Lambda controls vs baseline; fault-mode fallback, etc.

I suspect most manufacturers have thought this out in their control stratedgy, for some sort of overide. in 2 years with the same bosch lsm 11 industrial sensor it has not failed, but i do have a backup spare. when the power goes out, one damper closes and one stays open, not a problem for a garn type boiler. I am not sure if a failed o2 goes high, low but i think i will look into it.

02 sensor is quite likely a specialized and somewhat expensive part that might need to be ordered/ waited for.

Click to expand...

To check on automotive parts reliability I just ask the dealers parts dept. for the sales history of any part in question. The amount of parts sold that are similar across a number of platforms can give a fairly good idea as to the quality factor.

Good question on the fail safe mode. It would be nice if they could run in "dumb mode" Although with the manufacturers being Euro I imagine that the o2 sensors are a cut above the auto variety. Anybody know how much a sensor cost on any lambda unit?

I think that the technology behind the o2 setups are also meant to keep everything proprietary to each boiler or else second tier manufacturers would be lifting them for their own use.
On that note when are the Chinese gonna clone any modern wood burning technology ? Prolly not enough of a market just yet.

As one who is planning on a purchase in the coming year or so I would like to know as much as I can before pulling the trigger as I only have one round in the chamber so to speak.

Will

How would the boiler even know that the sensor was even failing, unless it was a nearly complete failure? In other words, how would the boiler know if the sensor was dirty or was starting to fail? Maybe as the operator you have to pay some attention to the combustion chamber temps and flue gas temps to make sure that they aren't far off what they've historically been.

I understand your skepticism regarding the lambda sensors. I plan on getting a boiler with a lambda sensor though. I know that there are plenty of people out there getting reasonably efficient burn cycles with non-lambda boilers, but I've also read enough comments from people who have been frustrated trying to get their primary and secondary air intakes set properly on non-lambda boilers. Maybe their problem was that they were burning wet wood. I just know that if I spend $10K+ on a system that I want it to be simple to use. If I can save the cost or labor involved in cutting, splitting, and stacking an extra cord of wood each year that a less efficient boiler would use, then I think I'll be happy with my choice. I guess time will tell.

It would be interesting if you could run some efficiency tests in both lambda-control mode and also in a manual mode with fixed primary and secondary air intakes over the course of several burn cycles to find out the relative efficiencies with the exact same boiler.

BTW, the Effecta is also available in a non-lambda version and I believe the that the Froling FHG-S is the non-lambda version of their boiler.

BTW, the Effecta is also available in a non-lambda version and I believe the that the Froling FHG-S is the non-lambda version of their boiler.

Click to expand...

I wonder how the wood consumption differs on the non lambda boilers. If it was a cord a year it would definitely be worth the extra on top of the cleaner set it and forget it burn.
Any test results out there on btu's released per 100 lb of wood burnt that anyone knows of?

Will

Pete Schiller said:

How would the boiler even know that the sensor was even failing, unless it was a nearly complete failure? In other words, how would the boiler know if the sensor was dirty or was starting to fail? Maybe as the operator you have to pay some attention to the combustion chamber temps and flue gas temps to make sure that they aren't far off what they've historically been.

Click to expand...

As my dad used to say, "And then the fun began.".

Self-diagnostics, sensor redundancy, alarm modes, prognostics, limp-modes, fail-safes, failure mode effects analysis, telemetry, performance monitoring, data recording, self-optimization, model-constrained control loops, operator displays, DDC system integration. Not your daddy's boiler, not anymore. All proprietary. All fun.

ewdudley said:

Not your daddy's boiler, not anymore.

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I'm surprised that you got yourself one of them newfangled wood boilers, what with all of the pump and fan motors that could break down. I mean, you could have had yourself a real simple pre-catalytic converter wood stove.

I appreciate your concern that adopting relatively new technology may not always be problem free. If your concern is that we will be temporarily left without heat should our lambda sensors fail, in my particular case I will have my existing oil boiler as a backup. If your concern is that our boilers won't be good for anything except boat anchors should our sensors or electronic components fail, if I purchase a boiler from a company with a proven track record that is designing best in class products, it is much more likely that they will still be around in years to come should I need replacement parts. Worst case, the stepper motors can be disconnected and the fan and loading pump can be run independently from the boiler electronics. Whatever boiler I choose, my system will have a pressure relief valve, a UPS backup for the loading pump, a high limit aquastat to turn off the fan (as a backup if the boiler controls fail to turn off the fan and shut the air intakes), and gravity feed if the UPS or loading unit fails as well.

