Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?

Richard wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?

Pressurised, by all means. Combi - why??

Combi boilers are horrid things, they are they definition of a
compromise. We currently have a combi oil fired boiler. In our last
house we had a thermal store heated by an oil boiler. The thermal store
performed much, much better.


--
Grunff
http://www.greendoug.com - a forum for all things environmental

On 20 Feb, 16:13, Grunff wrote:
Richard wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?

Pressurised, by all means. Combi - why??

Combi boilers are horrid things, they are they definition of a
compromise. We currently have a combi oil fired boiler. In our last
house we had a thermal store heated by an oil boiler. The thermal store
performed much, much better.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental

I thought combis were the way to go now, efficiency being the main
factor ?

Richard wrote:

I thought combis were the way to go now, efficiency being the main
factor ?

No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the confusion
arises.


--
Grunff
http://www.greendoug.com - a forum for all things environmental

On 20 Feb, 16:21, Grunff wrote:
Richard wrote:
I thought combis were the way to go now, efficiency being the main
factor ?

No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the confusion
arises.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental


Whats the theory behind a condensing boiler? making it more efficient

Richard wrote:

Whats the theory behind a condensing boiler? making it more efficient

The difference is in the design of the heat exchanger. A non-condensing
boiler exhausts the combustion gases at a temperature high enough for
the water to stay gaseous. A condensing boiler's heat exchanger
condenses the water in the exhaust gas, extracting more energy from it.
This increases overall system efficiency.



--
Grunff
http://www.greendoug.com - a forum for all things environmental

Richard wrote:
On 20 Feb, 16:21, Grunff wrote:
Richard wrote:
I thought combis were the way to go now, efficiency being the main
factor ?

No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the
confusion arises.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental


Whats the theory behind a condensing boiler? making it more efficient

They just extract more heat from the flame (by virtue of bigger heat
exchangers) to the point where water "condenses". By lowering the exhaust
temperature below the condensation point of water, it can extract more heat
energy (from the latent heat of condensation).

This is why you get the visible plume with condensing boilers. It's not
rocket science but it does mean that the inside of the boiler has to cope
with being "wet" and have a drain and be made of corrosion resistant
materials.

Tim

"Tim Downie" wrote in message
...
Richard wrote:
On 20 Feb, 16:21, Grunff wrote:
Richard wrote:
I thought combis were the way to go now, efficiency being the
main
factor ?

No, this is not true. Condensing boilers are the way to go
(wherever
possible), and most combis are condensing, which is where the
confusion arises.

--
Grunffhttp://www.greendoug.com- a forum for all things
environmental


Whats the theory behind a condensing boiler? making it more
efficient

They just extract more heat from the flame (by virtue of bigger heat
exchangers) to the point where water "condenses". By lowering the
exhaust
temperature below the condensation point of water, it can extract
more heat
energy (from the latent heat of condensation).

This is why you get the visible plume with condensing boilers. It's
not
rocket science but it does mean that the inside of the boiler has to
cope
with being "wet" and have a drain and be made of corrosion resistant
materials.

Tim



.... at least until the guarantee runs out G

AWEM

"Grunff" wrote in message
...
Richard wrote:

I thought combis were the way to go now, efficiency being the main
factor ?

No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the confusion
arises.

In a few weeks time (April 2007) installing a non condensing oil fired boiler
will only be possible in exceptional circumstances.

http://www.oftec.co.uk/consumers/reg...mmisioning.htm

--

Michael Chare

Richard wrote:
On 20 Feb, 16:13, Grunff wrote:
Richard wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?
Pressurised, by all means. Combi - why??

Combi boilers are horrid things, they are they definition of a
compromise. We currently have a combi oil fired boiler. In our last
house we had a thermal store heated by an oil boiler. The thermal store
performed much, much better.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental

I thought combis were the way to go now, efficiency being the main
factor ?

What makes you think that 'combi'=='efficiency'?

