Finally!

I think I've seen only one in the past 20 years. On an AS Arco Leader.

I am surprised it wasn't gone 45 years ago.

That being said they were pretty reliable and worked well for probably 100 years or so.

Slow acting was the biggest issue

One thing I liked about the 817 and 117 was when the fire was proven the ignition relay dropped out so you could tell the flame was proven.

Not so with the 116 or 816 which were constant/here we go again/intermittent ignition.

I wonder how many are still in use?

When I started working on Oil Burners, the Cadmium Cell eye was a magical thing that "would watch your oil burner flame to make sure that it was burning efficiently" This was a Quote from out sales pitch when selling a "Modernization" which included a flame retention oil burner, combustion chamber, vent connector pipe, barometric draft control, and control system including the Honeywell Round thermostat.

Most of the equipment had Stack Relays back then and I have installed my fair share of Rebuilt ones. I still have a Stack Relay tester on a shelf in my garage in NJ. It reminds me of a control station at 1960s NASA in Huston.

• Telemetry, Check,
• Speed, 1900
• Gimbal, Check
• Thrusters, 86%
• Stack relay, 90 seconds 'til flame failure

Huston we have a problem.

I agree with @Steamhead… It is about time to retire that technology!

It was the 1960, when no one actually knew exactly what the "magic eye" does. And if the flame was burning really bad, and did not make enough light to make 1700 Ohms resistance then the burner would stop! So that sort of loosely covers looking at an efficient flame.

But the salesman would usually be in the customers home with a Bacharach combustion kit and measure the efficiency of your old coal conversion, at somewhere around 50% and offer you a guaranteed savings of 75% combustion efficiency. After the math your oil usage would drop about 30%. With a guatante like that and a new gas boiler costing more that double the price of our modernization, I was never thrown out of anyones home for saying the Magic Eye was watching your efficient flame.

And I never said that "a light sensing control made your heater more efficient". I said it was "watching your efficient flame". The EYE didn't save the $$$. The entire job with all the proper adjustments was saving the $$$.

Matt is trying to put words in my mouth that just are not there.

@EdTheHeaterMan

What is a stack relay tester? What does it test, the bimetal or the electrical function?? Never knew there was such a thing.

There is this metal box about 18" deep, 20" wide and 14" tall with a sloped front.  On the left side is a hole with the smoke pipe bracket that holds the stack relay in place so the bimetal element is inside the box.  Inside that box was a porcelain light bulb socket. In the porcelain light bulb socket was an electric resistance heater that fits in a light bulb socket.  The back of the box was vented to allow the heat to dissipate.  

Across the bottom of the box were several wires that connected to the different terminals of the control you wanted to test.  There was a voltmeter,  and several switches that were labeled to provide different “problems” that you would like to see if the control was safe to put back in the field on a customer's heater. There were savaral indicator lamps that let you know the ignition was working and the motor was operating (without actually connecting to a live burner).  There was also a timer that counted down the 90 second safety timing to verify the reset was operating properly.  

By connecting the alligator clips from the wires on the proper terminals you can power the control, activate a call for heat and watch the stack relay power up the ignition, power up the motor and then the indicator lamps would show that the motor or the ignition transformer would be running.  When the burner motor was running the electric heater inside the box would activate the bimetal element and the pyrostat contacts would disengage the ignition, and disengage the safety heater and the motor indicator lamp and the flame indicator lamp would stay lit while the ignition lamp would go out.   

By opening a flame failure switch the resistance heater would lose power and the flame indicator lamp would go out while the motor would continue to operate.  The recycle timer clock would start to operate to see how long the burner motor would operate before the pyrostat contacts would drop out the motor and reset back in step for another trial for ignition.  (the operator would record that time)  once the control was back in step, the burner motor, and the ignition would restart and the clock timer would start (to measure the safety timing).  With The flame failure switch still open the burner and ignition indicator lamps would light but the flame lamp and the resistance heater would not light.  If the reset tripped as if there was a flame failure within the proper (90 seconds or less) time, that would be recorded.  The rebuilder would then initial the card and sticker if the control passed.  The card would be filed and the sticker placed on the inside of the control cover.  

I don’t have the instruction booklet from the Stack Relay Testing Station but I remember reading it one afternoon when I was a kid hanging around the shop, emptying trash cans and sweeping the yard for 50 cents an hour.  

@EdTheHeaterMan

Quite the contraption. I guess it wasn't something you took from job-job LOL

I can't imagine how many of those controls Honeywell sold. Of course, there were a few other brands that I can't recall right now. Mercoid maybe??

I remember one job I went on in the early 70s. 30 gallon/hour Petro burner in a factory where the maintenance people messed around with it. At that time as I recall 3.00 gph was the largest burner you could put on a stack switch.

This old burner had a pyrostat and some old control that still had a 90 sec safety switch timing, must have been legal when installed.

They messed with the electrodes and it had delayed ignition. The boiler room was built out of the old cinder blocks. The wall had moved over about 3/4".

@Steamhead recently gave a bunch of my books to off duty tech.

We saw Honeywell and White Rodgers here in northern NJ. I cringed every time I had to to work on them.

I used to hate replacing a stack switch. You would go on a no heat call and the SS was bad. You know you should put a cad cell on it but not an easy task. You have to figure out a way to mount the cad cell and then rewire things to make it work.

Not practical on a no heat call.

And the old SS rubber covered wire in the SS was always brittle and the insulation was falling off being overheated by the flue pipe

Isn't it type R. I forgot to look at the code book last night.

I have numerous questions even today about how boilers and furnaces are installed if wiring is in a place where it is within its insulation rating and does it require derating where it is installed(which is yet another long discussion for 10, 12, and 14 awg conductors because their ampacity is declared in a rule but you can use the engineering data when calculating derating).

@mattmia2

Derating is a PITA and the code makes it twice as complicated as it needs to be.

Derate for ambient temperature

Derate if more than 3 current carrying wire in a pipe

Temperature rating of terminations. ETC ETC

Then there is Romex which the new stuff is rated at 75C but your only allowed to use it at 60C

Ask 10 electricians get 10 different answers.

@mattmia2

Yes THHN is rated @90C but in most cases you can't use it at that temp. The general rule is everything under 100 amp you size the wire (after any derating is applied) to the 60C column. So you do the calculation so that all wire under 100 amp is not run at over 60 C (unless the equipment and terminations allow a higher temp….the weakest link)

Over 100 amp its the same thing except you can run at 75C

This is a UL rule may not be specifically in the code

But in either case (60 or 75C) you can use the THHN rating of 90C and derate from their

Except that

THHN cannot be used in a wet location, outside, underground or in a slab on grade.

Since THHN and THWN are the same wire now (The wire is dual rated) if installed in a wet location the THWN rating is used to derate at 75 C and that is the temp to be used for derating