Burning wood that has seasoned down to 18% but has got wet due to rain blowing in on it

[cessna]

Will mixing some damp wood, that has got wet due to rain blowing in on it,cause the flue to soot up as much as burning wet wood that has still got the sap in it.?

What is the most efficient heat to run a wood stove at?

Does operating a wood burner at a high temp help avoid creosote/ soot build up in the wood burner/ flue pipe?

Edited Monday at 18:56 by cessna

[GarethM]

No, it's just surface wet and will dry off quickly.

[Steven P]

Adding to Gareth - very correct, it is surface water and will dry off and burn easy enough. You'll be fine. Imagine it takes months to years for a log to dry to 18% moisture in the air, it will take that long again to get wet (unless it is sat on wet earth or similar) in the rain. Most rain water will simply run off the log (however I tend to pack my winter logs away under cover at the end of September to make sure they are nice and dry when needed).

 

 

 

As for most efficient heat... don't be hung up about flue thermometers, temperatures and so on, look at the fire itself. I can burn some woods, smouldering away on a big bed of fire that will be hot and some woods will be bright flames, a small fire and relatively cool... so look at the fire, you want a bright lively fire most of the time - the flames burn off the soot, smouldering is more smoky, more soot. So flames are a good thing.

 

 

Personal view, I'll try to get a couple of good hot fires in every now and then to give the chimney a good blast... but be warned... get it wrong, a real hot fire is a danger for chimney fires if there is a soot and creosote up there (so never skip cleaning the chimney in the hope of "I had a good hot fire, it'll be OK"). Far better to burn dried wood and not a smouldering fire.

 

[openspaceman]

44 minutes ago, cessna said:

Does operating a wood burner at a high temp help avoid creosote/ soot build up in the wood burner/ flue pipe?

Essentially yes, the saying is that you need the 3 Ts for good combustion:

 

Temperature

Turbulence

Time

 

Just thinking about temperature and wood burning the consensus is that one needs the firebox to reach 800C  to completely burn wood. Hence the firebox in modern stoves are lined with insulating bricks.

 

This is easy to attain with wood at sub 20% mc but when you have more moisture  the heat required to vaporise it means the fire can struggle to get hot enough. 

 

The turbulence thing is so the air and combustible gases mix well enough and the time is the 1.5 seconds that the combining gases dwell in that 800C temperature to burn completely.

[cessna]

1 hour ago, Steven P said:

Adding to Gareth - very correct, it is surface water and will dry off and burn easy enough. You'll be fine. Imagine it takes months to years for a log to dry to 18% moisture in the air, it will take that long again to get wet (unless it is sat on wet earth or similar) in the rain. Most rain water will simply run off the log (however I tend to pack my winter logs away under cover at the end of September to make sure they are nice and dry when needed).

 

 

 

As for most efficient heat... don't be hung up about flue thermometers, temperatures and so on, look at the fire itself. I can burn some woods, smouldering away on a big bed of fire that will be hot and some woods will be bright flames, a small fire and relatively cool... so look at the fire, you want a bright lively fire most of the time - the flames burn off the soot, smouldering is more smoky, more soot. So flames are a good thing.

 

 

Personal view, I'll try to get a couple of good hot fires in every now and then to give the chimney a good blast... but be warned... get it wrong, a real hot fire is a danger for chimney fires if there is a soot and creosote up there (so never skip cleaning the chimney in the hope of "I had a good hot fire, it'll be OK"). Far better to burn dried wood and not a smouldering fire.

 

This how my wood burner is going most of the time.

 

 

[Will Marsh]

I got a fan to sit on top of the burner that came with a temperature gauge that sits magnetically on the burner.  It tells you if the wood burner is operating within the best efficiency range.  Quite useful.

 

[GarethM]

1 minute ago, Will Marsh said:

I got a fan to sit on top of the burner that came with a temperature gauge that sits magnetically on the burner.  It tells you if the wood burner is operating within the best efficiency range.  Quite useful.

 

Its a gimmick, even more so on a modern stove as they're designed to rob as much heat as possible from the flue gases.

 

Whilst yes you get "free" airflow, it's no indicator of efficiency.

[Muddy42]

Yep, I've never believed in those magic stove top fans.  People say they send hot air immediately out into the room, rather than heating the space near the ceiling, but I just can't believe that their puny "free airflow" (with energy robbed from the heat of the stove) can overcome convection.  

[GarethM]

1 minute ago, Muddy42 said:

Yep, I've never believed in those magic stove top fans.  People say they send hot air immediately out into the room, rather than heating the space near the ceiling, but I just can't believe that their puny "free airflow" (with energy robbed from the heat of the stove) can overcome convection.  

It's free so, anything will be a bonus.

 

But in all honesty a tiny desk fan would work wonders too. Ceiling fans work wonders in warehousing, had one in the old warehouse and it was like 300w but knocked 20-30% off the gas bill.

[Muddy42]

6 minutes ago, GarethM said:

It's free so, anything will be a bonus.

 

But in all honesty a tiny desk fan would work wonders too. Ceiling fans work wonders in warehousing, had one in the old warehouse and it was like 300w but knocked 20-30% off the gas bill.

 

I understood stove fans used heat from the stove to create electricity to drive the fan (energy cannot be created or destroyed and all that), so not technically free.  But the advocates say this is worth it because it mixes and averages out the air in the room.  And yes it will probably have more effect with a higher ceiling like your workshop, but I'm not sure about my tiny home office!