# Electrical conundrum!



## cathead (Jan 31, 2021)

My torpedo heater decided to run a few seconds and shut off so the problem has to be somewhere in the
photocell circuit.  I replaced the photocell with a good one with the same results.  There is a circuit breaker
that shuts down the unit when there is no fire, I can understand that.  On disassembly, what I can't understand 
is how could the photocell that is connected to a small circuit board which is connected to the breaker with only
ONE WIRE have any effect on the circuit breaker?  I did disassemble the little box and found what appears
to be a bad transistor(overheated).  Actually it looks like a small signal transistor but in actuality it is an SCR
(silicon controlled rectifier), an X0203 to be exact.  Well, I didn't have one but did have another SCR so
soldered that in and tried it.  Well, the heater fires up and runs but doesn't shut off if you disconnect the
photocell so I know I need to find an X0203...  Sure, I could throw some money at this thing and get a new
fire sensing unit but that isn't going to happen because they seem to sell for somewhere in the 100 dollar range. 

In the meantime....  I connected the breaker wires together and of course the heater works even without
the photocell of course.  That's probably not the safest thing to do but will provide 150,000BTUs of heat
as long as it isn't left unattended.   I have another one so it isn't a big deal...

So, now for the next step I intend to find an X0203 and solder it in and see if it solves the conundrum.   
The photocell leads to the blue and white wires that go to the circuit board and only one wire connects to
the breaker.  I just don't get it.  Maybe someone else on here can understand this but for the time
being, I am truly perplexed.  If you look at the photos and expand them, you can see the single wire going 
from the board to the breaker.  How can this be??


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## Flyinfool (Jan 31, 2021)

Digi-Key has that SCR for less than a buck. Heck, Digi-key is in Thief River Falls, MN, so almost in your back yard.




__





						Discrete Semiconductor Products | Thyristors - SCRs | DigiKey
					

Discrete Semiconductor Products - Thyristors - SCRs are in stock at Digikey.  Order Now!  Discrete Semiconductor Products ship same day




					www.digikey.com
				




There are 2 big terminals on the breaker, are you sure a connection did not fall off before you pulled it off? I can see marks on one of the terminals that says there was a wire on it.


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## markba633csi (Jan 31, 2021)

One lead must have fallen off, Cat. It wouldn't work otherwise
Why a photocell in a heater?  Is this a gas fired heater?  The SCR controls a gas valve?
BTW (and this is for everyone) got to post smaller files- takes a light year to open them when they are 5 meg +
-Mark


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## cathead (Jan 31, 2021)

I'm positive there is (and or was) only one wire to the circuit breaker!  The two spade terminals are for powering the
unit of course.  The photocell senses the fire and dumps the breaker if the fire is lost, a safety feature to be sure.


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## markba633csi (Jan 31, 2021)

That doesn't make sense.  Breakers don't normally work that way- the photocell circuit must be cutting the gas valve when you lose flame
How does this heater normally operate?  Is there a start button? Or does the breaker act like a start button?  The "breaker" could be a latching relay, that would make more sense.


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## cathead (Jan 31, 2021)

Normally, one just plugs it in and it fires up.  If the flame should fail for any reason, it dumps the breaker somehow
and with one wire(and I'm sure on that part).


Edit:  It's a 150,000btu Reddy heater.

The breaker will act as a start button if the flame sensor has caused the unit to fail.


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## markba633csi (Jan 31, 2021)

I was going to say, it could be a sensitive gate SCR in that circuit.  A regular one won't work, which explains your substitute not working
There is a gas valve though, right?  A sketch would help


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## cathead (Jan 31, 2021)

There is no gas valve.  The fan motor has an air pump on the back of it and it causes the fuel to be siphoned
from the tank and atomized. 

On the bottom right are the two spade terminals.  One of the spade terminals is connected to hot(black)
and the other goes to the load(fan).  The arrow in the photo shows the single wire going to the breaker.
It runs on kerosene or #1 fuel oil.

It looks like MAGIC to me!   Stuff like this really gets me so I can't leave one turn unstoned!


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## markba633csi (Jan 31, 2021)

No gas valve!? Hmm..yep it's magic all right.   OK, I'll bite- where does the neutral connect?  Don't tell me there isn't one LOL


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## cathead (Jan 31, 2021)

The X0203 is a sensitive gate SCR according to the data sheets...

Thanks to Flyinfool and to markba633 for your responses.  I ordered from
Digikey a few SCRs so will try to follow up when I get the control unit
put back together and hopefully working.


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## Skierdude (Jan 31, 2021)

web search shows the Reddy 150,000 btu heater is a kerosene heater that uses the airflow to siphon kerosene from the tank. Here’s a link to the wiring diagram:


			https://www.kerosene-wicks.com/heater-manuals/R155.pdf
		

Hope that helps you track down the wiring issue


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## homebrewed (Jan 31, 2021)

The one spade terminal on the switch/breaker has marks on it like _something_ was plugged into it.  When everything's assembled, do the spade terminals stick out of the box?  Maybe the box plugs into something?

The schematic shows 4 connections to the flame-out control box, labeled Black, White, Blue and Red.  Your photos show two of the four so where are the other two?  They could be spades the control box plugs into.


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## cathead (Jan 31, 2021)

Two of the connections are the spade connectors on the breaker and the other two are blue and white wires
coming out of the control that go to the photo cell.


