Prog/stats. quite how do they work... i.e. do they have a "fuzzy logic"
so the temp you want at a set time is the time they know from previous
days that needs the heating switching on X hrs prior or are they really
just nothing more than a "programmer" fitted in place of a T/Stat but
with t/stat capabilities?

I know "Optimum start" t/stat's delay coming on to the last moment. is
this for all programs in day or just the first.

Also.... lets say, at 1700 hrs you have a temp change from 16 deg.C to
21 deg.C which temp takes priority 16 or 21.

Am I making any sense at all?

TIA
Pete
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In message , "Pet @
www.gymratz.co.uk" writes
Prog/stats. quite how do they work... i.e. do they have a "fuzzy logic"
so the temp you want at a set time is the time they know from previous
days that needs the heating switching on X hrs prior or are they really
just nothing more than a "programmer" fitted in place of a T/Stat but
with t/stat capabilities?


They are generally programmers which alter the thermostat at times which
you set. E.g. if there is a change from 16 to 20 at 1700, it starts
heating up to 20 at 1700 and reaches 20 when it reaches it.

I know "Optimum start" t/stat's delay coming on to the last moment. is
this for all programs in day or just the first.

Also.... lets say, at 1700 hrs you have a temp change from 16 deg.C to
21 deg.C which temp takes priority 16 or 21.


Presumably, the optimum stats will start heating from 16 to 20 before
1700, so that they aim to be at 20 at 1700 - I havent used one, so am
guessing here.

Am I making any sense at all?

Kind of g

--
Richard Faulkner

On Tue, 12 Apr 2005 03:17:40 +0100, Richard Faulkner wrote:

They are generally programmers which alter the thermostat at times
which you set. E.g. if there is a change from 16 to 20 at 1700, it
starts heating up to 20 at 1700 and reaches 20 when it reaches it.

Correct, variations on the number of set points during the day, 6 is
common but cheaper ones only have 4.

Presumably, the optimum stats will start heating from 16 to 20
before 1700, so that they aim to be at 20 at 1700 - I havent used
one, so am guessing here.

Optimum Start only works on the first set point of the day. This
ensures that the building is at the set point temp by the time that
set point arrives. No more getting up to a cool house because it's
cold outside. Though the real saving is in fuel as the heating doesn't
come on until it needs to, with a normal stat the heating would most
likely be programmed to come on well before the point in time that a
certain temp was required. So during the not so cold parts of the year
it's on too early and thus too long.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:

Optimum Start only works on the first set point of the day. This
ensures that the building is at the set point temp by the time that
set point arrives. No more getting up to a cool house because it's
cold outside. Though the real saving is in fuel as the heating doesn't
come on until it needs to, with a normal stat the heating would most
likely be programmed to come on well before the point in time that a
certain temp was required. So during the not so cold parts of the year
it's on too early and thus too long.

Would the saving in fuel be significant though as I'd have thought the
initial heat up from cold is the main gas guzzler which will take as
long whichever way you look at it. Once up to temp it would just be a
quick burst of energy now and again to maintain temp which shouldn't
make a huge difference I would have though.


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On Tue, 12 Apr 2005 16:23:17 +0000, Pet @ www.gymratz.co.uk wrote:

Dave Liquorice wrote:

Optimum Start only works on the first set point of the day. This
ensures that the building is at the set point temp by the time that
set point arrives. No more getting up to a cool house because it's
cold outside. Though the real saving is in fuel as the heating doesn't
come on until it needs to, with a normal stat the heating would most
likely be programmed to come on well before the point in time that a
certain temp was required. So during the not so cold parts of the year
it's on too early and thus too long.

Would the saving in fuel be significant though as I'd have thought the
initial heat up from cold is the main gas guzzler which will take as
long whichever way you look at it. Once up to temp it would just be a
quick burst of energy now and again to maintain temp which shouldn't
make a huge difference I would have though.

According to some sources (The EST) the saving for fitting a complete set
of modern controls (Compliant to Part L) is 18% relative to the worst case
gravity water + timer switch and wall thermostat. No figures are given for
set-back savings. I would guess it is at most a few percent.


--
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On Tue, 12 Apr 2005 16:23:17 GMT, Pet @ www.gymratz.co.uk wrote:

Would the saving in fuel be significant though as I'd have thought
the initial heat up from cold is the main gas guzzler which will
take as long whichever way you look at it. Once up to temp it would
just be a quick burst of energy now and again to maintain temp ...

True enough I guess but it depends on how long you maintain that set
temp for. The optimum start here is set for 90 mins but then this is a
large, exposed, draughty, poorly insulated, 17C stone farmhouse,
rather than an modern, hermeticaly sealed, insulated box. With a bit
of wind blowing and exterior temp down to near zero the 38kW boiler
can only just cope...

