Incredibly clever oil furnace burner controller (very perplexing)
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- Опубликовано: 16 май 2024
- This is very clearly one of those gadgets from the electromechanical era that was so simple and reliable, that few changes have been made to it over time. My guess is that maybe it was just a large LDR (Light Dependent Resistor) in series with the coil in an early version, but electronics have been added to allow use of a cheaper LDR and maybe add under/over voltage detection.
I've got to admit that this was a very complex puzzle to get my head round. It achieves so much functionality with so few parts that I had to emulate every fault scenario to see what happened, and even then it wasn't initially clear. The magnetically restrained contacts were the most perplexing.
Here's a functional tour from left to right. There's a bimetallic strip with 20W heating element that causes linear movement of an actuator.
The set of contacts on the left are the shutdown/alarm contacts. If the linear actuator hits the end while the heater remains powered, it will actuate the latching contacts, which will shut the unit down and signal a fault until manually reset.
The middle set of contacts had me confused for a while. They only become active on the return stroke when the oil valve contact is closed. It creates a time lag for the second stage oil valve if used.
The oil valve contact is super-complicated. It is normally activated by the thermal linear actuator, but can be locked against actuation my a premature magnetic field on the flame detector coil. If the flame detector coil is active at the end of stroke of the linear actuator, the oil valve contact is held closed by a plastic pin, even when the linear actuator has retracted.
The power to the bimetallic linear actuator's heater is switched through a contact on the flame sensor coil. It can only open when a successful ignition sequence has been completed.
This was another piece of treasure from a dumpster-dive that yielded an entire oil burner assembly.
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Full marks to BC for working it all out, logically explaining it and brilliant close up photography/lighting.
Priceless education.
That must have taken so much trial and error to design. Everything is so precise in movement and action.
What amazes me even more is fact it can be cheaply manufactured with sufficient precision to (presumably) provide a useful production yield. Just image the headaches a worn bit of production machinery could cause.
@@akak5128 Probably what happened was they designed it decades ago, it failed in some way and caused a few houses to burn down, then they fixed it in the next version, and a new failure mode came up, etc. until most of the failure modes got figured out.
Yeah this is insanely complex.
Biggest question I have is why not just go solid state. You could go with a microcontroller and relays/transistors to do the same job for a lot less money, or am I missing something? Maybe this design is just more rugged?
I suppose if we ever get EMPed or hit by a super powerful solar flare people can still hotwire their central heating if they have a generator.
@@ferrumignis Was wondering the same.
@@daviddavidson2357 I've messed around with enough HVAC stuff to know that yeah, solid state controllers kinda suck and somehow cost MORE to buy. The mechanical ones, when they fail, just get more and more intermittent and can usually be fixed by smacking them with something to un-stick a stuck contact, giving you enough warning to order a new one and just live with intermittent heat for a few days, instead of just failing outright at 1am on a January Saturday.
Speaking of, the tolerances on this stuff aren't particularly tight, especially by stamping and injection-molding standards. The timing on this actually leaves quite a bit more wiggle room than solid-state ones do, so even worn-out molds and bad quality stamping on the sheet metal will usually still pass QC and work fine. Microcontroller stuff is REALLY prone to dying of things like back-emf from the relays or the ignition transformer, cooked electrolytic caps, shorted FETs, etc, the MOST solid state I'd go if I had a choice is one of the older designs built around a couple 555 timers - those are almost as reliable as these electromechanical ones.
Such a clever and well thought out design. It's an electromechanical system that has lasted for years.
Probably 40 years ...
If it ain't broke...
The implied check to make sure the sensor hadn't failed (as, for instance, if the sensor reports the flame is on when the oil valve is shut) is an example of what is called in the computer industry a "sanity check". I've often coded them myself, but this is the first time I've seen one implemented electromechanically!
The implied check is also there to check if the solenoid is leaking oil and burns before the actual ignition.
@@janhu3953 oh.. neat
@@janhu3953
And It's probably fail-safe as well, pretty important in things like these where failures can get "exiting"
The formal name for this in safety-critical systems is "plausibility check".
