Trying to understand how Condenser boiler works?

Andy From Sligo

Just trying to get my head around this condenser boiler running in most efficiant mode malarkey.

So if I have my fact right these condensing oil boilers are most efficient when the return water in the return pipe to boiler is 50c or less - is that right?

So even if after the boiler has been on for a while say after 20mins and is over 50c on the return pipe the boiler is still efficient than older boilers but its not condensating over 50c so therefore its not in its most efficient mode .

But because as the boiler is heating up from cold the return pipe will be under 50c water temp .... so the boiler will be working in its most efficient mode as the boiler warms up then from cold yes? until it gets to 50c ? - have I got that bit right?

Also at what temp does it start condensing at if it stops condensing at around 50c? - is it something like 30c start condensing and 50c stop condensing or waht?

Many thanks, it would be good to know. .. oh and even better in layman's non technical terms (condenser boilers for dummy's like lol )

Tom44

Andy,
Heat (fumes) that normally go straight out the chimney go through a seperate boiler that absorbs that (normally wasted) heat.
This pre heates the return water from the radiators before it goes into the main boiler.

Forget the complicate equations as no two day's weather are the same in Ireland .

In laymans terms, just except the fact that the first paragraph makes sence no matter what the conditions and it works.:rolleyes:
That's all you need to know. 👍
But I bet you won't be happy with this basis answer.





Or do the normal 4 years apprenticeship + years of experience.

Andy From Sligo

Tom44 wrote: »

Andy,
Heat (fumes) that normally go straight out the chimney go through a seperate boiler that absorbs that (normally wasted) heat.
This pre heates the return water from the radiators before it goes into the main boiler.

Forget the complicate equations as no two day's weather are the same in Ireland .

In laymans terms, just except the fact that the first paragraph makes sence no matter what the conditions and it works.:rolleyes:
That's all you need to know. 👍
But I bet you won't be happy with this basis answer.





Or do the normal 4 years apprenticeship + years of experience.

Haha - thank you for answering tom

hatchman

Andy this looks like good info in layman's term cant post links so just replace the dot with a "." condensingboiler dot org dot uk

Tom44

Andy has been given all the information he needs. !!!!


We have to consider Sligo, Ireland, and the planet.

Andy From Sligo

hatchman wrote: »

Andy this looks like good info in layman's term cant post links so just replace the dot with a "." condensingboiler dot org dot uk

Thanks for the link. Had a read, a lot of it I didnt understand fully but I think I got the basic grip on it I think.

On my Euroflame boiler I cannot seem to set my flow to under 50c when the flow is 65c or get a 20c difference at all no matter what i do, I think the radiators are not sized big enough and not losing enough heat , maybe because the house is very well insulated as well with cavity wall insulation too. - bit of a shame if its not running in condensing mode all the time, but it does sound like its working in condensing mode when its heating up

hatchman

More expensive to buy and service condensing boiler and they probably not running any more efficiently most of the time !

JamesM

hatchman wrote: »

More expensive to buy and service condensing boiler and they probably not running any more efficiently most of the time !

As Tom explained above, by having the extra section which heats the return water as it enters the boiler, a condensing boiler is much more efficient than a non condensing type, even when not in condensing mode.

Andy From Sligo

JamesM wrote: »

As Tom explained above, by having the extra section which heats the return water as it enters the boiler, a condensing boiler is much more efficient than a non condensing type, even when not in condensing mode.

still surprising the heat that still comes out on the flue of a condensing boiler really - I suppose they cannot use the heat coming out of the flue or get it down to or near zero heat but im still surprised the amount of heat that still comes out of the flue when the burner is running.

Before having a condenser boiler if you asked me does heat still come out of a condenser boilers flue I would have said no, or very little and just fumes and vapour. If I put my hand in front of a condenser boiler flue, and put my hand in front of a conventional boiler flue - I would be hard to notice a difference of temperature of heat coming out of the flue to be honest (.... maybe hooking up an LCD thermometer might paint a different picture though)

hatchman

JamesM wrote:

As Tom explained above, by having the extra section which heats the return water as it enters the boiler, a condensing boiler is much more efficient than a non condensing type, even when not in condensing mode.

So what exactly is condensing mode ? I assumed condensing only occurred when the return water was under a certain temperature ? Is the extra section you refer to separate to the condensing part ? My understanding is the return water can only take on heat from the exhaust of combustion if it is at under a certain temperature if above this temp no heat is gained from exhaust and no condensing takes place. Would it be possible that in some circumstances a condensing boiler would not have a return on investment ?

gctest50

hatchman wrote: »

.............. Would it be possible that in some circumstances a condensing boiler would not have a return on investment ?

