the thermostat "under my heater" for the boiler has setings Lo/1-4/Hi.
After the last annual service i note that i has been set to hi whereas
as it used to be 2-3.

I have thermostatic valves on most radiators but i find that if the
central heating is on for a while [ie allnight during the recent cold
snap] and all the house is hot, even if the temp is higher than the
room-thermostat-temp the boiler is still "on".

the hot water is also very hot so i dont see why that would cause the
need for conitnued curning.
i turned the boiler thermostat down to 2 and it stopped immediately and
since then the house is as hot as it was before and the water is as hot
as before so what does this boiler-thermostat setting affect? can i not
just turn it down to 1 or low?[apologies for the wordy post but i
couldnt explain my confusion succinctly]

In an earlier contribution to this discussion,
riz1 wrote:

the thermostat "under my heater" for the boiler has setings Lo/1-4/Hi.
After the last annual service i note that i has been set to hi whereas
as it used to be 2-3.

I have thermostatic valves on most radiators but i find that if the
central heating is on for a while [ie allnight during the recent cold
snap] and all the house is hot, even if the temp is higher than the
room-thermostat-temp the boiler is still "on".

the hot water is also very hot so i dont see why that would cause the
need for conitnued curning.
i turned the boiler thermostat down to 2 and it stopped immediately
and since then the house is as hot as it was before and the water is
as hot as before so what does this boiler-thermostat setting affect?
can i not just turn it down to 1 or low?[apologies for the wordy post
but i couldnt explain my confusion succinctly]

The boiler thermostat controls the temperature at which the water leaves the
boiler. Unless you have a boiler interlock, the boiler will cycle on and off
on its own stat, just to keep itself hot, even when no heat is required by
the CH or HW - which is wasteful (and against the regs for recent
installations).

What you need is a room thermostat which turns the whole lot off when the
house is hot. This needs to be located in a room whose radiator *does not*
have a TRV - otherwise there is a conflict.

You also need a tank stat on the hot water cylinder to indicate when the HW
is hot enough - with the whole lot integrated into one of the recognised
control schemes (called 'plans' by Honeywell).

Do you currently have any stats besides the one on the boiler and the TRVs
on the rads? Do you have any motorised zone or diverter valves in the
system? [Have a look at the plans in
http://content.honeywell.com/uk/homes/systems.htm and see whether any are
similar to what you have].
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

the thermostat "under my heater" for the boiler has setings Lo/1-4/Hi.
After the last annual service i note that i has been set to hi whereas
as it used to be 2-3.

I have thermostatic valves on most radiators but i find that if the
central heating is on for a while [ie allnight during the recent cold
snap] and all the house is hot, even if the temp is higher than the
room-thermostat-temp the boiler is still "on".

the hot water is also very hot so i dont see why that would cause the
need for conitnued curning.
i turned the boiler thermostat down to 2 and it stopped immediately
and since then the house is as hot as it was before and the water is
as hot as before so what does this boiler-thermostat setting affect?
can i not just turn it down to 1 or low?[apologies for the wordy post
but i couldnt explain my confusion succinctly]

The boiler thermostat controls the temperature at which the water leaves
the
boiler. Unless you have a boiler interlock, the boiler will cycle on and
off
on its own stat, just to keep itself hot, even when no heat is required by
the CH or HW - which is wasteful (and against the regs for recent
installations).

Was interested in the point about against current regs. Recently (Within
last week) weve had a combi boiler installed in a 3 bed house all rads have
TRVs but there is no room stat. Is this required by the regs then or can
some boilers get away without having one?

What you need is a room thermostat which turns the whole lot off when the
house is hot. This needs to be located in a room whose radiator *does not*
have a TRV - otherwise there is a conflict.

You also need a tank stat on the hot water cylinder to indicate when the
HW
is hot enough - with the whole lot integrated into one of the recognised
control schemes (called 'plans' by Honeywell).

Do you currently have any stats besides the one on the boiler and the TRVs
on the rads? Do you have any motorised zone or diverter valves in the
system? [Have a look at the plans in
http://content.honeywell.com/uk/homes/systems.htm and see whether any are
similar to what you have].
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

I have thermostatic valves on most radiators but i find that if the
central heating is on for a while [ie allnight during the recent cold
snap] and all the house is hot, even if the temp is higher than the
room-thermostat-temp the boiler is still "on".

The thermostats in the system should do the following:

1. The hot water cylinder thermostat should cause the boiler to fire up when
the hot water gets too cold.

2. The room thermostat should cause the boiler to fire up when the room it
is in gets too cold.

3. The thermostatic radiator valves should turn the individual radiator down
when the room gets too hot, but won't make the boiler fire or stop at all.

4. The boiler thermostat sets the temperature of the water that goes through
the radiators and reheats the hot water.

There appears to be something wrong with the control systems if the boiler
doesn't stop firing when neither the room thermostat nor cylinder thermostat
calls for heat. Either a wiring fault or a thermostat fault could cause
this. Does the boiler fire even with the room thermostat and cylinder
thermostat set really low?

can i not just turn it down to 1 or low?[apologies for the
wordy post but i couldnt explain my confusion succinctly]

As for setting the boiler thermostat, there's a few parameters to juggle.

Advantages of setting low:
Better thermodynamic efficiency
Safer radiator temperatures

Advantages of setting high:
Greater radiator heat output (especially useful in cold weather)
Prevents condensing operation and corrosion

Christian.

In an earlier contribution to this discussion,
The Question Asker wrote:


Was interested in the point about against current regs. Recently
(Within last week) weve had a combi boiler installed in a 3 bed house
all rads have TRVs but there is no room stat. Is this required by the
regs then or can some boilers get away without having one?

AIUI, there *must* be a boiler interlock - which turns the boiler right off
when the heating demand is satisfied. There *are* ways of doing it other
than with a room stat - but a stat is by far the easiest.

Ask your plumber how he has addressed this requirement!
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Was interested in the point about against current regs. Recently (Within
last week) weve had a combi boiler installed in a 3 bed house all rads
have
TRVs but there is no room stat.

The requirement is for a boiler interlock. This means that the boiler must
entirely shut down when there is no call for heat from the house or hot
water system. This is possible on an all TRV system by having a flow switch
that shuts down when the flow through the radiator gets below a certain
level. However, I'm 95% certain that you don't have such a system, but just
an ignorant installer, although I suppose there is always that 5% chance.

Christian.