Eh? But mfrs instructions don't show this for any boiler I ever installed (as far as I remember)
Can u post extract from standards? - for everyone's benefit?
I already posted an extract from the BS in post 31 with the relevant diagrams.
Since you are familiar with Logic's if you read page 23 of the MI's you will find this
and read page 7 and it says this as do almost every other MI out there
Detailed recommendations are contained in the following British
Standard Codes of Practice:
BS. 5440:1 Flues (for gas appliances of rated input not
exceeding 70 kW).
BS. 5440:2 Ventilation (for gas appliances of rated input not
exceeding 70 kW).
BSEN. 12828:2003 Heating Systems in buildings: Design for
water based heating systems.
BSEN 12831:2003 Heating Systems in buildings: Method for
calculation of the design heat load.
BSEN 14336:2004 Heating Systems in buildings: Installation
and commissioning of water based heating
systems.
BS. 5546 Installation of gas hot water supplies for domestic
purposes (2nd Family Gases)
BS. 6798 Installation of gas fired hot water boilers of rated
input not exceeding 70 kW.
BS. 6891 Low pressure installation pipes.