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Ed
 
Posts: n/a
Default CH control, or lack thereof...

Where to begin? The symptoms: CH doesn't always start in the morning,
it seems that the colder the house the less likely it is to start, but
that may just be our perception..! Secondarily it seems to be ignoring
the DHW tank stat.
The system is a very dull indirect setup with a Baxi back boiler at
the front, a Tower / Grasslin Mid pos'n valve (replaced two years ago)
controlled by a Tower roomstat (with acc), an old Tower tankstat and a
Honeywell digital 2 channel programmer, the square type. All has been
fine until a few weeks ago.
The timer is a 2nd hand one fitted 3years ago (give by a mate whose
system I updated) and seems fine, it replaced an old Towerchron
mechanical (DHW only or CH+DHW, no CH only) timer with pins (for which
previous student tenants had lost almost all the pins,how?). The 3 way
replaced what you woud have expected to be a 3 port diverter due to
the old type timer it had been installed with when new, but it was a
mid pos'n one and after much learning I got it all wired and it worked
fine for about a year (until a small crack in the baseplate allowed it
to distort enough under the spring pressure that the cam sometimes
missed the second microswitch, depending on whether heat from the
pipework had made it expand a little more. I only mention this in case
someone finds it useful in the future.)
I have been all through the wiring and am sure that both stats and the
timer are working fine. Having fiddled with the stats to study every
possible permutation of inputs to the 3 way (not just in isolation but
also trying every input that can follow from each possible previous
set of inputs.) The only consistent weirdness I can find is:
With BOTH stats enabled by the timer and Both calling for heat, the 3
way moves to the centre AB pos'n as it should. If you then reduce the
setting on the room stat (to simulate the room coming up to temp) so
that the room stat is now satisfied I would expect the 3way to spring
return to the DHW ony pos'n, but instead it stays in the AB permiting
heat to flow to both rads and DHW. This can't be right, can it? The
only way to get it to spring return from there is to turn DHW stat to
Satisfied, or to remove the mains power from the system. You can
disconnect ALL the wires in the 3way and it still stays in the AB
pos'n. Aha! thought I, that'll be the flow from the pump holding it
open, disconnected the pump, no change, gave-up. However it doesn't
explain either of my symptoms, tank too hot and CH not starting.
I have a feeling but have been unable to confirm yet that the Ch
starts on mornings when the DHW stat AND the CH stat are BOTH calling
for heat when the timer powers the system up at 6.30. If the DHW isn't
calling for heat, then the CH takes a lie-in too regardless of what
it's own stat has to say. As I say this is a hunch so far but I'll be
provoking it at the weekend when I have time, otherwise it's over to
you lot, help!
  #2   Report Post  
Ed Sirett
 
Posts: n/a
Default CH control, or lack thereof...

On Fri, 13 Feb 2004 07:06:34 +0000, Ed wrote:

Where to begin? The symptoms: CH doesn't always start in the morning,
it seems that the colder the house the less likely it is to start, but
that may just be our perception..! Secondarily it seems to be ignoring
the DHW tank stat.
The system is a very dull indirect setup with a Baxi back boiler at
the front, a Tower / Grasslin Mid pos'n valve (replaced two years ago)
controlled by a Tower roomstat (with acc), an old Tower tankstat and a
Honeywell digital 2 channel programmer, the square type. All has been
fine until a few weeks ago.
The timer is a 2nd hand one fitted 3years ago (give by a mate whose
system I updated) and seems fine, it replaced an old Towerchron
mechanical (DHW only or CH+DHW, no CH only) timer with pins (for which
previous student tenants had lost almost all the pins,how?). The 3 way
replaced what you woud have expected to be a 3 port diverter due to
the old type timer it had been installed with when new, but it was a
mid pos'n one and after much learning I got it all wired and it worked
fine for about a year (until a small crack in the baseplate allowed it
to distort enough under the spring pressure that the cam sometimes
missed the second microswitch, depending on whether heat from the
pipework had made it expand a little more. I only mention this in case
someone finds it useful in the future.)
I have been all through the wiring and am sure that both stats and the
timer are working fine. Having fiddled with the stats to study every
possible permutation of inputs to the 3 way (not just in isolation but
also trying every input that can follow from each possible previous
set of inputs.) The only consistent weirdness I can find is:
With BOTH stats enabled by the timer and Both calling for heat, the 3
way moves to the centre AB pos'n as it should. If you then reduce the
setting on the room stat (to simulate the room coming up to temp) so
that the room stat is now satisfied I would expect the 3way to spring
return to the DHW ony pos'n, but instead it stays in the AB permiting
heat to flow to both rads and DHW. This can't be right, can it? The
only way to get it to spring return from there is to turn DHW stat to
Satisfied, or to remove the mains power from the system. You can
disconnect ALL the wires in the 3way and it still stays in the AB
pos'n. Aha! thought I, that'll be the flow from the pump holding it
open, disconnected the pump, no change, gave-up. However it doesn't
explain either of my symptoms, tank too hot and CH not starting.
I have a feeling but have been unable to confirm yet that the Ch
starts on mornings when the DHW stat AND the CH stat are BOTH calling
for heat when the timer powers the system up at 6.30. If the DHW isn't
calling for heat, then the CH takes a lie-in too regardless of what
it's own stat has to say. As I say this is a hunch so far but I'll be
provoking it at the weekend when I have time, otherwise it's over to
you lot, help!


