Hi All,

I have a Y-plan heating system with a Honeywell mid position valve of
indeterminate age. Lately, I've noticed that, on cold mornings when
the heating is working hard, the domestic hot water becomes much
hotter than normal (I have the cylinder stat set quite low). From
fiddling with the thermostats and feeling pipes, It seems that the
valve isn't able to completely close off either the CH or the HW. It
goes most of the way, but the "closed" leg still has a small flow.

Is this normal, or should I be able to get a total shut-off in both
directions?

Thanks in advance,

Colin.

Colin Stamp laid this down on his screen :
Hi All,

I have a Y-plan heating system with a Honeywell mid position valve of
indeterminate age. Lately, I've noticed that, on cold mornings when
the heating is working hard, the domestic hot water becomes much
hotter than normal (I have the cylinder stat set quite low). From
fiddling with the thermostats and feeling pipes, It seems that the
valve isn't able to completely close off either the CH or the HW. It
goes most of the way, but the "closed" leg still has a small flow.

Is this normal, or should I be able to get a total shut-off in both
directions?


It should manage a complete shut off for either one and be able to
provide some flow to both at the same time. Is the actuator moving the
valve all the way, or sticking at part way round?

Try taking the actuator off and moving the valve by hand. It should
move with just slightly more than the grip you can get between finger
and thumb.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Sat, 19 Apr 2008 20:30:19 +0100, Harry Bloomfield
wrote:

Colin Stamp laid this down on his screen :
Hi All,

I have a Y-plan heating system with a Honeywell mid position valve of
indeterminate age. Lately, I've noticed that, on cold mornings when
the heating is working hard, the domestic hot water becomes much
hotter than normal (I have the cylinder stat set quite low). From
fiddling with the thermostats and feeling pipes, It seems that the
valve isn't able to completely close off either the CH or the HW. It
goes most of the way, but the "closed" leg still has a small flow.

Is this normal, or should I be able to get a total shut-off in both
directions?


It should manage a complete shut off for either one and be able to
provide some flow to both at the same time.

Thanks for the confirmation. I wouldn't have wanted to change it, only
to find the new one was just the same.

Is the actuator moving the
valve all the way, or sticking at part way round?

Difficult to tell. I've peered in at the works with the lid off. It
seems to run at a constantish speed and then stop suddenly in one of
the three positions, regardless of whether it's the motor or the
spring that's doing the driving. I get the impression that it's
positively stopping rather than running out of puff.


Try taking the actuator off and moving the valve by hand. It should
move with just slightly more than the grip you can get between finger
and thumb.

I think it'll be difficult to get the head off and leave the valve in
situ. It's been installed very close to the airing-cupboard door-frame
- there was quite a lot of metal bending involved, just in getting the
lid off.

Still, I think I'll just change the whole thing. It's at least ten,
probably twenty, years old. If I can be sure the new one will shut off
completely, I think it'll be worth it. Aside from the hot water
problem, I bet the current one wastes loads of gas heating the
radiators in the summer.

Cheers,

Colin.

"Colin Stamp" wrote in message
...
On Sat, 19 Apr 2008 20:30:19 +0100, Harry Bloomfield
wrote:

Colin Stamp laid this down on his screen :
Hi All,

I have a Y-plan heating system with a Honeywell mid position valve of
indeterminate age. Lately, I've noticed that, on cold mornings when
the heating is working hard, the domestic hot water becomes much
hotter than normal (I have the cylinder stat set quite low). From
fiddling with the thermostats and feeling pipes, It seems that the
valve isn't able to completely close off either the CH or the HW. It
goes most of the way, but the "closed" leg still has a small flow.

Is this normal, or should I be able to get a total shut-off in both
directions?


It should manage a complete shut off for either one and be able to
provide some flow to both at the same time.

Thanks for the confirmation. I wouldn't have wanted to change it, only
to find the new one was just the same.

Is the actuator moving the
valve all the way, or sticking at part way round?

Difficult to tell. I've peered in at the works with the lid off. It
seems to run at a constantish speed and then stop suddenly in one of
the three positions, regardless of whether it's the motor or the
spring that's doing the driving. I get the impression that it's
positively stopping rather than running out of puff.


Try taking the actuator off and moving the valve by hand. It should
move with just slightly more than the grip you can get between finger
and thumb.

I think it'll be difficult to get the head off and leave the valve in
situ. It's been installed very close to the airing-cupboard door-frame
- there was quite a lot of metal bending involved, just in getting the
lid off.

