I know I am talking to myself but I think I have just figured out what
happens if the HW tank looses it's bubble. Ever since we got the house
the HW tap in the kitchen has dripped when the hot water is turned on
and we get a burst of hot water the first time we turn the tap on. As it
has always been like that I assumed that was how it was supposed to be
but thinking about it it probably means that there is little or no
bubble left to take up the expansion of the HW. Re-reading the
instructions on the side of the HW tank I think I have labelled the
temperature and pressure relief valve wrongly and it should be the valve
directly above the tundish on the side of the HW cylinder.
Many thanks for all your help. It's really appreciated.
Graham
doozer wrote:
Hmmm, I'm a little concerned now. I have taken another photograph and
labelled it up with what I think each bit is. Could you take a look at
it and tell me if it's correct? If it's any help this system was
installed about 10 years ago. I think I have found the tundish. As a
previous poster suggested it was hiding behind a piece of card. I am
hanging my head in shame for missing that before 
).
If you are on a dial up this is a full size picture of about 650KB
http://www.crazysquirrel.com/images/heating/5.jpg
Is it normal to have what we have which is basically just a cut out bit
of pipe for a tundish? Surely that would cause water to flood out all
over the floor rather than down the emergency vent pipe if there was a
problem. As you can see there is a tiny bit of water staining around the
tundish hole but it is dry now and it looks like it has been dry for a
long time.
so any water coming out of the expansion valve indicates a fualt
There is no water coming out what I have marked as the expansion valve.
As you can see from the picture at some point it looks like water has
come out of the multifunction control valve but it has looked like that
since we got the house so whatever caused that crusty build up happened
at least 18 months ago.
If the user thermostat and also the overheat thermostat fail
your next line of defence is the tpr valve. The discharge pipe d1 from
this should also drop to the tundish.
What I have marked as the D1 (Expansion Vessel) doesn't run to the
tundish but it does go to the outside world.
It is OK for the two d1's to join before the tundish.
I am pretty sure they join after the tundish.
the discharge pipe after the tundish d2 has be one
pipe size larger than d1, and must drop straight down 300mm before the
first bend, then gradually all the way to the exit.
The D2 is certainly at least one size bigger. The drop from the tundish
to the D2 join is about 300mm I would guess. The drop from the top of
the expansion vessel to the D2 is probably 300mm but it is in a smaller
bore pipe (the drop is hidden behind the door frame on the left in the
picture).
but that you won't get scalded by any discharge
Any discharge from the tundish will come straight out at us. Brill.
There is a zone valve for the central heating connection to the
cylinder
I could tell which this part was. But I'm glad we have one )
What would be the effect of having no bubble? I haven't done anything
about the bubble as the hot water system works. Wait, don't tell, me no
bubble could result in a catastrophic failure ). What I wouldn't give
for a nice simple vented system right now.
What I have marked as the immersion heater I only assume is an immersion
heater as we don't have a switch or anything to turn on an electric
immersion heater.
I would recommend you have it checked by a qualified person.
As soon as we have the money I will get a decent plumber in to have a
look at it.
Paul Barker wrote:
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.
Yes I too am a little worried, because the quality of installation
doesn't look like it was done by a person with an unvented certificate.
I am also conscerned that I can't clearly see the tundish.
The item to the left with a large black knob on is your Multifunction
control valve, this has a number of duties, it prevents back flow to
the water mains, filters incoming water and sets a maximum pressure. To
the right of that a much smaller device usually in blue with a number 8
on the front is your expansion valve. In Europe it is normal to allow
for expansion of the water as it heats to simply eject from the
expansion valve. In the water conservation conscious UK we allow for
expansion with either a bubble top or an expansion vessel, so any water
coming out of the expansion valve indicates a fualt. Deepending how and
when there are different causes behind that fualt. The output pipe of
this valve is called D1 and it should fall towards a visible break in
the pipework where you could view the water rushing through (or just
dripping) this visible thing is called a tundish. The connection at the
top right of your cylinder is called a temperature and pressure relief
valve. If the user thermostat and also the overheat thermostat fail
your next line of defence is the tpr valve. The discharge pipe d1 from
this should also drop to the tundish. It is OK for the two d1's to join
before the tundish. the discharge pipe after the tundish d2 has be one
pipe size larger than d1, and must drop straight down 300mm before the
first bend, then gradually all the way to the exit. The size of d1 and
d2 depend on distances and have to be calculated. The position of the
tundish should be such that you can tell what is going on, but that you
won't get scalded by any discharge, it is acceptable to put them to the
side of the cylinder not right in your face, but they shouldn't be
hidden behind it. Your tundish could well be behind that tag on the
right.
There is a zone valve for the central heating connection to the
cylinder, which is correct. This fails shut in the evnt of a power cut
which is the right thing.
I won't carry on about the position of the discharge pipe and so on, it
gets more involved.
The bubble in this type of cylinder naturally becomes smaller until it
is ineffective, but it is very easy to reform. The instructions are on
the side of the tank. In a nutshell, shut of the cold water supply,
switch off all forms of heating, open the nearest hot tap and hold open
manually the tpr valve until all gurgling stops, this could take some
time. Then let go the tpr valve, shut the tap and turn on the water
supply. The bubble will naturally form.
IF YOU EVER SENSE ANY KIND OF DANGER you must A/ turn off all heating
sources, i.e. central heating and or immersion heater/s. B/ Open a hot
tap. C/ turn off the cold supply to the cylinder. Everything will
settle down after that, get an expert in.
When water is under pressure the boiling point is much higher. If any
part of the integrity of that vessel or directly connected controls
should fail water under pressure would on changing to atmospheric
pressure flash over to steam. There is enough power in that flash over
from water to steam to blow your house out of the ground.
This particular cylinder is extremely safe and ruggedly constructed,
all the necessary controls are designed into the fitting kit to prevent
such an event occuring. But you should know it is not something to take
lightly. I would recommend you have it checked by a qualified person.