Richard wrote:
On 20 Feb, 16:21, Grunff wrote:
Richard wrote:
I thought combis were the way to go now, efficiency being the main
factor ?
No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the confusion
arises.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental


Whats the theory behind a condensing boiler? making it more efficient

Reduced outflow tempeature== less heat going up the flue==more heat in
the water.

The Natural Philosopher wrote:
Richard wrote:
On 20 Feb, 16:21, Grunff wrote:
Richard wrote:
I thought combis were the way to go now, efficiency being the main
factor ?
No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the
confusion arises.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental


Whats the theory behind a condensing boiler? making it more efficient

Reduced outflow tempeature== less heat going up the flue==more heat in
the water.

Outflow temperature doesn't have to be reduced. Of more importance with
regard to efficiency is reduced inflow temp. The cooler the return, the
greater the amount of heat extracted from the combustion gases.

Tim

Tim Downie wrote:
The Natural Philosopher wrote:
Richard wrote:
On 20 Feb, 16:21, Grunff wrote:
Richard wrote:
I thought combis were the way to go now, efficiency being the main
factor ?
No, this is not true. Condensing boilers are the way to go (wherever
possible), and most combis are condensing, which is where the
confusion arises.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental

Whats the theory behind a condensing boiler? making it more efficient

Reduced outflow tempeature== less heat going up the flue==more heat in
the water.

Outflow temperature doesn't have to be reduced. Of more importance with
regard to efficiency is reduced inflow temp. The cooler the return, the
greater the amount of heat extracted from the combustion gases.


I think we are talking at cross purposes. I meant exhaust outflow temp -
what gases goe up the flue, essentially.

I suspect you are talking about the water circulation, in which case I
agree with you.

Tim

The Natural Philosopher wrote:
Tim Downie wrote:
The Natural Philosopher wrote:
Reduced outflow tempeature== less heat going up the flue==more heat
in the water.

Outflow temperature doesn't have to be reduced. Of more importance
with regard to efficiency is reduced inflow temp. The cooler the
return, the greater the amount of heat extracted from the combustion
gases.

I think we are talking at cross purposes. I meant exhaust outflow
temp - what gases goe up the flue, essentially.

Got ya. Thought you meant water temp.

Tim

On Feb 20, 3:58 pm, "Richard" wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?

Richard

Consider a system with a cylinder rather than a combi boiler. This
way, you can hedge against future rises in the cost of heating oil by
supplementing your water heating with a solar water heater. Our
calculations, you'd save over £7,000 in oil bills over the life time
of the panel*. Full details at www.growyourownenergy.co.uk We are an
impartial advisory site.

* Assuming heating oil rises as much in the future as much as it has
in recent years.

Grow Your Own Energy wrote:

Consider a system with a cylinder rather than a combi boiler. This
way, you can hedge against future rises in the cost of heating oil by
supplementing your water heating with a solar water heater. Our
calculations, you'd save over £7,000 in oil bills over the life time
of the panel*. Full details at www.growyourownenergy.co.uk We are an
impartial advisory site.

* Assuming heating oil rises as much in the future as much as it has
in recent years.


You keep mentioning these calculations - it would be a good idea to show
the calculation you're basing your statement on, since a well worked out
calculation would lend your statement greater validity. (or is it top
secret?)


--
Grunff
http://www.greendoug.com - a forum for all things environmental

On Wed, 21 Feb 2007 10:55:15 +0000, The Natural Philosopher wrote:

Richard wrote:
On 20 Feb, 16:13, Grunff wrote:
Richard wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?
Pressurised, by all means. Combi - why??

Combi boilers are horrid things, they are they definition of a
compromise. We currently have a combi oil fired boiler. In our last
house we had a thermal store heated by an oil boiler. The thermal store
performed much, much better.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental

I thought combis were the way to go now, efficiency being the main
factor ?

What makes you think that 'combi'=='efficiency'?

