I have installed two new Worcester 30 CDi system boilers at home. (They work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy Conservation", if the property has TRVs and room thermostats (which is my case), the boilers should be set at the maximum temperature setting and use the thermostats and TRVs to regulate the temperature as needed in each room.

I certainly agree that that arrangement gives the most flexibility. However, based on my reading of condensing boilers, the most condensing and thus, the highest efficiency is achieved at 55 degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about 92 degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is about 62 degrees and still gets the house warm enough (at least now that it is not too cold outside)

What is then the most energy efficient setting?

Thanks,

Antonio

On Sun, 26 Oct 2008 22:23:45 +0000, asalcedo wrote:

I have installed two new Worcester 30 CDi system boilers at home. (They
work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy Conservation",
if the property has TRVs and room thermostats (which is my case), the
boilers should be set at the maximum temperature setting and use the
thermostats and TRVs to regulate the temperature as needed in each
room.

I certainly agree that that arrangement gives the most flexibility.
However, based on my reading of condensing boilers, the most condensing
and thus, the highest efficiency is achieved at 55 degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about 92
degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is about
62 degrees and still gets the house warm enough (at least now that it
is not too cold outside)

What is then the most energy efficient setting?

I think the user's manual is wrong in this respect. As you percieve, the
lowest possible flow temperatures which actually keep the house warm will
result in /marginally/ greater efficiency. Note that condensing boilers are
more efficient than non-condensing types, even when they aren't
condensing: because they /can/ safely condense the designers can get more
heat out of the combustion than in non-condensing designs which have to
allow a margin of safety (and inefficiency) to avoid any possibility of
prolonged condensing in normal operation.

So in practice I'd say set the boiler temperature control about halfway to
start with and experiment. If it doesn't get the house up to temperature
in very cold weather turn it up until it does. Not ideal in this age of
programmable, automatic controls, I know.

There are boilers which wring the last drops of efficiency out of their
designs by modulating their flow temperature to achieve the necessary heat
output to the building, using controls which "tell" the boiler the actual
room temperatures rather than giving a simple stop/go signal as a normal
thermostat (programmable or otherwise) does. Unfortunately such boilers
cost half as much again, or more, than an ordinary good quality condensing
boiler costs[1], and the extra money can usually be better spent on
improving draught-proofing, insulation etc rather than on very marginal
improvements in boiler efficiency.

[1] there doesn't seem any good reason why this should be, except "because
they can".

--
YAPH http://yaph.co.uk

The clairvoyants' meeting has been cancelled due to unforseen circumstances.

In article ,
YAPH writes:
On Sun, 26 Oct 2008 22:23:45 +0000, asalcedo wrote:

I have installed two new Worcester 30 CDi system boilers at home. (They
work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy Conservation",
if the property has TRVs and room thermostats (which is my case), the
boilers should be set at the maximum temperature setting and use the
thermostats and TRVs to regulate the temperature as needed in each
room.

I certainly agree that that arrangement gives the most flexibility.
However, based on my reading of condensing boilers, the most condensing
and thus, the highest efficiency is achieved at 55 degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about 92
degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is about
62 degrees and still gets the house warm enough (at least now that it
is not too cold outside)

What is then the most energy efficient setting?

I think the user's manual is wrong in this respect. As you percieve, the
lowest possible flow temperatures which actually keep the house warm will
result in /marginally/ greater efficiency. Note that condensing boilers are

Agreed.
Most efficient is to set the boiler temperature low
enough such that the room stat never quite switches off.
That's the coolest water setting you can get away with,
which equates to highest boiler efficiency. The setting
will vary according to outside temperature (which is where a
temperature compensation system wins through), and it will
need boosting when the house is being heated up from a
temperature below the thermostat set point. A good control
system will do this all automatically for you.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

YAPH wrote:

So in practice I'd say set the boiler temperature control about halfway to
start with and experiment. If it doesn't get the house up to temperature
in very cold weather turn it up until it does. Not ideal in this age of
programmable, automatic controls, I know.