Such systems are so common in safety systems.
Hmmm, was expecting a deep analysis of the circuit board, but got an in-depth vieuw of a very nice build relay. Thx for your hard work.
vieuwu
I found those type controls to be very reliable. The problem was usually the customer resetting the control numerous times and filling up the bottom of the combustion chamber with unburned fuel oil. It can be quite exciting lighting a burner into a chamber with a lot of unburned oil. The inspection door blowing open with a vengeance and a rumbling felt. A dirty oil filter or nozzle will soot up the chamber and often the flame sensor causing lock out. Big Clive always has something interesting to show. Love the channel!!
Yup, user error rules!
Great idea for an industrial woofler though 🔥
I had to take mine apart last April following fuel starvation. I've a 20+ year old tank, you can imagine the state of the filter and the pump. Flame sensor was sooted up. A good wash out with white spirits and all was well except I smelled of kerosene for three days after.
I often use Landis and Gyr LGK type controls, the only issues we have are on LPG when the burner shuts off, even though the valves are good, the flame will tend to waffle around on the burner causing a lockout, and the need to use permanent pilot on big burners because the turn down ratio isn't sufficient to stop the process running away when there is no product load.
The standard Honeywell oil controller in the US has a safety for this. It will allow the user to press the reset for a hard lockout up to 3 times, then it goes into 'restricted' lockout. To reset from this mode requires holding the reset for 10 seconds or more. This isn't something the homeowner would stumble upon.
Many of these controls will test for ignition for 45 seconds. Times 3 with a .75 GPM nozzle would still result in over a gallon of oil in the furnace, so it will get puffy and bangy when it does light!
A state diagram would be a good way to explain this.
I just want to do an hierarchical state machine for this. It looks so interesting
@@MrPmjg do not limit yourself to state diagram. go full set of UML. Structure, Behavior and Interaction diagrams. Quite an exercise!
@@NoHandleToSpeakOf I was actually thinking about in coding in C the HSM (hierarchical state machine) and tested with some unitest for my satisfaction. But that sounds exactly like what I do for my job, so I am still considering if I even should. But if you do it, please share, as I would like to see it. Have a good weekend
You lost me at some point, but when you showed it up close and personal in action, it all made sense again. An excellent video as always. 👍
The lamps to show operation was a brilliantly effective teaching aid.
God, can remember fault finding on those in the late 80s, early 90s. The beauty of all of the controllers was that they had a similar fault process whether on gas or oil fired pressure jet burners. On the gas systems there was a pre-alarm state triggered by pressure sensors. The gas feed would have a section of pipe, before the burner, that would have valves and pressure sensor. First stage was a check of the pipe integrity by closing the valves and checking that the pressure was equal on the feed and burner side and didn't drop. If it dropped the system would halt and go into alarm. If all ok, it would then open the valves to allow gas to flow and start the ignition sequence. Depending on the size of the burner you would have either a thernocouple or IR sensor to detect the flame and keep the valves open.
Lovely job but my wife hated that I would come home smelling of diesel and my skin black from servicing waste oil heaters in garages! Had to go back to being an electrician instead.
So it's basically an electro-mechanical Rube Goldberg computer/machine? Very cool device and very cool that you could figure out how it all worked and the logic behind it all.
Should also have said a big "thank you" for the never boring content that makes life interesting in these strange times
It’s an amazingly economical design. If I did it with a microcontroller I’d use at least four relays, but here there’s just one fancy relay and a bimetallic strip and heater - Magic!
I love watching electromechanical devices in operation. Beautifully designed and see you can the different stages coming in and being taken out unlike the cheaply made, overly expensive circuit which just has a chip which isn't worth watching.
That was terrific. Thank you Clive. I wouldn't mind betting that most boiler techs don't understand this module. Almost every time I've had a tech in for a boiler, it's the first thing they replace and then chase down the actual fault... I wonder if this is just standard practise.
