We have a new condensing boiler retro-fitted to our existing system:
Baxi Solo He 15, 8 rads some with TRVs.

With the pump at its lowest setting, I set the flow to about 64 C and
the return to about 52 C.

I balanced the rads as per faq, all now have a 12 deg C drop across
all rads except a kick space heater which i didn't touch. (There are
ball valves on its two supply flexible pipes so I could tweak that as
well)

I haven't quite grasped the theory behind condensing boilers. Am I
right in thinking that if the return is below 55 C then the boiler
should be operating in condensing mode?

Thanks to all who replied to my original post: Fred, Ed and Dr D.


Francis Kirby

On Dec 12, 8:51*pm, wrote:
We have a new condensing boiler retro-fitted to our existing system:
Baxi Solo He 15, 8 rads some with TRVs.

With the pump at its *lowest setting, I set the flow to about 64 C and
the return to about 52 C.

I balanced the rads as per faq, all now have a 12 deg C drop across
all rads *except a kick space heater which i didn't touch. (There are
ball valves on its two supply flexible pipes so I could tweak that as
well)

*I haven't quite grasped the theory behind condensing boilers. Am I
right in thinking that if the return is below 55 C then the boiler
should be operating in condensing mode?

Thanks to all who replied to my original post: Fred, Ed and Dr D.

Francis Kirby

A temperature differential of 11 deg C is the ideal drop across a
radiator the absolute maximum recommended is 16 deg C through really
larger radiators. I am pretty sure if you read your boiler instruction
manual you will find that a difference of 20 deg C is what you are
looking for at your boiler. This can be achieved by altering pump
speed or adjusting a bypass if one is fitted depending on your system
layout. (I know your boiler does not require a bypass even if fitted
to an S-plan as there is no pump overrun on it)
Your boiler should be in condensing mode all the time if the
temperature differential is correct.

Owl

On Dec 12, 2:51*pm, wrote:
We have a new condensing boiler retro-fitted to our existing system:
Baxi Solo He 15, 8 rads some with TRVs.

With the pump at its *lowest setting, I set the flow to about 64 C and
the return to about 52 C.

I balanced the rads as per faq, all now have a 12 deg C drop across
all rads *except a kick space heater which i didn't touch. (There are
ball valves on its two supply flexible pipes so I could tweak that as
well)

*I haven't quite grasped the theory behind condensing boilers. Am I
right in thinking that if the return is below 55 C then the boiler
should be operating in condensing mode?

Thanks to all who replied to my original post: Fred, Ed and Dr D.

Francis Kirby

Flow should be under 60c that is the highest temp for max efficency,
go over and efficency drops, im sure its high efficency rating is at
temps under 58- 60c. Eventualy you loose about 6% near 85c. Longer
cycles are better also easier on equipment and longer run time at
highest efficency level.

On Dec 12, 11:34*pm, ransley wrote:
On Dec 12, 2:51*pm, wrote:





We have a new condensing boiler retro-fitted to our existing system:
Baxi Solo He 15, 8 rads some with TRVs.

With the pump at its *lowest setting, I set the flow to about 64 C and
the return to about 52 C.

I balanced the rads as per faq, all now have a 12 deg C drop across
all rads *except a kick space heater which i didn't touch. (There are
ball valves on its two supply flexible pipes so I could tweak that as
well)

*I haven't quite grasped the theory behind condensing boilers. Am I
right in thinking that if the return is below 55 C then the boiler
should be operating in condensing mode?

Thanks to all who replied to my original post: Fred, Ed and Dr D.

Francis Kirby

Flow should be under 60c that is the highest temp for max efficency,
go over and efficency drops, im sure its high efficency rating is at
temps under 58- 60c. Eventualy you loose about 6% near 85c. Longer
cycles are better also easier on equipment and longer run time at
highest efficency level.- Hide quoted text -

- Show quoted text -

Read here this will answer a few of your questions.

http://www.west-norfolk.gov.uk/pdf/CE52.pdf

Owl

On Fri, 12 Dec 2008 23:17:55 -0800 (PST), Awesometoday
wrote:

On Dec 12, 11:34*pm, ransley wrote:
On Dec 12, 2:51*pm, wrote:





We have a new condensing boiler retro-fitted to our existing system:
Baxi Solo He 15, 8 rads some with TRVs.

