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Old May 18th 19, 01:18 PM posted to uk.d-i-y
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On 18/05/19 10:33, Harry Bloomfield wrote:

Our new Vailant can inteligently decide just how much heat it needs to
produce to meet its desired room temperatures, taking into
consideration the outdoor temperature and indoor. It doesn't overshoot,
rather it learns what is needed and can modulate right down to match
the demand. The pipes don't creak and moan anymore.


Well, I really am willing to be educated, but I really don't understand
what it is supposed to be doing to "intelligently" decide something.
Firstly, I assume that as with almost any device, it will have a "sweet
spot" where it is working at its highest efficiency. Its specs may state
"85%" efficient, but in practice that might mean from a low of 82% to a
high of 88%. Now it should be operating as near to 88% all the time as
it can, but obviously there are constraints - it won't be so efficient
starting from cold, for example.

As far as I am concerned, when the room thermostat calls for heat, the
boiler should go flat out to heat the room as quickly as possible. In
any case, it's the room thermostat which tells the boiler what to do,
and it's the thermostat's hysteresis which is the arbiter of how
comfortable or uncomfortable you will be. I've switched ours to the
lowest hysteresis possible, which is +/- 0.5 deg C. That may mean the
boiler in on/off more frequently, but I'm a lot more comfortable with
the room at a steady 20.5 - 21.5 deg C, than I would be at 19 - 23 deg C.

And does it really matter most of the time what the outside temperature
is? It will almost always be much lower than the room temperature, and
so maximum heat will be required to warm the room up.

The previous boiler either ran and produced full heat, or none, though
it did modulate, it only modulated based on its internal temperature.


Having said all the above, I see from the manual of my W-B Greenstar that :
"The gas supply to the burner is controlled according to the level of
demand for heat. The boiler operates with a low flame if the demand for
heat reduces. The technical term for this process is modulating control.
Modulating control reduces temperature fluctuations and provides an even
distribution of heat throughout the home. This means that the boiler may
stay on for relatively long periods of time but will use less gas than a
boiler that continually switches on and off."

Out of interest, does your boiler's spec state that it is most efficient
when it is ticking over (or whatever it is doing to decide what heat it
needs to supply)?

So exactly how does the boiler do what it's supposed to do? You set the
boiler hot water temperature to the rads at, for example, 60 deg C, and
you set the room temperature thermostat to 20 deg C, and the hysteresis
to 1 deg C. How exactly does it (in the case of my W-B Greenstar)
"operate with a low flame if the demand for heat reduces"? How often
does the "demand for heat" reduce?

--

Jeff

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Old May 18th 19, 02:10 PM posted to uk.d-i-y
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On 18/05/2019 08:15, Brian Gaff wrote:
The problem is that companies like British gas seem to always condemn
boilers


True, often saying the parts are obsolete. What they mean is that BG no
longer stock the parts but often they are still available from the
manufacturer for very many years afterwards.


and then offer what seems a good deal on a new one.


Not true. They will start with a very high price and then offer a large
discount and/or trade-in on the old boiler ending up with a price that
is often twice that of the competitors.

I suspect some
kind of scam going on myself.


They get commission when selling or providing a lead that results in a
new boiler.




--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk
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Old May 18th 19, 09:29 PM posted to uk.d-i-y
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Jeff Layman brought next idea :
Out of interest, does your boiler's spec state that it is most efficient when
it is ticking over (or whatever it is doing to decide what heat it needs to
supply)?

So exactly how does the boiler do what it's supposed to do? You set the
boiler hot water temperature to the rads at, for example, 60 deg C, and you
set the room temperature thermostat to 20 deg C, and the hysteresis to 1 deg
C. How exactly does it (in the case of my W-B Greenstar) "operate with a low
flame if the demand for heat reduces"? How often does the "demand for heat"
reduce?


I had the boiler installed 14 months ago and I only recently added the
fancy controls. Until then it just had simple time clock and switching
stats controlling it. Then the boiler in operation was very noticeable
from both the noise from the boiler in operation and the ticking of
heating and cooling pipework.

Now the entire system is much quieter, because it knows it doesn't have
to run flat out, it knows how much heat input is needed so it can
modulate to run at a much lower level of burn. Before, it only
modulated down, based on its return temperature and often shut down
completely only to then light up again a few minutes later, because the
demand was still not satisfied. Rather like someone driving flat out,
then banging the brakes on, then flat out again - very wasteful of
fuel.
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Old May 19th 19, 08:49 AM posted to uk.d-i-y
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On 18/05/19 21:29, Harry Bloomfield wrote:
Jeff Layman brought next idea :
Out of interest, does your boiler's spec state that it is most efficient when
it is ticking over (or whatever it is doing to decide what heat it needs to
supply)?

