Another question:

After being recommended to us a S plan system with 2 port valves, I'm
thinking why 2 valves and why not one 3 port valve?

What happens if you were to use 1 2 port valve?

Christmas Greetings to all.

In an earlier contribution to this discussion,
wrote:

Another question:

After being recommended to us a S plan system with 2 port valves, I'm
thinking why 2 valves and why not one 3 port valve?

What happens if you were to use 1 2 port valve?

Christmas Greetings to all.


An S-Plan system has 2 or more 2-port valves - one for each heating or HW
zone, and provides independent control over the zones - only running the
boiler and pump when one or more zone is demanding heat.

If you only have one 2-port valve, you cannot control your CH and HW
separately - so you might as well have no valves at all!

A 3-port valve is used by Y-Plan systems - and also enables you to have CH
or HW, or both together. It's main disadvantage is that the valve actuator
plays a more strategic role in the overall control of the system than other
plans, and is more complex than a 2-port actuator, and prone to failure,
causing the whole system to stop working. It also limits you to 2 zones so
you can't, for example, have separate upstairs and downstairs heating zones
in addition to hot water. With S-Plan+ systems you can have as many zones as
you like.

See http://content.honeywell.com/uk/homes/systems.htm for information about
several different heating plans.

--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 2007-12-25 12:20:42 +0000, said:

On 25 Dec,
"Roger Mills" wrote:

A 3-port valve is used by Y-Plan systems - and also enables you to have CH
or HW, or both together. It's main disadvantage is that the valve actuator
plays a more strategic role in the overall control of the system than other
plans, and is more complex than a 2-port actuator, and prone to failure,
causing the whole system to stop working.

Agreed, the microswitches regularly fail.

It also limits you to 2 zones so you can't, for example, have separate
upstairs and downstairs heating zones in addition to hot water.

Untrue, I had 3 zones with 3 port valves with a (modified) Y plan system (the
supplier was out of 2 port valves when the system was installed).

With S-Plan+ systems you can have as many zones as you like.

You could with Y plan, but it gets complicated and unreliable.

I've converted to S plan. It has been much more reliable since. With Y plan I
had to change microswitches at least annually. I don't think I've had a
failure in the 5 years or so with S plan.


Which seems kind of odd, because the motor units are similar and there
would be as many operations as before.

However, I agree with you. A system that I installed many years ago
was fitted with two port valves because that seemed to be a better
design decision. No failures. On the one that had been installed
in the current house as original, there was a three way valve.
These would fail about every 3 years or so and not always at the
obvious times of the start of the heating season.

When I renewed the system, I switched to using 2 port Honeywell valves.
I also fitted 28mm versions for the main ones to reduce flow
restriction and 22mm ones in smaller zones. No problems at all with
these in 5 years, although the boiler does have an automatic valve
exercising function.

On 24 Dec, 23:33, Owain wrote:
wrote:
Another question:
After being recommended to us a S plan system with 2 portvalves, I'm
thinking why 2valvesand why not one 3 port valve?

Because 2 portvalvesare simpler and more reliable than one 3-port,
probably.

What happens if you were to use 1 2 port valve?

You don't get separate control of heating and hot water.

Owain

The main thing is that I want to be able to have HW only or CH only or
both at the same time if a S plan system can do this then thats what
is right for me

On 2007-12-25 14:56:38 +0000, said:

On 24 Dec, 23:33, Owain wrote:
wrote:
Another question:
After being recommended to us a S plan system with 2 portvalves, I'm
thinking why 2valvesand why not one 3 port valve?

Because 2 portvalvesare simpler and more reliable than one 3-port,
probably.

What happens if you were to use 1 2 port valve?

You don't get separate control of heating and hot water.

Owain

The main thing is that I want to be able to have HW only or CH only or
both at the same time if a S plan system can do this then thats what
is right for me

You can do that, although often controllers work in a hot water priority mode.

