Bit the bullet - lambda sensor on order

[Nofossil]

I couldn't stand it any more. I've ordered a wideband oxygen sensor with driver electronics. It has an analog output that's compatible with my data collection / control system.

I'm going to make a retractable housing for it on the top of the flue thimble at the back of the boiler. My thought is that I'll start the boiler and get it up to gasification with the sensor retracted. Once it's going, I'll drop the sensor into the exhaust stream and get measurements as I play around with primary / secondary air, fan speed, and so on. My hope is to be able to learn enough so that I can get close to optimum combustion throughout the course of a burn.

Too bad I won't be having another fire until October......

 

[free75degrees]

I am new to this whole lambda concept, so please excuse me if I don't make sense. Is the point to measure the oxygen output and use that to vary the fan for optimal combustion? I have heard people mention that the sensors typically have degradation issues to the the high temps. Why not place the sensor at the top of the chimney where the temps are the lowest and the output gas mixture should be the same as downstream?

 

[Nofossil]

I am new to this whole lambda concept, so please excuse me if I don't make sense. Is the point to measure the oxygen output and use that to vary the fan for optimal combustion? I have heard people mention that the sensors typically have degradation issues to the the high temps. Why not place the sensor at the top of the chimney where the temps are the lowest and the output gas mixture should be the same as downstream?

The idea is that you want enough secondary combustion air to ensure that you have complete combustion. Any more than that and you're wasting heat by heating excess room air and pushing it up the chimney. Any less than that and you're wasting energy in the form of incomplete combustion.

Lambda sensors are fragile beasts, but it's chemical contamination that kills them more than heat. In particular, you don't want flue gas or creosote to condense on them. The one that I ordered has an electric heater to help ensure that it's warm enough.

My flue temp is well within the temperature range that they like, and it's relatively easy for me to design a retractable sensor housing that fits onto the flue thimble. The top of my chimney is three floors away and made of brick and ceramic.

 

[free75degrees]

Gotcha, if it is chemical degradation then putting it higher wouldn't help anyway.

 

[free75degrees]

Did you order an automotive sensor?

 

[Nofossil]

Did you order an automotive sensor?

Aftermarket 'wideband' automotive sensor designed for tuning high performance cars - not a normal OEM sensor. The OEM sensor has a much less useful output - basically 'rich / not rich'.

 

[TCaldwell]

nofossil, is this one of the 3 websites of earlier correspondence or a new find? you know i am curious, thanks tom

 

[Nofossil]

nofossil, is this one of the 3 websites of earlier correspondence or a new find? you know i am curious, thanks tom

New / cheap - $200 for everything. I'll post results as soon as I build another fire.

 

[Redox]

You really going to make us wait till October? Just leave the lid off the hot tub and fire it up! I'll be stir crazy by October...

Chris

 

[free75degrees]

Are you planning to use it mainly as a learning tool to figure out how to make manual adjustments to get the best efficiency, or are you planning on automating it so that it makes real time adjustments, or both?

 

[Nofossil]

I may fire it up next time we change the water in the hot tub, just to get some data.

My intent is to use it to learn what's going on. I hope that I can learn enough to be able to infer the correct settings from other measurements such as combustion temperature, time since last refuel, or other easier to measure parameters.

Certainly the ultimate would be to run 'closed loop' all the time. However, I think I can do much better than the current situation without sacrificing a lamda sensor to the efficiency gods every couple hundred hours.