With the pump at its *lowest setting, I set the flow to about 64 C and
the return to about 52 C.

I balanced the rads as per faq, all now have a 12 deg C drop across
all rads *except a kick space heater which i didn't touch. (There are
ball valves on its two supply flexible pipes so I could tweak that as
well)

*I haven't quite grasped the theory behind condensing boilers. Am I
right in thinking that if the return is below 55 C then the boiler
should be operating in condensing mode?

Thanks to all who replied to my original post: Fred, Ed and Dr D.

Francis Kirby

Flow should be under 60c that is the highest temp for max efficency,
go over and efficency drops, im sure its high efficency rating is at
temps under 58- 60c. Eventualy you loose about 6% near 85c. Longer
cycles are better also easier on equipment and longer run time at
highest efficency level.- Hide quoted text -

- Show quoted text -

Read here this will answer a few of your questions.

http://www.west-norfolk.gov.uk/pdf/CE52.pdf

Owl


Found a good graphic

http://www.rvr.ie/default.aspx?subj=...ingboiler.ascx

On Fri, 12 Dec 2008 23:17:55 -0800 (PST), Awesometoday
wrote:

On Dec 12, 11:34*pm, ransley wrote:
On Dec 12, 2:51*pm, wrote:





We have a new condensing boiler retro-fitted to our existing system:
Baxi Solo He 15, 8 rads some with TRVs.

With the pump at its *lowest setting, I set the flow to about 64 C and
the return to about 52 C.

I balanced the rads as per faq, all now have a 12 deg C drop across
all rads *except a kick space heater which i didn't touch. (There are
ball valves on its two supply flexible pipes so I could tweak that as
well)

*I haven't quite grasped the theory behind condensing boilers. Am I
right in thinking that if the return is below 55 C then the boiler
should be operating in condensing mode?

Thanks to all who replied to my original post: Fred, Ed and Dr D.

Francis Kirby

Flow should be under 60c that is the highest temp for max efficency,
go over and efficency drops, im sure its high efficency rating is at
temps under 58- 60c. Eventualy you loose about 6% near 85c. Longer
cycles are better also easier on equipment and longer run time at
highest efficency level.- Hide quoted text -

- Show quoted text -

Read here this will answer a few of your questions.

http://www.west-norfolk.gov.uk/pdf/CE52.pdf

Owl

thanks Owl and ransley

Have read some posts by Phil Addison and Andy Hall.

Downstairs rads are new and large and take nearly 20 c drop. Upstairs
are old single panel, no fins and take a much smaller drop. We hope to
replace these soon

trying for a 15/16 C drop, if my knees hold out :-)

"Awesometoday" wrote in message
...
On Dec 12, 11:34 pm, ransley wrote:
On Dec 12, 2:51 pm, wrote:

Flow should be under 60c that is the highest temp for max efficency,

Maximum condensing efficiency is the "lowest" return temperature that can be
obtained. Condensing "starts" at a notional 56C return water temperature.

This is where integral outside weather compensation promotes efficiency.
With rads a typical flow temperature of 50C give given with an outside
temperature of 10C. balance to give 20C across the rads and boiler that
gives a return temperatures of 30C, which is very high efficiency. At 15C
outside temperature the flow temperature will rise and even greater
efficiency. It is done by modulating the burner. External stand-alone
weather compensators can be fitted tending to switch the burner on and off
to obtained the temperatures.

Only on start up from cold and outside temperatures near or are below
freezing will the return temperatures rise above condensing dew-point - but
very rare, and never with rads sized for 60-40C. Room temperature influence
can be incorporated that lowers the boiler temperature even more when inside
air room temperature nears, or is reached.

Unfortunately most boilers are selected and fitted by "plumbers" who know
next to nothing about heating control or boiler operation. Plumbers should
stick to drains. Get heating engineers.