Hi,

I'm having a problem with my central heating boiler, the safety cutoff
keeps 'popping' out when ever the room thermostat is *not* calling for
heat. Looking at my system I can see the flow feed from the boiler
passing through the pump (high speed setting), through two 'T'
piece's, and then the motorised valve (and onto the rads). The two
'T' pieces are for (I think) a) a loop circuit and b) to feed the hot
water storage tank. There are also two gate valves on these two
pipes.

Can anyone give me ideas on why my system keeps cutting out like this?

How open should the two valves be? Should the loop valve be more
closed than the others?

Thanks in advance

Danny

PS: I've just flushed the system completely, used cleanser for a
week, flushed twice, re-filled and treated with inhibiter.
Boiler does not cut out when the room thermostat is calling for heat

"Danny" wrote in message
om...
Hi,

I'm having a problem with my central heating boiler, the safety cutoff
keeps 'popping' out when ever the room thermostat is *not* calling for
heat. Looking at my system I can see the flow feed from the boiler
passing through the pump (high speed setting), through two 'T'
piece's, and then the motorised valve (and onto the rads). The two
'T' pieces are for (I think) a) a loop circuit and b) to feed the hot
water storage tank. There are also two gate valves on these two
pipes.

Can anyone give me ideas on why my system keeps cutting out like this?

How open should the two valves be? Should the loop valve be more
closed than the others?

Thanks in advance

Danny

PS: I've just flushed the system completely, used cleanser for a
week, flushed twice, re-filled and treated with inhibiter.
Boiler does not cut out when the room thermostat is calling for heat

When everything *stops* calling for heat, and the boiler burner shuts down,
the water needs to continue circulating for a little while. If this does not
happen, the residual heat in the metal parts of the water get transferred to
the static water inside - causing the temperature to rise to a point where
the safety cutout operates.

In order to prevent this, two conditions must be satisfied:
1. The pump must be controlled by the boiler - so that it goes on pumping
until the boiler has cooled down sufficiently
2. The water must have somewhere to go! If you have individual motorised
valves for central heating and hot water, there *must* be a by-pass circuit
to allow the water to circulate when both of these are closed. [If you have
a single 3-port valve, this is not usually a problem - since it can never
close both of its outlets at the same time].

The first thing to check is that the pump is wired correctly, so as to be
controlled by boiler, as described above.

Then - if you have separate motorised valves for CH and HW - identify the
by-pass circuit, which should short-circuit the boiler flow and return pipes
without going through any motorised valves or through the CH or HW circuits.
The by-pass may well have a gate valve to stop *all* the flow from going
straight back to the boiler without going through the CH or HW circuits. If
this gate valve is fully closed, you ain't got a working by-pass!

Start by opening it fully, and check that it cures the problem. Then close
it progressively in order to find the position where it is open as little as
possible without causing the boiler to trip.

HTH,
Roger

Hi Roger,

Thanks for the info. The pump runs for approx 10 minutes after the
boiler shuts down, I guess this means its wired correctly.

The two valves (one for HW tank, and the other for by-pass) were only
slightly cranked open. My concern for opening the by-pass valve fully
was that the water would simply travel the easiest path, thus reducing
the efficiency of the CH when the motorised valve is actually open.
However I take your point about opening it fully and workng backwards
to find the 'best' position.

With regards to the valve that regulates the water supply to the HW
tank, do you recommend that this be fully open also? Can adjusting
this vavle help to stop my boiler from short-cycling? (I think thats
the correct terminology!)

Regards,

Danny

"Roger Mills" wrote in message ...
"Danny" wrote in message
om...
Hi,

I'm having a problem with my central heating boiler, the safety cutoff
keeps 'popping' out when ever the room thermostat is *not* calling for
heat. Looking at my system I can see the flow feed from the boiler
passing through the pump (high speed setting), through two 'T'
piece's, and then the motorised valve (and onto the rads). The two
'T' pieces are for (I think) a) a loop circuit and b) to feed the hot
water storage tank. There are also two gate valves on these two
pipes.

Can anyone give me ideas on why my system keeps cutting out like this?

How open should the two valves be? Should the loop valve be more
closed than the others?

Thanks in advance

Danny

PS: I've just flushed the system completely, used cleanser for a
week, flushed twice, re-filled and treated with inhibiter.
Boiler does not cut out when the room thermostat is calling for heat

When everything *stops* calling for heat, and the boiler burner shuts down,
the water needs to continue circulating for a little while. If this does not
happen, the residual heat in the metal parts of the water get transferred to
the static water inside - causing the temperature to rise to a point where
the safety cutout operates.

In order to prevent this, two conditions must be satisfied:
1. The pump must be controlled by the boiler - so that it goes on pumping
until the boiler has cooled down sufficiently
2. The water must have somewhere to go! If you have individual motorised
valves for central heating and hot water, there *must* be a by-pass circuit
to allow the water to circulate when both of these are closed. [If you have
a single 3-port valve, this is not usually a problem - since it can never
close both of its outlets at the same time].

The first thing to check is that the pump is wired correctly, so as to be
controlled by boiler, as described above.

Then - if you have separate motorised valves for CH and HW - identify the
by-pass circuit, which should short-circuit the boiler flow and return pipes
without going through any motorised valves or through the CH or HW circuits.
The by-pass may well have a gate valve to stop *all* the flow from going
straight back to the boiler without going through the CH or HW circuits. If
this gate valve is fully closed, you ain't got a working by-pass!

Start by opening it fully, and check that it cures the problem. Then close
it progressively in order to find the position where it is open as little as
possible without causing the boiler to trip.

HTH,
Roger

"Danny" wrote in message
om...
Hi Roger,

Thanks for the info. The pump runs for approx 10 minutes after the
boiler shuts down, I guess this means its wired correctly.

The two valves (one for HW tank, and the other for by-pass) were only
slightly cranked open. My concern for opening the by-pass valve fully
was that the water would simply travel the easiest path, thus reducing
the efficiency of the CH when the motorised valve is actually open.
However I take your point about opening it fully and workng backwards
to find the 'best' position.

With regards to the valve that regulates the water supply to the HW
tank, do you recommend that this be fully open also? Can adjusting
this vavle help to stop my boiler from short-cycling? (I think thats
the correct terminology!)

