rabeye, can i ask a civil question without you resorting to speaking to me the way you speak to others on here (who are more helpful to you than you deserve)
you come on asking a******e questions, but are never done telling us how wonderful you are ie you make more in a week than someone does in a month, but you want to know about this boiler or how to fit that system, why the f**k do you even bother with the likes of us on here?
edit i now want to ask another question, and apologies if its been covered but can you briefly tell me your work experience/qualifications in gas so i can decide whether i want to assist you or not ( if you need my advice that is as i have only been doing plumbing since 1978 and gas since about 1995)
ya fud