Well... this is not a straight forward subject.
Essentially there are trade offs between the storage losses of a non-combi
system and the losses during the start up sequence of a combi.

Frankly in the list of criteria whether to select a combi or not the
energy saving/losses is relatively minor.

Firstly, space heating is the major consumer of energy and there is
more or less no difference in the performance of either system. Maybe the
non-combi can do a little better if it is a smaller unit better suited to
match the heating loads than a 24kW+ combi.

Secondly not having the water pressure/flow for a combi or not having the
location for a vented cylinder/cistern would be absolute criteria whereas
as efficiency would only be relative.



--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

"Ed Sirett" wrote in message
...
On Wed, 21 Feb 2007 10:55:15 +0000, The Natural Philosopher wrote:

Richard wrote:
On 20 Feb, 16:13, Grunff wrote:
Richard wrote:


Firstly, space heating is the major consumer of energy and there is
more or less no difference in the performance of either system. Maybe the
non-combi can do a little better if it is a smaller unit better suited to
match the heating loads than a 24kW+ combi.


That might be a more important consideration in the case of oil fired boilers
which I think are typically non modulating.

--

Michael Chare

"Grunff" wrote in message
...
Grow Your Own Energy wrote:

Consider a system with a cylinder rather than a combi boiler. This
way, you can hedge against future rises in the cost of heating oil by
supplementing your water heating with a solar water heater. Our
calculations, you'd save over £7,000 in oil bills over the life time
of the panel*. Full details at www.growyourownenergy.co.uk We are an
impartial advisory site.

* Assuming heating oil rises as much in the future as much as it has
in recent years.


You keep mentioning these calculations - it would be a good idea to show
the calculation you're basing your statement on, since a well worked out
calculation would lend your statement greater validity. (or is it top
secret?)


Well heating oil has quadrupled in price over the past 8 years - if it does the
same again it might not be to difficult to get up to £7000 if the panels have a
reasonable life time. - I just hope that the assumption is wrong!.


--

Michael Chare

Michael Chare wrote:

Well heating oil has quadrupled in price over the past 8 years - if it does the
same again it might not be to difficult to get up to £7000 if the panels have a
reasonable life time. - I just hope that the assumption is wrong!.


I suspect that assumption is incorrect, but one can hedge against it in
a number of ways - for instance, by buying oil company stocks, or an oil
based ETF.


--
Grunff
http://www.greendoug.com - a forum for all things environmental

Ed Sirett wrote:
On Wed, 21 Feb 2007 10:55:15 +0000, The Natural Philosopher wrote:

Richard wrote:
On 20 Feb, 16:13, Grunff wrote:
Richard wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?
Pressurised, by all means. Combi - why??

Combi boilers are horrid things, they are they definition of a
compromise. We currently have a combi oil fired boiler. In our last
house we had a thermal store heated by an oil boiler. The thermal store
performed much, much better.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental
I thought combis were the way to go now, efficiency being the main
factor ?

What makes you think that 'combi'=='efficiency'?

Well... this is not a straight forward subject.
Essentially there are trade offs between the storage losses of a non-combi
system and the losses during the start up sequence of a combi.

Frankly in the list of criteria whether to select a combi or not the
energy saving/losses is relatively minor.

Firstly, space heating is the major consumer of energy and there is
more or less no difference in the performance of either system. Maybe the
non-combi can do a little better if it is a smaller unit better suited to
match the heating loads than a 24kW+ combi.

Secondly not having the water pressure/flow for a combi or not having the
location for a vented cylinder/cistern would be absolute criteria whereas
as efficiency would only be relative.



My take is that a combi is an ideal system for a small flat with just
one or two people in it, where it can cope with occasional hot water
demand well, and doesn't have a lot of CH to do. The lack of hot water
and header tanks saves space, complexity and cost.