Regards,

Danny

The valve on the HW circuit is there to balance the flow when the motorised
valves for CH and HW are both on - i.e. to make sure that most of the water
goes to the radiators. You need to find the right position for this, so that
the HW gets hot in a reasonable time without stopping the radiators heating
up quickly. I would experiment with positions around half open - or maybe a
bit less.

Assuming that the boiler only trips when both motorised valves are closed
(i.e. when CH and HW demands are both satisfied) the position of the manual
valve on the HW circuit won't affect this. It only comes into its own when
both motorised valves are open. [If the boiler trips when the HW is still
being heated, this valve definitely needs to be opened more].

Incidentally, "short-cycling" is something different - and not what I
believe you've got. Short cycling is when the boiler runs for a few seconds
at a time and then go off. And then comes on a bit later, and does it all
over again. AIUI, your problem is that the overheat stat trips - and has to
be re-set manually before the boiler will light again. Is this right?

Roger

Again Roger, thanks for all of your help.

Thats right, it only trips when the CH motorised valve is closed. I
fully opened the by-pass valve, with the CH circuit off, I noticed
that the water wasn't passing through the by-pass valve, massive
temperature difference on either side of the valve. I'm thinking that
this valve may be faulty and is stuck closed (it's not motorised),
should I replace this or is there another method of fix?

Regards

"Roger Mills" wrote in message ...
"Danny" wrote in message
om...
Hi Roger,

Thanks for the info. The pump runs for approx 10 minutes after the
boiler shuts down, I guess this means its wired correctly.

The two valves (one for HW tank, and the other for by-pass) were only
slightly cranked open. My concern for opening the by-pass valve fully
was that the water would simply travel the easiest path, thus reducing
the efficiency of the CH when the motorised valve is actually open.
However I take your point about opening it fully and workng backwards
to find the 'best' position.

With regards to the valve that regulates the water supply to the HW
tank, do you recommend that this be fully open also? Can adjusting
this vavle help to stop my boiler from short-cycling? (I think thats
the correct terminology!)

Regards,

Danny

The valve on the HW circuit is there to balance the flow when the motorised
valves for CH and HW are both on - i.e. to make sure that most of the water
goes to the radiators. You need to find the right position for this, so that
the HW gets hot in a reasonable time without stopping the radiators heating
up quickly. I would experiment with positions around half open - or maybe a
bit less.

Assuming that the boiler only trips when both motorised valves are closed
(i.e. when CH and HW demands are both satisfied) the position of the manual
valve on the HW circuit won't affect this. It only comes into its own when
both motorised valves are open. [If the boiler trips when the HW is still
being heated, this valve definitely needs to be opened more].

Incidentally, "short-cycling" is something different - and not what I
believe you've got. Short cycling is when the boiler runs for a few seconds
at a time and then go off. And then comes on a bit later, and does it all
over again. AIUI, your problem is that the overheat stat trips - and has to
be re-set manually before the boiler will light again. Is this right?

Roger

"Danny" wrote in message
om...
Again Roger, thanks for all of your help.

Thats right, it only trips when the CH motorised valve is closed. I
fully opened the by-pass valve, with the CH circuit off, I noticed
that the water wasn't passing through the by-pass valve, massive
temperature difference on either side of the valve. I'm thinking that
this valve may be faulty and is stuck closed (it's not motorised),
should I replace this or is there another method of fix?

Regards

Sounds like you need to replace the valve. You might consider using an
automatic by-pass valve - which only opens when a certain (adjustable)
pressure is reached, so that nothing goes through it when either or both CH
and HW circuits are operating. Screwfix do a suitable valve for about £25.

Roger

Thats right, it only trips when the CH motorised valve is closed. I
fully opened the by-pass valve, with the CH circuit off, I noticed
that the water wasn't passing through the by-pass valve, massive
temperature difference on either side of the valve.

Sounds knackered, just like most gate valves ten minutes after installation.
When you replace it, use an "Automatic Bypass Valve" instead of a gate
valve. This stays closed when the zone valves are open, but when they close,
it detects the pressure differential from the pump and opens fully. This
way, you get an effective bypass and no short circuit when the system is
actually working.

Christian.

Thanks for the advice. I will give the automatic by-pass valve a go
and let you know how I get on!

Again, thanks for Roger, Chrisian for all of your help

Regards,

Danny

"Christian McArdle" wrote in message et...
Thats right, it only trips when the CH motorised valve is closed. I
fully opened the by-pass valve, with the CH circuit off, I noticed
that the water wasn't passing through the by-pass valve, massive
temperature difference on either side of the valve.

Sounds knackered, just like most gate valves ten minutes after installation.
When you replace it, use an "Automatic Bypass Valve" instead of a gate
valve. This stays closed when the zone valves are open, but when they close,
it detects the pressure differential from the pump and opens fully. This
way, you get an effective bypass and no short circuit when the system is
actually working.

Christian.

I noticed that when I removed the gate valve, the pipe was completely
full of sludge - I would have thought the Fornox sludge remover would
have fixed this! Anyway I've clean the pipe as best as I could then
ran the pump on full. My system now gets to 65 degrees, a 15 degree
improvement!!!

Thanks for the advice!
(Danny) wrote in message . com...
Thanks for the advice. I will give the automatic by-pass valve a go
and let you know how I get on!

Again, thanks for Roger, Chrisian for all of your help

Regards,

Danny

"Christian McArdle" wrote in message et...
Thats right, it only trips when the CH motorised valve is closed. I
fully opened the by-pass valve, with the CH circuit off, I noticed
that the water wasn't passing through the by-pass valve, massive
temperature difference on either side of the valve.

Sounds knackered, just like most gate valves ten minutes after installation.
When you replace it, use an "Automatic Bypass Valve" instead of a gate
valve. This stays closed when the zone valves are open, but when they close,
it detects the pressure differential from the pump and opens fully. This
way, you get an effective bypass and no short circuit when the system is
actually working.

Christian.

On 22 Oct 2003 06:15:38 -0700, (Danny)
wrote:

I noticed that when I removed the gate valve, the pipe was completely
full of sludge - I would have thought the Fornox sludge remover would
have fixed this! Anyway I've clean the pipe as best as I could then
ran the pump on full. My system now gets to 65 degrees, a 15 degree
improvement!!!

