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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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.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
I just had one of these fail on my boiler as the coil on the bi-metallic strip had fried, resulting in the burner fan and spark working but solenoid staying shut. Interesting device and great video thanks.
Is it NSIT approved ???
Amazing!
Really good explanation can Do these units fail as I have oil to the bleed valve but the vaporised oil is not being sprayed out the nozzle I did put a new solenoid on last year ?
Excellently explained and the demonstration was easy to follow. Thanks for dedicating your time and knowledge, 10/10.
These are also used in inshore ships.
We got one for the diesel burner for the heating of the accomodation and hot water.
Those are reliable controls, but I still prefer modern solid state oil burner control. Less variability and can even flash trouble codes at you
This is amazing, worked on burners with these but never thought how it worked. Would be interesting to see you disassemble and analyze how a Siemens LFL 33 burner control box works.
i wonder if a 12-24v ac/dc variant exists
I would use this for a dual level propane/butane/city gas heater scenario with oil 2 being run via a thermal switch+555 delay(after say 5 minutes of active "oil 2" when it is below 5c outside it would then allow the "high flow" mode via the second higher flow gas into the flame zone) for extreme temps outside and as 24vac is a common usa thermostat voltage and would simply power a 24vac unit via the "heat enable" signal and the main air fan would simply force the local distribution fan to circulate the room/house air
this would allow any fire based heating system with dual level control to be used safely assuming the main house blower also has a "hot exchanger" thermal switch that forces the main blower active whenever there is too much heat in the "fire zone" (ie about 80-120c so a simple heat pump can be used as "heat 1" for tepid days)
this would also allow safer operation of personal propane heaters as using a simple control stack that locks out fuel flow upon a failed ignition(possibly using a heat switch rather than light based flame sensor) as a 24vac low current transformer is a common item so economies of scale exist
I want a 24vac version of this for simply using the simple but highly safe sequence to control all manners or flame heated systems
my wish in the future is a bioreactor with post-purification gas cracking to butane/propane and those reactors need an ideal 45c to keep the bacteria happy so a dual level burner with outside temp sensing and second stage delay/second thermostat relay for extreme cold would be ideal to use the extra H4S to keep the reactor happy
sure if the H4S is not enough on it's own I would then use a slightly lower regulator output from the main propane/Hydrogen waste tanks to sequence the burnoff of secondary products to keep the grass clipping to methane reactor happy
if it gets too cold the gas slows and eventually it dies and as 45c is quite warm for most areas it should be very happy with only a mix of PC waste heat from the server farm and a bit of flames
Cool vid and info.
That’s so cool. What a clever device.
They are called boilers in Britain. They say Furnace in America. Lets be correct. As an old steelworker I can tell you they are not like furnaces at all !!
The old boiler controllers where an incredible design, such delicate intricate internal parts. Good old fashioned engineering. I remember many of the old Landis & Gyre step controllers for the big industrial boilers back in the 1970s. My mates dad worked for Hamworthy and his garage was stocked full of this old stuff plus circuit boards that looked like they come from a Maplins Electronic shop, big components. 👍👍👍👍
PS – another intricate and complicated design are the old paper chart recorders, remember them? 🤔
Mine has an additional wrinkle that the blower is controlled by a temperature sensor on the heat exchanger. So the blower doesn't come on immediately (and blow cold air) when there's a call for heat, the flame starts, the heat exchanger warms up, and the blower kicks in. When the call for heat goes off, the burner shuts down, but the blower keeps going, extracting the remaining heat from the heat exchanger, and adding a little hysteresis to the system. When the heat exchanger cools off, the blower shuts down. It works quite well, except for when people get confused/worried when the blower doesn't follow the thermostat exactly.
This type of design is great for highly radioactive areas. Since none of the components would be affected or damaged by radiation.
Wow! Amazing device. I don't know where to put it in. Electric? Mechanic? Electronic? Alien technology for shure.
That was astonishing; thank you!