In old systems which used "gravity" for heating the HW cylinder,
convection was used in the primary circuit to it to transfer the heat
from boiler to cylinder. This ran pretty much continuously with the
boiler thermostat effectively controlling the temperature. The
central heating was controlled by a thermostat effectively operating
the pump. This gave simultaneous hot water and central heating, but
the cylinder would take quite a time to reheat because the transfer
rate is poor. However, at least the house didn't get too cold while
it was doing it.

With 3 port valve systems, the hot water takes priority. This means
that if there is a demand from the cylinder, then the valve opens in
that direction, and the boiler and pump run. This gives much faster
reheating but even then because the coil in most cylinders is of
limited surface area, it can still take quite a time to reheat and now
the boiler output is directed away from the CH. Of course that will
be worse if the cylinder is large and the transfer rate poor. In bad
scenarios, the boiler will even cycle.

However, you can use a fast recovery cylinder. These have a coil of
much larger surface area than traditional ones by having more turns or
multiple small tubes and can take all or most of quite a large boiler's
output. Reheat on these can be very short indeed and thus the boiler
is returned to CH operation much sooner, and thus there is little drop
in room temperature and probably nothing noticable if the system is
designed well.

Another factor is that the boiler will run more efficiently in this
way. During HW operation, the return temperature from the cylinder
coil will be quite low and a lot of heat will be transferred. The
boiler will thus modulate up to full power or close to it and
condensing models will be well down the curve into efficient operation.
When the boiler is returned to CH only operation, it will modulate
down and run at lower power and temperature, again putting it into an
efficient part of its working curve.

Certainly you can arrange the controls such that there are separate
timed periods for CH and HW. That simply means that one or the other
or both *can* operate. However, running the system such that both
CH and HW demands are met simultaneously may well not achieve a
desirable result of fastest results and best efficiency.

Why are the letters Y and S used, what do they stand for?
--
Graham

%Profound_observation%

On 2007-12-25 15:47:12 +0000, "Graham." said:


Why are the letters Y and S used, what do they stand for?

They are two of the so-called Sundial plans

http://content.honeywell.com/UK/homes/Sundial.htm

It would be interesting to know whether anybody at Honeywell still
knows what the letters mean, if anything. I bet they don't.

In an earlier contribution to this discussion,
Andy Hall wrote:


The main thing is that I want to be able to have HW only or CH only
or both at the same time if a S plan system can do this then thats
what is right for me

You can do that, although often controllers work in a hot water
priority mode.
A strange answer to this particular point! Some plans - notably W-Plan - do
indeed give priority to HW, but as far as I am aware, all zones - space
heating or hot water - in S-Plan systems have *equal* priority,



With 3 port valve systems, the hot water takes priority. This means
that if there is a demand from the cylinder, then the valve opens in
that direction, and the boiler and pump run.

Not necessarily. It is true for W-Plan systems, which use a 3-port diverter
valve - but Y-Plan systems use a 3-port mid-position valve which simply sits
at its mid position when there are simultaneous HW and CH demands.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 2007-12-25 18:18:40 +0000, "Roger Mills" said:

In an earlier contribution to this discussion,
Andy Hall wrote:


The main thing is that I want to be able to have HW only or CH only
or both at the same time if a S plan system can do this then thats
what is right for me

You can do that, although often controllers work in a hot water
priority mode.
A strange answer to this particular point! Some plans - notably W-Plan - do
indeed give priority to HW, but as far as I am aware, all zones - space
heating or hot water - in S-Plan systems have *equal* priority,

That depends on the implementation.

If you have separate thermostats and timeswitches perhaps. However,
it is possible for thermostats and time control to be combined or even
that the valves are controlled by or integral to the boiler anyway.
Under these circumstances, the HW can be given priority.






With 3 port valve systems, the hot water takes priority. This means
that if there is a demand from the cylinder, then the valve opens in
that direction, and the boiler and pump run.