I used to carry a couple of types with me to use as a diagnostic tool, after the usual checks (blocked or dirty oil nozzle, flame sensor dirty, oil supply fire valve closed etc). Was fascinating to see it work through the logic process as I never usually had the time to.
In many fields, an early diagnostic item is "Replace with known-good component". It eliminates a potential source of problems during later diagnostics. Afterward you should generally re-install the original part to determine whether it _was_ faulty, but many people skip that step.
In the automotive field particularly, more and more "diagnostic" trees are end-to-end repetitions of that task with different components. By the end, you may not have fixed the fault but you _will_ have added thousands of dollars to the invoice - and isn't that what really matters?
@@Azlehria That's pretty much what I was diplomatically avoiding saying ;)
@@Azlehria I moved into a flat and took me a while to get the gas boiler lit. A year or two later, for fun, I followed the 'troubleshooting flow chart' running the same symptoms. It concluded with 'replace gas valve'.
It was completely wrong but very close to what it should have said:
'Replace gas'.
The flat hadn't been used for a while and the gas I was trying to burn wasn't flammable ! Disconnected the meter and turned on the 'gas' until I could smell 'gas' then reconnected, bled it through and it fired up.
@@millomweb I encounter that from time to time - without even moving!
A line may have been disconnected and then not purged of air. If I don't switch over to the backup cylinder before the pilot lights go out, I have to purge the whole system again before they'll stay lit. Happens about once a year.
I'd have changed to an auto-switching regulator years ago, but being able to bleed off pressure into the lighter cylinder has come in handy some summers.
Mechanical logic. I love it!
There's a reliability to mechanical items which cannot be beat.
Not so sure about that. I think a well designed electronic circuit is more reliable.
If those contacts are slightly bent, that is probably already enough to, for example, start the burner 2 before burner 1.
@@TheRailroad99 You'll not find a lift that does not have mechanical safety features. At one time - and probably still, in places, electrical safety features aren't relied upon.
Honestly I think Clive is a bit like the Internet. Before it was there you knew how to learn and do everything but now that its there you really don't want to go back because its faster / easier / more fun this way.
Im really glad i stumbled across your channel a few years ago. Please keep it up. Great work!
Whoever designed this is a genius.
There's a certain visceral pleasure seeing something quite complex being realised by so few moving parts, so much more satisfying than an innocuous black box.
And people say microcontrollers are complicated.
Microcontrollers are all logic. This is kind of mechanical logic so same but different.
Look up electromechanical coke vending machine. That shit is insane.
@@Ryan6.022 I saw a documentary here on youtube about 19th century automata. That was also insane.
@@rimmersbryggeri Any chance of a link? I love automata, my favourite is the silver Swan
@@sofa-lofa4241 Ill try to find it but i has been years since I saw it so might have been copyright struck. I know it was british so probably bbc then.
What a clever piece of kit. As someone who has used microcontrollers for years I find these mechanical devices fascinating.
Thanks BigClive for solving a mystery of over 40 years! I can recall getting soaked in diesel trying to troubleshoot a De Detrich burner that would "lock-out" and fail to ignite. It had a Honeywell controller very much like shown (installed in 1972)...I figured that the contacted were a bit pitted, so I polished with sandpaper. Finally figured that the flame sensor was all sooted over the LDR and needed a clean. When it fired up with a mighty trump and roar I was a very very happy 12 year old kid! Only problem was my "school shoes" stank of diesel for months after...
I've been having the same experience with a older Cuenod NC-4 burner that would not fire at all, even with a new controller fitted it would still lock out.. As I was helping the tech dismantle the darned thing.
I remember we tested the flame sensor (using a lighter to simulate a light presence, the sensor was temporarily connected to a DMM) and it was good.. Then we tested the coil on the pump, yup, it was completely open, so we swapped it, did it solve the problem? Nope! Still no flame... The tech threw in the towel and swapped the whole pump assembly. Nearly had the oil tank empty itself in the basement, I remember the moment I rushed for the shut-off valve.. Good times lol
We smelled like oil for about a week after this whole ordeal, definitely not something I'd like to experience again!