Yes - if the return temperature was too high

so maybe :

1. Reduce boiler power output or

2. More / bigger rads ?

gctest50

The "problem" is a condensing system ( the whole setup ) is almost the opposite of an ( older) non-condensing setup

In the older non-condensing setup you want the return temperature to be nice and warm to prevent condensing

( the stuff that condenses is acidic ( nitric acid and sulfuric acid ) - over time it'd rot a non-condensing boiler

the newer condensing boilers are made of stainless and magic so they won't corrode because of condensing mode )

Andy From Sligo

gctest50 wrote: »

Yes - if the return temperature was too high

so maybe :

1. Reduce boiler power output or

2. More / bigger rads ?

Yeah , our return temperature is too high when the flow is set to 65c - and strangely enough there is only 2 Double radiators in our house, all the others are single. 1 double in the lounge and 1 Double in the Main bedroom. I should imagine when the TRV's on the rads are satisfied as well you have no heat loss and that hot water returns back to the flow of the boiler

Our boiler as well is a 70-90btu as well with just 2 double radiators (couldnt say what jet is in it ie, what btu the burner is set to, or maybe its just fitted with the factory fitted jet)

- is that overkill do you reckon? feels like it to me (havent counted how many radiators on the circuit in total in house but its a 4 bed dormer)

Tom44

Onces the returning temperature is below the flue gas temperature it will absorbe heat.
That's a fact in laymans terms. And reality.
Quite simplified.

Equally quite simplified, I would love to have a pint with Andy.
But I would end up strangling him.

Tom

gctest50

If it's not condensing in this weather - must be mighty insulation job you have done

Andy From Sligo

Tom44 wrote: »

Onces the returning temperature is below the flue gas temperature it will absorbe heat.
That's a fact in laymans terms. And reality.
Quite simplified.

Equally quite simplified, I would love to have a pint with Andy.
But I would end up strangling him.

Tom

could guarantee it - im a bit of a headcase

browner85

Undersized rads would technically be better for a condensing boiler. They would loose more heat trying to heat the room and the return temp would be lower

Andy From Sligo

gctest50 wrote: »

If it's not condensing in this weather - must be mighty insulation job you have done

I notice the condensing pipe after the trap just goes straight to the gravel next to path, it dont terminate into outside drain or soil pipe or anything - so proof in the pudding , one day I should put a plastic measuring jug where the condensing pipe is , if there is water in jug then its proof the boiler has been condensing ya? .... or does it condense in trap first and only to outlet pipe when trap is full ie when float ball floats to top? ... it could be quite satisfying (to me anyway) and answer my suspicions of whether the boiler is condensing or not if I see some water/fluid in the plastic measuring jug?

Tom44

Andy,
You have a good boiler, leave it at that.
But like a Lexus, it need "proper" servicing.




I have a 1.6HDI engine in my van.
Haven't a clue how it works but except the fact that it's good and efficient.
Which it is. That's good enough for me.


And it doesn't smell.

hatchman

Tom44 wrote: »

Onces the returning temperature is below the flue gas temperature it will absorbe heat.
That's a fact in laymans terms. And reality.
Quite simplified.

Equally quite simplified, I would love to have a pint with Andy.
But I would end up strangling him.

Tom

Physics too ! But is the return on investment worth it ? Is it wrong to question this ? Throw in a condensing boiler on an existing system and sit back and count the savings !

Tom44

hatchman wrote: »

Physics too ! But is the return on investment worth it ? Is it wrong to question this ? Throw in a condensing boiler on an existing system and sit back and count the savings !

Hatch
You don't know Andy like we do.
(No offence Andy):)


Surface area and design principle of condensing boiler, no matter where its fitted is a big improvement.

Andy From Sligo

Tom44 wrote: »

Hatch
You don't know Andy like we do.
(No offence Andy):)

No offence taken ...

ere, you know your van , if you read somewhere that your van should go up to 120 miles per hour but yours was only going up to 100mph as a maximum ... would you not be curious as to why it werent doing 120? ... or would you just leave it into a garage straight away?

Tom44

Andy From Sligo wrote: »

No offence taken ...

ere, you know your van , if you read somewhere that your van should go up to 120 miles per hour but yours was only going up to 100mph as a maximum ... would you not be curious as to why it werent doing 120? ... or would you just leave it into a garage straight away?

130 MPH when using 10% petrol with the diesel.
( regularly serviced)
80mpg

gctest50

Really what you need is a natural gas boiler ( they can modulate way down in power output )

You're probably miles from a gas main - i'd guess the next best thing is a buffer tank with a few valves ( to stop the boiler "stealing heat" & to bypass it for rapid house warm-up )

You'd need to ask someone to size it correctly for you or the boiler will cycle on-off-on too much

Would go a little like this :

Walk into cold house and turn on heating :

-boiler heats rads same way as it is at the moment

-return temperature starts increasing ? blend in cold water from buffer tank

-buffer tank hot ? turn off boiler

-rads need more heat after a while ? draw it from the tank

-tank cooled down again ? fire up boiler etc etc

gctest50

gctest50 wrote: »

Really what you need is a natural gas boiler ( they can modulate way down in power output )

You're probably miles from a gas main - i'd guess the next best thing is a buffer tank with a few valves ( to stop the boiler "stealing heat" & to bypass it for rapid house warm-up )

You'd need to ask someone to size it correctly for you or the boiler will cycle on-off-on too much

Would go a little like this :

Walk into cold house and turn on heating :

-boiler heats rads same way as it is at the moment

-return temperature starts increasing ? blend in cold water from buffer tank

-buffer tank hot ? turn off boiler

-rads need more heat after a while ? draw it from the tank

-tank cooled down again ? fire up boiler etc etc

Err.... can we keep him away from gas please.