Not necessarily. It is true for W-Plan systems, which use a 3-port diverter
valve - but Y-Plan systems use a 3-port mid-position valve which simply sits
at its mid position when there are simultaneous HW and CH demands.

Which is not a very good idea in a modern setup where lots of heat can
be transferred rapidly to the cylinder.

In an earlier contribution to this discussion,
Andy Hall wrote:

On 2007-12-25 18:18:40 +0000, "Roger Mills"
said:
In an earlier contribution to this discussion,
Andy Hall wrote:


The main thing is that I want to be able to have HW only or CH only
or both at the same time if a S plan system can do this then thats
what is right for me

You can do that, although often controllers work in a hot water
priority mode.
A strange answer to this particular point! Some plans - notably
W-Plan - do indeed give priority to HW, but as far as I am aware,
all zones - space heating or hot water - in S-Plan systems have
*equal* priority,

That depends on the implementation.

If you have separate thermostats and timeswitches perhaps. However,
it is possible for thermostats and time control to be combined or even
that the valves are controlled by or integral to the boiler anyway.
Under these circumstances, the HW can be given priority.


OK, but in that case you will have departed considerably from the standard
S-Plan definition.


With 3 port valve systems, the hot water takes priority. This means
that if there is a demand from the cylinder, then the valve opens in
that direction, and the boiler and pump run.

Not necessarily. It is true for W-Plan systems, which use a 3-port
diverter valve - but Y-Plan systems use a 3-port mid-position valve
which simply sits at its mid position when there are simultaneous HW
and CH demands.

Which is not a very good idea in a modern setup where lots of heat can
be transferred rapidly to the cylinder.

Yes, an interesting one! My impression is that diverter valves were invented
before mid-point valves, and that W-Plan has largely been superceded by
Y-Plan once mid-point valves were in common supply. Maybe with fast recovery
cylinders W-Plan systems are coming back - I don't know?!

I have a Y-Plan system with a programmable stat on the CH and usually [1]
succeed in arranging the timing so that CH and HW are not both on at the
same time.

[1] With optimum start on the CH stat, it may sometimes come on before the
HW is fully hot - but it seems to cope ok!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 2007-12-25 20:42:09 +0000, "Roger Mills" said:

In an earlier contribution to this discussion,
Andy Hall wrote:

On 2007-12-25 18:18:40 +0000, "Roger Mills"
said:
In an earlier contribution to this discussion,
Andy Hall wrote:


The main thing is that I want to be able to have HW only or CH only
or both at the same time if a S plan system can do this then thats
what is right for me

You can do that, although often controllers work in a hot water
priority mode.
A strange answer to this particular point! Some plans - notably
W-Plan - do indeed give priority to HW, but as far as I am aware,
all zones - space heating or hot water - in S-Plan systems have
*equal* priority,

That depends on the implementation.

If you have separate thermostats and timeswitches perhaps. However,
it is possible for thermostats and time control to be combined or even
that the valves are controlled by or integral to the boiler anyway.
Under these circumstances, the HW can be given priority.


OK, but in that case you will have departed considerably from the standard
S-Plan definition.

I've always considered it to be defined by the valve types used rather
than a specific control logic.

Honeywell says:

The main operating requirements of Sundial Plans a

1.The controls should provide full independent temperature control of
both living space and stored domestic ho****er.

2. If there is no demand for either living space or domestic hot
water heating, the central heating boiler and pump must both be
switched off.

It doesn't say anything about whether or not one can circuit can
pre-empt the other. The timers and thermostats are essentially the
same and it has been the valves that have limited what's possible.

IOW

W plan is the most restrictive because it permits flow in only one
direction at a time.

Y plan less restrictive, but mid position valves do restrict flow.

S plan fully flexible in terms of what the valves can do.






With 3 port valve systems, the hot water takes priority. This means
that if there is a demand from the cylinder, then the valve opens in
that direction, and the boiler and pump run.

