In an earlier contribution to this discussion,
wrote:

Hi - I'm looking for advice, please.

We have an oil fired boiler and recently I've noticed that our heating
doesn't seem to be working properly. Normally, the boiler will fire
when the heating comes on and it will go off when the house has
reached the required temp (around 20 degress as controlled by our room
thermostat) - usually within 30 - 45 minutes. The radiators normally
begin to feel warm within 10 mins of the boiler firing. What I'm
seeing at the moment is that (occasionally - maybe three or four times
a week) the heating will come on and the boiler will fire up as
normal. However, the radiators do not get hot. The boiler continues
to fire for as long as the heating is on, but the radaiators do not
get warm.

Another occasional problem is that when the heating and water come on
at around the same time in the morning, the heating may work but the
water does not get hot. I assume this is probably related?

We had a plumber come out last week and he inspected the system. He
said the electronic valve is fine and he re-mounted the pump as he
said it had been fitted on an angle, which is incorrect. He also
vented the pump, having confirmed it's working okay. Although the
system now seems quieter, we're still having the intermittant
problems mentioned above.

I suspect we have an intermittant problem with the pump. As well as
being concerned that the system isn't working as it should, I imagine
that we're using far more oil than necessary as the boiler is
continuing to fire with little or no effect? Or am I misunderstanding
what is happening here?

Any advice gratefully received.

Thanks - Paul.

We need to know a lot more about the way your system is controlled to be
able to make any sensible suggestions. Is it fully pumped, or gravity
(convection) HW and pumped CH? [Clue: how many water pipes are connected to
the boiler? What size are they, and where do they go?] How many motorised
valves are there, and what type? [If system is fully pumped, there will
likely be one 3-port valve or two 2-port valves]. Is there a thermostat
strapped to the HW cylinder? (not the one incorporated into an immersion
heater, if any).

As a general point, if the boiler comes on but the radiators don't get hot,
it means that no water is flowing through them. This could be for any number
of reasons, including:
* faulty room thermostat (which thinks that the heating doesn't need to be
on, so the boiler is running just for the benefit of the HW)
* faulty zone valve
* faulty pump
* air-lock or blockage

If the boiler is purely keeping itself warm but not heating the HW or
radiators, it will be wasting energy - but not using as much it would when
there was proper circulation.
--
Cheers,
Roger
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