power spike removal 2

[ruggb]

Not sure if this is the right place for this as it involves a couple things.
I have an oil burner on a rural electric supplier. It is a vacation home and the temp is at a minimum when vacant.
The issue is the reset keeps tripping - occasionally when someone is there to reset it. Last year we broke 2 toilets because it stopped in dead cold weather.
I have tried everything to stop it. My conclusion now is that it is power spikes on the line getting thru to the triac that trips the breaker.
All burner flame out circuits are the same and there is no devices on them to prevent this. The power company says they can't monitor for short power interruptions or spikes. I have a TD relay on the input neutral side which trips in 10ms, then resets in 3 min. The oil control trips in about 15 sec for a flame out (a little short of the 30 sec spec).
The motor and HV xfmer supply runs thru the line input which is why the TD relay it in the neutral.
SO, is there a reasonable why to suppress these transients either externally or with a circuit mod?
Attached is the schematic.
thx
bill

 

[jghrist]

And the one time it happened when I was there, there was indications something was happening with the power by VERY short duration flickering of the lights - and you want to tell me it is something other than a spike.

What makes you think a very short duration flickering of the lights indicates a spike? It is more likely a temporary fault on the primary distribution system causing a voltage sag or trip and fast reclose on the distribution or transmission system.

If you think it is a spike, then get a transient analyzer and measure the spike.

 

[itsmoked]

As for your TVS I'm not sure where exactly you are putting it. They always work vastly better and tend to not go up in pink smoke if they have impedance to work thru - in fact it is an absolute requirement.

That said, are you saying you want to put it on the 24V side or a low voltage side? That's superior because then it gets to work with the transformer's considerable impedance. What is the nominal voltage you want to put it across? Are you specifically going to use a Metal Oxide Varistor? (MOV) Or something else?


Keith Cress
kcress -

http://www.flaminsystems.com

 

[HamburgerHelper]

I don't know how cold it gets where you are but just having your toilet run a little could hold off freezing. I suppose you would have to be sure your drain can't freeze then.

 

[waross]

On a rural line, observable power issues?
Re-closer events are common on long rural lines, particularly if the roads are narrow and tree lined. A re-closer trips the line off circuit when there is a fault on the circuit. The most common fault on a rural line is tree branches or large birds across the line. The second most common fault is failed transformers.
The typical operation of the pre digital re-closers was 3-5 seconds off and and then back online. If the fault was still re-closer would immediately trip open for another three seconds. It would re-close three times hoping that the tree branch or bird would drop free. If this did not clear the fault, then a failed transformer was suspected. The re-closer would close back in for a longer time, sufficient to blow the fuse on a shorted transformer and clear the line. That would happen twice. a total of 5 operations. The re-closer stays open after the 5th try. If you are downstream from a re-closer you may experience several outages of a few seconds duration in less than a minute. If you are fed from a small rural substation, a re-closer event on an one circuit may cause voltage dips on the other circuits out of the sub.
Try tripping the power off and on at 3 second intervals. If your circuit trips you have found the problem.

I thought that I had already posted this link but I don't see it. Sorry, here it is now.

http://www.ebay.com/itm/Refrigerato...945038?hash=item3cd1ec0a4e:g:ZBwAAOSwZjhXI684

This will protect against spikes and surges.
It will also protect against low voltage and the three minute safety delay will protect against re-closer events.
The problem may be low voltage or re-closers, but you can put this surge protector on and if it fixes the problem that must prove that there were surges, right? (Even if there never were any surges.)
It always proved it to the customers in the third world.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

That does indeed look pretty handy Bill. Clever product. Too bad it's not listed.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Looks a lot like my Nuclear Power Filter, which I once proposed. It surely was a good device - but I realized that the LAW may have thought otherwise.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[LionelHutz]

From what I understand of those circuits, the safety switch uses a heater element to trip it. Basically, it's a mechanical time delay that should delay for something like 30-45 seconds. So, it should never trip instantaneously.

The circuit basically has the safety switch contact, thermostat, relay coil, safety switch heater and triac all in series. When the thermostat calls, it starts out with the triac triggered which pulls-in the relay. The relay energizing causes it to latch itself via relay contact #1 and to start the burner via relay contact #2.

The relay #1 contact makes the circuit so the safety heater and triac are in series across the power. Once a flame is detected, the flame detector turns the triac off which stops current from flowing through the safety switch.

So, even is a "spike" triggered the triac on, it would go back off within a cycle of the AC voltage, which is a far shorter time for the current to flow then the safety switch should require current to trip.

Know the above, it certainly appears the circuit does has an issue. The safety switch should not be tripping instantaneously and should never trip from a single cycle of the triac being noise triggered on.

