Installing a Combi/flue routing

[andrewpreece]

Yes,

I know there was a thread a few days back about theoretically installing a combi in your own home, but has any diyer here actually done this? I've heard the arguments about insurance, armageddon, the law etc, but I've read the detailed Vaillant combi installation instructions and some of the Regs etc, and see nothing I can't handle ( albeit slowly ). I intend to keep the house for a long time so not having a Corgi certificate is no problem.

My plumber is messing me around, since his original visit two promises to come around in two weeks have come to nothing, and he never 'phones and says why, I just wait around days, finally call him and get another "next week" excuse. I want some hot water before Christmas!

A question has come to mind though; can the flue pipe go down after exiting the combi ( more than the 1 degree recommended fall of the outpipe )? I see no reason why not, the flue is fan assisted room-sealed. I wish to place the combi as high up in an outhouse as possible so as to use the space beneath, and since the flue has to exit on the adjacent wall at a lower level ( flue siting regs ), it will need to twist and turn it a little. The alterative is through the outhouse pitched slate roof, which I don't fancy. Anyone out there have an unusual flue installation?

cheers,

Andy.

[Toby]

my old girlfriend used to say the same about me...

You could try random ones from the find-a-Corgi website, if he's very local you've got more chance of him coming round.

But I sympathise and encourage you to get on with it. The DIY route would cause problems with the warranty especially if any parts are DOA. For peace of mind you can get a Landlords certificate at some point in the future more convenient to your plumber / heating engineer, that is if he is still speaking to you and has not regressed to a permanent sulk. Anyone who says once you have done the majority, just get a Corgi to commission it for £50 is living in fantasy land.

Straight up works OK for me. More expensive tho :-( If it's a condenser it should slope so that condensate runs into the boiler anyway.

[BigWallop]

These pages give some good advice:

not specifically for your system, the pages show some of the flue designs that could be used, and also some specific points on what can and what shouldn't be done.

[BillR]

I've installed a couple of combis, non-condensing as replacements. It was a doddle to do. I guess they have to be easy for the average muppet that fits these things... The manufacturers, Vokera and Ariston were both very helpful on the phone and by email before I bought the boilers, with info on wiring diagrams etc. I took great care with the short runs of gas pipe I had to do. Both checking all joints with leak detector fluid and doing a manometer leak test at the meter.

I suggest you ask the boiler manufacturer's help line.

[Ed Sirett]

Essentially you must decide on the flueing method before purchasing the boiler and flue and the parts are completely different.

The vertical flue would also require you obtain a metal-slate-with-a-rubber-cone in it to replace a real slate or tile. The big gotcha is finding you have a rafter or joist in the way ater you have hung the boiler in the only place it can go.

The standard flue will mean the top of the boiler will need to be something like 200mm below the top of the ceiling to allow for the bend. (205 IIRC).

A rear flue would allow you to put the boiler much nearer the ceiling but you need to make sure that the flue will not be too near the soffit/eaves or guttering outside?

The rear flue is totally different peice of kit to the standard flue and will require that you disassemble the fan cowl and reowrk things into a new position inside the boiler - straight forward if you follow the instructions.

There is some room for adjustment in the angle of the flue parts before you commit it by drilling and self tapping screws. However the idea is to install things in accordance with the book.

[andrewpreece]

room-sealed. I

metal-slate-with-a-rubber-cone

I will install by the book if I go ahead with things. There are a large number of combinations of flues that can be assembled using the parts available ( essentially straight pipes, offsets, 90 degree, 87 degree and 45 degree bends, as you know ). My flue run is short, only about 60cm in a straight line, so I can use plenty of elbows if necessary before the back-pressure exceeds limits.

My query really is caused by the fact that the specs only really show the commonest installations ( i.e. straight up through the roof, back through the wall, or sideways through the wall.). BTW, a bit of poking around through the sloping lathe and plaster ceiling reveals a rafter right on the centreline of where a simple vertical flue would go - another reason not to go down that route! I cannot use the rear flue option as that would blot out the window if the combi were hung on the outside wall - it also would be in the way of a proposed toilet.

I am confident that on a fan-assisted room-sealed flue, after exiting the combi to the side, I can go down a little with a 90 or 45 degree elbow then straighten up with an appropriate elbow and exit from the wall at right angles ( ok, a drop of 1 degree as specified ). No-one is going to show a picture of such an installation as it must be uncommon. It gives me an extra 6" of headroom under the combi which is desirable. The flue casing come out 200mm below the edge of outhouse roof tiles, 300mm away from the house corner, and more than 300mm above from the outhouse window, so I've got a solution as far as BS5440 or whatever it's called is concerned.

Today I read the Wickes combi boiler installation guide pamphlet and feel that it's a good start* for people who want to have a crack at this and feel they have the necessary technical skills. It also shows several common flue arrangements. As noted in a thread on this group last week, Wickes tell you on no account to get involved in the gas side of things, which I understand; their legal department would have bauled at any suggestion otherwise!

I may give their listed corgi engineers a call when I finish the water side of the installation to see if they will do the gas for me, if not, then I will plough on.

cheers for replies,

Andy

• But studying the regs and the manufacturers installation and commissioning guides is of course necessary in addition.

[Ed Sirett]

ISTR that you were thinking of fitting a Vaillant Turbomax this can only use a side flue if it exits the top. There are other makes and models which will let you bring the flue straight out sideways.

[andrewpreece]

soffit/eaves

back-pressure

Interesting; thanks Ed, I had become wedded to the idea of a Vaillant as it was what I had before and though pricey it seems to be respected as a make ( German engineering ), but I will have a look at some others, as it's always better to keep it simple! I'll start with Worcester-Bosch...

Andy.

[Ed Sirett]

These seem well respected. They are fitted by BG which is no particular recomendation except they fit so many. So if the boilers were lemons they would have stopped long ago. Round here they cost another 100-200 quid over the equivalent Vaillant at trade prices.

I get no benefit from fitting Vaillants all the sweeteners/bribes/cash- backs/holidays/air-miles go to people who fit 100 units at a time, like LA and HA heating maintenance managers.