From the sypmtoms you give I would expect the 3-port valve is sticky and
the valver head is not returning to the HW only position under spring
power alone.
When the HW cylinder is up to temp then the boiler will only fire if the
valve winds all the way to the radiators only position.

The boiler is fired when the orange wire on the 3-port valve is on.




--
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


  #3   Report Post  
Set Square
 
Posts: n/a
Default CH control, or lack thereof...

In an earlier contribution to this discussion,
Ed wrote:

Where to begin? The symptoms: CH doesn't always start in the morning,
it seems that the colder the house the less likely it is to start, but
that may just be our perception..! Secondarily it seems to be ignoring
the DHW tank stat.
The system is a very dull indirect setup with a Baxi back boiler at
the front, a Tower / Grasslin Mid pos'n valve (replaced two years ago)
controlled by a Tower roomstat (with acc), an old Tower tankstat and a
Honeywell digital 2 channel programmer, the square type. All has been
fine until a few weeks ago.
The timer is a 2nd hand one fitted 3years ago (give by a mate whose
system I updated) and seems fine, it replaced an old Towerchron
mechanical (DHW only or CH+DHW, no CH only) timer with pins (for which
previous student tenants had lost almost all the pins,how?). The 3 way
replaced what you woud have expected to be a 3 port diverter due to
the old type timer it had been installed with when new, but it was a
mid pos'n one and after much learning I got it all wired and it worked
fine for about a year (until a small crack in the baseplate allowed it
to distort enough under the spring pressure that the cam sometimes
missed the second microswitch, depending on whether heat from the
pipework had made it expand a little more. I only mention this in case
someone finds it useful in the future.)
I have been all through the wiring and am sure that both stats and the
timer are working fine. Having fiddled with the stats to study every
possible permutation of inputs to the 3 way (not just in isolation but
also trying every input that can follow from each possible previous
set of inputs.) The only consistent weirdness I can find is:
With BOTH stats enabled by the timer and Both calling for heat, the 3
way moves to the centre AB pos'n as it should. If you then reduce the
setting on the room stat (to simulate the room coming up to temp) so
that the room stat is now satisfied I would expect the 3way to spring
return to the DHW ony pos'n, but instead it stays in the AB permiting
heat to flow to both rads and DHW. This can't be right, can it? The
only way to get it to spring return from there is to turn DHW stat to
Satisfied, or to remove the mains power from the system. You can
disconnect ALL the wires in the 3way and it still stays in the AB
pos'n. Aha! thought I, that'll be the flow from the pump holding it
open, disconnected the pump, no change, gave-up. However it doesn't
explain either of my symptoms, tank too hot and CH not starting.
I have a feeling but have been unable to confirm yet that the Ch
starts on mornings when the DHW stat AND the CH stat are BOTH calling
for heat when the timer powers the system up at 6.30. If the DHW isn't
calling for heat, then the CH takes a lie-in too regardless of what
it's own stat has to say. As I say this is a hunch so far but I'll be
provoking it at the weekend when I have time, otherwise it's over to
you lot, help!