I asked the tech if these control boxes would go bad often, and unsurprisingly (at the time it was surprising for me), he told me that they rarely go bad, and if they do, it's usually the contacts inside that need to be cleaned.
For years I was always wondering how these worked, but I really didn't think they would be so simple yet complicated at the same time.
Fascinating, thanks for including the detail that everyone else would've left out!
The people who design stuff like this are my gods. This is just next level engineering.
Not sure what's more impressive, the engineering our how well you explained it in use.
Amazing bit of technology and not a microprocessor in sight. Tryed and tested over years. Thanks for making it so clear.
I love these electromechanical devices. This thing is clever. Awesome presentation Clive!
As others have said. Mechanical logic is so cool...
Especially in fault condition. ;)
Electromechanical is so much more fascinating than electronic... It always reveals the thought process someone had during the development. Great video as always.
I was a tele exchange engineer for 25 years, initially strowger (electro-mech). We used thermal relays, slow to operate and slow to release relays, (these had “slugs” fitted at one end or other of the coil to slow down the build up/collapse of the magnetic field to slow them), big stacks of contacts with make, break, change-over, make b4 break, ratchet relays used to count X operations of the relay before operating a contact. Literally thousands of them but loved it!
In my home (built 1905) in the states we have an Aquastat control with a sub burner control.
One of the first things I did was modernize these control boxes with digital circuitry, but I still kept the older controls as they were equally interesting to the one shown in this video.
I had a lot of fun reading electrical schematics and explanations clearly written for a 1930s plumber to understand.....
That was an amazing tour of an incredibly clever (and incredibly fault-tolerant) bit of technology. Thank you so much, Clive!
How incredibly mechanically precise!
Impressive bit of kit and a brilliant explanation and demonstration!!
Very impressive diagnostic! Excellent video! Well done Clive! Thanks so much for taking me on this journey. Very clearly illustrated sequence of events and explanation. Wow!
i love electro-mechanical things like this. just plug and play, no need to worry. until the contact corrode...
More chances of a software update breaking all your apps and programs then contacts corroding.
Then good luck fixing a software problem.
@@Fly0High I dunno man. A large chunk of my work is some sort of contact not contacting but it's fun to trace the bugger after scouring the cabinet for a single faulty pole in a 4 pole relay. But there's still 30 year old machines with original PLCs in them and they work fine, rarely having a hiccup. It's a scary ordeal when the old computers eventually do fail as there's only a handful of people who can fix those PLCs now and it's £££s because they're a lost art as they are not made anymore.
@@Fly0High are you mainly talking about smartphones? i am using a PC since the early one in the 90's and it was true that we needed to constantly reinstall everything to reset because it was always becoming so corrupted. these days stuff is way more reliable. 99% of the time its the power supply that gives-out and the logic board is still good. programing is always an issue yes, but if it worked the first day it will still work 10years later.
i think maybe because the processing power is so great even on things like watches now, it might hide some flaws in the softwares.
sorry because i am not so good in English. i tried to explain my point of view, but re-reading this i am not satisfied.
@@Francois_Dupont I was mainly talking about Windows actually. Smart phones... useless for general use.
Amazing.
This one is going on the 'Favorites' list.
This is an amazing piece of art. It reminds me with old-school overload switches.
Thank you for doing this.
Well that was really cool and interesting. Seeing stuff like this makes me regret dropping out of my engineering degree to pursue a different career that I stumbled into. Maybe someday I'll go back and finish what I started.
Sometimes it's better to keep the technical stuff has a hobby. Less red tape and more fun.
Excellent video - incredibly clear explanations and demonstrations
Superb investigative effort. Thanks Prof!
Most of my work is on Gas boilers but this has been a great eye opener on what a great piece of engineering this is!
That's a good one, it's a well thought out bit of kit.
The video analysis of it's operation is nicely done, I like.
