If you change old radiators for modern ones the same size, the Btu
value will be higher. How will this affect the boilers ability to
supply if the collective value is above the boilers output rating?

In article .com,
"jaycee" writes:
If you change old radiators for modern ones the same size, the Btu
value will be higher.

Possibly, but not inevitably. Depends on the respective designs.

How will this affect the boilers ability to
supply if the collective value is above the boilers output rating?

The boiler won't be able to get them up to the boiler's design
temperature. If it's a really long way out, then a non-condensing
boiler could end up operating in condensing mode for extended
periods, and rapidly corrode internally.

You should be able to see how near the boiler's output is to your
system currently by observing the boiler operation. With the
boiler set to maximum temperature, once the boiler has got the
radiators up to temperature and assuming the room thermostat and
all TRV's are still calling for heat, see what percentage level
your boiler is operating at. If it's a modulating boiler, you'll
need to know what the modulation level is. If the boiler doesn't
tell you, you could work it out from the rate of gas consumption.
For a non-modulating boiler that cycles on and off, work out the
total 'on' time as a percentage over a period of time (or you
again work out the average gas consumption rate over a period
which includes many on/off cycles).

--
Andrew Gabriel

On 10 Feb 2006 14:46:20 -0800, "jaycee"
wrote:

|If you change old radiators for modern ones the same size, the Btu
|value will be higher. How will this affect the boilers ability to
|supply if the collective value is above the boilers output rating?

Not much! because the Btu/watts radiated/convected to the air depends on
the area/surface finish/colour of the radiator, which will have changed
little. Boilers have traditionally been much overrated and still are.
The insulation of existing houses has been increasing as people want to
decrease the amount of fuel used to heat the house.
--
Dave Fawthrop dave hyphenologist co uk Please quote, with quote
character, previous post sniped to only the bit you are replying to.
Threads often contain 100s of posts dozens layers deep. Other people
use different newsreaders, they do not see or do what you see and do.

Dave Fawthrop wrote:
On 10 Feb 2006 14:46:20 -0800, "jaycee"
wrote:

|If you change old radiators for modern ones the same size, the Btu
|value will be higher. How will this affect the boilers ability to
|supply if the collective value is above the boilers output rating?

If not already fitted them how about fitting a thermostatic radiator
valve, then at least you will not waste heat.

In an earlier contribution to this discussion,
Dave Fawthrop wrote:

On 10 Feb 2006 14:46:20 -0800, "jaycee"
wrote:

If you change old radiators for modern ones the same size, the Btu
value will be higher. How will this affect the boilers ability to
supply if the collective value is above the boilers output rating?

Not much! because the Btu/watts radiated/convected to the air depends
on the area/surface finish/colour of the radiator, which will have
changed little.

Er . . except if the new one has fins and the old one didn't, the effective
surface area for convention will have increased dramatically.
--
Cheers,
Roger
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