I can't pinpoint the exact problem - but I'm pretty sure that it's something
to do with your mid-position valve and/or its actuator. This device - and
its horrible little microswitches - plays a key role in the control logic
for a Y-plan system - and your symptoms are typical of what happens when all
is not well in that department.

The first thing to check is that the spring return takes the valve to the HW
only position when you remove *all* power from the system. This means
turning it off at the FCU which powers the whole caboodle - not just at the
programmer and stats.

If it doesn't return, there is either something wrong with the spring return
mechanism in the actuator, or the valve itself is seized. With many of these
things (but not all) the actuator can be removed from the valve with no
danger of water spillage. If yours is like this, remove the actuator and
check that the spindle of the valve turns fairly freely. You should be able
to turn it with finger and thumb - or at any rate with a pair of pliers,
exerting only a small force. If it is seized, you'll need to replace the
valve - which requires draining the system. If the valve is free, the
actuator is duff. With many of these valves, it is possible to replace just
the actuator - or even to rebuild it with new motor or microswitches if you
are good at soldering and like small fiddly things!

If the spring return does work when you remove all the power, but the CH
still doesn't work, the most likely cause is still a duff actuator.

[I know you replaced the 3-port valve a couple of years ago - but some of
them don't last any longer than that!].
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!


  #4   Report Post  
Ed
 
Posts: n/a
Default CH control, or lack thereof...

"Set Square" wrote in message ...
In an earlier contribution to this discussion,
Ed wrote:

Where to begin? The symptoms: CH doesn't always start in the morning,
it seems that the colder the house the less likely it is to start, but
that may just be our perception..! Secondarily it seems to be ignoring
the DHW tank stat.
The system is a very dull indirect setup with a Baxi back boiler at
the front, a Tower / Grasslin Mid pos'n valve (replaced two years ago)
controlled by a Tower roomstat (with acc), an old Tower tankstat and a
Honeywell digital 2 channel programmer, the square type. All has been
fine until a few weeks ago.
The timer is a 2nd hand one fitted 3years ago (give by a mate whose
system I updated) and seems fine, it replaced an old Towerchron
mechanical (DHW only or CH+DHW, no CH only) timer with pins (for which
previous student tenants had lost almost all the pins,how?). The 3 way
replaced what you woud have expected to be a 3 port diverter due to
the old type timer it had been installed with when new, but it was a
mid pos'n one and after much learning I got it all wired and it worked
fine for about a year (until a small crack in the baseplate allowed it
to distort enough under the spring pressure that the cam sometimes
missed the second microswitch, depending on whether heat from the
pipework had made it expand a little more. I only mention this in case
someone finds it useful in the future.)
I have been all through the wiring and am sure that both stats and the
timer are working fine. Having fiddled with the stats to study every
possible permutation of inputs to the 3 way (not just in isolation but
also trying every input that can follow from each possible previous
set of inputs.) The only consistent weirdness I can find is:
With BOTH stats enabled by the timer and Both calling for heat, the 3
way moves to the centre AB pos'n as it should. If you then reduce the
setting on the room stat (to simulate the room coming up to temp) so
that the room stat is now satisfied I would expect the 3way to spring
return to the DHW ony pos'n, but instead it stays in the AB permiting
heat to flow to both rads and DHW. This can't be right, can it? The
only way to get it to spring return from there is to turn DHW stat to
Satisfied, or to remove the mains power from the system. You can
disconnect ALL the wires in the 3way and it still stays in the AB
pos'n. Aha! thought I, that'll be the flow from the pump holding it
open, disconnected the pump, no change, gave-up. However it doesn't
explain either of my symptoms, tank too hot and CH not starting.
I have a feeling but have been unable to confirm yet that the Ch
starts on mornings when the DHW stat AND the CH stat are BOTH calling
for heat when the timer powers the system up at 6.30. If the DHW isn't
calling for heat, then the CH takes a lie-in too regardless of what
it's own stat has to say. As I say this is a hunch so far but I'll be
provoking it at the weekend when I have time, otherwise it's over to
you lot, help!



I can't pinpoint the exact problem - but I'm pretty sure that it's something
to do with your mid-position valve and/or its actuator. This device - and
its horrible little microswitches - plays a key role in the control logic
for a Y-plan system - and your symptoms are typical of what happens when all
is not well in that department.

