S Viemeister wrote:
Our out-dated, hard-to-control, inefficient heating system is due to be
replaced this year. Currently, we have an oil-fired Rayburn (converted
from solid fuel), _and_ a back-boiler in the livingroom fireplace.
The Rayburn is to be removed, and an externally mounted condensing
boiler will be installed.
The back boiler concerns me - it will, of course, be disconnected from
the heating system, but I wish to be able to continue to use the
fireplace. How does one safely decommission a back boiler? Can this be
done without wrecking the fireplace?

It seems that our short term solution will likely be to
drain/disconnect/remove the piping, making sure that combustion products
can't find their way into the house, and drill holes into the boiler
body. I've seen mention of filling the boiler with sand - but am not
sure how feasible this is - or why it should be done.
The fireplace only gets occasional use, but eventually we'll need to
remove all of the back boiler bits.