Hi I do plumbing a big four floor house in st johns wood with 2 bathroom huge kitchen one cloakroom and about 14 radiator no underfloor heating As the house is huge there is lots of pipe work and i use the main pipes 28 mm from boiler room (flow and return cold and hot all 28 mm and secondary return on 22 mm ) The main cold pipe from street is 32 mm I run 22 mm cold water main for kitchen and garden and the rest of house will be connected to water softener I am also run another cold pipe for kitchen ( dishwasher and w/m to be connected to water softener) Is a 42 kw vailant boiler and 300 litter megaflow will be good enough for this house ? Do i have to use two separate expansion vessel for hot water and heating or one for heating is enough . What size of pump for heating do i have to use And is a system boiler will be good so we have cold water all the house or i have to use conventional system Do i need booster for cold water ? Regards Ghasem
Big Dunk has said it correctly, get a qualified installer in, he/she will size the house and qoute for the correct boiler, the same goes for the unvented cylinder, which again has to be installed and commissioned by a qualified engineer. From your post it would appear to me that your a DIY'er who's won a contract to do the plumbing for someone, your lack of basic plumbing knowledge is evident from the questions your asking. If your doing this job for profit you need tyo be very careful my friend, you could have the health and safety all over you like a rash
Thanks for your reply but i have no contract i am working as plumbing assisstance with a very cheap day working salary I have done many jobs but with plumber assisstance and giude B
So you have not yet reached the stage for you to specify products for installation, surly if you have supervision he will be directing the project and giving you the details of what to do. In which case why the question on an open forum?
This time i am donig the job alone with no supervision to direct me Eventhogh is not my first time i have install system boiler and combi and builder bring a plumber for certificate but this job is very big Anyway i approciate if any guide you can give me
Sorry mate but by law you cannot install a boiler unless you are Gas Safe registered or touch any of the gas in the house. You can most defiantly NOT install an unvented cylinder without the appropriate qualification. You and your builder are breaking the law and risking a prison sentence. You shall recieve no advice here Get in someone qualified. Oh yeah one last thing what was that address in St Johns wood
Lots of questions there If you ask any UHWSC tech they will say the coil for in your case a 300 cyl requires eg 25kw, this is due to the input required for the 25min recovery from cold. Now that's very rare more so with large volume due to demand evident in cyl capacity, This is all very simple, don't use a cyl with an internal exp vessel, then get cyl sized with manufacturer based on occupants, outlets etc, the hot Rtn should be 15mm only, Add all the rads kW together, then add 15% then add 3kw for cyl, that's boiler size, Record water flow & pressure values, Compare with demand, If in doubt over performance then fit an accumulator, cold exp vessel needs to be 10% of cyl capacity, don't use a sytem boiler as the pump will be ****, split the system into zones on each floor & if needed a pump for each from SL from zone valve,
coming from someone who appears to be a qualified engineer you've just helped someone who clearly has no idea about the regulations, to calculate what he needs to go out and buy the materials to install himself. I thought the idea was to stop illegal gas installations. I know we're here to be helpful and give correct advice, but in this case you should not have posted this info, you have now put many people's lives at risk.
Ok How do you know he's not gas safe? He just wanted some design help? There's tons of engineers who can't answer this question and there's tons who don't need too. He is clearly new to designing his own jobs so fair play to him as it takes balls to design a job that size, his client clearly is new to the build industry as he has no idea of the complexity required for this task, normally a mechanical design specification is provided with the drawings
Don't it again! Sorry though it was a 4 storey block of flats!!! It's pretty basic my man & im happy to help, but if your not a plumber it's pointless explaining all the tech to someone who can't apply to the most basic task, it's like asking to explain what normally takes 4yrs and a lot of college to learn,
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