How to guarantee maximum condensing?

[D_Hailsham]

A flow temp of 63°C is the optimum setting for maximum condensing mode.

That is not enough. It depends on what the temperature drop is across the radiators. If 10C then on when -1C outside 53C should be at the return. But when the house is up to temperature and on part load (the most common operation) the differential may narrow to 2, 3, 4 or 5C, giving a return temperature above condensing point.

If the flow is 63C and the return is 53C, each radiator will producing approx 70% of the manufacturers quoted heat output at 75C/65C/20C. But, if the flow if 73C and the return is 53C, the output is 81% of the quoted output. A 10C differential requires a flow rate twice that of a 20C differential.

 

[BigBurner]

A flow temp of 63°C is the optimum setting for maximum condensing mode.

That is not enough. It depends on what the temperature drop is across the radiators. If 10C then on when -1C outside 53C should be at the return. But when the house is up to temperature and on part load (the most common operation) the differential may narrow to 2, 3, 4 or 5C, giving a return temperature above condensing point.

If the flow is 63C and the return is 53C, each radiator will producing approx 70% of the manufacturers quoted heat output at 75C/65C/20C. But, if the flow if 73C and the return is 53C, the output is 81% of the quoted output. A 10C differential requires a flow rate twice that of a 20C differential.

Many weather compensators sense the return temperature rather than the flow pipe. By keeping the return as low as possible the boiler can just raise the flow temperature as it wants. Many boilers aim to keep the temperature differential as wide as possible to promote efficiency,. The wider the more efficient and combined with the lowest return temperature achievable even better.

 

[oilman]

Many boilers aim to keep the temperature differential as wide as possible to promote efficiency,. The wider the more efficient and combined with the lowest return temperature achievable even better.

Unfortunately there are no free lunches. When the temperature is low enough, it means that water from combustion is condensing in the combustion chamber, mixes with the CO2, and causes corrosion, giving a short boiler life.

Weather compensators aren't a perfect solution either. When it is cold, frosty and windless, it is much easier to heat a house than when it is a few degrees above freezing, damp, and windy.

 

[Agile]

Unfortunately there are no free lunches. When the temperature is low enough, it means that water from combustion is condensing in the combustion chamber, mixes with the CO2, and causes corrosion, giving a short boiler life.

Isn't that just what we want in a condensing boiler?

Which is why the best have a stainless HE and the not so good a thicker aliminimum hE.

Tony

 

[BigBurner]

Many boilers aim to keep the temperature differential as wide as possible to promote efficiency,. The wider the more efficient and combined with the lowest return temperature achievable even better.

Unfortunately there are no free lunches. When the temperature is low enough, it means that water from combustion is condensing in the combustion chamber, mixes with the CO2, and causes corrosion, giving a short boiler life.

I think you got the wrong end of the stick.

Weather compensators aren't a perfect solution either. When it is cold, frosty and windless, it is much easier to heat a house than when it is a few degrees above freezing, damp, and windy.

What do you mean?

 

[oilman]

Many boilers aim to keep the temperature differential as wide as possible to promote efficiency,. The wider the more efficient and combined with the lowest return temperature achievable even better.

Unfortunately there are no free lunches. When the temperature is low enough, it means that water from combustion is condensing in the combustion chamber, mixes with the CO2, and causes corrosion, giving a short boiler life.

I think you got the wrong end of the stick.

You are entitled to your opinion. What have sticks got to do with it? are you going on to solid fuel?

Boilers, condensing, even with stainless HE, still have shorter lives than the old cast iron non-condensers. For oil boilers, condensation in the combustion chamber makes the life much shorter than the non-condensers, with only a few % improvement in efficiency.

Weather compensators aren't a perfect solution either. When it is cold, frosty and windless, it is much easier to heat a house than when it is a few degrees above freezing, damp, and windy.

What do you mean?

I would have thought it was obvious. There is a lot of theory posted above dealing only with temperature measurements. Temperature is not the only consideration when it comes to heating, as anyone will have noticed when in a room with someone else who says the room is cold/hot, while you think it is hot/cold.

I have a weather compensator, when it's cold and blowing a gale, I put another log on the woodburner.

People have programmable thermostats, weather compensators, TRVs, and it's still not comfortable, despite what theory and a thermometer would seem to indicate.

 

[D_Hailsham]

People have programmable thermostats, weather compensators, TRVs, and it's still not comfortable, despite what theory and a thermometer would seem to indicate.

The major source of discomfort would appear to be temperature fluctuation.

My last house was a three story Edwardian pile with the thermostat in the hall. There were TRVs on most radiators, but that did not stop the wife complaining that it was too cold and turning the thermostat up two or three degrees; then it was too hot and she turned it down again.

Two years ago we moved to a smaller modern house, also with stat in the hall and TRVs. The same thing occurred: to cold - turn the stat up; too hot - turn it down again. As the programmer was on its way out, I decided to invest in a Honeywell CM67 Wireless Optimizing Programmer.

Since then there has been no complaints about being too hot or too cold. The reason being that the new stat maintains the temperature within about half a degree of the required temperature. If we do feel a bit on the cold side, we only have to raise the temperature by half a degree and we feel comfortable again.

 

[oilman]

If I feel hot I move away from the wood burner, if I feel cold, I move towards it.

Total bill tonight, 3 logs!

 

[Biggles..]

Two years ago we moved to a smaller modern house, also with stat in the hall and TRVs. The same thing occurred: to cold - turn the stat up; too hot - turn it down again. As the programmer was on its way out, I decided to invest in a Honeywell CM67 Wireless Optimizing Programmer.

Since then there has been no complaints about being too hot or too cold. .

Is that down to how the stat functions or the wife not knowing how to turn it up yet.

 

[WDIK]

the answer is quite simple.

stat, double sided adhesive tape,

atatch stat to wall,

sit back and feel smug

 

[simond]

As far as I know, one of the few boilers to run in condense mode for HW and CH is the ACV Heatmaster TC.

 

[tonybhoy]

As far as I know, one of the few boilers to run in condense mode for HW and CH is the ACV Heatmaster TC.

I thought the WB Greenstar CDI range did the same?

 

[WDIK]

greenstar 30he does thats why i bought it.
also has a variable speed pump to maintain condensing
again why i bought it
and modulates the burner

couldnt give a fig about that

 

[simond]

Greenstar does not run full condense mode on HW. Unless you take cold baths

 

[WDIK]

Greenstar does not run full condense mode on HW. Unless you take cold baths

wrong
2005 greenstar he 30kw does