Not necessarily. It is true for W-Plan systems, which use a 3-port
diverter valve - but Y-Plan systems use a 3-port mid-position valve
which simply sits at its mid position when there are simultaneous HW
and CH demands.

Which is not a very good idea in a modern setup where lots of heat can
be transferred rapidly to the cylinder.

Yes, an interesting one! My impression is that diverter valves were invented
before mid-point valves, and that W-Plan has largely been superceded by
Y-Plan once mid-point valves were in common supply. Maybe with fast recovery
cylinders W-Plan systems are coming back - I don't know?!

I have a Y-Plan system with a programmable stat on the CH and usually [1]
succeed in arranging the timing so that CH and HW are not both on at the
same time.

[1] With optimum start on the CH stat, it may sometimes come on before the
HW is fully hot - but it seems to cope ok!

That can all be avoided by using separate valves and controlling them
with HW priority.

In an earlier contribution to this discussion,
Andy Hall wrote:


If you have separate thermostats and timeswitches perhaps. However, it
is possible for thermostats and time control to be
combined or even that the valves are controlled by or integral to
the boiler anyway. Under these circumstances, the HW can be given
priority.

OK, but in that case you will have departed considerably from the
standard S-Plan definition.

I've always considered it to be defined by the valve types used rather
than a specific control logic.

But the S-Plan as defined in
http://content.honeywell.com/uk/homes/systems.htm just has a timer and stat
controlling each valve with equal priority. Although you *could* muck about
with that to provide HW priority, Honeywell haven't actually done that - in
any of the examples I have seen, at any rate.


Honeywell says:

The main operating requirements of Sundial Plans a

1.The controls should provide full independent temperature control
of both living space and stored domestic ho****er.

2. If there is no demand for either living space or domestic hot
water heating, the central heating boiler and pump must both be
switched off.


That applies to *all* plans - even the C-Plan


It doesn't say anything about whether or not one circuit can
pre-empt the other. The timers and thermostats are essentially the
same and it has been the valves that have limited what's possible.

IOW

W plan is the most restrictive because it permits flow in only one
direction at a time.

Y plan less restrictive, but mid position valves do restrict flow.

S plan fully flexible in terms of what the valves can do.


*And* it's possible to invent lots of additional variants which don't match
*any* of the published plans - such as modifying the logic to change the
priority.

--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"Andy Hall" wrote in message news:47712c25@qaanaaq...
On 2007-12-25 15:47:12 +0000, "Graham." said:


Why are the letters Y and S used, what do they stand for?

They are two of the so-called Sundial plans

http://content.honeywell.com/UK/homes/Sundial.htm

It would be interesting to know whether anybody at Honeywell still knows
what the letters mean, if anything. I bet they don't.



Interesting that, seems a UK thing, I wonder it discourages heating
engineers from being more inventive when designing a system
for a particular property, but I suppose there won't be many
situations where some variant of an S+ won't be suitable.

When I moved into this house in the mid 70's there was
an S plan system with two Honeywell 2 port valves installed
well it *would have been an S plan except the mechanical
Randall 102 timeclock had only
DHW ONLY - OFF - DHW+CH
settings so you couldn't have CH with no DHW even
though the cylinder stat would put it in that condition.
I made my own control box with two three way
switches for DHW and CH marked
TIMED - OFF - CONT and a third on/off switch
that bypasses the cylinder stat marked BOOST
neon lamps indicate when each circuit is ON
or calling for heat. Still going to this day.
--
Graham

%Profound_observation%

On 2007-12-25 23:35:52 +0000, "Roger Mills" said:

In an earlier contribution to this discussion,
Andy Hall wrote:


If you have separate thermostats and timeswitches perhaps. However, it
is possible for thermostats and time control to be
combined or even that the valves are controlled by or integral to
the boiler anyway. Under these circumstances, the HW can be given
priority.

OK, but in that case you will have departed considerably from the
standard S-Plan definition.