I'm viewing my purchase of a wood boiler as a long-term investment that I hope will last for 20+ years. Buying one with a lambda sensor adds less than 10% to the total system cost, but will probably save me upwards of a cord of wood per year. It doesn't make sense for me to hold off on purchasing a wood boiler just so I can see how reliable the lambda sensors are, and I don't want to forego the benefits it provides for the next 20 years. If you have had a negative experience with a particular brand in the past, then by all means, let it be known so that others can benefit from your experience. But I don't think that you should be discouraging others from purchasing products that offer technological improvements by trying to relate them to old fuel injection technology. If you're happy with the boiler that you've chosen, and there isn't a thick cloud of smoke coming out of it and floating in the direction of my house, then you made a good choice and I'm happy for you.

I bought a lambda sensor to add to my EKO. Haven't had time to install it yet :-(

One concern I have is sensor life. Lambda sensors are supposedly very sensitive to some types of contaminants, and I assumed that at the very least I'd need to protect it from gunk that's present in the flue gas during startup.

My strategy is to use the lambda sensor to determine the 'ideal profile' for primary / secondary air flow rates over the course of several burns, then remove the sensor.

From that point on, use time and combustion temperature to estimate where the boiler is in the burn cycle, and use the relevant 'ideal profile' settings.

I wouldn't be surprised if I weren't the first person to think of that approach, even though it's more sophisticated than what our cars do when they have no functioning lambda sensor. Of course, whatever solution they have is doubtless proprietary.

nofossil said:

I bought a lambda sensor to add to my EKO. Haven't had time to install it yet :-(

One concern I have is sensor life. Lambda sensors are supposedly very sensitive to some types of contaminants, and I assumed that at the very least I'd need to protect it from gunk that's present in the flue gas during startup.

My strategy is to use the lambda sensor to determine the 'ideal profile' for primary / secondary air flow rates over the course of several burns, then remove the sensor.

From that point on, use time and combustion temperature to estimate where the boiler is in the burn cycle, and use the relevant 'ideal profile' settings.

I wouldn't be surprised if I weren't the first person to think of that approach, even though it's more sophisticated than what our cars do when they have no functioning lambda sensor. Of course, whatever solution they have is doubtless proprietary.

Click to expand...

So, if I understand your strategy correctly, you would average out your findings with a lambda sensor to dial-in a "sweet spot" that would give you the best overall performance through the burn?
I adjust my secondary air after the unit is burning at least an hour so that it is up to temperature, has a nice bed of coals, and is gasifying strong.
If I adjust the intake so that I see a nice blue flame during that period, the unit should be working at a high point of efficiency during that period of the burn, for any given burn.
At the beginning and end of a burn, I would think that the unit is not running as efficient due to the lower temps, and lack of coals.
What I am doing is trying to get the most efficiency out of the unit during the period of time of the burn cycle that the most energy is available from the wood.
Is that your strategy with the lambda? To dial-in your unit?

BTW, your contributions to this site, and assistance to others is greatly appreciated.

nofossil said:

I bought a lambda sensor to add to my EKO. Haven't had time to install it yet :-(

One concern I have is sensor life. Lambda sensors are supposedly very sensitive to some types of contaminants, and I assumed that at the very least I'd need to protect it from gunk that's present in the flue gas during startup.

My strategy is to use the lambda sensor to determine the 'ideal profile' for primary / secondary air flow rates over the course of several burns, then remove the sensor.

From that point on, use time and combustion temperature to estimate where the boiler is in the burn cycle, and use the relevant 'ideal profile' settings.

I wouldn't be surprised if I weren't the first person to think of that approach, even though it's more sophisticated than what our cars do when they have no functioning lambda sensor. Of course, whatever solution they have is doubtless proprietary.

Click to expand...

:cheese:

nofossil, I am so glad to find that you have been working on this air flow rate control stuff. I just posted that I needed to contact you about this very subject. Have you seen my "didn't sleep well ... " post? What do you think? Am I spinning my wheels? I own everything but the air induction, catalytic converter and controller of course.

