Boiler questions - confused layperson

originalww

Hi all, :hello:
We are getting the old knackered boiler and equally knackered radiators in our house changed over at the same time as getting building work done. I am at the quotes stage with builders and am getting very confused about boilers. Current boiler is a potterton netaheat (that broke down last december at height of snow) that's at least 16 years old. Radiators count for 4 bedroom house will be 15 (including 3 towel heaters). We'll have 3 showers (one family bathroom, one master ensuite and one guest ensuite) and one bath.

I've got 2 people (builders) telling me I need a megaflow and one of them saying that in a pressurised system I'll need to redo all the pipework or it'll spring a leak and cause problems in a few years time.
A third (plumber) is telling me my water pressure is only about 1bar so I'd need to put in a new pipe between me and the nearest main if I wanted megaflow. For various reasons (that this plumber isn't aware of) that is not straightforward and would be too much money to do. He is recommending a Worcester Greenstar 24Ri boiler and a pump and a hotwater cylinder and says I don't need a megaflo. Conveniently enough he is accredited for Worcester.

If I've understood all the stuff I've been reading about boilers (O.M.G!!!) the Worcester and Megaflo are both condensing boilers so why is water pressure important for one but not the other?

Do I need to measure my water pressure - and if so, how do I do that? And I remember the chap who came to fix the netaheat in December saying I needed to check my gas pressure too before picking a new boiler... so how do I do that? And why is that significant?

I'm leaning towards using the plumber who recommeded the Worcester. He was the only one who looked at the water flow out of the tap and his plans for relocating the boiler were logical and worked for the main build. I am deeply suspicious of the chap saying I should replace all my pipework - that seems a little extreme!

Sorry for the stream of questions, I hope someone here can help. I am not a stupid person but this whole boiler question is beginning to melt my brain!:o

thanking you humbly in advance for helping!!!

OriginalWW

Canucklehead

Hi: a Megaflo is a brand of unvented cylinder (provides hot water at mains pressure) and requires sufficient mains flow/pressure. Gas pressure can be measured by a RGI using a manometer. You can DIY your water mains pressure and flow rates ). Converting to a sealed system can reveal underlying weaknesses in the existing pipework and the rads as the system will now be under mains pressure. I recommend you have a look at the HHIC website. More on DHW supplies here. Can't advise on what is best for your property without a site survey.

HTH

Canucklehead

originalww

thanks for the additional info sources..... just had a quick scan and that's my reading material for the day. Brilliant. Sorry my original post wasn't too clear (more a cry from the heart!)- I am looking for information to help me make sense of what each builder/ plumber is telling me. Wouldn't expect anyone to give me the answer If I've understood all the stuff about Worcesters correctly, they are vented boilers - i.e. flue gases are vented to air and the condensed fluid is disposed of via normal waste pipe. Hence the pump? Will check my various pressures - that may make the decision for me! THanks again.

OrginalWW

gas4you

To make a megaflo worthwhile you will need a minimum of 3.5 bar pressure and at least 20 litres/min flow.

Replacing your cold mains from the street will not have any effect on your pressure, but if made larger will increase the flow rate.

Flow and pressure are not related