There is another issue here, which is the central heating pump.

A higher water temperature will mean that the pump runs for less time
each day. Lowering the water temperature to the point where the pump
runs almost all the time might be more energy efficient at the boiler,
but it definitely uses more energy to run the pump for longer.

How the additional energy used running the pump almost all the time
compares with the energy saved by using a lower water temperature, I
don't know.

Apart from the additional energy, there is also the question of the
reduced pump life resulting from extended running.

"Andrew Gabriel" wrote in message
...


Agreed.
Most efficient is to set the boiler temperature low
enough such that the room stat never quite switches off.

That may not be true..
my boiler is most efficient at full output and is a few % less if the output
is reduced.
Don't ask me why, that is what the manufacturer says.

In article ,
"dennis@home" writes:


"Andrew Gabriel" wrote in message
...


Agreed.
Most efficient is to set the boiler temperature low
enough such that the room stat never quite switches off.

That may not be true..
my boiler is most efficient at full output and is a few % less if the output
is reduced.
Don't ask me why, that is what the manufacturer says.

I suspect full output is referring to burner power, not
the water temperature.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" wrote in message
...
In article ,
"dennis@home" writes:


"Andrew Gabriel" wrote in message
...


Agreed.
Most efficient is to set the boiler temperature low
enough such that the room stat never quite switches off.

That may not be true..
my boiler is most efficient at full output and is a few % less if the
output
is reduced.
Don't ask me why, that is what the manufacturer says.

I suspect full output is referring to burner power, not
the water temperature.

True but at full output it will heat the water rather quickly,
So it will only fire for a few tens of seconds if the water temp is set low.

"YAPH" wrote in message
...
On Sun, 26 Oct 2008 22:23:45 +0000, asalcedo wrote:

I have installed two new Worcester 30 CDi system boilers at home.
(They work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy
Conservation", if the property has TRVs and room thermostats (which
is my case), the boilers should be set at the maximum temperature
setting and use the thermostats and TRVs to regulate the temperature
as needed in each room.

I certainly agree that that arrangement gives the most flexibility.
However, based on my reading of condensing boilers, the most
condensing and thus, the highest efficiency is achieved at 55
degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about
92 degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is
about 62 degrees and still gets the house warm enough (at least now
that it is not too cold outside)

What is then the most energy efficient setting?

I think the user's manual is wrong in this respect.
As you percieve, the lowest possible flow temperatures
which actually keep the house warm will result
in /marginally/ greater efficiency. Note that
condensing boilers are more efficient than
non-condensing types, even when they aren't
condensing: because they /can/ safely condense
the designers can get more heat out of the
combustion than in non-condensing designs
which have to allow a margin of safety (and
inefficiency) to avoid any possibility of
prolonged condensing in normal operation.

Condensing boiler heat exchangers are bigger so even when not condensing
they are still extracting more heat.

There are boilers which wring the last drops of efficiency out of
their designs by modulating their flow temperature to achieve the
necessary heat output to the building, using controls which "tell" the
boiler the actual room temperatures rather than giving a simple
stop/go signal as a normal thermostat (programmable or otherwise)
does. Unfortunately such boilers cost half as much again, or more,
than an ordinary good quality condensing boiler costs[1],

That is wrong. The Glow Worm xi range can have a proprietary controller and
integrated weather compensation as standard. Look at the Broag boilers with
OpenTherm controllers and weather compensation integrated too.
They will modulate the burner to the room and outside temperatures. Broag
Remeda are cheap are excellent.

On 27 Oct 2008 15:30:56 GMT, Andrew Gabriel wrote:

Most efficient is to set the boiler temperature low enough such that
the room stat never quite switches off.

That may not be true.. my boiler is most efficient at full output and
is a few % less if the output is reduced.

I suspect full output is referring to burner power, not the water
temperature.

I'd add full output with the return temperature low enough such that
maximum condensing occurs.

--
Cheers
Dave.