Thanks for the advice!


If the system is as sludged as this, then a chemical sludge remover
won't make too much impact. There is, however, likely to be a
fairly low flow rate through the bypass, so it can be a collection
point for grot.

When you have some more time, you might want to try a more thorough
clean of the system by flushing the radiators separately - I've posted
on how to do this recently. If you can get rid of most of the sludge
mechanically - i.e. by flushing through with a hose, and then treat
the system with chemical sludge remover, you will get much better
results

Also, if you have gate valves, apart from the bypass which is best
with an automatic valve, it is worth replacing them with lever ball
valves. These shut off properly and easily and are much less
likely to seep.
..andy

To email, substitute .nospam with .gl

one problem after another! Now I'm back to my orginal problem, CH
valve shuts off, boiler cuts out! Interestingly enough though, when I
fully open the gate valve into the HW storage tank, turning the pump
on full speed, you can hear water rushing through, air being expelled,
and then gushing water into the FE tank? I've heard about
over-pumping (?) but why would this cause water to be expelled though
the FE tank this way? I would have thought that considering the pump
is sited after the pipe work leading to the FE tank (ie water is being
sucked rather than pumped) that the water would only flow up this pipe
if there were a blockage?



Andy Hall wrote in message . ..
On 22 Oct 2003 06:15:38 -0700, (Danny)
wrote:

I noticed that when I removed the gate valve, the pipe was completely
full of sludge - I would have thought the Fornox sludge remover would
have fixed this! Anyway I've clean the pipe as best as I could then
ran the pump on full. My system now gets to 65 degrees, a 15 degree
improvement!!!

Thanks for the advice!


If the system is as sludged as this, then a chemical sludge remover
won't make too much impact. There is, however, likely to be a
fairly low flow rate through the bypass, so it can be a collection
point for grot.

When you have some more time, you might want to try a more thorough
clean of the system by flushing the radiators separately - I've posted
on how to do this recently. If you can get rid of most of the sludge
mechanically - i.e. by flushing through with a hose, and then treat
the system with chemical sludge remover, you will get much better
results

Also, if you have gate valves, apart from the bypass which is best
with an automatic valve, it is worth replacing them with lever ball
valves. These shut off properly and easily and are much less
likely to seep.
.andy

To email, substitute .nospam with .gl

On 25 Oct 2003 10:54:56 -0700, (Danny)
wrote:

one problem after another! Now I'm back to my orginal problem, CH
valve shuts off, boiler cuts out! Interestingly enough though, when I
fully open the gate valve into the HW storage tank, turning the pump
on full speed, you can hear water rushing through, air being expelled,
and then gushing water into the FE tank? I've heard about
over-pumping (?) but why would this cause water to be expelled though
the FE tank this way?
I would have thought that considering the pump
is sited after the pipe work leading to the FE tank (ie water is being
sucked rather than pumped) that the water would only flow up this pipe
if there were a blockage?


If the feed pipe and the vent pipe are on opposite sides of the pump,
pumping over or sucking down of air will tend to occur depending on
which way round they are. This would in any case be a fault in the
design.

However, you can get the same effect if they are both on one side but
that there is a pressure differential between them - it doesn't have
to be very much.
This can happen if they are connected to points on the circuit that
are too far apart or if there is a flow restriction. Winding up
the pump speed will exacerbate this.

Based on what you've found at the bypass, I suspect that other parts
of the system are full of sludge as well......

I would suggest you drain the system and if you can undo a fitting
near the points that the feed and vent pipes join the system see if
there is more sludge, or take a look at a nearby radiator.

I'd be willing to bet that there is a lot of grot in the system.




..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
news
On 25 Oct 2003 10:54:56 -0700, (Danny)
wrote:

one problem after another! Now I'm back to my orginal problem, CH
valve shuts off, boiler cuts out! Interestingly enough though, when I
fully open the gate valve into the HW storage tank, turning the pump
on full speed, you can hear water rushing through, air being expelled,
and then gushing water into the FE tank? I've heard about
over-pumping (?) but why would this cause water to be expelled though
the FE tank this way?
I would have thought that considering the pump
is sited after the pipe work leading to the FE tank (ie water is being
sucked rather than pumped) that the water would only flow up this pipe
if there were a blockage?


If the feed pipe and the vent pipe are on opposite sides of the pump,
pumping over or sucking down of air will tend to occur depending on
which way round they are. This would in any case be a fault in the
design.

However, you can get the same effect if they are both on one side but
that there is a pressure differential between them - it doesn't have
to be very much.
This can happen if they are connected to points on the circuit that
are too far apart or if there is a flow restriction. Winding up
the pump speed will exacerbate this.

Based on what you've found at the bypass, I suspect that other parts
of the system are full of sludge as well......

I would suggest you drain the system and if you can undo a fitting
near the points that the feed and vent pipes join the system see if
there is more sludge, or take a look at a nearby radiator.

I'd be willing to bet that there is a lot of grot in the system.




.andy



Or it could be a leak from the coil in the HW tank.


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On Sat, 25 Oct 2003 20:01:56 GMT, "BigWallop"
wrote:





Or it could be a leak from the coil in the HW tank.



True, although generally those seem to start as small seeping with the
FE tank filling slowly and water through its overflow.........


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sat, 25 Oct 2003 20:01:56 GMT, "BigWallop"
wrote:





Or it could be a leak from the coil in the HW tank.



True, although generally those seem to start as small seeping with the
FE tank filling slowly and water through its overflow.........


.andy


That's the bit that's getting to me too. That's why I first thought of an
over heating problem, but turning the cylinder 'stat down didn't seem to
help. Others have also brought up an over speed on the pump, but adjusting
this also didn't help. Now it's just still a mystery. :-))

Hi Andy, I've followed your suggestions from other postings regardin
flushing the system, here's what I've done so far:

1. Drained system, noticed water was clean
2. Removed each rad and flushed through with hose pipe
3. Ruined a carpet in the process!
4. Removed pump, inspected, no sludge build-up
5. Checked by-pass circuit, no sludge build-up
6. Half filled system
7. Added heavy duty central heating restorer (sluge, scale remover)
8. Continued to fill, bleed system

Three days later I still have the same problem, the boiler keeps
popping off. The rads get hot really quickly so I don't think that
there is a circulation problem. The by-pass circuit is 15mm with an
isolater valve (b&q 74p!), again no sludge here.