The first thing to check is that the spring return takes the valve to the HW
only position when you remove *all* power from the system. This means
turning it off at the FCU which powers the whole caboodle - not just at the
programmer and stats.

If it doesn't return, there is either something wrong with the spring return
mechanism in the actuator, or the valve itself is seized. With many of these
things (but not all) the actuator can be removed from the valve with no
danger of water spillage. If yours is like this, remove the actuator and
check that the spindle of the valve turns fairly freely. You should be able
to turn it with finger and thumb - or at any rate with a pair of pliers,
exerting only a small force. If it is seized, you'll need to replace the
valve - which requires draining the system. If the valve is free, the
actuator is duff. With many of these valves, it is possible to replace just
the actuator - or even to rebuild it with new motor or microswitches if you
are good at soldering and like small fiddly things!

If the spring return does work when you remove all the power, but the CH
still doesn't work, the most likely cause is still a duff actuator.

[I know you replaced the 3-port valve a couple of years ago - but some of
them don't last any longer than that!].


The spring return is smooth and fast, no problems there. As I write
the system is behaving fine so it's a little hard to do diagnosis.
When I did the wiring checks I did find one wire in the connection
unit that could have been tighter but really didn't seem loose enough
to be a troublemaker. I've given it a little tweak anyway so now I
just have to wait for the next cold morning. Still baffelled by the
way it sits on AB with ALL wires disconnected, what is holding it
there? If you pull the power at the FCU it spring returns sharply...
Watch this space...
  #5   Report Post  
Set Square
 
Posts: n/a
Default CH control, or lack thereof...

In an earlier contribution to this discussion,
Ed wrote:


The spring return is smooth and fast, no problems there. As I write
the system is behaving fine so it's a little hard to do diagnosis.
When I did the wiring checks I did find one wire in the connection
unit that could have been tighter but really didn't seem loose enough
to be a troublemaker. I've given it a little tweak anyway so now I
just have to wait for the next cold morning. Still baffelled by the
way it sits on AB with ALL wires disconnected, what is holding it
there? If you pull the power at the FCU it spring returns sharply...
Watch this space...



It is possible for mid-position valve actuators to get "confused"
sometimes - maybe a microswitch doesn't quite make when it's supposed to, or
something like that. Sometimes when this happens, the thing can be reset by
removing all the power and starting again. This may have happened in your
case.

If you disconnect ALL 5 wires to the actuator, this should have the same
effect as pulling the power. Can't explain it if it didn't! Are you sure
that *something* wasn't still connected?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!




  #6   Report Post  
Harry Bloomfield
 
Posts: n/a
Default CH control, or lack thereof...

Set Square wrote on Saturday (14/02/2004) :
Ed wrote:


The spring return is smooth and fast, no problems there. As I write
the system is behaving fine so it's a little hard to do diagnosis.
When I did the wiring checks I did find one wire in the connection
unit that could have been tighter but really didn't seem loose enough
to be a troublemaker. I've given it a little tweak anyway so now I
just have to wait for the next cold morning. Still baffelled by the
way it sits on AB with ALL wires disconnected, what is holding it
there? If you pull the power at the FCU it spring returns sharply...
Watch this space...


If it is a Sunvic valve actuator, it is a well known problem...

The two positions away from the 'home' position are held by constantly
cycling the motor on and off against the spring.....
The motor runs until the microswitch controlling the motor is opened by
the cam, the spring causes it to back off a little, microswitch closes,
motor runs again until the switch opens.

Sometimes the mechanisms sticks, with the spring unable to return the
valve to the home position. Undo the two screws when the valve is
stuck, and it will likely then go to its correct position. Sometimes
just knocking the actuator is enough to make it return.

The long term solution is to replace the valve with new, about £45-ish.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

  #7   Report Post  
Ed
 
Posts: n/a
Default CH control, or lack thereof...

