Why do plumbers rate Worcester Bosch when Which doesn't?

[kevplumb]

class

fella

 

[gas4you]

Can anyone explain this simply enough for me to understand how a boiler can be more than 100% efficient?

I wish I was clever enough to do this Tony, but I only just grasp the basics of it myself

I think it is something to do with the latent heat in the water vapour

I understand it whilst being shown, but unfortunately after a few days it all gets forgotten at my age

 

[kevplumb]

err i think most of us are in the same boat
dave

 

[EddieM]

Can anyone explain this simply enough for me to understand how a boiler can be more than 100% efficient?

I wish I was clever enough to do this Tony, but I only just grasp the basics of it myself

I think it is something to do with the latent heat in the water vapour

I understand it whilst being shown, but unfortunately after a few days it all gets forgotten at my age

It's all to do with the BS co-efficient.

 

[Agile]

It's all to do with the BS co-efficient.

Yes, its obvious that the manufacturers who say their boilers are over 100% efficient are talking B.... S....

But Dave genuinely believes that he found it possible to follow an argument which convinced him for at least a few minutes!

But what is that argument?

Tony

 

[oilman]

Only quoted Nett figures claim efficiencies greater than 100%.

The usual UK figures used are gross which include about 13% water vapour.

Add this water vapour figure to a gross efficiency e.g 92% and you will get the nett of about 105%.

Can anyone explain this simply enough for me to understand how a boiler can be more than 100% efficient?

A 92% figure would be a nett figure. The gross figures come in at around 10% less, as this is what would contain water vapour. So the max is then just under 100% when you add this spoof 13%. This may be total garbage, but oil boilers are more efficient than gas, I always measure nett efficiency, and I have never seen one better than 98%.

 

[Agile]

I cannot understand any of that either!

Do I have a comprehension gap or do others have the same problem?

Tony

 

[oilman]

The gross figure you can measure if you can get access to a port before the secondary heat exchanger. The gross efficiency is the power put into the water from the fuel. You cant get the extra bit of heat as it was from the fuel needed to vapourise the water formed from the hydrogen/oxygen combination. When you cool the gases through the secondary exchanger, you can recover some of the heat as the water vapour condenses. As far as I can see, the >100% figure is a devious trick, as there will always be some of the heat which escapes from the boiler directly, and another bit from the flue, so it just cannot be >100%. (Unless you fit a magnet on the flue and the fuel pipe ).

 

[Agile]

As far as I can see, the >100% figure is a devious trick, as there will always be some of the heat which escapes from the boiler directly, and another bit from the flue, so it just cannot be >100%. (Unless you fit a magnet on the flue and the fuel pipe ).

I understand that bit but Dave was convinced for a few minutes!

Now there were magnets to fit to the petrol line of your car to improve fuel consumption. Obvioualy an oil boiler could give more output by exploiting that technology!

There is an interesting device being sold on the Ebay:-

Uses generator/battery power to electrolyse water.

Resultant oxygen and hydrogen is then added to the inlet to the carburetter.

Sellers claim a 20% improvement in MPG !

Tony

 

[oilman]

This is turning into a hijack.

What those people claim is that it's not the burning of the H/O that provides the power, but that it allows the un-burnt fuel in the potential exhaust to be burnt, and so you get the extra 20%. If you had 20% unburnt fuel in your exhaust (or more correctly your vehicle's exhaust), it would stink to high heaven, and probably wouldn't pass the MOT, and the government could meet its carbon emissions targets just by fitting the devices to all vehicles. Yet another ludicrous claim by a scam merchant.

 

[gigz]

Just came in after fitting my first WB 28 junior, hands cut to bits off all the sharp edges, nearly came to blows with the ch return nut, the condense traps a pain, then to top it all got everything connected the lever fell off the prv. Early night for me.

 

[nickso]

This is turning into a hijack.

What those people claim is that it's not the burning of the H/O that provides the power, but that it allows the un-burnt fuel in the potential exhaust to be burnt, and so you get the extra 20%. If you had 20% unburnt fuel in your exhaust (or more correctly your vehicle's exhaust), it would stink to high heaven, and probably wouldn't pass the MOT, and the government could meet its carbon emissions targets just by fitting the devices to all vehicles. Yet another ludicrous claim by a scam merchant.

petrol is a pretty poor fuel for an internal combustion engine. there is a bit of unburnt fuel in the exhaust, and a lot of high performance cars do stink if they are tuned for power and not economy. then there is bore wash and the fact the combustion engine isnt an efficient way of burning any fuel anyway. gas is better but has its delivery problems of course.

 

[gas4you]

I understand that bit but Dave was convinced for a few minutes!

I still am convinced Tony, only that I can't remember how to fully describe it to you

A boiler that is quoted at, say 104% nett, is the same efficiency as a boiler quoted at 91% gross.

Using nett efficiency tends to be a european way of quoting efficiency and gross the British way.

Try to think of it in terms of amplifier power. An amplifier rated at 20watts RMS is going to be more powerful than one quoted at 50 watts PMPO.

(figures are only a rough example, not mathematicaly accurate)