--
Cheers
Dave. pam is missing e-mail

Re programmable stats


Another saving with these is that they keep a more constant temp than
bimetallic stats. If you set it to 20 it will be at 20 +/- .25 deg C,
whereas with a bimetal you're looking at 1 deg C hysteresis or more.
Real life setting is decided by what is warm enough, so with bimetals
the average temp is slightly higher for the same level of comfort,
since it is the min temp that will be set the same.

Due to having a separate program for weekdays and weekends, again there
are savings in many cases.

If a progstat cost =A340, and your annual heat bill is =A3400, saving
just 4% will mean it pays for itself in 2.5 years, and goes on making
savings for the rest of its life. IRL I would expect larger savings in
most cases. It just doesnt make sense to use bimetal stats any more.


NT

wrote:

Due to having a separate program for weekdays and weekends, again there
are savings in many cases.

A C/H timer does that though.

If a progstat cost £40, and your annual heat bill is £400, saving
just 4% will mean it pays for itself in 2.5 years, and goes on making
savings for the rest of its life. IRL I would expect larger savings in
most cases. It just doesnt make sense to use bimetal stats any more.

What about where you have a stat in each room. (UFH)
One main programmer to do all rooms on a regular 'stat would be easier
to operate than having to program and adjust each separate room stat.

Also cost saving would be fairly significant.

I am going to try the single C/H programmer with a regular stat per room
to start with and see (as I had it supplied as standard with my UFH kit)

I May well change to programmable stats should I see ones I like the
look of as most are just plain ugly.

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Pet @ www.gymratz.co.uk wrote:
wrote:

Due to having a separate program for weekdays and weekends, again
there
are savings in many cases.

A C/H timer does that though.

A CH timer just switches on and off, whereas a progstat will set
differing temps for many time zones. You dont need the same temp when
youre dropping in for 20 mins at lunchtime as when youre getting out of
bed as when youre wasting time watching tv in the evening etc.

Also of course many CH timers currently in use dont differentiate
between workday and weekend. Replacing either the timer or the stat can
give benefits, but a new stat does more and saves more.


If a progstat cost =A340, and your annual heat bill is =A3400, saving
just 4% will mean it pays for itself in 2.5 years, and goes on
making
savings for the rest of its life. IRL I would expect larger savings
in
most cases. It just doesnt make sense to use bimetal stats any
more.

What about where you have a stat in each room. (UFH)
One main programmer to do all rooms on a regular 'stat would be
easier
to operate than having to program and adjust each separate room stat.

Also cost saving would be fairly significant.

yes, certainly the numbers are different. A use for all those discarded
bimetal stats maybe.

On second thoughts though, if youer zoning up the house like that it
makes sense to keep some upstairs room temps low during the day, IOW a
progstat would return a lot more savings than fixed temp bimetals. I'm
sure this is the way forward with CH, every room its own zone. Its very
wasteful heating everything all day.


NT

wrote:

On second thoughts though, if youer zoning up the house like that it
makes sense to keep some upstairs room temps low during the day, IOW a
progstat would return a lot more savings than fixed temp bimetals. I'm
sure this is the way forward with CH, every room its own zone. Its very
wasteful heating everything all day.

When finally completed we'll have the upstairs
(Living/kitchen-Dining/Hall/Study) areas on individual bi/met stats and
the downstairs (bedrooms/bathroom) on separate timer using T/static
valves so we _should_ get the best of both worlds..... I a hope.
:¬)


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On Thu, 14 Apr 2005 17:14:17 GMT, Pet @ www.gymratz.co.uk wrote:

When finally completed we'll have the upstairs
(Living/kitchen-Dining/Hall/Study) areas on individual bi/met stats
and the downstairs (bedrooms/bathroom) on separate timer using
T/static valves so we _should_ get the best of both worlds..... I a
hope. :=AC)

I don't think you will unless you religiously adjust the simple stats
all the time. Remember when the system is on it's on and the rooms
will run to their set temps with no regards to the time of day.

I doubt that you'll knock each rooms stat back as you leave a room,
it'll be set at what ever that room is comfortable at and stay there,
whether the room is likely to be used or not. If you are going to the
trouble and expense of all those stats and zone valves (is it a wet
system?) a programmable stat, even a simple one for =A340, will give you=

much better control. Remember that heat loss is proportional to the
temp difference you loose more energy from a room maintained at 21C
than you do from one at 18C.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:

I don't think you will unless you religiously adjust the simple stats
all the time. Remember when the system is on it's on and the rooms
will run to their set temps with no regards to the time of day.

I doubt that you'll knock each rooms stat back as you leave a room,
it'll be set at what ever that room is comfortable at and stay there,
whether the room is likely to be used or not. If you are going to the
trouble and expense of all those stats and zone valves (is it a wet
system?) a programmable stat, even a simple one for £40, will give you
much better control. Remember that heat loss is proportional to the
temp difference you loose more energy from a room maintained at 21C
than you do from one at 18C.