The bosch industrial sensor is under $200.00, all o2 sensors are not the same, wide band , narrow band, 4 wire, 5 wire. If you wanted to use a specific sensor would need to research its compatibility with fluegas and temp requirements, as well a controller for the lambda or percentage range.my research found most automotive sensors although relatively inexpensive wont hold up in the wood enviornment for extended periods.

NYEDGE said:

I adjust my secondary air after the unit is burning at least an hour so that it is up to temperature, has a nice bed of coals, and is gasifying strong.

If I adjust the intake so that I see a nice blue flame during that period, the unit should be working at a high point of efficiency during that period of the burn, for any given burn.

At the beginning and end of a burn, I would think that the unit is not running as efficient due to the lower temps, and lack of coals.

What I am doing is trying to get the most efficiency out of the unit during the period of time of the burn cycle that the most energy is available from the wood.

Click to expand...

I've been running closed-loop flue gas temperature control for a month now, which makes it a lot easier to optimize primary and secondary air settings for a steady-state.

But a benefit I wasn't expecting is effect of being able to set an end-of-burn flue-temperature setpoint. The draft controller shuts the fan off and closes the air inlet tight when flue temperature drops below the end-of-burn setpoint, which I currently have set to 290 degF.

When the end-of-burn setpoint is set high enough there is still a full bed of coals, which turns into a bed of lump charcoal as soon as there's no more air. The nice part is that when it's time to light a new fire the charcoal gets very hot very fast and the new fuel burns blue from the get-go.

https://www.hearth.com/econtent/index.php/forums/viewthread/69395/P45/

Cheers --ewd

Pete Schiller said:

ewdudley said:

Not your daddy's boiler, not anymore.

Click to expand...

I'm surprised that you got yourself one of them newfangled wood boilers, what with all of the pump and fan motors that could break down. I mean, you could have had yourself a real simple pre-catalytic converter wood stove.

Click to expand...

You have no idea.

We've gots pumps and ECM pumps, aquastats and differential aquastats, mechanical controllers and electronic PID controllers, and motors and relays à gogo. And they can all fail. But there's spares for everything, and they're all reliable, affordable, commodity components that can be simply diagnosed as component entities without being at the mercy of Daryl and Daryl scratching their heads and swapping out sensors and control boards on my dime.

And the thirty year old VC wood stove with secondary combustion still sits in the family room, and it still burns hot and clean whenever we have occasion to fire it up, thank you very much.

I'm viewing my purchase of a wood boiler as a long-term investment that I hope will last for 20+ years. Buying one with a lambda sensor adds less than 10% to the total system cost, but will probably save me upwards of a cord of wood per year. It doesn't make sense for me to hold off on purchasing a wood boiler just so I can see how reliable the lambda sensors are, and I don't want to forego the benefits it provides for the next 20 years. .

Click to expand...

As you please.

But the fact remains that a few years back I bought two Ford Focuses for the price of one Prius, and more recently I bought a nice efficient downdraft non-lambda boiler and a new rice-coal boiler for the price of one state-of-the art wood boiler.

The Focuses burn precious little gas and I wouldn't notice a ten percent improvement in wood boiler efficiency, even if it were true.

--ewd

ewdudley said:

NYEDGE said:

I adjust my secondary air after the unit is burning at least an hour so that it is up to temperature, has a nice bed of coals, and is gasifying strong.

If I adjust the intake so that I see a nice blue flame during that period, the unit should be working at a high point of efficiency during that period of the burn, for any given burn.

At the beginning and end of a burn, I would think that the unit is not running as efficient due to the lower temps, and lack of coals.

What I am doing is trying to get the most efficiency out of the unit during the period of time of the burn cycle that the most energy is available from the wood.

Click to expand...

I've been running closed-loop flue gas temperature control for a month now, which makes it a lot easier to optimize primary and secondary air settings for a steady-state.

But a benefit I wasn't expecting is effect of being able to set an end-of-burn flue-temperature setpoint. The draft controller shuts the fan off and closes the air inlet tight when flue temperature drops below the end-of-burn setpoint, which I currently have set to 290 degF.

When the end-of-burn setpoint is set high enough there is still a full bed of coals, which turns into a bed of lump charcoal as soon as there's no more air. The nice part is that when it's time to light a new fire the charcoal gets very hot very fast and the new fuel burns blue from the get-go.

https://www.hearth.com/econtent/index.php/forums/viewthread/69395/P45/

Cheers --ewd

Click to expand...

