Boiler flue length

[John]

Trying to get around to creating a short-list of potential boilers. Need to arrange for flue to go from ground floor through existing chimney to terminal at chimney pot height.

Am I right in assuming that a twin tube system give more scope for a longer flue than a concentric arrangement? If so, why? (Then we need to consider if a twin pipe would fit up the chimney) Any thoughts on boilers - 4 bedrooms -

2 bathrooms (not mine)

[Mr Uncalled-For]

Nobody's replied, so I'll offer my uneducated guesses.

Presumably there would be more friction in a concentric arrangement than in a twin tube setup, making the maximum run shorter?

[John Stumbles]

Probably not

You ought also consider that it is, according to CORGI's 'Gas Installaer' magazine, a requirement of the Gas Safety Installation and Use Regulations

flues should be accesible for inspection prior to initial comissioning of the appliance and during routine servicing or maintenance of the appliance.

(I can't see that in the regs myself unless one interprets section 28 "No person shall install a gas appliance except in such a manner that it is readily accessible for operation, inspection and maintenance" to include flues within the meaning of 'appliance', which is not explicit in section 2 "General interpretation and application")

[Ed Sirett]

Sounds to me that the OP might not be fully aware of the details of how modern boiler systems are intended to be used.

Twin pipe is generally more versatile (and cheaper) for the more awkward arrangements, concentric pipe is more common and it more usual in the vast majority of installations.

There is (IME at least) many other options that are better before reusing a brick chimney as a pipe work duct.

[John]

(kitchen - internal wall - with brick flue to chimney.) although he realises that considerable work will be required to change the pipework, etc. an alternative may be to use the upstairs airing cupboard (where cylinder is located). Much depends on the routing options for pipes. The house is well decorated, tiles, wooden floors, etc. I am merely discussing over a pint or two the various options before he gets a Corgi guy in who we feel may have a narrow bias and will not have an intimate knowledge of the house layout for considering pipe runs. The solution may not be a combi.

OP

John

[Ed Sirett]

The trouble with chimneys is

1) Access arrangements 2) They usually aren't straight.

This makes there initial attractiveness wear off pretty quickly IME.