Ok, when it's a little warmer (in case I can't get the thing back
together) I will have a bit of a better go at getting the Honeywell box
off the wall. I noticed the screw on the underside before but was a
little scared to remove it till I knew what it was doing ). As for
there being a screw missing in the backing box I don't think so as that
is firmly attached to the wall. It is just the Honeywell box that
wobbles but I suppose I will find out why soon enough.

Not sure what a tundish is. A quick googling seems to indicate that it
is a see-through overflow check point. If it is then we don't have one
(well I've certainly not seen anything that matches that description and
I have had a good look). If you want more pictures I can get some.

There is a large copper pipe (22mm?) that runs down the outside wall to
ground level which I assume is the safety overflow. As some point in the
distant past it has has water down it but I certainly not in the last
couple of years (I suspect from when the system was being installed).

There are no drips or leaks from any of the valves so I assume
everything is working fine. Once in a while I have to top up the water
(where does the lost water go?) but other than that the plumbing seems
to work. I wouldn't be surprised if it was incorrectly installed though.
The previous owners of this place were cowboy magnets.

Thanks.

Graham

Aidan wrote:
doozer wrote:


As you can see the Honeywell timer box has been bodged to the wall;


There are, I think, screws underneath the Honeywell box. Loosening
these will allow the controller to swivelled forward away from the
backplate; pull the plug first since live terminals will be exposed.
You don't have to remove the screws. They are often lost by those who
do remove them, which may be why it's wobbly.


using a standard electrical box.


Probably only one fixing screw will be holding it.

(I believe unvented is the technical term)

It is. Get the installation & maintenance manual from the
Heatrae-Sadia website.

I do not think that the discharge pipes from the two safety valves
(Expansion relief [downstream of the pressure reducing valve] and the
Temperature & Pressure relief [in the cylinder]) have been done
correctly.

There should be a tundish (it could be behind the cardboard label).
There is a 15mm branch below the cardboard label going to the left; I
suspect this is the boiler safety valve discharge. It should have a
separate pipe.

Either one of the two safety valves on the unvented cylinder should be
able to discharge full-bore without causing a flood. You also need to
see is either of them is dripping or discharging, since this indicates
a fault that needs fixing.