"dsnd_medic" wrote in message

I now have a good 2nd
hand back boiler but have been told it won't be as easy as I thought to
plumb it into my existing system. I have an open system, ie not
pressurised, My flow and return pipes are 22mm with 15mm pipes being
used to supply all the radiators. Some people say it will work fine if
I just attach the back boiler to the flow and return others say I will
have major problems regulating and dissapating the heat.

Am I making a big mistake or is it a feasable idea......any comments or
tips would be greatly appreciated

Most heating systems work by the thermostat calling for heat, thus starting
the circulator, the water moves around giving off heat. When it drops to a
pre-set temperature, the boiler starts up to heat the water again.

In the case of an added heating source, the circulator will still work as
needed. The oil fired boiler will do that also, but now the water coming
back in is going to be hot already so the burner will not have to work as
hard or at all. I see many benefits, a few potential problems.

If the back boiler heats the water and it is not circulating, it may turn to
steam and increase pressure. You may want an aquastat that will start the
circulator to prevent that.

The water passing through the back boiler may be hotter than the incoming
water on the other side of the cottage making a little unbalance in room
temperature. Probably not a big deal.

I'd pipe it so you have a choice of flowing through or not through the back
boiler by opening and closing a couple of valves. This avoids heating it in
mild weather when a coal fire is not going, or to remove it for service if
ever needed.
--
Ed
http://pages.cthome.net/edhome/