Still, I think I'll just change the whole thing. It's at least ten,
probably twenty, years old. If I can be sure the new one will shut off
completely, I think it'll be worth it. Aside from the hot water
problem, I bet the current one wastes loads of gas heating the
radiators in the summer.

Cheers,

Colin.

Do you have TRVs on all your rads? and if so, do you have a bypass circuit?
you problem could be due to back pressure

Steve

On Sun, 20 Apr 2008 08:52:45 +0100, "Mr Sandman"
wrote:

Do you have TRVs on all your rads? and if so, do you have a bypass circuit?
you problem could be due to back pressure

That's an interesting point. The rads all have TRVs and there isn't a
bypass. I've worried about it in the past, but then the kids broke the
head off one of the TRVs, so I stopped worrying.

I guess it could still be a problem, but the extra-hot water thing
happens when the house is cold and the TRVs are mainly open. Also, the
valve seems unable to shut completely off in either direction, not
just on the HW side.

Cheers,

Colin.

Colin Stamp explained :

Difficult to tell. I've peered in at the works with the lid off. It
seems to run at a constantish speed and then stop suddenly in one of
the three positions, regardless of whether it's the motor or the
spring that's doing the driving. I get the impression that it's
positively stopping rather than running out of puff.


The motor drives against the spring until a micro switch pens, the
switch removes power to the motor - at which point the spring ties to
return the actuator back, which then closes the switch powers the
motor. Basically it should oscillate back and forth.


Try taking the actuator off and moving the valve by hand. It should
move with just slightly more than the grip you can get between finger
and thumb.

I think it'll be difficult to get the head off and leave the valve in
situ. It's been installed very close to the airing-cupboard door-frame
- there was quite a lot of metal bending involved, just in getting the
lid off.

Usually a couple of screws inserted from below, hold the actuator head
on to the valve.


Still, I think I'll just change the whole thing. It's at least ten,
probably twenty, years old. If I can be sure the new one will shut off
completely, I think it'll be worth it. Aside from the hot water
problem, I bet the current one wastes loads of gas heating the
radiators in the summer.

Changing the actuator takes a few minutes and it the most common cause
of these problems - you can buy just the actuator for £25 to £40.
Changing valve is much more involved. You need to drain down the system
to change it and usually they don't fail.

As said, start by taking the head off and manually turning the valve.
The range of positions ought to be obvious by looking at the actuator.
It should turn smoothly and easily through the complete 360 degrees. It
should also control the flow directions. If it passes those tests, then
there is nothing wrong with it.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Sun, 20 Apr 2008 10:55:22 +0100, Harry Bloomfield
wrote:

Colin Stamp explained :

Difficult to tell. I've peered in at the works with the lid off. It
seems to run at a constantish speed and then stop suddenly in one of
the three positions, regardless of whether it's the motor or the
spring that's doing the driving. I get the impression that it's
positively stopping rather than running out of puff.


The motor drives against the spring until a micro switch pens, the
switch removes power to the motor - at which point the spring ties to
return the actuator back, which then closes the switch powers the
motor. Basically it should oscillate back and forth.

What - oscillate continuously? I didn't think they did that. This one
never has. I thought there were three rest positions:-

1. Motor off, spring pushing the "bung" against one valve seat.
2. Motor on, stalled against the other valve seat
3. Mid position, motor held stationary with DC via a diode



Try taking the actuator off and moving the valve by hand. It should
move with just slightly more than the grip you can get between finger
and thumb.

I think it'll be difficult to get the head off and leave the valve in
situ. It's been installed very close to the airing-cupboard door-frame
- there was quite a lot of metal bending involved, just in getting the
lid off.

Usually a couple of screws inserted from below, hold the actuator head
on to the valve.

This one has four, inserted from inside the cover. Two of them are
inaccessible without removing either the valve or the door-frame.
Actually, I might just be able to fiddle them out by fabricating some
kind of cunning tool but even then, I'm not sure I can move the head
far enough away from the valve to clear the spindle. It's a
masterpiece of "I'll never see this job again" installation. Also, I'm
not sure how easy it'll be to get a new head for this particular
valve.


Still, I think I'll just change the whole thing. It's at least ten,
probably twenty, years old. If I can be sure the new one will shut off
completely, I think it'll be worth it. Aside from the hot water
problem, I bet the current one wastes loads of gas heating the
radiators in the summer.

Changing the actuator takes a few minutes and it the most common cause
of these problems - you can buy just the actuator for £25 to £40.
Changing valve is much more involved. You need to drain down the system
to change it and usually they don't fail.