So exactly how does the boiler do what it's supposed to do? You set the
boiler hot water temperature to the rads at, for example, 60 deg C, and you
set the room temperature thermostat to 20 deg C, and the hysteresis to 1 deg
C. How exactly does it (in the case of my W-B Greenstar) "operate with a low
flame if the demand for heat reduces"? How often does the "demand for heat"
reduce?


I had the boiler installed 14 months ago and I only recently added the
fancy controls. Until then it just had simple time clock and switching
stats controlling it. Then the boiler in operation was very noticeable
from both the noise from the boiler in operation and the ticking of
heating and cooling pipework.

Now the entire system is much quieter, because it knows it doesn't have
to run flat out, it knows how much heat input is needed so it can
modulate to run at a much lower level of burn. Before, it only
modulated down, based on its return temperature and often shut down
completely only to then light up again a few minutes later, because the
demand was still not satisfied. Rather like someone driving flat out,
then banging the brakes on, then flat out again - very wasteful of
fuel.


That's fair enough. I waded through this and it supports your findings:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/648337/heating-controls-compensation-tpi-bre.pdf

I guess a 3% or so saving is worth having, particularly if repeated over
millions of gas boilers. But then they'll all be disappearing in a few
years to be replaced by renewables...

--

Jeff
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Old May 19th 19, 10:36 AM posted to uk.d-i-y
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Jeff Layman laid this down on his screen :
That's fair enough. I waded through this and it supports your findings:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/648337/heating-controls-compensation-tpi-bre.pdf

I guess a 3% or so saving is worth having, particularly if repeated over
millions of gas boilers. But then they'll all be disappearing in a few years
to be replaced by renewables...


Well, the main point is that my heating doesn't constantly over react
on temperature - the house temperature is much more even now than
before, due to the more consistent steady heat input.


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Old May 19th 19, 12:55 PM posted to uk.d-i-y
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On 18/05/2019 11:22, Dave Plowman (News) wrote:
A non balanced flue boiler is going to be about as inefficient as they
come.


Not necessarily.

My house, like millions of others, had a BAxi Bermuda back
boiler (about 15Kw) with a 3/6 Kw radiant fire.

The flue was Class 2 flue blocks built into the inner leaf
of the cavity wall, which passed through the upstairs front
bedroom and kept that North-facing room quite comfortable on
its own.

Even the radiator was only half the size of the other,
in a south facing bedroom.

If the original numpty builders hadn't chucked the cement
snots inside the flue blocks and mortared the joints correctly
I might still have it today, but eventually the metal work
that directs the gas fire flue into the main flue corrodes
and then the fire is condemned even if the boiler works fine.

Oddly enough, a neighbour fell for the BG boiler scam and
allwoed them to remove their back boiler and fit a WB
condenser in an upstairs bedroom cupboard. They also removed
all the flue pipe work that connected to the
ridge tile (the class 2 blocks had been replaced with
aluminium single skin stuff that had to be boxed in where
it passed through the bedroom, many years earlier).

However, despite removed ALL the flues, they left the
gas fire and told them they could still use it (even
without a flue ??). They are still alive so I guess they
only use central heating.
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Old May 19th 19, 03:12 PM posted to uk.d-i-y
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In article ,
Andrew wrote:
On 18/05/2019 11:22, Dave Plowman (News) wrote:
A non balanced flue boiler is going to be about as inefficient as they
come.


Not necessarily.


Yes, necessarily.

My house, like millions of others, had a BAxi Bermuda back
boiler (about 15Kw) with a 3/6 Kw radiant fire.


A cheap job, then.

The flue was Class 2 flue blocks built into the inner leaf
of the cavity wall, which passed through the upstairs front
bedroom and kept that North-facing room quite comfortable on
its own.


Just what you want on a nice day when the boiler is only heating the
water...

Even the radiator was only half the size of the other,
in a south facing bedroom.


If the original numpty builders hadn't chucked the cement
snots inside the flue blocks and mortared the joints correctly
I might still have it today, but eventually the metal work
that directs the gas fire flue into the main flue corrodes
and then the fire is condemned even if the boiler works fine.


Think you mean as well as it ever worked.

But I'd guess you are one of those who don't mind throwing their pound
notes up the chimney.

--
*Tell me to 'stuff it' - I'm a taxidermist.

Dave Plowman London SW
To e-mail, change noise into sound.
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Old May 19th 19, 09:09 PM posted to uk.d-i-y
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On 17/05/2019 23:13, wrote:
You haven't given us the slightest clue of information to assess whether it's had it. Do you think that might help?


