Boiler replacement

[a/c_man]

Hi all

My first post on this forum, hope somebody can help. We moved into a bungalow a couple of months ago, it has an existing gravity fed heating system which works ok but I would imagine somewhat inefficiently? We plan to convert the loft into 2 bedrooms, ensuite and bathroom next year so need to lose the expansion tank and water cylinder. My plan is to change to a 30KW combi boiler which will be located approx 1.5metre from the gas metre with the main 22mm gas pipe running along side. As we are on a tight budget I intend to do as much of the work as possible. I intend to reroute the flow and return pipework to the new boiler location and alterations to the pipework in the loft to remove existing pump, cylinder etc. I will also run in a new cold water feed to the boiler and new hot water pipework, being a bungalow it is very easy as it is all in the loft.
Am i correct in assuming that the cold water feed to the boiler and all hot water pipework will be 15mm, existing hot water pipework is 22mm being gravity fed. I am NOT gassafe registered and will be using a gassafe engineer to do all gas pipe sizing installation and testing. I also intend to drill the hole for the flue.
My 2 questions are as follows.
I will have to replace a lot of the main run of flow and return in the loft, am I better running this in copper or sppedfit(or similar), I am quite happy / competent to do either as my work requires installaing both copper and plastic for condensate drains on air conditioning systems. I realise if i use a plastic product that the tails to the boiler will need to be copper.
Secondly can I mount the boiler myself? I am purchasing from a plumbers merchant who I have an account with.
As said I am NOT a gas engineer, I will be using a gassafe engineer to do any gas work and testing, the guy i'm using has done a lot of work for other family members and does a good job.

Any help appreciated

 

[Bernie2]

I suppose its a case of first things first.

Regarding fitting a boiler.

If its your own house and you are classed as competent to do so.
I am not suggesting your incompetent its just how they word it in the gas regs.
What competence means and how you would prove it if your not GaSafe registered is anybodies guess.

I suppose if you installed it and follow all relevant Building Regs and manufacturers instructions, you could be classed as competent.
I once asked the same question about hanging boilers for money and whether you where required to be CORGI (GaSafe) registered.

The answer that came back was "Yes," the reason stated was that it required fixing a flue which is really part of the gas train. But that was for paid work not your own home.

I suppose as your getting it all checked out anyway, and its in your own home, I would say its okay providing your competent.

The next part about pipe sizes depends on what pressure and flow rate you have on the water main. The utility company is only required to supply 9 liters a minute at 1 bar pressure and that is at the outside stop tap by the house boundary. Its not much.

The thing is, with a combi, both hot and cold are going to be fed off the one water main.

I assume your going to finish up in the bungalow with 2 bathrooms a sink possibly a shower and a bit more.

I would check it all very carefully if I where you, its quite a lot to run off one water main if its not very big or strong. Although you can get water boosters, a sort of storage tank for mains water. Have a look at mains boosters. But they are expensive. You could then upsize your pipe work if need be.

Even if you have enough pressure, check the flow velocities to make sure its not going to be noisy or wear the inside of the pipe away.

Don't forget a combi may have a flow rate of 20 liters per minute but the water main may only be able to supply 9 liters, so the combi will only be able to supply 9 litres.

Hope this helps!　
　

 

[stevetheplumber]

as its your own house and your obviously competent to hang heavy equipment on a wall(aircon units ) i cant see what anyone could do. fixing the flue takes you into gas work for which it would be difficult to prove competency at the end of the day no one will be checking who has done what unless it goes bang

 

[radswilldo]

Get the engineer to do the flue and boiler, ring gas safe with regards to legalise, its what they're there for. If you want an ensuite and bathroom a combi is not the option, it will not run multiple hot draw-offs, eg 2 x showers. If your short on space a stored water combi will do, get the plumber to check your WORKING pressure.