I gathered this from a 10-minute look at the circuit. During this look, I also determined that the diagram you posted shows relay contact #1 wrong - it should go to a center tap on the transformer, otherwise the circuit simply can't work. But, I'm sure a BSEE skilled in circuit analysis who's been working on the circuit for 20 years would has already figured all of this out.

You need to go directly back to the excellent advice already posted:

The very first step in effective problem solving is to determine what the problem actually is.

I really should have flagged this hobbyist or homeowners post when I first saw it even though other valued forum members had already responded.

 

[waross]

What exactly is tripping.
I see no indication of any tripping or reset components on the device labled "Reset Switch".
Is it the high limit that is tripping? It is generally the high limit that has a reset button.
That would be either the high limit calibration is off.
Or re-closer events are causing a combustion problem.
Normally when the thermostat is satisfied the burner shuts off and the fan keeps running to cool the heat exchanger.
Compared to all other burners that I have worked on:
The Fan Switch should be labelled "Lower Limit".
The Lower Limit should be labelled "Upper Limit".
The Upper Limit Should be labelled "High Limit Trip".
Typical operation:
1> Burner starts.
2> When the heat exchanger is up to temperature, the Lower Limit starts the fan.
3> If the heat exchanger gets too hot, the upper limit shuts down the burner until the temperature drops and then restarts the burner.
4> When the thermostat is satisfied, the burner stops and the fan keeps running to cool the heat exchanger The Lower Limit cycles the fan off when the heat exchanger is sufficiently cooled.
5> If for any reason, generally a failure of a component, the temperature of the heat exchanger keeps rising, the High Limit Trip shuts down the furnace and waits for manual intervention.

A re-closer event may be interfering with the normal shut down cycle and somehow causing the heat exchanger temperature to rise past the set point of the safety limit.
Have you checked your air filters? Dirty filters may cause higher than normal heat exchanger temperatures. If this is the case, it would take less of an operating cycle abnormality to trip the high limit safety.
A surge suppressor similar to the one that I suggested will probably avoid short cycle issues overheating the heat exchanger.
And you will be vindicated. You suspected a surge problem and installed a surge suppressor and the problem was solved.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Bill, much like many appliances, the posted diagram is a crappy drawing of the circuit. The reset switch is really a contact from the protection module that trips if the burner does not light. The safety heater is the coil that trips this protection module. The protection against the burner not lighting generally requires a manual reset once it trips.

The upper limit protection is likely one of those 2 terminal metal case click switches that resets itself.

 

[waross]

High Lionel. I will concede the points on the action of the trip device.
In addition to the upset cycle issue, there may be a case where there is not enough voltage properly run the "Gun" burner, and so the flame doesn't light.
Alternately, there may not be enough voltage to initiate the ignition spark.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

Hi, I'm back again. I promised myself not to dig any deeper into this, but...

I think that the main problem is that of communication. When OP says "spike" he probably means any main anomaly. For most of us, a spike is a short duration overvoltage - like an inductive kickback or some other short-lived phenomenon. So a spike is usuallly something like a 200 - 500 peak with a width that can be anything from tens of microseconds to one or two milliseconds.

Such a disturbance cannot be observed with the eye. Impossible.

Next, if you look at the diagram, the triac, flame detector and relay are completely and galvanically separated from the grid and fed from the 24 V secondary of the "TRANS" which is NOT the ignition transformer.

To make the influence of a spike even less probable, there are Three Components forming a low-pass filter in series with the triac and diac. The latter also has an RC Circuit that defines the gating angle and makes the sensitivity to external spikes extremely low. An unvoluntary triggering of the triac does not stop the burner. So one can forget about spikes altogether.

A transient voltage suppressor will not help at all. There are a few other recommendations in this thread. Please consider them, but I doubt the PipeMan gadget very much. It sounds very much like the "SineTamer" which is also a hoax. Like my Nuclear Filter was.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

Hi Gunnar. Those Pipeman gadgets worked well on under-voltage. I don't know about surges because our surges were actually low voltage.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

The worry about the triac triggering says it's the flame detection circuit tripping. Since the flame detection circuit should be time delayed, any solution attempted is a complete crap-shoot until the root cause behind the flame detection circuitry tripping immediately instead of being delayed is actually found.

The device you posted Bill could work if it reacts quickly enough to the power transients.

