"Phil Addison" wrote in message
...
The term 'index' is a very old one deriving from a crude rule of thumb
design method. What they mean by 'index' is simply the radiator that has
the most resistance to flow. It is the one that has the longest/thinnest
pipe run and is often (but not always) the furthest from the boiler.
This one should have both its valves wide open during balancing.

and work back to the boiler or do I
start from the radiator closest to the boiler?

Start by opening all of the valves on both sides. Then generally the
Rads closest to the boiler will take more than their fair share of the
flow so you will start by turning them down to get a larger temperature
drop.

From what I understand I might have to adjust the speed of the pump. I
have
no idea how to do that! I have a Potterton Puma 100 boiler and I can't
even
see a pump let alone adjust the speed! I understand that some boilers
have
automatic pumps - is that right? Does my boiler have one?

There is usually a switch or dial on the pump itself, marked 1, 2, 3 (3
being fast) or similar. The pump may even be under the floor, in which
case don't worry unless you really suspect a problem with it.

Is it correct that the drop needs to be 20 deg F?

No. What matters is that all rads have roughly the same drop and have
really hot water reaching them. In other words they are all getting HOT!

Cheers Phil, that's very helpful advice. The pump is inside the boiler
casing according to the installation booklet, and I can't see anyway of
adjusting it so it will just have to stay as it is!!

I have managed to borrow an infrared thermometer..........I can't stop
playing with it - Although I can't think of a single use for one apart from
balancing radiators!!!

Angela