Heat from my gas Boiler - how can it be harnessed

[Resurgam]

Every day I walk outside and the little silver tube sticking out of my wall behind the boiler is pumping out tons of heat. Is there an easy way that this can be harnessed. I feel that I am trying to heat the whole of Wessex!

There must be something that I can do.

Any suggestions - turning off the boiler is not a suggestion that will go down well.

[Rich_]

The exhaust is likely to contain carbon monoxide so tampering with the flue or redirecting it in any way could be dangerous. I should think this is why it is vented outside.

Condensing boilers are supposed to be more efficient apparently?

[nightshade]

As Rich says do not tamper with the balanced flue,you will just have to accept the "waste" heat but check your thermostats to make sure you are using the boiler as efficiently as possible

[Rich_]

It's the same with your gas fire, this has to be vented up the chimney, on cold still mornings you can see the warm air turbulence around the cowl on the top of some houses.

This heat is not wasted , it would seem, as the houses behind me usually have a huddle of jackdaws warming their backsides up there.

[Resurgam]

That is a real bore. The temp is very high indeed. The temptation is to extend the flue and wrap a hot water pipe round it just to increase the temp of water going into the boiler.

[eeyore]

if the temp is that high the first thing i'd look at is why ? is the boilker a new efficient type? is the boiler coming on more than it should ? is the boiler timer working properly ?, is the tank stat working propperly etc if all answers are yes then look at fitting individual stats on all rads and turn them down when rooms arent in use, or indeed just turning the stats down permanently and wearing more jumpers.

[Rich_]

Extending or modifying the flue on a gas appliance could effect the efficiency of the way it gets rid of the potentially dangerous gasses. It would probably void any warranty you have too.

if you do this you are likely to have the boiler condemned by the first CORGI plumber who services it. Also you are unlikely to be able to raise the temperature enough by this method to make any difference at all.

Is it not the hot water pipes that exit the burners, the ones entering will be cold mains water. It is this way on the one we have.

[eeyore]

Originally Posted by Rich_

Is it not the hot water pipes that exit the burners, the ones entering will be cold mains water. It is this way on the one we have.

that is likely - some eco houses however take the cold water feed and run it through solar heaters on the roof before putting it into the boiler so he could do that with the heat exchanger principal ( though i agree with you about the unwisdom of carrying out any diy mods on a gas appliance)

[Ipso Facto]

Originally Posted by Resurgam

That is a real bore. The temp is very high indeed. The temptation is to extend the flue and wrap a hot water pipe round it just to increase the temp of water going into the boiler.

In order to transfer heat from the exhaust gas to the circulating water you need a temperature driving force: in other words, even in the most efficient boilers, the exhaust gas is likely to run 5-10 degrees hotter than the temperature of the water you are returning to the boiler from your heating circuit.

If you have a combi boiler, the exhaust gas should theoretically be cooler when you are heating domestic water because the final exhaust is being cooled by contact with the incoming cold water supply. Do you notice a difference when the tap is running?

However, all of this assumes that the heat exchanger(s) are piped up for counter-current flow. If the flow is actually co-current the exhaust gas will be much hotter (5-10 degrees hotter than the water you are feeding to your radiators) and will cost you dear. Is your boiler piped up correctly?