I've always considered it to be defined by the valve types used rather
than a specific control logic.

But the S-Plan as defined in
http://content.honeywell.com/uk/homes/systems.htm just has a timer and stat
controlling each valve with equal priority. Although you *could* muck about
with that to provide HW priority, Honeywell haven't actually done that - in
any of the examples I have seen, at any rate.

They don't exclude anything in their specifications.



Honeywell says:

The main operating requirements of Sundial Plans a

1.The controls should provide full independent temperature control
of both living space and stored domestic ho****er.

2. If there is no demand for either living space or domestic hot
water heating, the central heating boiler and pump must both be
switched off.


That applies to *all* plans - even the C-Plan

Exactly. The functionality is not limited by the specs. It is
the valves that limit the functionality.






It doesn't say anything about whether or not one circuit can
pre-empt the other. The timers and thermostats are essentially the
same and it has been the valves that have limited what's possible.

IOW

W plan is the most restrictive because it permits flow in only one
direction at a time.

Y plan less restrictive, but mid position valves do restrict flow.

S plan fully flexible in terms of what the valves can do.


*And* it's possible to invent lots of additional variants which don't match
*any* of the published plans - such as modifying the logic to change the
priority.

Of course. That's why Y plan was added when mid position valves became
available, and S plan has developed with newer technologies such as
Smartfit.

In an earlier contribution to this discussion,
Andy Hall wrote:

On 2007-12-25 23:35:52 +0000, "Roger Mills"
said:

But the S-Plan as defined in
http://content.honeywell.com/uk/homes/systems.htm just has a timer
and stat controlling each valve with equal priority. Although you
*could* muck about with that to provide HW priority, Honeywell
haven't actually done that - in any of the examples I have seen, at
any rate.

They don't exclude anything in their specifications.


But by the same logic you could argue that a car is the same as a motorbike
because it has an engine which causes the driving wheel(s) to rotate. The
fact that you've added extra wheels and seats and a steering wheel and roof
is insignificant.



Honeywell says:

The main operating requirements of Sundial Plans a

1.The controls should provide full independent temperature control
of both living space and stored domestic ho****er.

2. If there is no demand for either living space or domestic hot
water heating, the central heating boiler and pump must both be
switched off.


That applies to *all* plans - even the C-Plan

Exactly. The functionality is not limited by the specs. It is
the valves that limit the functionality.


I don't see what you're getting at. The functionality of an S-Plan system is
achieved by means of a combination of the valves, timers and stats. You
could, if you wished, achieve a different fuctionality with the self-same
valves, simply by changing the external control logic. It's just that it
would no longer be an S-Plan system.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 2007-12-26 10:31:10 +0000, "Roger Mills" said:

In an earlier contribution to this discussion,
Andy Hall wrote:

On 2007-12-25 23:35:52 +0000, "Roger Mills"
said:

But the S-Plan as defined in
http://content.honeywell.com/uk/homes/systems.htm just has a timer
and stat controlling each valve with equal priority. Although you
*could* muck about with that to provide HW priority, Honeywell
haven't actually done that - in any of the examples I have seen, at
any rate.

They don't exclude anything in their specifications.


But by the same logic you could argue that a car is the same as a motorbike
because it has an engine which causes the driving wheel(s) to rotate. The
fact that you've added extra wheels and seats and a steering wheel and roof
is insignificant.

If the spec. was for a means of transport using wheels then both would qualify.

Not all cars have to be basic Ladas. They can have air conditioning as well






Honeywell says:

The main operating requirements of Sundial Plans a

1.The controls should provide full independent temperature control
of both living space and stored domestic ho****er.

2. If there is no demand for either living space or domestic hot
water heating, the central heating boiler and pump must both be
switched off.


That applies to *all* plans - even the C-Plan

Exactly. The functionality is not limited by the specs. It is
the valves that limit the functionality.


I don't see what you're getting at.

Evidently.

