We are looking at replacing 21 year old boiler and changing over to a pressurised water system. We have used a local guy for boiler servicing and he helped us over the cold spell when the boiler packed up. He never seems to have work on (he always is able to come over at short notice….even when other plumbers were mad busy), and he comes across as nervous. When I’ve asked him technical stuff, he sounds like he knows basically what he’s doing, but perhaps not giving a total feeling of confidence.

He comes across as trustable, and his soldering looks tidy, but he’s not a registered fitter for Viessmann (so we don’t get a full 5 year warranty)…would you trust him to redo the heating?

I guess what I’m after is a feeling for how good his technical knowledge needs to be to do a good job (are there loads to tricks to fitting which make a difference, or do you bolt the stuff down, plum it in and switch it on?). He did mention putting in cleaner(?) for a week before the installation and fitting a mag. filter to improve the like of the boiler, which I guess are good signs?

If you mean unvented hot water cylinder, then that is a sepertate qualification. It was given for life, however, that has been changed to 5 years, so a lot of people are un-knowingly fitting without being qualified

Unvented DHW is **** mega though!

Yes, unvented hot water cylinder is what we are after.

He needs to be corgi registered.
If he isn’t I’d look elsewhere for a fitter.

They come in kit form, but all safety devices must be fitted. That is a doddle.

The wiring is a bit tricky if you’re not clued up though, you usually have an S Plan (two zone valves) with electrical thermal cut out on the cylinder

You have to have the relevant certificate to fit unvented. They are very good, but will only perform as well as your cold water main. Usually this is upgraded in size to cope with the extra demand on the supply. It should be checked for pressure and flow before proceeding.
The other thing with them that has to be checked is the discharge pipework arrangement. This is one of the most common faults that I see when I go and fault find stuff for the NHBC. Like most pipework it needs to be sized which is something that most plumbers seem incapable of.

As above, qually needed for unvented is a G3 cert, only a 1 day course, costs about 150 quid usually. If he doesn’t have it, it’ll worth him doing it anyhow. He’s probably gas safe already, but you don’t need that just for unvented.

easy to get right if you’re clued up, easy to get wrong if not

Professional plumber sat next to me says you should have an inline descaler on the cold pipe entering the boiler to save the heat exchanger. You should also have the system powerflushed rather than just cleansed prior to fitting a new system. looks like that is why he blows the warranty.

Without any other info it looks about £2K to supply and fit properly. clearly more information would give a more accurate quote. A bad job could screw your system real quick rather than getting the job done properly.

He needs to be corgi registered

try gas safe which took over the register from corgi

oops.forgot it had changed.
ta.

WCA – he’s not talking about a combi therefore you don’t need a scale device (most of the inline ones are s*** anyway unless it is a polyphosate dosing type)

Without any other info it looks about £2K to supply and fit properly. clearly more information would give a more accurate quote. A bad job could screw your system real quick rather than getting the job done properly.

Surely £2000 wouldn’t cover materials for full unvented system?

Unvented cylinder still needs to be heated unless you are suggesting an immersion which won’t do the central heating.

What is being put in?

What heats the water and what is keeping it hot?

Plumber has left the building so I am now without his knowledge.

He is talking about protecting the plate heat exchanger from limescale. in a heat only boiler it the corrosion inhibitor protects the primary heat exchanger and should not suffer from scale deposits.