It's a pain, I know, but in this case, just changing the head has a
lot of ball-ache about it too, and a significant risk that it won't
cure the fault. It's probably about time I gave it a bit of a flush
anyway.


As said, start by taking the head off and manually turning the valve.
The range of positions ought to be obvious by looking at the actuator.
It should turn smoothly and easily through the complete 360 degrees. It
should also control the flow directions. If it passes those tests, then
there is nothing wrong with it.

The one I fiddled with in a shop just moved through around 30 degrees,
and needed some torque applied to close the valve at either end. I
don't think I would easily be able to get any meaningful results from
trying to test the valve without the head, with only pipe-feeling to
test for flow.

Normally, I'm all for doing loads of testing so I can isolate the
fault completely and change the absolute minimum of parts to get a
system working again. In this case though, I reckon I've gone as far
as is practical before just changing the whole lot.

Cheers,

Colin.

In article ,
Colin Stamp writes:
On Sun, 20 Apr 2008 10:55:22 +0100, Harry Bloomfield
wrote:
The motor drives against the spring until a micro switch pens, the
switch removes power to the motor - at which point the spring ties to
return the actuator back, which then closes the switch powers the
motor. Basically it should oscillate back and forth.

Sounds like a broken one.

What - oscillate continuously? I didn't think they did that. This one
never has. I thought there were three rest positions:-

1. Motor off, spring pushing the "bung" against one valve seat.
2. Motor on, stalled against the other valve seat
3. Mid position, motor held stationary with DC via a diode

That's right.

1 "Motor off" actually has a small leakage AC current supplied
to the motor to kill any residual magnetism resulting from
position 3, but insufficient to drive it. If you just remove
the power from a valve in mid-position, it can otherwise stay
there until it's touched.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sat, 19 Apr 2008 19:25:22 +0100, Colin Stamp wrote:

Hi All,

I have a Y-plan heating system with a Honeywell mid position valve of
indeterminate age. Lately, I've noticed that, on cold mornings when the
heating is working hard, the domestic hot water becomes much hotter than
normal (I have the cylinder stat set quite low). From fiddling with the
thermostats and feeling pipes, It seems that the valve isn't able to
completely close off either the CH or the HW. It goes most of the way,
but the "closed" leg still has a small flow.

Is this normal, or should I be able to get a total shut-off in both
directions?

Thanks in advance,

Colin.

If the primary water has collected some sludge over the years a bit can
stick to the ball in the 3 port valve. This will cause the valve to not
shut off 100% in either or both of the end positions.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On 20 Apr 2008 13:20:55 GMT, (Andrew
Gabriel) wrote:

In article ,
Colin Stamp writes:
On Sun, 20 Apr 2008 10:55:22 +0100, Harry Bloomfield
wrote:
The motor drives against the spring until a micro switch pens, the
switch removes power to the motor - at which point the spring ties to
return the actuator back, which then closes the switch powers the
motor. Basically it should oscillate back and forth.

Sounds like a broken one.

What - oscillate continuously? I didn't think they did that. This one
never has. I thought there were three rest positions:-

1. Motor off, spring pushing the "bung" against one valve seat.
2. Motor on, stalled against the other valve seat
3. Mid position, motor held stationary with DC via a diode

That's right.

1 "Motor off" actually has a small leakage AC current supplied
to the motor to kill any residual magnetism resulting from
position 3, but insufficient to drive it. If you just remove
the power from a valve in mid-position, it can otherwise stay
there until it's touched.

Ah, that makes sense. I quite like the idea of giving the motor a bit
of forward drive in order to help it turn backwards...

Cheers,

Coin.

On Mon, 21 Apr 2008 19:59:46 +0000 (UTC), Ed Sirett
wrote:

On Sat, 19 Apr 2008 19:25:22 +0100, Colin Stamp wrote:

Hi All,

I have a Y-plan heating system with a Honeywell mid position valve of
indeterminate age. Lately, I've noticed that, on cold mornings when the
heating is working hard, the domestic hot water becomes much hotter than
normal (I have the cylinder stat set quite low). From fiddling with the
thermostats and feeling pipes, It seems that the valve isn't able to
completely close off either the CH or the HW. It goes most of the way,
but the "closed" leg still has a small flow.

Is this normal, or should I be able to get a total shut-off in both
directions?

Thanks in advance,

Colin.

If the primary water has collected some sludge over the years a bit can
stick to the ball in the 3 port valve. This will cause the valve to not
shut off 100% in either or both of the end positions.

Sounds quite plausible. I haven't done any draining or flushing for a
good few years...

Cheers,

Colin.