I did follow your recent thread and I applaud you on your gumption, and advances.
While my unit does not do what you have been able to do with your mods, I am able to set up the boiler control module to shut down the fans at a preset flue temperature.
When the unit's flue temperature drops to 80C (176F), the unit shuts down the blower ends the cycle. I can change that end temperature, but I have found that around that temperature I am not creating anymore useful heat for the water, and it leaves me with a nice bed of black coal for the next firing.

nofossil said:

I bought a lambda sensor to add to my EKO. Haven't had time to install it yet :-(

One concern I have is sensor life. Lambda sensors are supposedly very sensitive to some types of contaminants, and I assumed that at the very least I'd need to protect it from gunk that's present in the flue gas during startup.

My strategy is to use the lambda sensor to determine the 'ideal profile' for primary / secondary air flow rates over the course of several burns, then remove the sensor.

From that point on, use time and combustion temperature to estimate where the boiler is in the burn cycle, and use the relevant 'ideal profile' settings.

Click to expand...

This can work nicely.

We used stepper motor controlled needle valves to control superheat on marine containerized refrigeration units, which relied on pressure sensor accuracy on the order of 15 millibars to perform well and not destroy the compressor. But the pressure sensors weren't as reliable as we would have liked, especially in the middle of the ocean with, for instance, a million and half dollars or more worth of pharmaceuticals at stake, per container.

With a little data mining and elementary statistics I was able establish what the probability was that the pressure sensor was performing correctly by modeling stepper motor position as a function of ambient temperature and controlled space temperature. The control range of the valve was constrained inside a probability range, and if it rode along the rails of the range for too long the pressure sensor input was abandoned and the stepper motor was controlled by the temperature model.

It turned out the pressure sensor was only necessary for optimal performance, and the unit could work quite well without it, until it could be replaced at the next scheduled preventive maintenance.

So yeah, I would say using the unreliable sensor to develop a model that can operate according to more reliable sensors is a good way to go. Just don't try to market it until you're sure you're not running afoul of the relevant patents.

--ewd

Great thread -- hate to see it die. Nofossill what do you think of Bosch's 411 5 wire Wide band Oxygen sensor? At first glance it look's worth a try to me (Although I've yet to see a price). Who's sensor have you chosen to try?

I like the fact that it is self heating. I think if we could figure a way to sample the flue gasses only when a drop in flue temperature is detected. The 5 wire being preheated could quickly determine if the drop in temperature is due to air/fuel ratio being too rich or to lean and make appropriate adjustments to the air induction. Need to figure a clever way to get the flue gasses to pass over the sensor only when the control wants to determine the reason for a drop in temperature, this should prolong the life of the sensor.

I have absolutely no knowledge of how the Europeans are setting up their solid fuel lambda controls, but it seems to me that it would valuable for the controller to know approximately how much fuel is available for each burn. To know if the temperature readings and lambda sensor readings are behaving in reasonable manner given the fuel available to system. Do you think a set of load cells under my boiler is taking this all a little to far? :lol:

That's funny - I'll swear I posted to this thread yesterday with some clarification. If so, the post evaporated....

I currently apply different control strategies based on where I am in the life of the fire - during startup I circulate water from storage through the zones and boiler to help get the boiler water jacket up to temp quickly (the ONLY time I have two circulators running). During ramp-up, I minimize heat loads and keep the recirc valve open to get the boiler outlet temp up as quickly as possible. During normal burn I modulate loads and boiler circ speed to maintain desired outlet temp. During burn-out I cycle the boiler circ as necessary to scavenge any remaining heat down to the lowest possible outlet temp.

My thought is that during each of these phases, there's a different ideal ratio of primary/secondary air. If I can get a better sense of what those ideal ratios are by using a lambda sensor, then I can apply those ratios even without having the lambda sensor connected.

I don't know the brand of my lambda sensor. It's a five wire self-heated wideband sensor that came with an amplifier / signal conditioner as a tuning kit for automotive use.

To answer the question regarding "limp" mode if the sensor on my effecta lambda 35 boiler fails, YES it does have a feature for this.

By hitting buttons A & B at the same time for 5 seconds puts the boiler in emergency mode and runs the boiler throughout the entire burn cycle at 70% secondary open and 30% primary open.

