"John" wrote in message
...

"Hzatph" wrote in message
...

Where did the 240,000 BTU boiler come from? What size is your house? or
has
an extra nought crept in here?

To answer some confusion, the room stat etc would be on the boiler
heating system - not the Aga.

At present we have two 110,000 boilers on two separate heating circuits
and I want to rationalise with a single circuit and efficient modern
boilers - we have a rambling Victorian place with 28 radiators. Both
installers I have spoken to think we will need a boiler of up to 240,000
BTU capacity.


Ah so IMHO perhaps what you should think about is a large hot water
cylinder with two indirect coils. One fed from the Aga output and one fed
from the heating system. During especially hot weather an immersion heater
might be a useful extra also. In this way the Aga could heat the water in
the cylinder with its slow but useable heat, The main heating system could
under time/temperature control supply any additional requirement and you
have the option of an immersion if and when needed. If the cylinder is
sized appropriately your Aga should be able to look after all your needs
except under occasional heavy demand periods.
I'm surprised by the loading you suggest for the house even if it is
rambling. Have you done any calcs or tried a heatloss program yourself? I
have done a fair amount of work on a house which did have a 210,000 BTU
boiler installed by others but it was never running for any appreciable
length of time before its stat was satisfied. The house pipework was left
over from a coke boiler and under the ground floor was in 4" Cast iron
pipe, reducing to 3" & 2" branches around the (three) floors and serving
big old cast iron school type rads. The house was bloody huge and could
have been a stately home if out in the country rather than in a town.
Draining down was an all day job as was filling up again so the boiler may
have been deliberately (grossly) oversized simply to speed up the time
taken to raise the water temp from cold to working.
I think the old pile would have benefitted vastly from repiping to
seperate the floors into independent controlled zones with smaller pipe
and new rads to reduce volume and speed up the response times but client
(as usual in these cases) wasn't interested in changing

John,

You must have been reading my mind - A large cylinder is exactly what I have
in mind so there is lashings of hot water and the Aga can reheat take all
night to reheat it if it needs to. We have a normal size cylinder at the
moment and if we a large amount of water it causes the Aga temperature to
plummet which is annoying at the same time as one is trying to cook.

With regard to heat loss, I do have the Myson program but I have not run it.
We do not have the cast iron pipes you encountered, but one of the boilers
runs 18 radiators and struggles, plus the response time is slow. The other
with only nine and a hot water tank (not all our water is from the Aga!) is
more responsive. I am advised that they may install a smaller jet so the
240,000 BTU unit is throttled back a little - for example the Worcester
Danesmoor Utility 50/70 can be configured from 170-240,000 BTU. I would also
like to create some zones and the heating is configured so some can be
fairly easy way to do

Thanks for your advice - it is much appreciated.