Alterations to central heating system

[AndrewSchofield]

We are currently carrying out a loft conversion of our home and will need to add two new radiators to the system for the new rooms in the loft. I have read other posts on DIYnot and understand how to work out if our existing boiler will take the extra load but have a couple of other queries relating to this.

We have a Worcester Bosch 28CDi combi boiler. I will need to drain the system to carryout the new work and understand i should turn the boiler off. Can i still use the boiler for hot water while the central heating system is drained or should i leave the boiler completely off until the heating system is re-filled.

When i re-fill the system, how do i calculate how much inhibitor to put in? Our existing system consists of two large single radiators on the ground floor. 1 medium and 2 small single rads on the first floor together with a small double rad in the bathroom and i intend to install two medium single rads in the loft. One of the large ground floor rads may also be downsized.

Any advice will be gratefully received.

 

[Agile]

Your boiler has plenty of capacity to heat both your house and the one next door.

IF you first close the systen isolating valves under the boiler you can continue to get hot water as long as the boiler does not have any internal leaks.

You use a full can of inhibitor.

Tony

 

[AndrewSchofield]

Tony,

Thanks for the advice. When you say the isolating valve do you mean the plastic key used for filling the system? I can't see any other valves under the boiler (or anywhere in the system) - although this may be another thing the engineers failed to do when they installed the new boiler!?!?

 

[Agile]

I think that the isolating valves are underneath at the back and are where the heating pipes connect onto the boiler.

They usually have screwdriver slots and must be turned by a wide bladed screwdriver or you will risk damaging them.

If they have never been operated then they may leak afterwards and need to be replaced but thats fairly rare on your model!

Tony