Hi, l found this video very interesting as l work for many years at an NHS hospital with the maintenance department. The hospital had duel fuel ( natural gas or oil ) steam boilers plus a medical incinerator which had those units fitted. The biggest problem we found with them as you highlighted due to the rather hostile environment they operated in they failed on a regular basis mechanically more often than not. The flame sensor on our units had ultraviolet detectors which look like a tubular lamp with an indexing base so it could only be fitted with it viewing the flame. Keep up the good work and stay safe.
I assume nobody considered re-locating the units to a better environment.
Hi, l did relocate unit away from the vibration of burner itself which helped but as they had installed a medical incinerator in the boiler house didn't help as it produced very high working temperatures and a very aggressive dusty atmosphere due to the high use of lime to neutralise the acidic gases which were produced in the incinerator's burning process.
I'd bet all of the failures were safe, i.e. shut down instead of causing a fire or explosion. Annoying, but safe.
Excellently explained and the demonstration was easy to follow. Thanks for dedicating your time and knowledge, 10/10.
A genuine "wow" - this is a truly amazing piece of design.
It's the sort of "extreme cleverness" that makes you wonder though if the inventor ended up rocking himself gently in an asylum somewhere - I think this level of complexity is more likely from someone that is at least partly savant. Remarkable design - and great explanation too, thank you.
I wonder if this started as a simple (ish!) controller and then was added to over time to meet the demands. Can you add a second oil jet? Yep. Oh, now can you add an alarm trigger? No problem! Actually, we need to sanity check the flame sensor, can you add that now too ....turning it into the fiendishly complex structure we see here.
@@Wirralguy It was probably the result of many years (decades?) of problems and regulations. Look at current electrical safety regulations or aviation maintenance requirements. All of those are built upon the injuries and deaths of the past.
Stop asking for my real name! Absolutely - incrementally refined over probably 100 years now by reviewing catastrophic failure modes, until it will almost always fail in a safe mode. This wasn't a single inventor or even a single team - it was a community trying to keep people safe.
That is a very clever implementation of electromechanical timing and switching. I approve!
That's the most amazing one-time programmed PLC I've ever seen!! Thanks for the explanation Clive!
Love this thing! Very clever electro-mechanical interlocking. Really nice engineering.. Thanks for showing it off and going thru the effort of actually simulating it's operation for us tweakers! Keep on tweaking! Stu
What an amazing piece engineering. And your explanation and understanding of it was even more amazing. I really liked the last bit as seeing everything up close in great detail helped me understand the concept.
beautiful demonstration, such a cool little board
Can see this being one of your most watched. Amazing how you have worked out the wizardry, I always have one of these spare - a few failed over the years.
I reckon it won't get a huge audience, as it's a bit specialized.
@@bigclivedotcom it'll be huuuge, a viral video for nerds!
Maybe it'll be a slow burner...
@@prduguid haha.... Groan 😖
@@bigclivedotcom The secret life of engineers, techs, and hobbyists. lol
Many thanks Clive. That really is quite clever!
Thank you for that video! It is fascinating, how engineers have designed logic circuits into such a piece of hardware.
Blimey ! those mechanical guys never cease to amaze, a lot of work to figure this out...cheers.
That was astonishing; thank you!
Fantastic explanation of mechanical logic, some operations still can not be replaced by solid-state logic. Another very well explained device by the Big guy! Thanks ever so much Clive.
I just had a historic version of a oil burner controller stripped down, which was exactly the same design as yours, just without SMD tech involved. Really interesting to see how it works in detail and that essentially nothing has changed in this technology for the last thirty/fourty years. Thank you very much for your work! Always a pleasure to watch and learn.
OMG this is like pr0n for us geeks. A compactly packaged electromechanical computer complete with its preprogrammed subroutine, I/O and registers. Hats off to its designer(s)! Thanks, big guy!
Great job on the breakdown Clive. That's one complex little mechanical controller. A+
It is. All the better for understanding how it actually works.
Never knew I wanted to know that but lucky for me you did. That is incredibly complex. Thanks for another awesome video.
Thank you for your work! Brilliant
You're not buying central heating one little bit at a time and afraid to tell us, are you Clive???