The functionality of an S-Plan system is
achieved by means of a combination of the valves, timers and stats. You
could, if you wished, achieve a different fuctionality with the self-same
valves, simply by changing the external control logic. It's just that it
would no longer be an S-Plan system.

According to Honeywell's specs. the requirements are listed above.

What if the controller is a PID type with automatic learning and
prediction of heat requirement? Does that mean that it's not S-plan
any longer because it's not the T6360B1028 Room Thermostat listed on
the web site.

Honeywell's description of S-plan says:

"The Sundial 'S' Plan is designed to provide independent temperature
control of both heating and hot water circuits in fully pumped heating
installations. Time control may be provided by a time switch or
programmer."

It says nothing about whether or not one can be given priority over the other.

Roger Mills wrote:
In an earlier contribution to this discussion,
wrote:

Another question:

After being recommended to us a S plan system with 2 port valves, I'm
thinking why 2 valves and why not one 3 port valve?

What happens if you were to use 1 2 port valve?

Christmas Greetings to all.


An S-Plan system has 2 or more 2-port valves - one for each heating or HW
zone, and provides independent control over the zones - only running the
boiler and pump when one or more zone is demanding heat.

If you only have one 2-port valve, you cannot control your CH and HW
separately - so you might as well have no valves at all!

A 3-port valve is used by Y-Plan systems - and also enables you to have CH
or HW, or both together. It's main disadvantage is that the valve actuator
plays a more strategic role in the overall control of the system than other
plans, and is more complex than a 2-port actuator, and prone to failure,
causing the whole system to stop working. It also limits you to 2 zones so
you can't, for example, have separate upstairs and downstairs heating zones
in addition to hot water. With S-Plan+ systems you can have as many zones as
you like.

See http://content.honeywell.com/uk/homes/systems.htm for information about
several different heating plans.

Good summary.

Its a bit like a combi, is Y plan. Simple and cheap if it suits in a
small limited installation, but a PITA if its goes wrong or you need
more flexibility.

wrote:
On 24 Dec, 23:33, Owain wrote:
wrote:
Another question:
After being recommended to us a S plan system with 2 portvalves, I'm
thinking why 2valvesand why not one 3 port valve?
Because 2 portvalvesare simpler and more reliable than one 3-port,
probably.

What happens if you were to use 1 2 port valve?
You don't get separate control of heating and hot water.

Owain

The main thing is that I want to be able to have HW only or CH only or
both at the same time if a S plan system can do this then thats what
is right for me

Y plan can do it as well. Its more a reliability issue than anything
else IMHO.

At least when one of my zone valves stuck 'ON' I just pulled the wires
out and had the other CH zones and the hot water working..if a Y plan
valve goes.,.you are screwed totally.

In an earlier contribution to this discussion,
Andy Hall wrote:


According to Honeywell's specs. the requirements are listed above.

What if the controller is a PID type with automatic learning and
prediction of heat requirement? Does that mean that it's not S-plan
any longer because it's not the T6360B1028 Room Thermostat listed on
the web site.


No, because the two zones are still independently controlled by timers and
stats - even if one zone combines this in the form of a programmable stat.
[In fact, one of Honeywell's application notes describes just that - "S-Plan
with programmable room stat".]

It may be splitting hairs but I see a distinction between that and a system
which suppresses the feed to one zone until the demand of another unrelated
zone is satisfied.

Honeywell's description of S-plan says:

"The Sundial 'S' Plan is designed to provide independent temperature
control of both heating and hot water circuits in fully pumped
heating installations. Time control may be provided by a time switch
or programmer."

It says nothing about whether or not one can be given priority over
the other.

Surely, it's implicit in the word "independent".

I think perhaps it's time to call it a day. The OP - if he's still
watching! - must be thoroughly confused by all this!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 2007-12-26 12:12:07 +0000, "Roger Mills" said:

In an earlier contribution to this discussion,
Andy Hall wrote:


According to Honeywell's specs. the requirements are listed above.

