What boiler and do I need to re-pipe my house

peel66

our current system is about 36 years old - boiler in garage, copper cylinder in airing cupboard and cold water tank in loft.

Yes the 8mm microbore enters the radiators at the same end

C_Mababejive

peel66 wrote: »

our current system is about 36 years old - boiler in garage, copper cylinder in airing cupboard and cold water tank in loft.

Yes the 8mm microbore enters the radiators at the same end

In that case i would back up your installers suggestion of ditching the 8mm in favour of new pipework to radiators which allow more efficient cross flow utilising an inlet and outlet at opposite sides of each rad. Twin entry valves can be troublesome,especially so if you have to replace a radiator and cross flow is a much better way of distributing hot water across the rad.

peel66

both quotes involves modifications to the pipework immediately under the radiators but quote 2 recommended a complete re-pipe, do you see this as necessary ?

we had another company come in to have a look yesterday, they said ideally replacing all microbore would be better, although i haven't yet had their quote they did say they would recommend a Worcester Greenstar CDi Highflow boiler - how does this boiler compare with the veissmann and vailliant ?

27col

I fitted my house with micro bore when I built it in 1977. What ever problems the house has had over the years, they do not include any problems with the micro bore. I have repiped the radiator connections in some places. But only because of the problem in sourcing replacement double valves. it is simple to change from micro bore to 15mm where the pipes come out of the floor.

C_Mababejive

peel66 wrote: »

both quotes involves modifications to the pipework immediately under the radiators but quote 2 recommended a complete re-pipe, do you see this as necessary ?

we had another company come in to have a look yesterday, they said ideally replacing all microbore would be better, although i haven't yet had their quote they did say they would recommend a Worcester Greenstar CDi Highflow boiler - how does this boiler compare with the veissmann and vailliant ?

Well its perfectly possible to modify the 8mm under each rad so that you have a crossflow system rather than a twin entry one ended system as at present.

Other factors to take into account are the resistance to flow in the total system and the ability of the 8mm piping to deliver the correct heat input to the rads.

I cant recall but im guessing your existing boiler will be cast iron and have a fairly high water volume content.

You are going to replace that with a new high efficiency boiler with a low water content.

The installation manual for the boiler will likely contain some graphs related to flow rate required through boiler.

Maybe lots of 8mm piping will present to too great a flow resistance for your new boiler?

Is the 8mm for the downstairs rads for example dropped from above or fed from below the ground floor floorboards?

peel66

we have 28mm and 22mm pipes from the boiler and along the landing, the 8mm then branches off to all radiators upstairs and down.

peel66

Could I ask your opinion on the Worcester greenstar CDi Highline boiler please ? I was wondering if this boiler is better than the Vailliant would it work with a storage cylinder ?