Couple of times yesterday our boiler (Grant Vortex Eco) started up when
it shouldn't have (timer-controller in 'off' phase for both HW and CH,
no tell-tale 'on' lights on).

Only came on for a couple of minutes, warmed up and then stopped. Normal
service resumed later when timer came on.

First thought was it went into frost protection mode by mistake (it's
not cold here). Not really anything in the manual about it (except the
bare mention that the boiler may have a frost protection stat or pipe
stat). How would one check?

--
Evremonde

Most frost protection is set at around 7°C so that heating comes on well before pipes start to freeze. I suspect your boiler went into frost protection mode. If the boiler is a combi then you can often hear them firing up for a few minutes just to ensure there is a reservoir of warm water for DHW when you turn the tap on. You can stop it by putting the boiler in eco mode if it has one the draw back being that when you want hot water you have to wait a while for it to heat and flush the cold out of the pipework.

Richard

On Fri, 1 Nov 2019 08:54:23 +0000, The Marquis Saint Evremonde
wrote:

Couple of times yesterday our boiler (Grant Vortex Eco) started up when
it shouldn't have (timer-controller in 'off' phase for both HW and CH,
no tell-tale 'on' lights on).

Only came on for a couple of minutes, warmed up and then stopped. Normal
service resumed later when timer came on.

First thought was it went into frost protection mode by mistake (it's
not cold here). Not really anything in the manual about it (except the
bare mention that the boiler may have a frost protection stat or pipe
stat). How would one check?

This also happened with my heating system. Have a look at the
motorised valve. Even though the timer called for both CH and HW off
the heating was running.

The timer controls the motorised valve which in turn controls the
boiler. In my case the CH valve motor gears disintegrated leaving the
valve in such a position that the boiler was running and CH on.

Fortunately the motor separates from the valve easily so the repair
was simple.

Blimey we have been doing that for many years. modern lads don't know they
bin born laddie. grin.
Brian

--
--
From the Bed of Brian Gaff -

Blind user, so no pictures please!
Today is Yesterdays Tomorrow.
"Tricky Dicky" wrote in message
...
Most frost protection is set at around 7°C so that heating comes on well
before pipes start to freeze. I suspect your boiler went into frost
protection mode. If the boiler is a combi then you can often hear them
firing up for a few minutes just to ensure there is a reservoir of warm
water for DHW when you turn the tap on. You can stop it by putting the
boiler in eco mode if it has one the draw back being that when you want hot
water you have to wait a while for it to heat and flush the cold out of the
pipework.

Richard

On Fri, 01 Nov 2019 10:36:24 +0000
Richard Swaby wrote:

On Fri, 1 Nov 2019 08:54:23 +0000, The Marquis Saint Evremonde
wrote:

Couple of times yesterday our boiler (Grant Vortex Eco) started up
when it shouldn't have (timer-controller in 'off' phase for both HW
and CH, no tell-tale 'on' lights on).

Only came on for a couple of minutes, warmed up and then stopped.
Normal service resumed later when timer came on.

First thought was it went into frost protection mode by mistake
(it's not cold here). Not really anything in the manual about it
(except the bare mention that the boiler may have a frost protection
stat or pipe stat). How would one check?

This also happened with my heating system. Have a look at the
motorised valve. Even though the timer called for both CH and HW off
the heating was running.

The timer controls the motorised valve which in turn controls the
boiler. In my case the CH valve motor gears disintegrated leaving the
valve in such a position that the boiler was running and CH on.

Fortunately the motor separates from the valve easily so the repair
was simple.

I had the same thing, but instead of a disintegrated valvegear, it just
needed removing, cleaning, and reassembling.
Definitely the first thing to check.

--
Davey.