Built in gas oven under a inset gas hob

[Chris Cowley]

How does one go about installing a built-in gas oven with an built-in inset gas hob in the worktop above it in a compliant way?

The Gas Safety Regulations seem to imply that both the oven and the hob must have fixed pipework. The only possible way I can think of doing this would be to connect the oven first (access through the hole in the worktop above - dead easy) then attach enough fixed pipework to the hob itself for it to be lowered down and somehow threaded around the units and the oven to meet up with an isolation valve somewhere accessible (in the void below the oven perhaps).

Is this potentially very awkward/impossible procedure the only way to do it without the use of a (now apparently non-compliant) flexible hose for either appliance?

[Owain]

Well duh, knock a hole through the wall from the lounge and do it that way innit!

(No, I don't know seriously. I suspect the likes of Mr Sirret do it with very skilled pipework.)

Owain

[Chris Cowley]

Ahah! Inspired! very skilled pipework.)

The thing is, the union nuts on both the oven and hob have to be done up at some point, and I can't see how that could be done with both items in situ. So I'm either missing some clever trick of the trade or some of the pipework has to be attached to one or t'other before putting them in place.

[John Stumbles]

On the last (and only) such combo I installed IIRC I used a flexible for the oven. This was either recommended or at least not forbidden in the manufacturer's instructions. Since an oven is fairly easily removable (although obviously not intended to be so by the householder) this does not seem unreasonable, even though it is not strictly speaking a portable appliance (or whatever the form of worms is). The only way using fixed pipework would either require access from the side (or behind) or would require a lot of unsupported fixed pipework protruding below the oven, and this would be vulnerable to damage when removing and refitting the oven.

[Chris Cowley]

The instructions for the oven in this case state "Connection with flexible metallic pipes - mainland Europe only". The only option given for UK installs is "Connection with rigid metallic pipe".

However, it does recommend 8mm copper tube (and the oven is supplied with an 8mm to 1/2" BSP nut and olive). As 8mm is fairly "bendy", I guess I could leave enough extra for the oven to be pulled out the 200mm or so to allow the union nut to be connected before pushing the whole shebang into place, but I am not sure if doing that would be frowned upon or not.

[<richard]

Good God! Don't do that! The copper pipe will work harden and fracture behind the oven.

Can you fix pipework to the two units and pass it into ajoining cabinets. Then finalise the connections there ( to the side, so to speak )?

R.

[Lobster]

You might want to read this thread - I had just the same issue. In my case the CORGI ended up fixing the oven with a flexible pipe, and I didn't stop him...

or

David

[Ed Sirett]

I;d make a hole in the adjecent cupboard with a hole saw just enough to let tighten/undo and compression nut on the 8mm pipewoirk. But this may be much harder than it takes to write about it.

[Chris Cowley]

I did think about that, however the *only* way to access the compression nut on the oven is from above as it's totally obscured by the metal sides of the oven which have carry handles inset into them.

I'm currently thinking the best method would be to install the oven without the hob in place, using the fixed 8mm tube, and then drop the hob in with approx. 30cm of pipework pre-attached to union nut; enough to take it to the adjacent unit where a compression fitting can be used (as it will be accessible via the cupboard). Do you have any thoughts on that?

If the above is non-compliant then I believe there may be absolutely no way to do this in a complaint manner. I did read Lobster's thread about this prior to my original post and it seems his fitter was able to get away with using a cooker hose on the basis that a flexible cooker hose is not the same thing a "rubber hose" as forbidden in his oven's installation manual. My oven's manual expressly forbids the use of "flexible metallic pipe" outside of mainland Europe (dunno why it's safe in Europe, but not in the UK, but there you go).

[Chris Cowley]

I've just re-read the installation instructions and I must have missed it previously, but this is exactly how the installation instructions for the oven tell you how to do it, in fact:-

1. Partially insert the oven into the recess (about 30cm) and operate on the connection ramp from above...

1B. Insert the 8mm copper pipe into the connection ramp after fitting the proper nut and olive... 2. Tighten the nuts by means of a 22mm spanner... 3. Completely insert the oven into the recess and secure it as indicated... 4. Check for perfect sealing of the connection using leak detection fluid...

As I can't see that this contravenes any of the safety regs, I think I've just convinced myself that this is exactly what I'm going to do!

[<me9]

I see a problem here. How do you check the connection /after/ the oven is pushed back into the recess.

[Chris Cowley]

Heh, good point. Someone at Electrolux needs a thwack for that. But it's no problem in practice as I will be using a manometer. I've only ever used leak detection spray on the screw for the meter test point after completing the pressure drop tests.

BTW, just after the bit in the installation guide about using leak detection fluid, it says in bold type: "Never use a flame for the leak-proof test!". Which made me chuckle.

[Ed Sirett]

The hob needs to be fixed from below to secure it properly in its hole. Moving a pipe 30cm seems quite a way even for 8mm pipe. I agree the drop test with the manometer will probably be the only way to really check for leaks after it's in place.

[Chris Cowley]

Thanks Ed, your comments are much appreciated. The hob didn't arrive until today, and I didn't previously realise it needed to be fixed from below. It looks like the only option for this oven (regardless of whether it has a hob above it or not) is to use 8mm tube and slide it in

30cm after connecting it. I will fix the tube to the rear of the oven housing unit and put a reasonably large loop in it to avoid stressing the pipework any more than is necessary.

It doesn't seem like an ideal method of installation, and if I was choosing an oven now I would probably get one that has access to the gas connection from either the side or below. You live and learn.

[Lobster]

That's the same scenario I had, with the hob. I really can't see how what your proposing above can be a safer solution than using a proper flexible hose, even if the instructions stipulate it. Anyway I think that's where my Corgi was coming from when he fitted mine the way he did.

David

[Chris Cowley]

Yup - a flexible hose does seem like a potentially better solution on the face of it. Especially as my oven states that "flexible metallic pipe" (which is what I understand a typical cooker hose to be) is fine in mainland Europe. I might be inclined to do the same as your CORGI fitter if my particular oven's manual didn't expressly forbid it for UK installs, but as this is DIY and I will be taking ultimate responsibility for it, I am being completely anal about following the letter of the regs and the installation guide.

I don't have the same level of experience as a typical CORGI gas fitter, so I don't feel able to bend the rules in the same way that someone who does this sort of work day in and day out might do, but I certainly wouldn't have a problem if I got a trusted CORGI in and he chose to use a cooker hose for the oven.