"Set Square" wrote in message ...
In an earlier contribution to this discussion,
Ed wrote:


The spring return is smooth and fast, no problems there. As I write
the system is behaving fine so it's a little hard to do diagnosis.
When I did the wiring checks I did find one wire in the connection
unit that could have been tighter but really didn't seem loose enough
to be a troublemaker. I've given it a little tweak anyway so now I
just have to wait for the next cold morning. Still baffelled by the
way it sits on AB with ALL wires disconnected, what is holding it
there? If you pull the power at the FCU it spring returns sharply...
Watch this space...



It is possible for mid-position valve actuators to get "confused"
sometimes - maybe a microswitch doesn't quite make when it's supposed to, or
something like that. Sometimes when this happens, the thing can be reset by
removing all the power and starting again. This may have happened in your
case.

If you disconnect ALL 5 wires to the actuator, this should have the same
effect as pulling the power. Can't explain it if it didn't! Are you sure
that *something* wasn't still connected?



Sure as can be, Synchron has only two wires, both disconnected, +
orange white and grey for good measure, stays put on AB until you shut
off at the FCU, then instant smooth spring return. Anyone for an
exorcism?
  #8   Report Post  
Dave Plowman
 
Posts: n/a
Default CH control, or lack thereof...

In article ,
Set Square wrote:
This device - and its horrible little microswitches - plays a key role
in the control logic for a Y-plan system - and your symptoms are typical
of what happens when all is not well in that department.


On the ones I've seen, the micro switches are of a generic size used on
many other applications. However, as with much else, they vary
considerably in quality (and also price) between makers. A quality make
will give in its spec the expected life in number of operations - which is
vastly in excess of the likely use in this context. Assuming, of course,
they are kept within their rating.

--
*If at first you don't succeed, try management *

Dave Plowman London SW 12
RIP Acorn
  #9   Report Post  
Set Square
 
Posts: n/a
Default CH control, or lack thereof...

In an earlier contribution to this discussion,
Ed wrote:


Sure as can be, Synchron has only two wires, both disconnected, +
orange white and grey for good measure, stays put on AB until you shut
off at the FCU, then instant smooth spring return. Anyone for an
exorcism?



Well I'm sorry, but something *is* still connected! If the actuator is
*totally* disconnected from everything, turning off the FCU can have no
possible effect on it.

Tell us again where you are making the disconnections. The actuator should
have a 5 core cable going to it, with the opposite ends connected into a
junction box as per Y-plan in
http://content.honeywell.com/uk/homes/systems.htm

The synchron motor is an internal component inside the actuator. Have you
been disonnecting the internal wiring inside the actuator or the external
wiring in the junction box?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!


  #10   Report Post  
The Right Rev. Peter Parsnip
 
Posts: n/a
Default CH control, or lack thereof...

The Lord alerted my mind to the presence of this EVIL article by Harry
Bloomfield, and I thusly replied:

The long term solution is to replace the valve with new, about œ45-ish.


That's your solution to everything.

--
The Reverend Parson Peter Parsnip
Smiting Sinful Usenet Users Since 1874

"A ******* shall not enter into the congregation of the Lord; even to his
tenth generation shall he not enter into the congregation of the Lord."
- Deuteronomy 23:2


  #11   Report Post  
The Left Rev. P. Parsnipe
 
Posts: n/a
Default CH control, or lack thereof...

The Lord alerted my mind to the presence of this EVIL article by Pirx Teh
Caravan Pilot, and I thusly replied:

In article m,
The Right Rev. Peter Parsnip
wrote:
The Lord alerted my mind to the presence of this EVIL article by Harry
Bloomfield, and I thusly replied:

The long term solution is to replace the valve with new, about
œ45-ish.


That's your solution to everything.


It won't cure my piles.


How many piles do you have?

--
The Reverend Parson Peter Parsnip
Smiting Sinful Usenet Users Since 1874

"A ******* shall not enter into the congregation of the Lord; even to his
tenth generation shall he not enter into the congregation of the Lord."
- Deuteronomy 23:2
  #12   Report Post  
ah
 
Posts: n/a
Default CH control, or lack thereof...

Pirx Teh Caravan Pilot wrote:

In article m,
The Right Rev. Peter Parsnip wrote:

The Lord alerted my mind to the presence of this EVIL article by Harry
Bloomfield, and I thusly replied:

The long term solution is to replace the valve with new, about ?45-ish.


That's your solution to everything.


It won't cure my piles.


Try math!
--
ah
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