I am currently helping another effecta lambda 35 customer (who has a 5,000 sq. ft. house with a bunch of windows and 1,000 gallons of storage) data log a few burns in his boiler and once this is completed we will data log the effecta lambda boilers in this limp mode, thus getting a true, accurate comparison between lambda mode and no-lambda mode.

Regarding life of the lambda sensor, the engineering people at effecta have told me that they have had this lambda technology out for many years and have a very, very small failure rate. They use a very robust, high tolerance lambda sensor in the 35 and 60 kw effecta lambda boilers. They do recommend cleaning this sensor on an annual basis.

Knowing that effecta has been making gasifiaction boilers since 1983 and has a 40% market share of wood and pellet boilers in Sweden AND is now exporting to 10 different countries (up until 5 years ago they only sold their products in Sweden) tells me that they are a very outstanding company.

When I visited their facility last summer in Kungsbacka Sweden I was very impressed with the team of people they have there. It turns out the the owners of the company come to work everyday and play a very active role in the day-to-day business transactions. The owners of the company are the President, Quality Control Manager, Engineering Manager and Sales Manager.

I plan to be posting the lambda vs. non-lambda performance of the effecta lambda 35 boilers within a week or so so keep looking.

EBU

Effecta Boiler User said:

I plan to be posting the lambda vs. non-lambda performance of the effecta lambda 35 boilers within a week or so so keep looking.

EBU

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Excellent!

Effecta Boiler User said:

Regarding life of the lambda sensor, the engineering people at effecta have told me that they have had this lambda technology out for many years and have a very, very small failure rate. They use a very robust, high tolerance lambda sensor in the 35 and 60 kw effecta lambda boilers. They do recommend cleaning this sensor on an annual basis.

EBU

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Can you sell these sensors to non Effecta Boiler owners? If so, I'd be interested in purchasing one. Do have any specs. on them?

I think there is a Lambda version of the Tarm (Baxi) Solo Innova sold in Europe so I would guess I could do a retrofit on mine. Anyone have an idea what Lambda sensor they use, or would be comparable. What do you have to do to put in a Lambda sensor. Is it complicated? Hansson, a while back, mentioned the Lambda Solo Innovas were prohibitive in cost, but it doesn't sound that expensive to retrofit from what you are saying above.

Mike

Seems that some might think that adding an off the shelf lambda sensor is as easy as buying one, and just plugging it in somewhere.
In addition to mounting the sensor, it would have to be hard wired to a control board that would take the information the sensor was reading,
analyze it in some sort of algorithmic form, and then control the secondary air with some sort of mechanical actuator/device.
I for one am not smart enough to figure that all out, so it looks to be a little more complicated than just buying a sensor.
Right?

nofossil said:

Effecta Boiler User said:

I plan to be posting the lambda vs. non-lambda performance of the effecta lambda 35 boilers within a week or so so keep looking.

EBU

Click to expand...

Excellent!

Click to expand...

Really looking forward to this... Since I don't have a data logger of my own, the only data I have been able to glean is based on the performance of two very different boilers, the Econoburn and the Froling... and lets face it, there's a lot more differences between those two units than a lambda sensor. I suspect there's going to be a pretty decent margin between the two measurements on the Effecta. I don't doubt that the combustion efficiency of a gasser with static primary and secondary air settings can reach extremely high levels, but I don't believe the average combustion efficiency of the unit over the course of an entire burn will be quite as high as a boiler with lambda technology.

Mr. Dudely, as far as your take on the initial costs, reliability, and justification of more expensive and more complex lambda controlled units... I will concede to the notion that this perhaps should be a consideration for the homeowner, however, I don't think it's fair to say that simplicity of and by itself is the holy grail. Try having a score of wood gassers in the field with cheap "simple" controls that don't work worth a hoot. Talk about a boat anchor... I'll take a score of expensive and complicated controls that work well over a mess of cheap ill-perfoming controls any day. I'll also take a 0% vessel failure rate over a 15%... just sayin...

The other thing I want to mention is that the cost of the lambda portion of the control really isn't all that much... you're only talking about $700 hundred bucks between an FHG-S and and FHG-L. This covers the cost of the probe as well as the DC servos that control the dampers. I think most of the cost of the more expensive "high end" units comes from manufacturing quality differences(both structural integrity and fit/finish), and of course differences in distribution. Products that are backed by a large network of trained dealers are obviously going to cost more than products that are sold direct to the consumer over the internet from a single distributor... there's just more people involved in the process, ie the middleman. The thing to remember is that a lot of people are more than willing to pay extra for a competent middle man who can back up their investment with local support. For those who are comfortable with braving the waters of wood gasification on their own, there's plenty of cheap product out there for them to choose from... something for everyone.

