"Christian McArdle" wrote in message
t...
But there efficiency drops as the return temperature goes up.
And efficiency alters the time to repay - so with an old installation it
might make a difference.
All boilers drop in thermodynamic efficiency as the return temperature
goes
up. The differences between a condensing one and a traditional one a
1. The condensing type is ALWAYS much more efficient than the traditional
type at ANY flow or return temperature.
2. The condensing type has even greater efficiency still at lower return
temperatures.
Don't get bogged down thinking about item 2, when item 1 alone is enough
to
justify a condensing boiler. Remember also, that condensing boilers are
intelligent and will drop the return temperature if they detect they can
get
away with it.
Not all. some are quite dumb and have on-off control. My condensing boiler
does not modulate with a one fixed burner rate. I control it by using an
outside weather compensator, which reduces the return temp to suit . The
compensator has boiler anti-cycle control. Those with modulating load
compensation control are ones to fit on an existing system.
Thanks for the reply - but why wouldn't it improve the efficiency to put
it
in the return.
It would increase the instantaneous thermodynamic efficiency. However, it
will cost much more to run, as the controls would not actually be keeping
everything at the correct temperature. There is more money to be saved
ensuring everything is only heated as much as is required, than by trying
to
get an extra 5% on the thermodynamic efficiency.
Your scheme is likely to end up heating the swimming pool to higher
temperatures than you wish, which will cost you a fortune, even if that
heating was done efficiently.
From what I understand he wants a plate heat exchanger on the boilers return
to lower the return temp further, that would only work when the CH is on.
On a fixed rate boiler this will increase the flow/return delta T
alarmingly. On a load compensation boiler the flow temp may be reduced too
much as the boiler aims to keep the delta T and may think the house is up to
temp.
---
--
Checked by AVG anti-virus system (
http://www.grisoft.com).
Version: 6.0.524 / Virus Database: 321 - Release Date: 06/10/2003