But that still doesn't make it better. How will the prog-stat know when
anyone is in the room or not? The timer will be set for suitable times
for temps. a "living area" would want comfortable temps during times of
use so, all prog-stats would be set identically anyway.

(Yes it is a wet system)

Besides, as I mentioned before, I have only seen really ugly prog.stats
available so until one comes out that is really pleasing on the eye, the
current combination is the lesser of the 2 evils aesthetically.

:¬)

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Pet @ www.gymratz.co.uk wrote:
Dave Liquorice wrote:

system?) a programmable stat, even a simple one for =A340, will give
you
much better control. Remember that heat loss is proportional to the

temp difference you loose more energy from a room maintained at 21C

than you do from one at 18C.


But that still doesn't make it better. How will the prog-stat know
when
anyone is in the room or not? The timer will be set for suitable
times
for temps. a "living area" would want comfortable temps during times
of
use so, all prog-stats would be set identically anyway.

bedrooms can be set to warm in the evening and only semi-warm in the
day. Result is significant energy savings.

NT

On Fri, 15 Apr 2005 16:00:26 GMT, Pet @ www.gymratz.co.uk wrote:

How will the prog-stat know when anyone is in the room or not?

It wouldn't ...

The timer will be set for suitable times for temps. a "living area"
would want comfortable temps during times of use so, all prog-stats
would be set identically anyway.

.... but of you had prog stats in each room you wouldn't program the
same as each room has a different useage profile. You set them so that
when the room was most likely to be used it was at a comfortable temp
and when not likely to be used several C lower.

Even so remember that when your active you don't need quite such a
warm room as crashed in front of the telly. The single prog stat here
holds the house to 18.5C for most of the day and then increases it to
20C for early to mid evening then drops it back to 18.5C by late
evening before effectively switching the heating off by dropping to
15C for the night. That 1.5C temp difference will save energy compared
to simple stat holding the place at 20C all day.

--
Cheers
Dave. pam is missing e-mail

wrote:

bedrooms can be set to warm in the evening and only semi-warm in the
day. Result is significant energy savings.

WHy not just set bedrooms to off during day?
:¬)


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In message .com,
wrote:

Re programmable stats


Another saving with these is that they keep a more constant temp than
bimetallic stats. If you set it to 20 it will be at 20 +/- .25 deg C,
whereas with a bimetal you're looking at 1 deg C hysteresis or more.

Sorry to come in late to this thread, but I've been "away" for six
months or so :-)

I'd have thought that such fine-grain control, particularly of
gas-heated wet systems would be *worse* in terms of energy efficiency
than a system with 2 or 3 degrees of hysteresis. All past advice on this
group seems to point to the fact that boilers are most efficient when
they run for long periods, and least efficient when they short cycle on
and off.

Hwyl!

M.

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Martin Angove wrote:
In message .com,
wrote:

Re programmable stats


Another saving with these is that they keep a more constant temp
than
bimetallic stats. If you set it to 20 it will be at 20 +/- .25 deg
C,
whereas with a bimetal you're looking at 1 deg C hysteresis or
more.

Sorry to come in late to this thread, but I've been "away" for six
months or so :-)

I'd have thought that such fine-grain control, particularly of
gas-heated wet systems would be *worse* in terms of energy efficiency
than a system with 2 or 3 degrees of hysteresis. All past advice on
this
group seems to point to the fact that boilers are most efficient when
they run for long periods, and least efficient when they short cycle
on
and off.

Hwyl!

M.

why is that?

In terms of heat loss thru walls etc, a more costant temp will lose
less heat, so the q remains how the boiler efficiency will affect it.


NT

In message . com,
wrote:

Martin Angove wrote:
In message .com,
wrote:

Re programmable stats


Another saving with these is that they keep a more constant temp
than
bimetallic stats. If you set it to 20 it will be at 20 +/- .25 deg
C,
whereas with a bimetal you're looking at 1 deg C hysteresis or
more.

Sorry to come in late to this thread, but I've been "away" for six
months or so :-)

I'd have thought that such fine-grain control, particularly of
gas-heated wet systems would be *worse* in terms of energy efficiency
than a system with 2 or 3 degrees of hysteresis. All past advice on
this
group seems to point to the fact that boilers are most efficient when
they run for long periods, and least efficient when they short cycle
on
and off.

Hwyl!

M.

why is that?

In terms of heat loss thru walls etc, a more costant temp will lose
less heat, so the q remains how the boiler efficiency will affect it.



