As many of you will know, I have posted many times about Y-Plan systems and
have (hopefully) helped a few people to diagnose problems with them.

Until recently, I hadn't really studied W-Plan systems (which have a
diverter valve rather than a mid-position valve). However, the subject has
recently arisen in another thread.

Looking at the W-Plan wiring diagram in
http://content.honeywell.com/uk/homes/systems.htm it looks to me as if you
can't have CH until HW is satisfied - even if HW is turned off at the
programmer - because the valve is driven to the CH position by a feed from
the cyl stat's satisfied contact.

Is that the way it's meant to operate? Seems a bid odd to me!

Wouldn't it make sense to have a HW-OFF wire from the programmer (like
Y-Plan does) connected to 5 in the junction box? You could then have CH only
if you specifically didn't want HW.
--
Cheers,
Set Square
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"Set Square" wrote in message
...
As many of you will know, I have posted many times about Y-Plan systems
and
have (hopefully) helped a few people to diagnose problems with them.

Until recently, I hadn't really studied W-Plan systems (which have a
diverter valve rather than a mid-position valve). However, the subject has
recently arisen in another thread.

Looking at the W-Plan wiring diagram in
http://content.honeywell.com/uk/homes/systems.htm it looks to me as if you
can't have CH until HW is satisfied - even if HW is turned off at the
programmer - because the valve is driven to the CH position by a feed from
the cyl stat's satisfied contact.

Is that the way it's meant to operate? Seems a bid odd to me!

Wouldn't it make sense to have a HW-OFF wire from the programmer (like
Y-Plan does) connected to 5 in the junction box? You could then have CH
only
if you specifically didn't want HW.
--
Cheers,
Set Square

http://content.honeywell.com/uk/homes/Catalogue/Sundial%20Plans/3.3%20W%20Plan.pdf

http://tinyurl.com/b5wtw

says that that programmer should be of the type where heating cannot be
selected without hot water.

If I am following you correctly then I presume you are suggesting a HW off
connection from the programmer to terminal 5 to give seperate controls.

I have only ever seen one W plan and I cannot see any good sides to it

Adam

In an earlier contribution to this discussion,
ARWadsworth wrote:


http://tinyurl.com/b5wtw

says that that programmer should be of the type where heating cannot
be selected without hot water.

If I am following you correctly then I presume you are suggesting a
HW off connection from the programmer to terminal 5 to give seperate
controls.

Yes. There may be occasions - maybe when returning home from holiday to a
cold house, for instance - when you might want the heating on without
waiting for the hot water to heat up first.

Unfortunately, I can't get the pdf file, which you cite above, to load - so
I can't see what the rationale is for not having a CH-only mode.
--
Cheers,
Set Square
______
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In an earlier contribution to this discussion,
Set Square wrote:

In an earlier contribution to this discussion,
ARWadsworth wrote:


http://tinyurl.com/b5wtw

says that that programmer should be of the type where heating cannot
be selected without hot water.

If I am following you correctly then I presume you are suggesting a
HW off connection from the programmer to terminal 5 to give seperate
controls.

Yes. There may be occasions - maybe when returning home from holiday
to a cold house, for instance - when you might want the heating on
without waiting for the hot water to heat up first.

Unfortunately, I can't get the pdf file, which you cite above, to
load - so I can't see what the rationale is for not having a CH-only
mode.

I've now managed to get the pdf file to load.

It comes pretty close to contradicting itself - referring to independent
control of HW and CH in some places and then saying that the programmer must
not allow heating to be selected without hot water.

I can't see that it matters *what* the programmer does in this respect - the
effect will be the same. Even with no HW feed from the programmer, the HW
will still be heated (and CH not heated) until the cyl stat is satisfied. So
if you want CH only, you have to turn the cyl stat down below the
temperature of the water in the cylinder.

My suggestion of a HW-off feed from the programmer would enable the same
thing to be achieved without needing to frig about with the cyl stat.
--
Cheers,
Set Square
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Set Square wrote:
As many of you will know, I have posted many times about Y-Plan systems and
have (hopefully) helped a few people to diagnose problems with them.

Until recently, I hadn't really studied W-Plan systems (which have a
diverter valve rather than a mid-position valve). However, the subject has
recently arisen in another thread.

Looking at the W-Plan wiring diagram in
http://content.honeywell.com/uk/homes/systems.htm it looks to me as if you
can't have CH until HW is satisfied - even if HW is turned off at the
programmer - because the valve is driven to the CH position by a feed from
the cyl stat's satisfied contact.

Is that the way it's meant to operate? Seems a bid odd to me!

Wouldn't it make sense to have a HW-OFF wire from the programmer (like
Y-Plan does) connected to 5 in the junction box? You could then have CH only
if you specifically didn't want HW.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Is it usual for programmers on a Y-plan system (or even S-plan) to
allow for HW priority? There seems very little point in buying a
quick-recovery cylinder and finding that it still takes about an hour
to heat the tank because all the radiators are on!

In an earlier contribution to this discussion,
Sadly wrote:


Is it usual for programmers on a Y-plan system (or even S-plan) to
allow for HW priority? There seems very little point in buying a
quick-recovery cylinder and finding that it still takes about an hour
to heat the tank because all the radiators are on!

No - neither Y-Plan nor S-Plan provides for HW priority. They both allow for
HW and CH to be on concurrently with *equal* priority.

W-Plan does, of course, give HW priority - but can keep the CH off for a
very long if you *haven't* got a quick recovery cylinder.
--
Cheers,
Set Square
______
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Set Square wrote:

In an earlier contribution to this discussion,
ARWadsworth wrote:


http://tinyurl.com/b5wtw

says that that programmer should be of the type where heating cannot
be selected without hot water.

