On 04/10/2010 22:06, Another John wrote:
Howdy all

We have a back boiler installed behind our (60s) fireplace. However our
hot water comes from the gas CH system, which heats the water just once
a day for a couple of hours.


We hardly ever use the fire except in the depths of winter. (We _do_
enjoy it immensely, so we wouldn't consider _not_ having any fire at
all.)

I always used to think: back-boiler: bonus! Free hot water!

However recently a different thought occurred to me:
if the CH is providing a cistern full of hot water...
but the back boiler system is full of cold water ...
is it not going to slowly circulate the hot water down, by gravity,
through the back boiler, then back up to the hot water cistern ...
and slowly cool that expensive hot water?

I've a mind to take out the back boiler, in the hopes that our hot water
supply will stay hotter longer. (BTW there's only two of us in the
house now, and we don't have baths (we have showers instead!).)

I've been thinking about a wood stove for many a year, so now may be a
good time to do it. Yes, I am aware you can get stoves with back
boilers, but for the reason described above, I wouldn't fancy one.

Can anyone dispel my ignorance in this area?

Hot water always rises. It goes against the laws of physics to fall.

IHTH

Dave