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I currently have a conventional Thorn Gas Boiler installed in my cellar and exhausted via a lining up the chimney. The boiler is rated at 100,000 Btu's and is some 25 years old. Unfortunately corrosion has taken it's toll and I have to replace the boiler. Problems -
1. I have it seems to replace with a Condensing boiler
2. The Flue (in and out) has to exit the building more than 300mm above ground level. The ceiling level of my cellar is only Approx 200mm above Ground Level.
3.All my existing pipework terminates in the cellar (Boiler Room)
4.I have no room and do not want to mount upstairs
5. I am advised that I cannot use the Chimney to take the Flue, because any new boiler will have a balanced flue

Is there a way around the 300mm above ground rule and what boiler would you recommend for a vented system

Thanks
Peter

Hi Peter,

1. Yes you have to install a condensing boiler.
2.The flue could have an extension fitted to it as it will probably be fan flued to increase your 200mm.
3.No problem.
4.Good, install it in cellar, but perhaps improve ventilation for corrosion reasons.
5.See no. 2.

Regards

Steve

The termination is required to be 300mm above ground level, unless otherwise stated in the manufacturers instructions. Which I don't think any will - as there'll be a risk of flooding the combustion chamber if you get heavy rain/localised flooding.

Not sure what steve the gas means by 'The flue could have an extension fitted to it as it will probably be fan flued to increase your 200mm. ' Unless he thinks the problem is the flue length.

Wooden floor ? could the flue not come up through the floor and then out through the wall, as long as you have 25mm clearance from any combustible materials, and the seals are visible or accesiible for servicing purposes, this shouldn't cause any problems ??

There is no way of using an existing flue or chimney for condensing boilers. The flues are specially designed for the water vapour from the products of combustion to condense and then run back through the secondary heat-exchanger. This is where the efficiency of the boiler is increased - as the heat from the condensate is transferred to the heating/water section, and the waste water is discharged to a drain or soakaway. So in your case - this will probably require pumping from the cellar.


htg

Thanks guys for your quick an helpful responses. Some further info/questions.
1. Cellar is dry, boiler would be mounted in my heated workshop
2. Room above is our Breakfast Room, can't bring flue up through floor. Thought might have been able to get more height by taking flue into under floor space of B'fast Room, but unfortunately the joist runs parallel with the outside wall and would have to cut through - can't be done.
3. Can I take flue out at less than 300mm providing the inlet and outlet are ,say 3m above ground level i.e. taken up the wall. This would overcome the possible ingress of flood water/snow/leaves. Can such flues be obtained?
4.I have a drain for condensate in my workshop which has a sink.
Will be very grateful for any further comments

Thanks again
Peter

No, you have a verticale flue or horizontal flue. To go through a wall you use the horizontal flue terminal. You cannot use a vertical/roof flue terminal against a wall or a horizontal terminal pointing upwards.

What's outside ? do you have the option of dropping the ground level by 100mm ? this would give the 300mm clearance.

htg

Thanks your recent response htg. A horizontal flue would come out just above an ashphalted surface. I had thoughts along the same lines i.e. to make a small pit with drainage to an existing open drain at cellar floorlevel(outside the cellar window)and where I would drain the condensate to - this is connected to my main drain. Could make a grille to protect from leaves. Gloworm have a plume management kit which takes air in where the flue comes out through the wall and takes the exhaust up the wall to discharge at a higher level.
My concern was that this would not meet the regulations.
Do you know if the 300mm is a manufacturer requirement or is a mandatory regulation? If the former I could go along the pit solution providing I put in sufficient safeguards to ensure water drainage and leaf/rubbish avoidance.
Would be very interested in your comments.
Thanks again.
Peter