If I am following you correctly then I presume you are suggesting a
HW off connection from the programmer to terminal 5 to give seperate
controls.

Yes. There may be occasions - maybe when returning home from holiday
to a cold house, for instance - when you might want the heating on
without waiting for the hot water to heat up first.

Unfortunately, I can't get the pdf file, which you cite above, to
load - so I can't see what the rationale is for not having a CH-only
mode.

I've now managed to get the pdf file to load.

It comes pretty close to contradicting itself - referring to independent
control of HW and CH in some places and then saying that the programmer
must
not allow heating to be selected without hot water.

Pretty close to contradicting itself is generous, I thought it was a direct
hit on the Heating Only Requirement section.


I can't see that it matters *what* the programmer does in this respect -
the
effect will be the same. Even with no HW feed from the programmer, the HW
will still be heated (and CH not heated) until the cyl stat is satisfied.
So
if you want CH only, you have to turn the cyl stat down below the
temperature of the water in the cylinder.

I agree. So the only reason would be so the user can see a neon/led in the
programmer to say the water is on. There is no other reason


My suggestion of a HW-off feed from the programmer would enable the same
thing to be achieved without needing to frig about with the cyl stat.


Your suggestion would work fine IMHO. I might try it out as I have to fit an
electrical supply for an immersion on a W plan over Xmas (they need a back
up in the event of a boiler failure).

Adam

Set Square wrote:
In an earlier contribution to this discussion,
Sadly wrote:


Is it usual for programmers on a Y-plan system (or even S-plan) to
allow for HW priority? There seems very little point in buying a
quick-recovery cylinder and finding that it still takes about an hour
to heat the tank because all the radiators are on!

No - neither Y-Plan nor S-Plan provides for HW priority. They both allow for
HW and CH to be on concurrently with *equal* priority.

W-Plan does, of course, give HW priority - but can keep the CH off for a
very long if you *haven't* got a quick recovery cylinder.

Maybe I will come up with a cunning way to add one of these "1-hour
boost" type switches to my Y-plan system to allow the HW to take
priority for a while - this means that when taking a bath I can hit the
boost so that the hot water takes priority for the next hour...

Maybe I will first get the system working as standard and see how long
it does take to recover!

In an earlier contribution to this discussion,
Sadly wrote:


Maybe I will come up with a cunning way to add one of these "1-hour
boost" type switches to my Y-plan system to allow the HW to take
priority for a while - this means that when taking a bath I can hit
the boost so that the hot water takes priority for the next hour...

Maybe I will first get the system working as standard and see how long
it does take to recover!

I have a Y-Plan system with a Danfoss programmer which has a 1-hour boost
facility for the HW. But that just turns the HW on for an hour at a time
when it otherwise wouldn't be on. It doesn't turn CH off for that period.

It seems to me that you either need a very fast recovery cylinder and a HW
priority facility OR a method of allowing the HW to get hot while the CH is
on without interfering unduly with the CH. I have a balancing gate valve on
my HW circuit which can restrict the flow a bit so as not to interfere with
the CH. Obviously the water would take a bit longer to heat when this was
partially closed. This is not a problem unless you want a lot of baths in
quick succession.

My current modus operandi doesn't use the gate valve, but runs the HW and CH
asynchronously. I use the main programmer to time the HW, and a programmable
room stat to time the CH - so that they can be on at non-overlapping times.
This means that the gate valve can be fully open - allowing the water to
heat up as fast as its (non fast-recovery) heat exchanger allows. Admittedly
it doesn't cater explicitly for unscheduled hot water demands - but has
never caused any problems that I am aware of.
--
Cheers,
Set Square
______
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Set Square wrote:

In an earlier contribution to this discussion,
Sadly wrote:


Maybe I will come up with a cunning way to add one of these "1-hour
boost" type switches to my Y-plan system to allow the HW to take
priority for a while - this means that when taking a bath I can hit
the boost so that the hot water takes priority for the next hour...

Maybe I will first get the system working as standard and see how long
it does take to recover!

I have a Y-Plan system with a Danfoss programmer which has a 1-hour boost
facility for the HW. But that just turns the HW on for an hour at a time
when it otherwise wouldn't be on. It doesn't turn CH off for that period.

It seems to me that you either need a very fast recovery cylinder and a HW
priority facility OR a method of allowing the HW to get hot while the CH is
on without interfering unduly with the CH. I have a balancing gate valve on
my HW circuit which can restrict the flow a bit so as not to interfere with
the CH. Obviously the water would take a bit longer to heat when this was
partially closed. This is not a problem unless you want a lot of baths in
quick succession.

My current modus operandi doesn't use the gate valve, but runs the HW and CH
asynchronously. I use the main programmer to time the HW, and a programmable
room stat to time the CH - so that they can be on at non-overlapping times.
This means that the gate valve can be fully open - allowing the water to
heat up as fast as its (non fast-recovery) heat exchanger allows. Admittedly
it doesn't cater explicitly for unscheduled hot water demands - but has
never caused any problems that I am aware of.
--
Cheers,
Set Square
______
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We have a huge bath, probably 225ltrs (ISTR that this is the max
without needing to inform the water board) and using just an immersion
heater (set very hot with a blending valve on the output) there isnt
enough hot water to fill the bath. This should be better with the
boiler running as I expect that with the immersion heater it only
really heats the to 2/3rds or so.

My concern is that when running a bath I want to have the boiler
pumping loads of heat into the cylinder to keep it warm enough that I
can get a decent bath-full.