Lets not leave out the emissions factor... part of the move toward more sophisticated control technology is to be able to meet future emissions standards. Love or hate the EPA, tighter restrictions are coming and the only way to deal with them is through development of new methods for hotter, more efficient combustion with greater reduction in particulate emissions. Lambda controls are at least part of the answer.

As far as the reliability of the O2 sensors... so far I have not had any "issues." The probe has a shroud around it that helps protect it from debris, and since the controls allow for a generous bed of charcoal to be made available at the beginning of every burn, it's only a couple minutes on start up that the probe even sees any smoke. Nothing EVER accumulates in the hx or draft inducer except very fine fly ash. One thing I have found is that over time, fly-ash will skew the O2 reading a bit... but only to a point... and as long as you know the baseline, you can adjust parameters to compensate as the sensor becomes "seasoned."

I for one am all for moving ahead with newer and cleaner technologies in wood and biomass heating solutions... It's called progress and it's not a bad thing as Mr Dudely seems to imply with his satire, sarcasm and cynicism. I am not naive enough, however, to think that everyone can be on the cutting edge of technology all the time. It's an expensive place to be, though I firmly believe that you get what you pay for... at least most of the time - it's called the free market system, and it does usually work over time. You can look at just about any of our recent technology and point to naysayers that were dead set against it when it came out... from 8 tracks, to Cd's, from CRT televisions to plasma flat screens, from video cassettes to Blu-Ray disks... and perhaps someday from ford focuses to priuseeeeeees. The cool think about Europe having a head start with this type of stuff is that by the time it gets over here, it's pretty well tested and most of the bugs have been worked out. People adapt to progress for different reasons... some for a cause, some for financial gain, but most adapt because it improves their lifestyle. While the FHG-L I am using probably saves me somewhere between 10% and 20% in firewood over the previous unit I owned, the best thing about it is the lifestyle it offers.

cheers

For those who are comfortable with braving the waters of wood gasification on their own, there’s plenty of cheap product out there for them to choose from… something for everyone.

Lets not leave out the emissions factor… part of the move toward more sophisticated control technology is to be able to meet future emissions standards. Love or hate the EPA, tighter restrictions are coming and the only way to deal with them is through development of new methods for hotter, more efficient combustion with greater reduction in particulate emissions. Lambda controls are at least part of the answer.

As far as the reliability of the O2 sensors… so far I have not had any “issues.†The probe has a shroud around it that helps protect it from debris, and since the controls allow for a generous bed of charcoal to be made available at the beginning of every burn, it’s only a couple minutes on start up that the probe even sees any smoke. Nothing EVER accumulates in the hx or draft inducer except very fine fly ash. One thing I have found is that over time, fly-ash will skew the O2 reading a bit… but only to a point… and as long as you know the baseline, you can adjust parameters to compensate as the sensor becomes “seasoned.â€

I for one am all for moving ahead with newer and cleaner technologies in wood and biomass heating solutions… It’s called progress and it’s not a bad thing as Mr Dudely seems to imply with his satire, sarcasm and cynicism. I am not naive enough, however, to think that everyone can be on the cutting edge of technology all the time. It’s an expensive place to be, though I firmly believe that you get what you pay for… at least most of the time - it’s called the free market system, and it does usually work over time. You can look at just about any of our recent technology and point to naysayers that were dead set against it when it came out… from 8 tracks, to Cd’s, from CRT televisions to plasma flat screens, from video cassettes to Blu-Ray disks… and perhaps someday from ford focuses to priuseeeeeees.

Click to expand...

Well said!

In response to a recent prior posting,

Yes, as the US distributor for effecta lambda boilers, I am able to sell all the components for a complete effecta lambda control system. The cost for the lambda sensor, lambda motherboard/control panel, 12V dc transformer and (2) 12Vdc stepper motors (one for primary and one for secondary) is approx. $595.00.

Please email me at [email protected] and I can get your a fomal quote or answer additional quesitons.

By the way, the lambda sensor on the effecta lambda 35 and 60 kw boilers is a very robust, self heating sensor.

EBU