It would. I'll just get in the car an pop over. It's only 4 hours each
way

Andy
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Old May 19th 19, 09:14 PM posted to uk.d-i-y
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On Sunday, 19 May 2019 21:09:25 UTC+1, Vir Campestris wrote:
On 17/05/2019 23:13, tabbypurr wrote:


You haven't given us the slightest clue of information to assess whether it's had it. Do you think that might help?


It would. I'll just get in the car an pop over. It's only 4 hours each
way

Andy


I hear you. But I don't see what anyone can say without any info. You might look to see if parts are available, not excluding ebay where often a whole boiler's worth of parts can be had. If they're available you probably won't need a new one. Other than that we await that 8 hour drive.


NT
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Old May 20th 19, 05:59 AM posted to uk.d-i-y
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"Jeff Layman" wrote in message
...
On 18/05/19 10:33, Harry Bloomfield wrote:

Our new Vailant can inteligently decide just how much heat it needs to
produce to meet its desired room temperatures, taking into
consideration the outdoor temperature and indoor. It doesn't overshoot,
rather it learns what is needed and can modulate right down to match
the demand. The pipes don't creak and moan anymore.


Well, I really am willing to be educated, but I really don't understand
what it is supposed to be doing to "intelligently" decide something.
Firstly, I assume that as with almost any device, it will have a "sweet
spot" where it is working at its highest efficiency.


Not necessarily and it isnt always highest efficiency that matters,
in some situations getting the house up to the temperature you
want as quickly as possible without any overshoot at all is what
is needed when changing the house temperature significantly,
like when its been off when there is no one in the house and
someone has showed up, or when going between overnight
and normal temps when someone gets up etc.

Its specs may state "85%" efficient, but in practice that might mean from
a low of 82% to a high of 88%. Now it should be operating as near to 88%
all the time as it can, but obviously there are constraints - it won't be
so efficient starting from cold, for example.


And that last is what matters more to most comfort wise.

As far as I am concerned, when the room thermostat calls for heat, the
boiler should go flat out to heat the room as quickly as possible.


Not when that produces an overshoot in temperature.

In any case, it's the room thermostat which tells the boiler what to do,
and it's the thermostat's hysteresis which is the arbiter of how
comfortable or uncomfortable you will be. I've switched ours to the lowest
hysteresis possible, which is +/- 0.5 deg C. That may mean the boiler in
on/off more frequently, but I'm a lot more comfortable with the room at a
steady 20.5 - 21.5 deg C, than I would be at 19 - 23 deg C.


Yes, but that’s a different issue to how intelligent the control is.

And does it really matter most of the time what the outside temperature
is? It will almost always be much lower than the room temperature, and so
maximum heat will be required to warm the room up.


Not when you know that the difference between the inside and
the outside isnt as great and that it doesn’t need maximum heat
to adjust the house temperature in a reasonable time. It may well
be better to not use maximum heat when say it is changing from
overnight lower temp to normal daytime temp when the occupant
who has just got up has a shower as soon as they get up and so
wont notice that the house isnt at the daytime temp for a while.

Also when the control has been told to heat the house when
the first person has come home from work, it may well make
sense to use maximum heat when it has observed that the
house takes a long time to get up to temperature when the
outside temperature is so low the last time it had to do that,
say because the insulation leaves quite a bit to be desired.

The previous boiler either ran and produced full heat, or none, though
it did modulate, it only modulated based on its internal temperature.


Having said all the above, I see from the manual of my W-B Greenstar that
:
"The gas supply to the burner is controlled according to the level of
demand for heat. The boiler operates with a low flame if the demand for
heat reduces. The technical term for this process is modulating control.
Modulating control reduces temperature fluctuations and provides an even
distribution of heat throughout the home. This means that the boiler may
stay on for relatively long periods of time but will use less gas than a
boiler that continually switches on and off."

Out of interest, does your boiler's spec state that it is most efficient
when it is ticking over (or whatever it is doing to decide what heat it
needs to supply)?

So exactly how does the boiler do what it's supposed to do?


By observing what has happened the last time it
needed to heat the house in those circumstances.

You set the boiler hot water temperature to the rads at, for example, 60
deg C, and you set the room temperature thermostat to 20 deg C, and the
hysteresis to 1 deg C. How exactly does it (in the case of my W-B
Greenstar) "operate with a low flame if the demand for heat reduces"?


By knowing how often the thermostat calls for more heat in that situation,
basically getting a measure of how well insulated the house is etc.

How often does the "demand for heat" reduce?


When there is no one home.



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