To combat the problem so I can at least have some heat in the house I
have to open by-pass fully and open the 22mm gate valve feeding the HW
coil to 3/4 - full. but the rads don't get to full temp with this
config. I set the HW circuit to approx 1/4 open, rads getting piping
hot, room thermostat pops off, boiler safty cut-out soon follows!!

Could it be the boiler thermostat? If so, can I replace just the
thermostat, and approx how much are they?

BTW, temp of pipes is approx 65 degrees

Regards,

Danny

Andy Hall wrote in message . ..
On 25 Oct 2003 10:54:56 -0700, (Danny)
wrote:

one problem after another! Now I'm back to my orginal problem, CH
valve shuts off, boiler cuts out! Interestingly enough though, when I
fully open the gate valve into the HW storage tank, turning the pump
on full speed, you can hear water rushing through, air being expelled,
and then gushing water into the FE tank? I've heard about
over-pumping (?) but why would this cause water to be expelled though
the FE tank this way?
I would have thought that considering the pump
is sited after the pipe work leading to the FE tank (ie water is being
sucked rather than pumped) that the water would only flow up this pipe
if there were a blockage?


If the feed pipe and the vent pipe are on opposite sides of the pump,
pumping over or sucking down of air will tend to occur depending on
which way round they are. This would in any case be a fault in the
design.

However, you can get the same effect if they are both on one side but
that there is a pressure differential between them - it doesn't have
to be very much.
This can happen if they are connected to points on the circuit that
are too far apart or if there is a flow restriction. Winding up
the pump speed will exacerbate this.

Based on what you've found at the bypass, I suspect that other parts
of the system are full of sludge as well......

I would suggest you drain the system and if you can undo a fitting
near the points that the feed and vent pipes join the system see if
there is more sludge, or take a look at a nearby radiator.

I'd be willing to bet that there is a lot of grot in the system.




.andy

To email, substitute .nospam with .gl

On 3 Nov 2003 14:06:05 -0800, (Danny)
wrote:


To combat the problem so I can at least have some heat in the house I
have to open by-pass fully and open the 22mm gate valve feeding the HW
coil to 3/4 - full. but the rads don't get to full temp with this
config. I set the HW circuit to approx 1/4 open, rads getting piping
hot, room thermostat pops off, boiler safty cut-out soon follows!!

Could it be the boiler thermostat? If so, can I replace just the
thermostat, and approx how much are they?

It sounds like it could be and normally you can. Did you say which
boiler you have? If the thermostat is one of the capillary type then
it is pretty easy to replace - push on connectors normally.
I replaced one on a Glow Worm about two years ago and IIRC the
replacement was about £30.

If you have a boiler with electronic controls, then Geoff at CET is
your man - his company reconditions them.





BTW, temp of pipes is approx 65 degrees

Do you mean flow or return? 65 on a return is within spitting
distance but on a flow is too low. If anything, you should be
closing the bypass to encourage more water around the heating circuit.

Have you checked the diverter or other motorised valves? Does the
situation improve with higher pump speed?

If the boiler has good flow and is cutting out with a flow of 65
degrees then evidence does point to the thermostat or possibly an over
temperature sensor.





Regards,

Danny


..andy

To email, substitute .nospam with .gl

The temp is 65 degrees on the flow pipe. I've tried closing the
by-pass completely and opening the HW circuit fully, hoping that the
HW circuit will act as a by-pass.

If I put the pump on full speed then water begins to flow into the FE
tank - quite alot too. I have to keep the pump on medium to avoid
this and also ensure that by-pass and HW coil are not both fully open
(if they are water still comes out of the FE tank, but just a trickle)

How do I check the motorised valve? When the room thermostat calls
for heat I can hear the MV opening so I assumed that it works.

Is the boiler thermostat something that I (a novice) could do? Do I
have to be corgi registered or something?

Thanks

Andy Hall wrote in message . ..
On 3 Nov 2003 14:06:05 -0800, (Danny)
wrote:


To combat the problem so I can at least have some heat in the house I
have to open by-pass fully and open the 22mm gate valve feeding the HW
coil to 3/4 - full. but the rads don't get to full temp with this
config. I set the HW circuit to approx 1/4 open, rads getting piping
hot, room thermostat pops off, boiler safty cut-out soon follows!!

Could it be the boiler thermostat? If so, can I replace just the
thermostat, and approx how much are they?

It sounds like it could be and normally you can. Did you say which
boiler you have? If the thermostat is one of the capillary type then
it is pretty easy to replace - push on connectors normally.
I replaced one on a Glow Worm about two years ago and IIRC the
replacement was about £30.

If you have a boiler with electronic controls, then Geoff at CET is
your man - his company reconditions them.





BTW, temp of pipes is approx 65 degrees

Do you mean flow or return? 65 on a return is within spitting
distance but on a flow is too low. If anything, you should be
closing the bypass to encourage more water around the heating circuit.

Have you checked the diverter or other motorised valves? Does the
situation improve with higher pump speed?

If the boiler has good flow and is cutting out with a flow of 65
degrees then evidence does point to the thermostat or possibly an over
temperature sensor.





Regards,

Danny


.andy

To email, substitute .nospam with .gl

On 4 Nov 2003 00:20:16 -0800, (Danny)
wrote:

The temp is 65 degrees on the flow pipe. I've tried closing the
by-pass completely and opening the HW circuit fully, hoping that the
HW circuit will act as a by-pass.

If I put the pump on full speed then water begins to flow into the FE
tank - quite alot too. I have to keep the pump on medium to avoid
this and also ensure that by-pass and HW coil are not both fully open
(if they are water still comes out of the FE tank, but just a trickle)

OK. There are a few possible reasons for pumping over in this way.
However, the root cause is the same, which is that there is a large
enough pressure differential between the feed pipe at the bottom of
the FE tank and the vent pipe over it. The pressure difference
doesn't need to be a lot for this to happen - perhaps as little as
30cm of head. THe problem either manifests itself as pumping over or
sucking down of air, depending on which way round the differential is.
It is bad for this to be happening because it introduces air into the
system and that is an enabler for corrosion.

