially open/closed.
Turning the the HW thermostat on the boiler to a high setting permits the
boiler to make scaldingly hot water, it will not enable it to make more
useable HW.
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| Andy P replied to Ed Sirett on 10 May 2004 |
I'm trying to get my head round this...
The HW thermostat seems to control the max temp of the hot water but
does not alter the flow through the boiler. So with the thermostat on
the highest setting if I have 12.5 l/min running through the boiler I
will epxect it to be heated to 45C, assuming the cold is 10C. By turning
the HW thermostat down I can reduce this temperature. If I reduce the
flow of water through the boiler I can increase the maximum temperature
- if I can raise 12.5 l/min by 35C then I should be able to raise 10 l/m
in by more than 35C but will the thermostat limit the max temp of the water?
If I want a shower at say 42C through a thermostatic shower mixer valve
how does it work and where should the bolier HW thermostat be set? The
thermostatic shower mixer valve will take hot and cold water and mix it
to make it 42C. If, to do this, it has to reduce the hot water flow then
won't the boiler heat the hot water even hotter and so cause the
thermostatic shower mixer valve to reduce the hot flow even more etc
etc. If the hot water isn't at 42C to start with then my shower will
never be hot enough, but it would seem from the above that I should have
my HW thermostat set at the highest value, although I can see that this
isn't a good idew when it comes to non-thermostatically controlled taps
at washbasins and sinks.
I'm probably being dim here but I would be interested in the theory
behind all of this.
Andy
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| John Rumm replied to Andy P on 11 May 2004 |
That is right...
You would increase the temperature - but not the maximum. The boiler
should not produce water hotter than the maximum temperature set on its
thermostat regardless of how low the flow rate.
Yes.
It could also do it by leaving the hot flow untouched and raising the
cold flow rate. Not sure if they all use the same technique - guess I
will find out shortly when I install a thermostatic shower mixer ;-)
If that were the case it would end up reducing the flow until the max
temperature as set on the boiler was reached. Thereafter a further
reduction in flow rate will have the effect of lowering the mix
temperature.
True.
I would set it a bit hotter than the maximum temperature you are likely
to want for a bath or shower. That way the mixer can achieve the
required mix and you don' run the risk of boiling the next person
washing their hands under the hot tap.
Not dim really - good set of questions in fact - I will be interested to
hear the responses who have showers of this type on a combi.
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| Pete C replied to John Rumm on 11 May 2004 |
Hi,
I would have thought that if the boiler is non modulating, it will cut
out once the temperature set on the thermostat is reached.
If this is the case it may be best to use the mixer with the flow to
set to maximum, so the mixer does not restrict the flow from the
boiler.
Also thermostatic mixers have a maximum hot water operating
temperature, so it would be worth setting the thermostat on the boiler
some way below this.
cheers,
Pete.
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Archived message: Re: Hot water to the bath....? (UK D-I-Y House Repairs)