That's why his house is so cold - he's taken all the bits out to explain them to us and maybe having trouble getting them all working again!! Hence the opening comment about needing this part! :-D
Thats what I thought he was doing with the mini motorcycle with all the ignition parts and wire looms, keep waiting for each additional part until he had some Frankenstein scooter cobbled together from cheap Chinese parts.
Come on, we need to get real here. Clive, and central heating? Never going to happen! 😸🤦🦄
I think I heard Big Clive say a year or two ago on a video, he prefers a cooler house. He says it is because he spends most of his time working outside so, he just got comfortable with it. If the temperature drops he'll just put on a few extra clothes.
@@ronniepirtlejr2606 Nah, just a big softie Glaswegian who's finding the IOM breeze a bit brisk, it's a plan t'raise the temp-er-at-ure to 10 or 11° with wee, filtree bits of heating, that's centigrade not farenheight....... Sorry Clive.
A really interesting and clear explanation of how the controller works, excellent presentation as always. That took some time to put together ;) regards from Galway and yes, its snowing! Thank you, stay safe, stay healthy.
Got one of these units on my Worcester heat slave boiler. I used to get intermittent lockouts and I always suspected it was the control unit at fault because I couldn't understand how it worked and anyway it was electro-mechanical and therefore surely must be unreliable. When I finally found the source of the problem it was the spark sometimes failing to light the oil spray due to the electrodes being slightly out of alignment. The controller seems to be the most reliable part of the system even after 20 years of service. Hats off to whoever designed it.
Can't tell how many of these burners i helped my dad fit for people down through the years. never knew how class it was on the inside.. : ) that was a really cool video Clive!! i loved how you used the neon's to show how it worked..
Extremely fascinating ...
Holy moly. This is one that presumably has a really complicated flowchart or ladder logic diagram... Those close-up shots were really nice
Fascinating.
Seems likely to be very very reliable.
Dude, just...... Thank you for all you do!!
Brilliant explanation of something that is so complicated in the old-fashioned mechanical, analog sense of the word. It’s a safety critical component and so needs to be robust and fool proof. I have a pretty big (35KwH) oil boiler and it has a 2-stage pump. And now, thanks to you, I know how it kicks in - and uses even more oil! It does make a rather satisfying “whumpf” when it lights though. Thanks for posting.
Beautifully elegant. This is exaclty why I enjoy mechanical devices. It's all so cleverly put together and you can usually understand it even without a manual or schematic, just by watching it operate and seeing the movement of its parts.
Could you possibly put together a video about relays? A general introduction to relays, followed by uses and what can be done with a relay. Something a bit like your _A simple guide to electronic components_ or your videos about soldering, those are very good. I have some old and new and big and small relays in my parts bin and I have no idea what to usem them for. Thank you for the interesting content!
Truly elegant engineering!
I'll be linking the guys at work to this video. Been selling these boxes for years, but we never get to see them do their thing.
That’s so cool. What a clever device.
My gosh that’s some crazy engineering! Thank goodness for microcontrollers!
That's some cool electro-mechanical engineering! Thanks for making this video!
It's got the movement of a swiss watch, great intro to the workings of this. These bring back memories working with the gas control versions Satronic 810.1 on some Babcock Wanson boilers, DD ovens.
they were motor driven sequencer types all good gear.
brilliant work! Thank You
Neat little state machine
Oil burners have been around for quite a long time...and I guess the engineers finally figured out that you just can't beat a mechanical control unit :)
...sales figured out they could get bigger bonuses by selling the same system for more...
I&C Engineers would never use electromechanical in a modern system.
it's also a safety component you don't just redesign them without a very good reason
No, the engineers figured out you can beat a mechanical control unit - and it still works even after quite a beating. ;)
@@peterg.8245 Wrong - we still do.... LGK boiler control units. Yes I can program it it easily for PLC, but the hardware has to be intrinsically safe and it's not worth the grief. The LGK does all of the welded contact monitoring and will even do gas valve proving. Just plug it in and give it a start signal from the PLC, and monitor it's little outputs for system status.