This can happen because:

- The pipes are connected to the system on opposite sides of the pump.
This one is a real mistake of installation and should never happen.
If the pipework is like that it really needs to be corrected.

- The pipes are on the same side of the pump but there is a pressure
differential between them. This could be the boiler or it could
simply be that they are connected to points too far apart on the
system pipework. It could also be because there is a part
obstruction of some kind between the two places.

Could you trace where they are connected and then post back approx
distances between the major items of the system - e.g. boiler, pump,
motorised valve(s), points where feed pipe and vent pipe are
connected. It's useful to use ASCII art for this to make a simple
diagram, or perhaps you could sketch one and put it on a web server?
It's really to be able to see the layout more than anything else.

As I say, this problem should be fixed but I would deal with it if
necessary after resolving the temperature issue. For diagnosis
purposes of this, it doesn't matter if there is pumping over for a
short while. One solution can be simply to have the pump on the
lowest speed, but that may then not be fast enough to run the system
properly. The issue is that heat transfer rate from the boiler
depends on pump speed. However, if the pump speed is too low for the
system requirement, the effect would be that the boiler flow will get
hot - up to 80 degrees+, as will the flow side of the radiators, but
the return side of the radiators will be relatively cool and the
boiler will tend to cycle on and off - simply because you are not
getting the heat away fast enough.



How do I check the motorised valve? When the room thermostat calls
for heat I can hear the MV opening so I assumed that it works.

OK. You can check its movement by operating the manual lever on the
side. You can also take the head off and turn the valve stem
underneath by hand to see that it is reasonably free. These valves
have either a paddle or a rubber ball inside which is rotated to block
and open the ports as required. I did have one once where some crud
from the original installation (a piece of wood) had found its way
around the system and lodged against the ball, partly blocking the
flow. I would just do a simple check for rotation at this point.
You can also take the cover off of the valve head and watch the
mechanism working. If there is any obstruction or stiffness you will
tend to hear it from the motor and their may be the sound of gears
jumping. However, I don't think that the valve is likely to be No.1
contender at this point, from what you describe.


Is the boiler thermostat something that I (a novice) could do? Do I
have to be corgi registered or something?

The law, in the form of the Gas Safety (Installation and Use)
Regulations, 1998, states (section 3) that you have to be "competent"
to work on gas fittings. It doesn't define "competent", but does
require self employed and employed fitters and businesses (in effect)
to be CORGI registered. There is a definition of "fittings" (gas
carrying parts) and "appliances". If you read through the document

http://www.hmso.gov.uk/si/si1998/19982451.htm

Part E talks about work on gas appliances.

Changing a thermostat should not involve doing anything with gas
carrying parts such as the burner, gas valve, etc. If the boiler
is a simple one with a capillary tube and bulb on the heat exchanger
or flow pipe, it is a relatively simple job to change it. Normally
the control itself, behind the knob, has 4-6 wires with spade tags
that push on. The main point here is to label everything........
There are the obvious points about making sure that any parts removed
are properly refitted, all seals are in place etc. etc.

The acid test is really whether you are "competent". If you don't
feel 100% sure about what you are doing, then it is better to involve
a registered fitter.


..andy

To email, substitute .nospam with .gl

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Andy Hall wrote in message . ..
On 4 Nov 2003 00:20:16 -0800, (Danny)
wrote:

The temp is 65 degrees on the flow pipe. I've tried closing the
by-pass completely and opening the HW circuit fully, hoping that the
HW circuit will act as a by-pass.

If I put the pump on full speed then water begins to flow into the FE
tank - quite alot too. I have to keep the pump on medium to avoid
this and also ensure that by-pass and HW coil are not both fully open
(if they are water still comes out of the FE tank, but just a trickle)

OK. There are a few possible reasons for pumping over in this way.
However, the root cause is the same, which is that there is a large
enough pressure differential between the feed pipe at the bottom of
the FE tank and the vent pipe over it. The pressure difference
doesn't need to be a lot for this to happen - perhaps as little as
30cm of head. THe problem either manifests itself as pumping over or
sucking down of air, depending on which way round the differential is.
It is bad for this to be happening because it introduces air into the
system and that is an enabler for corrosion.

This can happen because:

- The pipes are connected to the system on opposite sides of the pump.
This one is a real mistake of installation and should never happen.
If the pipework is like that it really needs to be corrected.

- The pipes are on the same side of the pump but there is a pressure
differential between them. This could be the boiler or it could
simply be that they are connected to points too far apart on the
system pipework. It could also be because there is a part
obstruction of some kind between the two places.

Could you trace where they are connected and then post back approx
distances between the major items of the system - e.g. boiler, pump,
motorised valve(s), points where feed pipe and vent pipe are
connected. It's useful to use ASCII art for this to make a simple
diagram, or perhaps you could sketch one and put it on a web server?
It's really to be able to see the layout more than anything else.

As I say, this problem should be fixed but I would deal with it if
necessary after resolving the temperature issue. For diagnosis
purposes of this, it doesn't matter if there is pumping over for a
short while. One solution can be simply to have the pump on the
lowest speed, but that may then not be fast enough to run the system
properly. The issue is that heat transfer rate from the boiler
depends on pump speed. However, if the pump speed is too low for the
system requirement, the effect would be that the boiler flow will get
hot - up to 80 degrees+, as will the flow side of the radiators, but
the return side of the radiators will be relatively cool and the
boiler will tend to cycle on and off - simply because you are not
getting the heat away fast enough.



How do I check the motorised valve? When the room thermostat calls
for heat I can hear the MV opening so I assumed that it works.

OK. You can check its movement by operating the manual lever on the
side. You can also take the head off and turn the valve stem
underneath by hand to see that it is reasonably free. These valves
have either a paddle or a rubber ball inside which is rotated to block
and open the ports as required. I did have one once where some crud
from the original installation (a piece of wood) had found its way
around the system and lodged against the ball, partly blocking the
flow. I would just do a simple check for rotation at this point.
You can also take the cover off of the valve head and watch the
mechanism working. If there is any obstruction or stiffness you will
tend to hear it from the motor and their may be the sound of gears
jumping. However, I don't think that the valve is likely to be No.1
contender at this point, from what you describe.