 

[waross]

Hi Lionel. As a friendly discussion, I suggest that transient triggering of flame detection circuit of furnaces is not a known issue with the millions of furnaces in daily use.
The protection device works by keeping the circuit off-line for three minutes to avoid whatever line conditions are causing the problem. If the lights are flickering, then quite possibly the furnace is trying unsuccessfully to light. Each try adds heat to the trip heater because the flame never does light.
If the voltage is too low to generate an ignition spark, then the flame detector will trip.
To expand on Gunnar's suggestions; Transients generally have very steep wave fronts. Essentially the first half cycle of a very high frequency. This high frequency is easily blocked by the impedance of transformers.
Even if a "Surge was to trigger the triac it would turn off at the next zero crossing.
With 60 Hz there is a zero crossing each 8.3 milliseconds. If a surge does trigger the triac, it will shut itself off in about 8 milliseconds or less.
Are we to accept a series of surges at the correct time to be most effective every 8.3 milliseconds?
Consider 4 or 5 failed restart attempts in 20 or 30 seconds. That can easily happen on a rural distribution line.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Yes Bill, what you are posting is all correct and has been covered already. Yes, the millions of oil furnaces in daily use are quite reliable and trouble free.

The design of the flame detection circuit makes it rather immune to spikes. As Gunner pointed out, there is filtering on the circuit. As I pointed out, the triac would go off again in 1/2 cycle if it was triggered on by noise, which is way too short a time to cause a trip.

As you pointed out, you've got to know what the problem actually is before you can create a solution.

I should have probably asked, because details on that vaguely described delay timer protection would have been nice. The coil on some delay timers can cause the timer to hold-in until the voltage drops quite low. Much lower then you would want to use as an under-voltage trip level for a circuit like this. So, that timer circuit that is supposed to be protecting against low voltages might not be doing anything very useful.

 

[waross]

There is a voltage monitoring circuit that drops the device out at a predetermined voltage. It then must see a voltage within range for three minutes before it re-energises the output. Either a voltage dropout or a high voltage will trip the device off.
The device trips off above 140 Volts and below 90 Volts.
This may not help with transients but it sure works on most of the low voltage problems that are erroneously blamed on transients.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Not a description of your device Bill, a description of what the OP vaguely described as a timer providing full brownout/drop protection.

The oil burner control should take about 30-45 seconds to trip without a flame. The thing is rather dumb, there is not sequence of operation. Basically, it just calls for the oil pump and ignitor to be on the whole time the thermostat is calling. So, the question should not be how to stop it from tripping when I saw a short power line disturbance, but rather why does it trip when there is a short power line disturbance. 30 seconds of brown-out is rather different than seeing the lights flicker once or twice.

 

[waross]

Hi Lionel.
Now I undertand what you meant.
I have had issues with rural lines at different times and in different places.
A fairly common pattern for a tree failing across a rural line is a trip of the recloser and a dead line for a few cycles or a few seconds.
Then the recloser closes in. If the fault is still there it trips out again.
After a short time is closes again.
I have seen reclosers set to close in as many as five times before tripping off permanently.
I fortunate enough to see a tree fall across a line. The line didn't trip immediately.
The current started to track along the tree trunk. A bright pink line was seen on the tree trunk as the current built a breakdown path. It took several seconds. Then there was a flash and a bang and the recloser cut the power. A few seconds later the recloser closed and the pink line was seen again. Several seconds to trip.
This was repeated five times before the recloser cleared the line permanently.
I imagine that other lines fed from the same small rural sub would experience fluctuating low voltage.
Anyone between the sub and the fault would see the lights dimming and flickering.
I can see such an event being described as flickering lights on unfaulted lines from the same sub.
I theorise that voltage is too low for the ignition transformer even if the burner motor trys to run. However if the low voltage is enough to trigger the protection circuit for enough seconds it could trip off.
I understood the OP that the circuit trips in about 15 seconds.
Using the protector will also avoid the possibility that the burner motor is running and delivering fuel to the fire box that is accumulating rather than being ignited and burned properly.
Small amounts of unburned fuel, yes, but something that it may be well to avoid.
The OPs timer may well work, depending on the cutout voltage.
My point is that there is probably no spike or surge or transient.
The most likely issues is power drops and brownouts over a period of 20 to 40 seconds.
The solution is to stay off line until the power stabilizes.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Mbrooke]

The 5th reclose attempt might have actually been a non communicating tie recloser closing in on loss of potential. All the re-close control manuals that I have seen limit the max to 4. But who knows, there might be a reclose relay out there that can indeed do 5.

 

[waross]

Five was the standard for a West Coast Utility many years ago. Three fairly short closings to allow fallen branches and burning birds to fall followed by two longer closings to give the fuses on a possible failed transformer to clear. It was a long time ago.
I probably meant 5 trips and 4 reclosures.
Thanks for the clarification.

Bill
--------------------
"Why not the best?"
Jimmy Carter