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## cathead (Feb 6, 2021)

Yesterday I installed the XO203 sensitive SCR in the circuit board and test ran the heater. 
It runs now about two minutes and shuts off.  There is an adjustment screw on the relay
thing and turning it clockwise shortens the run time.  Interestingly, the wire wound resistor
was quite warm after my testing which completely baffles me as there is only one wire
connecting to the relay and the photocell doesn't generate electricity as far as I can tell.
There has to be more to this than I can see......  Counter clockwise on the adjustment screw
and the heater still shuts off in two or so minutes.............!


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## Papa Charlie (Feb 6, 2021)

The single wire probably is a ground that is opened or closed when the flame is present and causes the breaker to pop.


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## homebrewed (Feb 6, 2021)

The photocell probably is an IR sensitive photoresistor.  Sensors of this type don't generate voltage or current, they change their resistance according to the intensity of light hitting the element.  The old-as-dirt CdS photocell is in this category--but yours likely is made from something else like lead sulfide so it can detect IR.  Your photocell needs to "see" the flame in order for the heater to stay on  (you probably already know that).

You may be looking at a thermal intermittent.  They sometimes can be tracked down using freeze spray aimed at suspected components to see when the circuit starts to behave, or, conversely, a heat gun to see which part is heat sensitive.


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## cathead (Feb 6, 2021)

Papa Charlie said:


> The single wire probably is a ground that is opened or closed when the flame is present and causes the breaker to pop.



What is the probability that a single wire not connect to ground could ground anything?


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## Papa Charlie (Feb 6, 2021)

cathead said:


> What is the probability that a single wire not connect to ground could ground anything?



My thought was that it creates the continuity though its housing.


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## cathead (Feb 6, 2021)

Well, it's a complete mystery to me as the little circuit board is in a plastic box with one wire
going to the relay thing and the only other connections are the two wires that go to the photocell 
which is mounted on a rubber insulating material.  I appreciate everyone's comments.  It's
just frustrating.


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## homebrewed (Feb 6, 2021)

Wondering about the photocell connection.  If you look at the schematic (link in message #11), the white lead from the photocell connects to the terminal board/ignitor module, not the flame-out control.  The white lead from the flame-out control appears to go to the motor, via the terminal board.

It doesn't help that the manufacturer used the same color of wire in different parts of the circuit.  I see White and Red used in several places.  Lovely (not!).

You also may want to review the troubleshooting section of the manual.


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## Papa Charlie (Feb 6, 2021)

cathead said:


> Well, it's a complete mystery to me as the little circuit board is in a plastic box with one wire
> going to the relay thing and the only other connections are the two wires that go to the photocell
> which is mounted on a rubber insulating material.  I appreciate everyone's comments.  It's
> just frustrating.



According to the schematic, there is a white to the photocell and a blue coming off of it. I would still imagine there is something on the circuit board or the back of the circuit board that is making one of those two connections.

This of course is assuming that the schematic is your model and that I am reading it correctly. Maybe you could post a picture of the front and back of the circuit board.


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## cathead (Feb 7, 2021)

While looking for a circuit diagram of the control unit, I found this interesting photo on the web.





After some research, it looks like all the older heaters all used the same basic SCR circuit with the latch relay.
I still have not been able to find the diagram I am looking for.  Knipco, Master, Reddy, and Desa all used the same
control unit.  I can only guess there were law suits and thus the reason for so many names for the same
basic design.  At the moment, it is 31 degrees below zero and the heater is a few miles away so it will be
a while until I can work on it again.  It kinda makes one feel warm just looking at the photo. Meanwhile,
I'm still looking for the diagram of what is in the little box.

Actually, I am somewhat impressed by that photo with the what looks like airable tires.....hmmmmm... AllPro,
another one I have not heard of.


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## cathead (Feb 7, 2021)

This is beginning to make more sense to me now.  The last test I did when the heater was turning itself
off, I noticed the nichrome box resistor(on the little circuit board) was warm indicating that a fair amount 
of current was passing through it.  The photocell in darkness goes high in resistance and must cause the
SCR to become conductive causing current to flow through the resistor and through the bimetalic latch relay
and dumping the fan and ignition.  According to the diagram below,  the current to shut off the unit would have 
to flow through the photocell from the white(hot wire) to the latch relay.  If the photocell is failing or possibly
dirty,  the heater would shut down.  The part I was not understanding was that the photocell does not connect
directly to the circuit board.  If I disconnect one lead of the photocell in a test, I would think the heater would
not shut down, probably indicating that I had not only a bad SCR but also a flaky photocell.


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## Flyinfool (Feb 7, 2021)

It does not make sense because you are not looking at the whole circuit. just a piece.
No different that trying to figure out how a transister works with just 3 leads. It is those sneaky internal connections that get you every time.
The wite wire going to the PCB is the neutral, The black wire that goes to one of the terminals is the hot wire. Ill bet that the single wire connecting the board to the switch is also the hot wire. So you have a hot and a neutral connected to the PCB to power it. The blue wire is from the PCB to the photocell most likly supplying the hot and the other side of the photo cell is connected to neutral. ANother complete circuit. The red wire goes to the igniter and the fan to supply them with a hot when instructed to by the PCB and the other side of the igniter and fan connect back to neutral. It all makes sense as 3 seperate but complete circuits.


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## cathead (Feb 7, 2021)

Thanks for the post Flyinfool.  I will take along my VOM and a note pad the next time I look at it.


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