Is the boiler thermostat something that I (a novice) could do? Do I
have to be corgi registered or something?

The law, in the form of the Gas Safety (Installation and Use)
Regulations, 1998, states (section 3) that you have to be "competent"
to work on gas fittings. It doesn't define "competent", but does
require self employed and employed fitters and businesses (in effect)
to be CORGI registered. There is a definition of "fittings" (gas
carrying parts) and "appliances". If you read through the document

http://www.hmso.gov.uk/si/si1998/19982451.htm

Part E talks about work on gas appliances.

Changing a thermostat should not involve doing anything with gas
carrying parts such as the burner, gas valve, etc. If the boiler
is a simple one with a capillary tube and bulb on the heat exchanger
or flow pipe, it is a relatively simple job to change it. Normally
the control itself, behind the knob, has 4-6 wires with spade tags
that push on. The main point here is to label everything........
There are the obvious points about making sure that any parts removed
are properly refitted, all seals are in place etc. etc.

The acid test is really whether you are "competent". If you don't
feel 100% sure about what you are doing, then it is better to involve
a registered fitter.


.andy

To email, substitute .nospam with .gl

On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


..andy

To email, substitute .nospam with .gl

opps sorry, its

http://dognet.no-ip.com/ch.jpg



Andy Hall wrote in message . ..
On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


.andy

To email, substitute .nospam with .gl

Opp sorry, it should have been

http://dognet.no-ip.com/ch.jpg

Regards,


Andy Hall wrote in message . ..
On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


.andy

To email, substitute .nospam with .gl

On 5 Nov 2003 00:40:50 -0800, (Danny)
wrote:

opps sorry, its

http://dognet.no-ip.com/ch.jpg




Hmm.....

This doesn't seem to be quite as I'd expect.

Are you saying that the two pipes to the FE tank are 3" apart on the
flow pipe coming from the boiler? i.e. the amount of flow pipe between
the branches is only 3"? Normally if the distance between these two
pipes is less than about 6", and there is nothing other than pipe
between them, there should not be pumping over......

Are you sure about the arrangement of where the motorised valve is
located? This doesn't seem right somehow because there is then
nothing to control the operation of the hot water. Is there a
thermostat on the cylinder?

Also, can you indicate where the return pipe from the CH
connects......

There are certainly a few funnies that ought to be corrected and
improved (e.g. putting in a diverter valve or zone valve for the HW
and better controls). However, I can't see anything that obviously
leads to low temperatures from the boiler. Short cycling where the
boiler comes on for a very short time and then off, would be a symptom
of poor flow or something related to it. However, if the boiler
runs for several minutes and then turns off with its internal
thermostat, it is most likely that the thermostat is the culprit. Is
the thermostat set to full, and is the temperature of the flow less if
you reduce it?

Would others like to comment here?




..andy

To email, substitute .nospam with .gl

Yes the pipe is approx 3 inchs apart, with nothing but pipe between
them. The position of the motorised valve is correct, I assume the
gate valve located prior to the inlet on the HW coil was to control
the temperature inside the HW tank by restricting the water flow. The
HW tank also has an emersion heater (switched off at present) and a
thermostat located on top - this is set to 60 degrees


I'm not sure where the return pipe from the central heating connects -
I can't get to them without lifting half of my upstairs floor up!

The boiler thermostat is set to half way, because on anything more
cause the boiler to pop off. I was thinking that I may have sludge in
my boiler - but the fact that the rads get hot really quick tells me
that the water circulation in my system is good, ie, not blocked. But
the overflow of water into the FE tank leads me to think that the pipe
on the flow from the boiler is blocked just after the pipe which hangs
over the FE tank. Any comments on this?

What is a zone valve, and what are the controls to make my HW
connections more efficient?

Regards,



(Danny) wrote in message . com...
Opp sorry, it should have been

http://dognet.no-ip.com/ch.jpg

Regards,


Andy Hall wrote in message . ..
On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


.andy

To email, substitute .nospam with .gl

What is a zone valve, and what are the controls to make my HW
connections more efficient?

There should be a zone valve capable of shutting off the hot water flow
through the cylinder coil. This valve would be wired to open only when (a)
the programmer told you to heat the water and (b) the cylinder thermostat
said the cylinder wasn't hot.

You say there is a thermostat "on top". Normally the cylinder thermostat is
between the bottom and halfway up (but higher than the bottom coil tapping).
Are you sure the thermostat you mention isn't part of the immersion heater?

Christian.

"Danny" wrote in message
om...
The
HW tank also has an emersion heater (switched off at present) and a
thermostat located on top - this is set to 60 degrees

This is almost certainly the stat which controls the immersion heater - when
it is switched on - and is thus not doing anything useful at the moment.



What is a zone valve, and what are the controls to make my HW
connections more efficient?


"Zone valve" is a generic term for any automatically operated on/off valve
which controls the flow to different parts - or zones - of the system.

You appear already to have one for the heating circuit - controlled by a
room stat.

You need to add another one into the hot water circuit, and to control it by
a stat strapped to the cylinder. Each of these valves should have a
independent pair of contacts which close when the valve is fully open. These
need to be wired up to control the boiler and pump - so that they only come
on when the demand in either or both circuit is unsatisfied. This saves a
lot of energy otherwise wasted making the hot water unnecessarily hot and
keeping the boiler warm when it's not needed.

You'll see how this all works if you look at the S-Plan details in
http://content.honeywell.com/uk/homes/systems.htm

Roger

On 5 Nov 2003 06:56:40 -0800, (Danny)
wrote:

Yes the pipe is approx 3 inchs apart, with nothing but pipe between
them. The position of the motorised valve is correct, I assume the
gate valve located prior to the inlet on the HW coil was to control
the temperature inside the HW tank by restricting the water flow.

Probably, but it's a poor way to do it because there is no control to
prevent the tank from overheating when the CH is running.