The difference in heat loss between (say) 19C +/- 0.25C and 19C +/- 2C
can't be that great, surely? Intuition implies it should be exactly the
same, though I doubt it is in practice. My question was about boiler
running times. Received wisdom seems to be that running the boiler for 5
or 10 minutes repeated every 15 to "top up" the heat is going to be less
efficient than running it for a solid 30 minutes every hour. Of course
I'm guessing here with the timings which will vary hugely depending on
various factors including: insulation levels and ventilation levels of
the house, amount of thermal mass inside, outside temperature, exact
placement of thermostat, temperature setpoint of heating circuit, type
of heating (i.e. rads/ufh/other), occupancy of the house and so on and
so forth.

Just curious.

Hwyl!

M.

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In an earlier contribution to this discussion,
Martin Angove wrote:


The difference in heat loss between (say) 19C +/- 0.25C and 19C +/- 2C
can't be that great, surely?

Probably not. However, from a comfort point of view, you ain't going to
settle for the temperature dropping to 17 before the heating comes on
again - so you'll jack up the stat to run at 21 +/- 2, thus increasing the
overall heat loss.
--
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Set Square
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Martin Angove wrote:
In message . com,
wrote:

than a system with 2 or 3 degrees of hysteresis. All past advice
on
this
group seems to point to the fact that boilers are most efficient
when
they run for long periods, and least efficient when they short
cycle
on
and off.

why is that?

In terms of heat loss thru walls etc, a more costant temp will lose
less heat, so the q remains how the boiler efficiency will affect
it.

The difference in heat loss between (say) 19C +/- 0.25C and 19C +/-
2C
can't be that great, surely? Intuition implies it should be exactly
the
same, though I doubt it is in practice.

Humans set room temps according to whats comfortable. If eg 19C is
comfortable, you can either set it to 19.25 +/- .25 or 20 +/- 1. Hence
bimetals will lose more heat for the same comfort level, as the same
comfort level requires higher ave temp.


My question was about boiler
running times. Received wisdom seems to be that running the boiler
for 5
or 10 minutes repeated every 15 to "top up" the heat is going to be
less
efficient than running it for a solid 30 minutes every hour.

on what basis do you think its less efficient? Im not aware of any
mechanism that would make it so.


NT

In message .com,
wrote:

Martin Angove wrote:

My question was about boiler running times. Received wisdom seems to
be that running the boiler for 5 or 10 minutes repeated every 15 to
"top up" the heat is going to be less efficient than running it for
a solid 30 minutes every hour.

on what basis do you think its less efficient? Im not aware of any
mechanism that would make it so.



Neither am I, but that is what is commonly stated by all the usual
heating-types on this ng. Myself, I'm a 'lectric kind of a guy.

For a current thread which has several messages by several people
stating that it is desirable to have a boiler on for longish times
rather than cycling off and on, try "Heat Bank - space heating or not"
(and subsequent subjects) originated by "Jeff".

Hwyl!

M.

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On Wed, 20 Apr 2005 15:12:34 +0100, Martin Angove wrote:

My question was about boiler running times. Received wisdom seems
to be that running the boiler for 5 or 10 minutes repeated every
15 to "top up" the heat is going to be less efficient than running
it for a solid 30 minutes every hour.

on what basis do you think its less efficient? Im not aware of any
mechanism that would make it so.

Neither am I, but that is what is commonly stated by all the usual
heating-types on this ng. Myself, I'm a 'lectric kind of a guy.

I think there might be a misunderstanding about the term "short
cycling". I use it to mean that the boiler fires up on it's own
accord, to either keep itself hot or associated gravity pipework. This
is almost always down to a poor or non-existant control system.

Think of a gravity HW system with no tank stat. At switch on the
boiler fires non stop but eventually the water in the tank will
approach that in the primary and the boiler stat will operate
preventing the boiler and/or tank actually boiling. The boiler starts
to cool, it's got a whacking draft through it after all, after a
period of time the boiler stat will close and the boiler will fire
until the boiler stat opens again. This cycle is generally fairly
short 30" to a min firing, a few minutes off. With no tank stat to
turn the boiler truely off when the water is hot the boiler will
"short cycle" as long as it is powered.

I can't see that 30mins in every 60 is any different to 10 mins in
every 20. The boiler still fires for 30 min in every hour. What will
happen is the temperature fluctuations will be greater in the former.

For a current thread which has several messages by several people
stating that it is desirable to have a boiler on for longish times
rather than cycling off and on, try "Heat Bank - space heating or
not" (and subsequent subjects) originated by "Jeff".

I've not been following that thread but a heat bank is a little
different to a room with people in it. I would expect a decent heat
bank controller to have some anticipation, ie it doesn't keep the heat
bank fully heated when there is little demand for the energy, thus
saving losses that a higher maintained temperature would incur. It
would have course have to "know" when to start building up the stored
temp in anticpation of use, this it could learn over a period of time.

--
Cheers
Dave. pam is missing e-mail