What if the controller is a PID type with automatic learning and
prediction of heat requirement? Does that mean that it's not S-plan
any longer because it's not the T6360B1028 Room Thermostat listed on
the web site.


No, because the two zones are still independently controlled by timers and
stats - even if one zone combines this in the form of a programmable stat.
[In fact, one of Honeywell's application notes describes just that - "S-Plan
with programmable room stat".]

It may be splitting hairs but I see a distinction between that and a system
which suppresses the feed to one zone until the demand of another unrelated
zone is satisfied.

There is a distinction of course, but it isn't excluded from Honeywell's spec.




Honeywell's description of S-plan says:

"The Sundial 'S' Plan is designed to provide independent temperature
control of both heating and hot water circuits in fully pumped
heating installations. Time control may be provided by a time switch
or programmer."

It says nothing about whether or not one can be given priority over
the other.

Surely, it's implicit in the word "independent".

The controls remain independent. The timer(s) control the
operational times and the thermostats control the demand for heat,

The additional part is that if there is demand for CH *and* HW because
of the time range and the temperature, then the valve for the HW will
open and the CH one will remain shut until the either the HW thermostat
is satisfied or the HW on time expires.

Even before this, controller logic has been improved. For example,
optimised start is increasingly commonplace. Thus if I set the
controller to 21 degrees and a start time of 0700, it computes
approximately how long it will take before the house is up to the
setpoint temperature and start the boiler earlier to achieve that.
Now the boiler is starting at a time earlier than that set.





I think perhaps it's time to call it a day. The OP - if he's still
watching! - must be thoroughly confused by all this!

It's simple enough. With the controls integrated in the boiler,
wiring and operation is very easy.

On Mon, 24 Dec 2007 14:11:46 -0800, dawoodseed wrote:

Another question:

After being recommended to us a S plan system with 2 port valves, I'm
thinking why 2 valves and why not one 3 port valve?

What happens if you were to use 1 2 port valve?

Christmas Greetings to all.

When a motorized valve cost was about the same a say a half day's labour.
It made some sort of economic sense to fit one valve which took a bit
longer to fit.

Now the valves have come down in price (there under £20 in the BES
catalogue - Honeywell compatible), and the labour for 1/2a day has gone
up a lot. The whole balance is in favour of using 2 or more valves.

--
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

In message 47712c25@qaanaaq, Andy Hall writes
On 2007-12-25 15:47:12 +0000, "Graham." said:

Why are the letters Y and S used, what do they stand for?

They are two of the so-called Sundial plans

http://content.honeywell.com/UK/homes/Sundial.htm

It would be interesting to know whether anybody at Honeywell still
knows what the letters mean, if anything. I bet they don't.

Do their new SmartFit plans have any real advantages?

--
Si

Andy Hall wrote:

With 3 port valve systems, the hot water takes priority. This means
that if there is a demand from the cylinder, then the valve opens in
that direction, and the boiler and pump run. This gives much faster

This is true for three port diversion valves. A three port mid position
valve will also allow both to run at once. This is a better proposal for
slow recovery cylinders since it does not divert the heating for too long.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
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Graham. wrote:
Why are the letters Y and S used, what do they stand for?

Well, it's an aide-memoir for installers...


Y is an "icon" for a 3-way mid-position valve.

W is an "icon" for a 3-way diverter valve.

S stands for "separate" HW and CH valves.

C stands for "convection" (i.e. gravity) hot water.


HTH

Rumble wrote:
Graham. wrote:
Why are the letters Y and S used, what do they stand for?

Well, it's an aide-memoir for installers...


Y is an "icon" for a 3-way mid-position valve.

W is an "icon" for a 3-way diverter valve.

S stands for "separate" HW and CH valves.

C stands for "convection" (i.e. gravity) hot water.

Yup, makes sense to me... I had worked out that Y and W were
pictographic, but was struggling with S and C!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/