I think it’s more a case of if it ain’t broke don’t try to fix it, cheap and fairly reliable units these were
It's like relay logic and cam logic had a baby and it's really cool. I think this is one of your best videos, I really liked the explanation and the practical demo
I've really been enjoying this series of recent videos on UK oil heating control. While I'm not in the industry i do have a home with an oil boiler and hydronic radiators in the US, and i can see how different the wiring control and zoning is, even from the same component manufacturers.
You're my inspiration senpaii😳❤️
The knowledge you drop!
Very ingenious, and clearly explained. Cheers Sir 2x 👍
Pure dedication a master piece
Electromechanical designs like this are amazing
about a year ago I worked on a fuel oil furnace(which was prob made in the early 1960s)for an older relative. it wasnt lighting the fuel due to soot on the fuel nozzle and the flame sensor. my biggest fear was the large warning labels stating this unit was 15k-16k volts. So i fully disconnected all the power leads before disassembling everything. I had never taken one of these apart and i was surprised at how simple this furnace really was. Thanks for sharing your UK variant of this device!!
Extremely interesting! Thank you!
Classic Electro-Mechanical Computer programming. Love it.
Beautifully described Clive....👉💎👈
Reminds me of the "fun" I had trying to figure out the way the Poka Yoke ポカヨケsystem worked at the Honda car plant I worked at, which was used to stop the production line if a critical bolt was not fastened, missed, cross threaded or not tightened to its specific torque. Devilishly clever when you consider conveyors, pneumatic systems, transducers and tools and all sorts of stuff were all linked together.
A brilliant description I had to work this out 20 years ago when had a failure on our high efficiency gas boiler Kidd type. This used both solenoid outputs first pilot gas flame then second solenoid main burner. Same boiler could use oil if burner changed. I had to repair it after 10 years boiler lasted 30 years @96% efficiency . Thanks Clive
Thanks for the good explanation!
This same controller is used on some gas burners as well. At the units without blower they simply not use the contact.
Now I understand why there is so much dead time before the gas solenoid opens after the controller recives the call to fire.
That. Was. Awesome! Thanks for that!
Fascinating video thanks
Perfect demonstration of the term "fail safe". This applies to all fields of science. If something is going to fail, make sure when it fails it won't kill you or the patient... Words said to me by a spinal surgeon. The realible failure of a material is the greatest feature of that material rather than a flaw of that material.
I worked on an oil furnace on a friend's narrowboat, about 20 years ago... The furnace was very old even then, and the ignition spark was provided by a cam on the blower/oil pump shaft, and an automotive ignition coil..... The control unit was positively modern compared to this one, using standard time delay relays... If I remember correctly I added LED's to all the outputs to monitor it, and had to replace the LDR flame sensor to make it work.....
Genius electromechanical design, probably from an era before computers! The beauty of it is that the power contacts are already incorporated into the logic. There are probably additional fail-safe modes if contacts get welded closed. This is always going to be cheaper and more reliable than a microcontroller and relays.
Reminds me of the old thermally actuated photocells for streetlights, which had a big LDR in series with the heater coil. They lasted decades and it was usually the snap spring which broke or the connection to the heater failed eventually. For some reason these were superseded by a circuit board full of electronics and a relay or triac on a heat sink.
Then there’s the furnace controller I have which has a large swing moving-coil meter connected to a thermocouple. A synchronous motor and cam is arranged to mechanically “sample” the position of the needle every 20 seconds or so. I think it used a light beam to do this. If the needle is above the set point, the relay would drop out. If it was below, it would pull in. It can’t “chatter” because the decision is only made every 20 seconds. Genius, requires no electronics, will run for decades and any technician can fix it.
Very good video about an ingenious device! If tasked with creating that logic function, I would have immediately ordered a mini-PLC but it's amazing they kept this technology for so long!
I just got a different version with a custom labelled NEC 4-bit microcontroller in it.
@@bigclivedotcom I see how that would be very economical for a manufacturer to use that sort of part to create such a device. After all, the sequence of operation is very simple compared to many MCU based products!