The
HW tank also has an emersion heater (switched off at present) and a
thermostat located on top - this is set to 60 degrees


I'm not sure where the return pipe from the central heating connects -
I can't get to them without lifting half of my upstairs floor up!

OK, then I think we have to assume that it does the obvious thing and
rejoins the return after the cylinder.



The boiler thermostat is set to half way, because on anything more
cause the boiler to pop off.


What boiler is it BTW.?



I was thinking that I may have sludge in
my boiler - but the fact that the rads get hot really quick tells me
that the water circulation in my system is good, ie, not blocked.

Not necessarily. It can be that the heat exchanger is badly sludged
but allows some water through. Generally, when this happens, the
boiler sings or bumps when the burner is firing, or as in your case
the safety cut out operates.

But
the overflow of water into the FE tank leads me to think that the pipe
on the flow from the boiler is blocked just after the pipe which hangs
over the FE tank. Any comments on this?

Well it starts to look like it but I just looked back through the
symptoms in the whole thread.

I think forget the thermostat for the moment - the safety cut out is
operating for a reason. Either it's faulty or the water flow is not
what you think and there is localised heating when the burner fires.

Given this situation, I would focus next on making sure that the heat
exchanger really is clean. Since you already said that you had
sludging in the bypass and elsewhere, I am thinking that this is the
next area to look and I would do that before buying spare thermostats
and cutouts.



What is a zone valve, and what are the controls to make my HW
connections more efficient?

It would be a two port motorised valve similar to the CH one, operated
by a thermostat on the cylinder. You then need to have appropriate
wiring with the boiler, pump and timer to hook it all together. I
would expect that the current setup that you have is very simply
wired. Have a look at the Honeywell web site and S-plan
configuration for two valves, or Y plan if you would prefer a single
divert valve. I wouldn't bother with this until the boiler issue is
resolved, though.







Regards,



(Danny) wrote in message . com...
Opp sorry, it should have been

http://dognet.no-ip.com/ch.jpg

Regards,


Andy Hall wrote in message . ..
On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


.andy

To email, substitute .nospam with .gl

..andy

To email, substitute .nospam with .gl

I guess the thermostat that I've mentioned is for the immersion heater.



"Christian McArdle" wrote in message et...
What is a zone valve, and what are the controls to make my HW
connections more efficient?

There should be a zone valve capable of shutting off the hot water flow
through the cylinder coil. This valve would be wired to open only when (a)
the programmer told you to heat the water and (b) the cylinder thermostat
said the cylinder wasn't hot.

You say there is a thermostat "on top". Normally the cylinder thermostat is
between the bottom and halfway up (but higher than the bottom coil tapping).
Are you sure the thermostat you mention isn't part of the immersion heater?

Christian.

On Tue, 04 Nov 2003 00:20:16 +0000, Danny wrote:

The temp is 65 degrees on the flow pipe. I've tried closing the
by-pass completely and opening the HW circuit fully, hoping that the
HW circuit will act as a by-pass.

If I put the pump on full speed then water begins to flow into the FE
tank - quite alot too. I have to keep the pump on medium to avoid
this and also ensure that by-pass and HW coil are not both fully open
(if they are water still comes out of the FE tank, but just a trickle)

How do I check the motorised valve? When the room thermostat calls
for heat I can hear the MV opening so I assumed that it works.

Is the boiler thermostat something that I (a novice) could do? Do I
have to be corgi registered or something?

Sounds like any of the following:

1) Over sensitive over-heat cut out. This should operate around 85C + not
65C.
2) Pump over run thermostat faulty - followed by temporary overheating in
the boiler.

It can't be the main thermostat 65 for a middling setting is just fine.
Sounds like the general health of the system is other wise OK.

I doubt whatever the boiler is that the parts to fix this will be over 20
quid.
This is about as difficult as delving into the washing machine it all
depends on your level of experience with dealing with electrical
appliances repairs.

HTH

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

OK, I think we're making good progress here. Any suggestions on the
best/simplest way to 'flush' through the boiler so as I can clear it
of any sludge, hot spots?

My main concern is getting the boiler to stay on, thereafter I'll
focus on making the system more economical to run - the thermostat on
the cylinder and use of zone valves is really good - I was actually
wondering if I would have scale build up in my HW tank given the fact
that the HW would actually heat above the recommended 60 degrees, I
guess this has been answered!

My boiler is a Glowworm Ultimate 60F

How important is the clearance surrounding the boiler?

Andy Hall wrote in message . ..
On 5 Nov 2003 06:56:40 -0800, (Danny)
wrote:

Yes the pipe is approx 3 inchs apart, with nothing but pipe between
them. The position of the motorised valve is correct, I assume the
gate valve located prior to the inlet on the HW coil was to control
the temperature inside the HW tank by restricting the water flow.

Probably, but it's a poor way to do it because there is no control to
prevent the tank from overheating when the CH is running.



The
HW tank also has an emersion heater (switched off at present) and a
thermostat located on top - this is set to 60 degrees


I'm not sure where the return pipe from the central heating connects -
I can't get to them without lifting half of my upstairs floor up!

OK, then I think we have to assume that it does the obvious thing and
rejoins the return after the cylinder.



The boiler thermostat is set to half way, because on anything more
cause the boiler to pop off.


What boiler is it BTW.?



I was thinking that I may have sludge in
my boiler - but the fact that the rads get hot really quick tells me
that the water circulation in my system is good, ie, not blocked.

Not necessarily. It can be that the heat exchanger is badly sludged
but allows some water through. Generally, when this happens, the
boiler sings or bumps when the burner is firing, or as in your case
the safety cut out operates.

But
the overflow of water into the FE tank leads me to think that the pipe
on the flow from the boiler is blocked just after the pipe which hangs
over the FE tank. Any comments on this?

Well it starts to look like it but I just looked back through the
symptoms in the whole thread.

I think forget the thermostat for the moment - the safety cut out is
operating for a reason. Either it's faulty or the water flow is not
what you think and there is localised heating when the burner fires.

Given this situation, I would focus next on making sure that the heat
exchanger really is clean. Since you already said that you had
sludging in the bypass and elsewhere, I am thinking that this is the
next area to look and I would do that before buying spare thermostats
and cutouts.



What is a zone valve, and what are the controls to make my HW
connections more efficient?

