Which size/model boiler and unvented tank?

[Arjay12345]

Hi All

Need some advice. I am looking to install an unvented tank and boiler system in the following spec house, but need some advice on what size boiler and tank I should go for.

House spec:

- 5 bedroom detached house
- 3 reception rooms plus dining room downstairs
- 25 radiators throughout
- Have calculated around 80,000 BTU required in whole house
- One kitchen, one family bathroom, and two en-suites
- Two adults, and two kids
- Any other factors worth mentioning?

I'd like to stick to a Vaillant boiler, but undecided on the tank (Vaillant or Megaflow)

Can anyone advise?

Thanks
Arjay

 

[muggles]

23.4kw (80,000 BTU) seems small for the house you're describing, are you sure that's correct? How did you work it out? Why do you want a Vaillant boiler rather than any other make?

Are you sure your mains flow rate and pressure are up to running an unvented cylinder? These need to be tested before any decision is made on whether to have one or not. As for the make, Megaflo are overrated, I have no experience of the Vaillant but I gather they talk to the boiler if you have a Vaillant boiler, personally I'd install an OSO Super S

 

[bengasman]

I would leave the technical details to the engineer who will design and install the system; he is the one who you will blame if it does not perform as expected.

 

[Arjay12345]

The BTU's is just the sum total of all the rooms I have calculated using some website (can't remember which!).

Vaillant mentioned because I have grown up with it being banded around as always the best. I understand this is probably marketing. I'm also not a plumber (just a DIY enthusiast) and hence what some may call gullible in these things to an extent.

I just don't want my plumber to advise me on something that isn't worth it, in money and features terms. That's why I'm trying to get an independent view on what might be required

Thanks
Arjay

 

[muggles]

That's not the way to work out what output you need, and I still think it sounds low although of course I haven't seen your house. Your engineer will be able to do the calculations more accurately, and it's best if he does as well, that way if it turns out to be wrong it's his problem and not yours.

Vaillant are good, there are arguable better boilers out there, but the quality of the installation is just as important as the boiler itself. If you don't trust your plumber to advise you correctly, get a different one. Whoever you use, they will have a boiler make that they are familiar with and will normally be able to offer you an extended warranty on. As long as it's not Italian or English you should be fine...

 

[bengasman]

I just don't want my plumber to advise me on something that isn't worth it, in money and features terms.

Just make sure you have a good installer.
You could spend a year on here trying to find out what and how, and I could still run rings around you if I wanted to, and so can most of my colleagues, and ALL of the conmen.

You could actually do more harm than good with this. Only the RGI that has surveyed the situation can adequately judge it. If you then start telling him how to do his job, he will probably leave you to it.

 

[ianniann]

Don't tell your installer what to do, but learn enough that you can walk away from a conman or an idiot. Or show them the door ...

I think your BTU estimate is well within range but then I've never seen your house. My 5 bed detached runs at half that level, but it sounds like it is quite a bit smaller. Also remember that if you are keeping the existing radiators then there is rarely any point increasing the size of the boiler (unless the old one was utterly unable to keep them all full of warm water).