"Rebecca" wrote in message
om...
Very useful information Andy. Thanks.

I wonder if a bit more info will narrow it down then...

Our house has a mixture of new and old steel rads. The new ones are
fine (not as hot as they could be but they heat up more or less
evenly), but the steel rads are heating very badly (only the top 2
inches)- despite us removing them last year and cleaning them
thoroughly (and cleaning the system with Fernox etc).

So, we were recommended to buy new rads to replace these old ones,
which we have done - I must admit the plumber who told us the sizes to
buy did guestimate. Looking at the B&G catalogue, the output of these
4 new rads ranges from 4500 to 6200. 3 of them are currently on 8mm,
and the smallest is on 6mm.

From your figures Andy if the general rule of thumb applies, it looks
like we will have to replace most of the pipes (as 8mm generally deals
with up to 4500w). Have I interpreted this correct?

The plumber that recommended changing all the pipes to 15mm (but did
not recommend changing the rads) was the only one which was
recommended to us.

Your opinion with this extra bit of info would be much appreciated!

Changing tac slightly 0 another plumber told us that we would have to
change the pipes coming form the boiler (some sort of Potterton) from
22mm to 28mm and that is why the circulation is bad. This sounds dodgy
to me...we had about 6 plumbers round and no-one mentioned this. What
do you think?

Have you added rads, or have you just replaced defective rads. If just
replacing then did the system operate fine previously. If it did work fine
then you have blockage of some sort.



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