oil - condensing boiler or not?

19 Aug 2004
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United Kingdom
I welcome some experience on this question. I'm planning to change from coal room heater (lounge) to oil wall mounted (kitchen). Currently all WM oil boilers are non-condensing (~85%). The only sedbuk listed WM oil boiler (~91%) is no longer available from the importer. So after 1/4/05 I'm stuck (unless the rules only apply to new houses).

But HRM, for example, say they have a condensing WM under development. Still is it a good idea to buy an untested boiler? Plus will this new boiler be too big? I would have thought if it was easy to make a WM condensing it would have been done by now which suggests to me a WM condenser might be tricky to service or unreliable.

The maths don't look too good either. If my heating bill is 500pa (about what I pay for coal but I would expect oil to be less), then 6% saving is 30pa and assuming the boiler price difference is 300, the same as floor boilers, the payback is over 10yrs.

The other concern is the plume effect. The flue will exit into the top of a 0.9m passageway open to the air above. The opposite wall is a 6ft high fence and I think the flue will be about 6ft high, perhaps more. V.hot flue gases will just rise (i.e. not condensing). But will the condenser plume fall or worse, will it fall over the fence and in next door? Their washing line is a few metres from this fence.


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I was under the impression that most oil boilers are more efficent than standard gas ones.
Are you aware that you should be OFTEC registered to work on oil boilers.
Also have you heard of vertex flue kits that will fit most ff boilers.

Thanks for the info about vertex, might be useful. I know some WM have what looks like a standard size round flue pipe but some have integral square or retangular ones (i.e. Worcester Danesmoor WM).

I was planning to have an OFTEC man comission the boiler (see my other thread - building regs).

WM oil boilers seem to be all ~85% or less (sedbuk C). Floor standing condensing boilers top out at almots 95% (sedbuk A). I read the 1/4/05 the limit will be 86%.! You seem to be right about gas. Non condensing only just scrap into band C at 82% with most in band D. Condensing also are less then only at 92% tops.
Must the new boiler be wm? I don't know the layout of your house, could you do floor standing in the old boilers place and flue out through the back of the chimney or is it an inside wall.
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Old boiler is in the lounge - coal fired room heater. CH is pumped, HW is gravity. New boiler is oil fired in kitchen as oil fired room heaters are very few, mostly too low powered and/or ugly, plus not that efficent, and expensive.

The plan is to fit boiler in the kitchen as WM as just need to run pipes from cupboard to ceiling. Floor mounted would have to go up the wall and over tiles - not pretty. Also tricky (impossible?) to fit with worksurface in place and taking that out would likely knacker tiles. Whatever way I cut it the floor mount looks to make a lot more damage. WM just means taking cupboard off or perhaps not even that as some fit in a cupboard. But I expect it would be easier to take the cupboard off, fit the WM boiler, adjust cupboard and refit cupboard.

From boiler run pipes in ceiling (i.e. under floor upstairs) to HW tank. Fit new pump, motoring valve in aircupboard (also new tank as easier to repumb without tank and tank is old). Join pipes to gravity feed and back feed to coal fire. Remove coal fire and join gravity side to pumped side to complete CH circuit.

At least that's the theory :)
just an idea put boiler outside in cabin pack run flue up outside wall,or get boiler with fanflue/or low level making sure flue conforms to man spec ie will not discharge over boundary causing nuisiance,condensing boiler flues a real pain because of pluming oil condensors may give probs due to first generation.gas condensors now on 2/3rd generation still not as reliable as home owners /heat engineers would like :!:

It has been suggested to go for an external boiler. The other side of the lounge wall would be the obvious place except for the fact that this opens onto the street. Public path is 1m away. I don't like the idea of my boiler there (vandalism, hot gases, etc.).

Interesting your comments on condensing boilers and the "not discharge over the boundary causing a nuisance". Here http://www.braintree.gov.uk/housing/energy+conservation/condensing+boilers.htm
it says
The main feature of condensing boilers is that they sometimes produce a plume of water vapour around the flue terminal. Although this is in no way harmful it can be perceived as a nuisance. Therefore the siting of the flue terminal is important so that the plume does not discharge over neighbouring properties and preferably not within full view of windows.
The flue from the kitchen would face the fence to next door as I mentioned. The position is within the regs but they don't mention not discharge over boundary etc. so where does that come from?
Are you aware that you should be OFTEC registered to work on oil boilers.

Nonsense, where did you get this from? It's not true.

Yours sincerely

OFTEC registered.

Although this is in no way harmful...........

Then why can't we put the boiler in the living room and just have the flue sticking out of the top?

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