It would be a two port motorised valve similar to the CH one, operated
by a thermostat on the cylinder. You then need to have appropriate
wiring with the boiler, pump and timer to hook it all together. I
would expect that the current setup that you have is very simply
wired. Have a look at the Honeywell web site and S-plan
configuration for two valves, or Y plan if you would prefer a single
divert valve. I wouldn't bother with this until the boiler issue is
resolved, though.







Regards,



(Danny) wrote in message . com...
Opp sorry, it should have been

http://dognet.no-ip.com/ch.jpg

Regards,


Andy Hall wrote in message . ..
On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


.andy

To email, substitute .nospam with .gl

.andy

To email, substitute .nospam with .gl

On Wed, 05 Nov 2003 09:33:48 +0000, Andy Hall wrote:

On 5 Nov 2003 00:40:50 -0800, (Danny)
wrote:

opps sorry, its

http://dognet.no-ip.com/ch.jpg




Hmm.....

This doesn't seem to be quite as I'd expect.

Are you saying that the two pipes to the FE tank are 3" apart on the
flow pipe coming from the boiler? i.e. the amount of flow pipe between
the branches is only 3"? Normally if the distance between these two
pipes is less than about 6", and there is nothing other than pipe
between them, there should not be pumping over......

Are you sure about the arrangement of where the motorised valve is
located? This doesn't seem right somehow because there is then
nothing to control the operation of the hot water. Is there a
thermostat on the cylinder?

Also, can you indicate where the return pipe from the CH
connects......

There are certainly a few funnies that ought to be corrected and
improved (e.g. putting in a diverter valve or zone valve for the HW
and better controls). However, I can't see anything that obviously
leads to low temperatures from the boiler. Short cycling where the
boiler comes on for a very short time and then off, would be a symptom
of poor flow or something related to it. However, if the boiler
runs for several minutes and then turns off with its internal
thermostat, it is most likely that the thermostat is the culprit. Is
the thermostat set to full, and is the temperature of the flow less if
you reduce it?

Would others like to comment here?


This looks like a very typical arrangement for an older system and
correctly laid out.
It does not have fully independant control of CH and HW and HW temperture
is set by the boiler's thermostat.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

The pump does infact over run - but only when the boiler thermostat is
set to maximum (this is correct as per the boiler instructions)

I've priced up a new over-heat thermostat, I might try this option -
it doesn't seem too difficult to install


"Ed Sirett" wrote in message on.co.uk...
On Tue, 04 Nov 2003 00:20:16 +0000, Danny wrote:

The temp is 65 degrees on the flow pipe. I've tried closing the
by-pass completely and opening the HW circuit fully, hoping that the
HW circuit will act as a by-pass.

If I put the pump on full speed then water begins to flow into the FE
tank - quite alot too. I have to keep the pump on medium to avoid
this and also ensure that by-pass and HW coil are not both fully open
(if they are water still comes out of the FE tank, but just a trickle)

How do I check the motorised valve? When the room thermostat calls
for heat I can hear the MV opening so I assumed that it works.

Is the boiler thermostat something that I (a novice) could do? Do I
have to be corgi registered or something?

Sounds like any of the following:

1) Over sensitive over-heat cut out. This should operate around 85C + not
65C.
2) Pump over run thermostat faulty - followed by temporary overheating in
the boiler.

It can't be the main thermostat 65 for a middling setting is just fine.
Sounds like the general health of the system is other wise OK.

I doubt whatever the boiler is that the parts to fix this will be over 20
quid.
This is about as difficult as delving into the washing machine it all
depends on your level of experience with dealing with electrical
appliances repairs.

HTH

"Danny" wrote in message
om...
The pump does infact over run - but only when the boiler thermostat is
set to maximum (this is correct as per the boiler instructions)

I've priced up a new over-heat thermostat, I might try this option -
it doesn't seem too difficult to install



Most boilers today are designed around the aptitude of a
Monkey.....Sorry.....British Gas engineer, so the parts have to be easy to
replace or BG wouldn't have any engineers that are able to this type of
work.

Owww !!! That's better. Just had to get that off my chest after arguing
with one their towrags on the phone. :-))


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What is the best way of making sure that the heat exchange is clean?
(sorry if this should be way too obvious!)


Well it starts to look like it but I just looked back through the
symptoms in the whole thread.

I think forget the thermostat for the moment - the safety cut out is
operating for a reason. Either it's faulty or the water flow is not
what you think and there is localised heating when the burner fires.

Given this situation, I would focus next on making sure that the heat
exchanger really is clean. Since you already said that you had
sludging in the bypass and elsewhere, I am thinking that this is the
next area to look and I would do that before buying spare thermostats
and cutouts.



What is a zone valve, and what are the controls to make my HW
connections more efficient?

It would be a two port motorised valve similar to the CH one, operated
by a thermostat on the cylinder. You then need to have appropriate
wiring with the boiler, pump and timer to hook it all together. I
would expect that the current setup that you have is very simply
wired. Have a look at the Honeywell web site and S-plan
configuration for two valves, or Y plan if you would prefer a single
divert valve. I wouldn't bother with this until the boiler issue is
resolved, though.







Regards,



(Danny) wrote in message . com...
Opp sorry, it should have been

http://dognet.no-ip.com/ch.jpg

Regards,


Andy Hall wrote in message . ..
On 4 Nov 2003 13:13:02 -0800, (Danny)
wrote:

Hi Andy,

I've sketched a diagram using word, its not too clevor but I'm sure
you'll see how my system is setup.

Visit http://dognet.no-io.com/ch.jpg

My boiler is just a standard traditional one

I've located the manual lever on the motorised valve and operated this
whilst the cover was removed, it sounded free from obstruction, the
cogs inside were turning. However when I let go the vavle returned to
the starting position and then a small amount of water came out of the
FE tank. Is this relevant to your diagnosis?

Regards,


Danny, is the URL correct? I am not getting this as a site that
exists (no domain name).......


.andy

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.andy

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On 7 Nov 2003 10:44:33 -0800, (Danny)
wrote:

What is the best way of making sure that the heat exchange is clean?
(sorry if this should be way too obvious!)



Flush it through very thoroughly.


..andy

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