Horizontal boiler flue

pvr · Post by **pvr** » Sat Aug 05, 2023 6:01 pm

The boiler I bought has a 110mm flue opening and I want to put a flue over that. I just cannot find a 115 mm flue anywhere, the Ariston I bought was advertised as 115 mm but was 100 mm so had to go back.

Anyone know where I can get a 115 mm one?

inkey$ · Post by **inkey$** » Sat Aug 05, 2023 6:29 pm

Screwfix?
https://www.screwfix.com/p/ariston-hori ... -kit/34472

pvr · Post by **pvr** » Sat Aug 05, 2023 7:29 pm

That was the one I bought but is actually 100mm annoyingly enough

Pondrew · Post by **Pondrew** » Sat Aug 05, 2023 10:05 pm

pvr wrote: ↑Sat Aug 05, 2023 6:01 pm The boiler I bought has a 110mm flue opening and I want to put a flue over that. I just cannot find a 115 mm flue anywhere, the Ariston I bought was advertised as 115 mm but was 100 mm so had to go back.

Anyone know where I can get a 115 mm one?

What are you trying to do?
115mm is not a standard size for a balanced flue (horizontal). 100mm, 125mm and 150mm are pretty standard (cos they equate to roughly 4", 5" and 6"). 115mm is 4 1/2" which is a strange size.

It will depend on how they are measured; internally , or externally.

Normally you buy a 'flue kit' from whoever you bought the boiler from for that model of boiler. It should then be compatible.

pvr · Post by **pvr** » Sat Aug 05, 2023 10:26 pm

It is a Camplux 10l model, outdoors unit but if used indoors it needs a flue (Their documentation). They don’t supply it (useful) hence trying to find one. The outlet is 110mm so 115mm would fit perfectly over that.

Perhaps I need to put a reducer on it first to get it to 100mm

This unit will go inside the garage to get hot water, we discussed that one before and this is one of the few diy units on the market.

Pondrew · Post by **Pondrew** » Sat Aug 05, 2023 10:54 pm

pvr wrote: ↑Sat Aug 05, 2023 10:26 pm It is a Camplux 10l model, outdoors unit but if used indoors it needs a flue (Their documentation). They don’t supply it (useful) hence trying to find one. The outlet is 110mm so 115mm would fit perfectly over that.

Perhaps I need to put a reducer on it first to get it to 100mm

This unit will go inside the garage to get hot water, we discussed that one before and this is one of the few diy units on the market.

Yes I remember!
I would ask them who makes a flue kit that fits their termination diameter, then. You also need to ascertain whether it needs a balanced flue or a standard flue. If it is designed to be sited outdoors then unlikely to be a balanced flue IMO.

If a balanced flue, the flue will be fan-assisted. If there is no fan then it needs a standard, single walled, flue pipe. You cannot install a standard flue horizontally. It must be vertical, as the flue gases escape via thermal uplift and 'draw'.

pvr · Post by **pvr** » Sun Aug 06, 2023 7:45 am

On a standard flue, can you first go through the wall and then up to get the uplift/draw effect?

Thanks for your help by the way

Pondrew · Post by **Pondrew** » Sun Aug 06, 2023 11:52 am

pvr wrote: ↑Sun Aug 06, 2023 7:45 am On a standard flue, can you first go through the wall and then up to get the uplift/draw effect?

Don't think so. You can go vertical, then 'dog-leg' through a wall at 45 degrees but not 90.
Check with building regs online, it will show diagrams of what you can and cannot do.

If in any doubt, get someone who knows to advise/ do it!

inkey$ · Post by **inkey$** » Sun Aug 06, 2023 12:14 pm

Pondrew wrote: ↑Sun Aug 06, 2023 11:52 am If in any doubt, get someone who knows to advise/ do it!

Sounds as though he already has. I’d get the tools out ready, Pondrew

pvr · Post by **pvr** » Sun Aug 06, 2023 12:25 pm

I just don’t want to gas myself but want to fit it myself, trades tend to add M tax to anything they do for me and I enjoy the work.

So keep advising and i will do the donkey work

Pondrew · Post by **Pondrew** » Sun Aug 06, 2023 12:48 pm

pvr wrote: ↑Sun Aug 06, 2023 12:25 pm So keep advising and i will do the donkey work

I have to be careful, as I am NOT Gas Safe registered, so can only advise on what I know. As said read the building regs for gas flues!

pvr · Post by **pvr** » Sun Aug 06, 2023 1:26 pm

We are getting there

- need 45 degree angle out
- not a balanced flue
- then another one outside to get straight again and up-

Just need to find the size, chimney flue ok then as they seem to have those bends?

Pondrew · Post by **Pondrew** » Sun Aug 06, 2023 3:38 pm

pvr wrote: ↑Sun Aug 06, 2023 1:26 pm Just need to find the size, chimney flue ok then as they seem to have those bends?

Not 100% sure but think it has to be stainless steel. Look up "gas boiler flue" online. I am sure LPG or natural gas will require the same spec flue.

Did a quick search and found this: they also have a 102mm-127mm reducer. But ring them and talk to them to make sure you are getting what you need for the application.
https://directflues.co.uk/single-wall-flue-sw304-127

Edit:
Thinking about it you will probably need twin-walled flue for outside and possibly inside too if the garage isn't heated. Twin-wall has the flue inside, then a layer of insulation then another outer wall. This is to keep the temperature of the gases high. If you lose heat in the flue, you will lose all your draw and the gases will 'stall'. You really don't want that!
Pay attention to the height the flue needs to terminate, as it needs to be a certain distance from any structure. This is to prevent wind from gusting around the cap and causing 'blow down'. You really don't want that either.

Also twin-walled flue is VERY expensive. You will spend more on the flue materials than the appliance, easily.

Just do your homework and make sure you do it right. Don't take my advice as gospel!

Oh and don't forget the most important item; A CARBON MONOXIDE detector/ alarm
https://www.screwfix.com/p/kidde-2030-d ... larm/681ph

Another edit:
The more I think about this the more I would seriously recommend you get a professional to do it!

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