In article et,
"Dave Liquorice" writes:
On 27 Oct 2008 15:30:56 GMT, Andrew Gabriel wrote:

Most efficient is to set the boiler temperature low enough such that
the room stat never quite switches off.

That may not be true.. my boiler is most efficient at full output and
is a few % less if the output is reduced.

I suspect full output is referring to burner power, not the water
temperature.

I'd add full output with the return temperature low enough such that
maximum condensing occurs.

Well, yes. Ky Keston is most efficient when it switches on initially
at full power with the system cold -- 26kW+ and flue gases less than
25C. Keeping it operating like that is not possible though, as it will
by definition start warming up the water.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

asalcedo wrote:
I have installed two new Worcester 30 CDi system boilers at home. (They
work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy Conservation",
if the property has TRVs and room thermostats (which is my case), the
boilers should be set at the maximum temperature setting and use the
thermostats and TRVs to regulate the temperature as needed in each
room.

I certainly agree that that arrangement gives the most flexibility.
However, based on my reading of condensing boilers, the most condensing
and thus, the highest efficiency is achieved at 55 degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about 92
degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is about
62 degrees and still gets the house warm enough (at least now that it
is not too cold outside)

What is then the most energy efficient setting?

Thanks,

Antonio




We have a tandem system at our church (Keston 40s) and I was told by the
installer that the temperatures should be set so that one ts the 'lead'
boiler, coming on first with the other set a degree or so higher. From
cold both come on, but when maintaining temperature, only the lead
boiler comes on. I was also advised to switch lead boilers at intervals
(presumably to even out the wear)

Malcolm

Hello Malcolm,

That is exactly what I did.

I came to that exact same conclusion when observing how both boilers work.

I had both of them at the maximum temperature setting and noticed that when maintaining temperature only boiler one would come on. Boiler two would not fire.

Perhaps because boiler two's thermostat is not calibrated the same as boiler one's or because of the physical water pipes layout.

Anyway, it seemed like too much work for one boiler.

I changed boiler's one temperature setting to slightly lower than boiler's two and now boiler two is the one that maintains temperature.

I agree, I will change the temperature settings so that I even out the wear of each boiler.

I will also try to contact Worcester Bosch to confirm the optimal temperature setting.

Thanks,


Antonio

"asalcedo" wrote in message
...

I have installed two new Worcester 30 CDi system boilers at home. (They
work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy Conservation",
if the property has TRVs and room thermostats (which is my case), the
boilers should be set at the maximum temperature setting and use the
thermostats and TRVs to regulate the temperature as needed in each
room.

I certainly agree that that arrangement gives the most flexibility.
However, based on my reading of condensing boilers, the most condensing
and thus, the highest efficiency is achieved at 55 degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about 92
degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is about
62 degrees and still gets the house warm enough (at least now that it
is not too cold outside)

What is then the most energy efficient setting?

Thanks,

Antonio

http://www.warmworld.co.uk/026.html
You need boier sequencing. Look around there are many about.

"Doctor Drivel" wrote in message
...

"asalcedo" wrote in message
...

I have installed two new Worcester 30 CDi system boilers at home. (They
work in tandem, at the same time, as if they were one unit)

According to the user's manual, under "Tips for Energy Conservation",
if the property has TRVs and room thermostats (which is my case), the
boilers should be set at the maximum temperature setting and use the
thermostats and TRVs to regulate the temperature as needed in each
room.

I certainly agree that that arrangement gives the most flexibility.
However, based on my reading of condensing boilers, the most condensing
and thus, the highest efficiency is achieved at 55 degrees Celsius.

If I set the boilers to the maximum the boiler's water reaches about 92
degrees.

If I use a 5 setting, 7 being the maximum, the boilers' water is about
62 degrees and still gets the house warm enough (at least now that it
is not too cold outside)

What is then the most energy efficient setting?

Thanks,

Antonio

http://www.warmworld.co.uk/026.html
You need boier sequencing. Look around there are many about.

£190 + VAT
http://www.warmworld.co.uk/itemlist....s/2/findchil/1