In a bigger house, pressurised stored hot water beats it hands down. You
have the space and likely as not if you have two bathrooms, it's because
you are going to be using them simultaneously.

On Wed, 21 Feb 2007 16:55:36 +0000, The Natural Philosopher wrote:

Ed Sirett wrote:
On Wed, 21 Feb 2007 10:55:15 +0000, The Natural Philosopher wrote:

Richard wrote:
On 20 Feb, 16:13, Grunff wrote:
Richard wrote:
Im looking at having a complete new, oil fired central heating sytem
fitted, to replace the hopless storage heaters that were fitted in my
house when it was built.
Im thinking of going for fully pressurised with a combi boiler, and
downfalls with a pressurised system?
Pressurised, by all means. Combi - why??

Combi boilers are horrid things, they are they definition of a
compromise. We currently have a combi oil fired boiler. In our last
house we had a thermal store heated by an oil boiler. The thermal store
performed much, much better.

--
Grunffhttp://www.greendoug.com- a forum for all things environmental
I thought combis were the way to go now, efficiency being the main
factor ?

What makes you think that 'combi'=='efficiency'?

Well... this is not a straight forward subject.
Essentially there are trade offs between the storage losses of a non-combi
system and the losses during the start up sequence of a combi.

Frankly in the list of criteria whether to select a combi or not the
energy saving/losses is relatively minor.

Firstly, space heating is the major consumer of energy and there is
more or less no difference in the performance of either system. Maybe the
non-combi can do a little better if it is a smaller unit better suited to
match the heating loads than a 24kW+ combi.

Secondly not having the water pressure/flow for a combi or not having the
location for a vented cylinder/cistern would be absolute criteria whereas
as efficiency would only be relative.



My take is that a combi is an ideal system for a small flat with just
one or two people in it, where it can cope with occasional hot water
demand well, and doesn't have a lot of CH to do. The lack of hot water
and header tanks saves space, complexity and cost.

In a bigger house, pressurised stored hot water beats it hands down. You
have the space and likely as not if you have two bathrooms, it's because
you are going to be using them simultaneously.

Agreed, the matter of efficiency does not really make the top five
criteria when choosing to use a combi or not.


--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

On Wed, 21 Feb 2007 16:43:21 +0000, Michael Chare wrote:

"Grunff" wrote in message
...
Grow Your Own Energy wrote:

Consider a system with a cylinder rather than a combi boiler. This
way, you can hedge against future rises in the cost of heating oil by
supplementing your water heating with a solar water heater. Our
calculations, you'd save over £7,000 in oil bills over the life time
of the panel*. Full details at www.growyourownenergy.co.uk We are an
impartial advisory site.

* Assuming heating oil rises as much in the future as much as it has
in recent years.


You keep mentioning these calculations - it would be a good idea to show
the calculation you're basing your statement on, since a well worked out
calculation would lend your statement greater validity. (or is it top
secret?)


Well heating oil has quadrupled in price over the past 8 years - if it does the
same again it might not be to difficult to get up to £7000 if the panels have a
reasonable life time. - I just hope that the assumption is wrong!.

It turned out that the somewhat high prices of oil of late have been due
to reasons other than politics, reserves and productions. I am given to
understand they were due to a lack of refining capacity.

Oil and gas prices will rise eventually but not a quadruplng avery two
years.



--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Ed Sirett wrote:

It turned out that the somewhat high prices of oil of late have been due
to reasons other than politics, reserves and productions. I am given to
understand they were due to a lack of refining capacity.


I think burning up most of te USA's strategic reserves in a pointless
war, and having an Oil man in the White house, and having a lot of
capacity screed bu Katrina had a lot to do with it..however, whilst the
dizzy upwards swoops in price may have levelled off for now, OPEC wont
see it going south of the current prices if they can help it,.

Oil and gas prices will rise eventually but not a quadruplng avery two
years.

No..but they have't done that anyway.

I wopuld expect to see 25% upshift in the next two years at least.