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

 

[ruggb]

here is the flame out control

 

[itsmoked]

Two toilets? Man that sucks big-time!

I'm not sure why you think it's transients tripping it off. You say it's tripped-off while someone was there? It wasn't during a start? What is the normal "abnormal event" that's supposed to cause the trips?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ruggb]

When I was there and it tripped it was already running and there were indications of power abnormalities happening, though the power never cut out completely. Generally, the power there is subject to outages a lot more frequently than here at home. If I power the furnace on/off rapidly at the breaker I could not get it to fail, but I added the TD relay hoping that was it. When I do that now, of course, it is off for 3 min. It has been serviced (by me) so I know the sensor is clean and new and electrodes set, etc.
When it is running it seems like the circuit is primed so that a spike coming thru there causes an immediate reaction as opposed to the 15 sec delay. I'm not sure that is design intent, but I think that is what happens. Normal operation depends on the RC constant.

Maybe a bidirectional Transient suppressor diode on the secondary of the transformer?

 

[itsmoked]

Well. If while you were there it tripped-off and at the same time you could actually detect 'disturbances' I very much doubt any kind of transient suppressor will do the job. They only fix super-fast higher-than-normal spikes, something I doubt you could visually notice.

How much does this furnace draw when running? Got a motor nameplate picture or manual page that would tell us?

I expect what you really need is a UPS.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ruggb]

I initially considered a UPS, but the went for the TD relay because I thought that the problem was short term drops like 1/4 sec and a UPS would only serve to jump the gap at a very high cost. A power strip would also be cheaper than UPS but I thought at that time it was longer term than a power strip would handle. As long as the reset doesn't trip, it doesn't matter if the furnace shuts down for 5, 10, even 30 min or an hour. Obviously, the problem is under 10ms as that is the dropout that will trip the relay. It also only needs to affect the control circuit and the motor and HV xfmr draw too much I for a cheap solution.
If I put a TSV across the xfmr, the point is to kill any transients under 10ms.
It is cheap. So as an experiment it is not an issue. I think I have tried everything else except installing enough electric heat to ward off the freezing. I set the furnace at a min 50 deg, so if the elect is set @ 45 it will only operate if the furnace fails.

 

[itsmoked]

I believe the furnace issue is that any interruption even a 1/4 second could cause the fire to stop and the fuel would continue, so they're very sensitive on purpose. I predict that the MOV or TSV will not help but it shouldn't hurt either.

Your fallback electric heat scheme is a good one. Especially since it's so easy to implement. It leaves you exposed only to a power failure.

Everyone I know skips the heating because power failure during an especially cold storm is often a given. All my friends with cabins have a little check list for leaving:

1) Turn water off.
2) Drain pipes. (They use the lowest exterior faucet.)
3) They flush the toilets after turning the water off.
4) Pour a cup of eco-antifreeze into the toilet bowls.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[ruggb]

yes, that is exactly what I do. I also pour AF into the sink traps. My brother-in-law neglected to flush the toilets last time. He also bought the AF - I had to tell him auto AF was not so good for septic sys. We also had the refer water valve freeze. A dilemma is that water under pressure has a lower freezing point than not. And I am on a well so the pressure tank under the house and water heater are full.

Thx

 

[itsmoked]

That's the complaints that all my friends also have - "A friend or family member forgot." I had a boss who lent me his Tahoe Cabin with detailed exit instructions. He literally had me sign a piece of paper agreeing to pay for 'damages that will occur' if the instructions were not precisely followed. It certainly got my 'focus' on the issue.

Sink traps I forgot about.. His instruction included them. I don't have a cabin. :/

Exterior plumbing that's not deeply buried you have two choices on. Heat tracing with insulation or running the water. I'd probably put a few temp sensors in strategic plumbing places and when the temp gets down to 34F open a valve and run the water somewhere. The 55F well water will take a long while to cool down to 34F again. If a certain pipe or tank is found to reach 34F first and long before anything else then insulate it. That covers the pressure tank. Insulate it too to keep the water cool in the summer and warm in the winter. Or heat trace it too.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I spent some years in a third world country. Power surges were a famous cause of damage to freezers and refrigerators. Burn-out were frequent. Everyone in the city knew about "Power surges" and failed refrigerators and freezers. The more well to do families hired electricians to implement protection against "Power surges". There were a couple of schemes that worked.
But-- There were no "Power Surges".
Fortunately the mitigation schemes were also effective for the real problem.
The problem? Low voltage. Power outages were common on Sundays. The utility crews killed a lot of circuits to do maintenance.
The distribution was four wire circuits with transformer primaries connected phase to neutral.
A common scheme for industrial plants was a four wire Y:d connection.
That's where I learned to hate the delta.
The transformers were fuse connected with fused cut-outs. When the power was restored by closing a fused cut-out, one phase would be happy, but the other two phases would be back fed trough the wye:delta banks and two phases each developed approximately half voltage.
All the compressors would try to start but on 50% voltage would stall.
A basic hot stick has a peg with a mushroom head sideways on the end. The telescoping stick may be 25 feet long. The peg is inserted into a ring on the fuse holder and used to raise the fuse holder into position and then the peg must be carefully removed from the hole without knocking the fuse holder to the ground. The peg is then inserted into a second ring (about 25 or 30 feet in the air) to close the fuse holder. Then the lineman must carefully remove the peg from the second ring on the fuse holder. Then the fuse holder for the next phase is raised and inserted the same way.
Not a fast operation.
In the meantime, 2/3 of the compressors on the circuit are sitting stalled with 50% voltage applied.
What's the pint? Well if you are trying to suppress surges when the real problem is voltage surges, good luck.
Voltage sags are a fact of life on long rural lines. Relays and contactors tend to drop out during voltage sags. When the device drops out the impedance drops and the current goes up, and the coil may burn out, or the fuse or breaker may open.
This may be your solution.
It protects against both high and low voltage.
When healthy power returns there is a three minute safety delay before power is returned.
As I mentioned these were installed to protect against non-existent "Surges" but actually saved the compressors by protecting against the low voltages.

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

 

[ruggb]

@waross Thx,really, why don't they just attach the gen to a bicycle and let the crew pedal?

Anyway, if you look at the crt. you see that if the 24v drops that reset may never trip. The sensor drops the voltage across the cap when it sees flame. If the flame quits the voltage rises and trips the triac. That heats the heater tripping the relay which cuts the motor and HV xfmr out. If the 24v is low, the trigger V may not get high enough. But that wouldn't be good so I am sure they designed for that. The sensor goes from over 100k down to about 5k I think. So it probably would get to trip V anyway. I may not get to test the TSV this year. It will be a while b4 I get back up there.

 

[Skogsgurra]

Bill 19 Mar 17 22:33

Yes, you are soo right. There are so many people telling each other about spikes that it becomes a truth. I still try to get a recording of one of those spikes. I really never found one that was powerful enough to kill anything like a relay coil, a thyristor or triac or even a photo resistor.

But I have found many brown-outs and fast-and-short drops that reset relay circuits or upset mico-processors without causing a proper reset, which kicks them into never-never land.

Recorders not fast enough? Not tried enough times? Pls, don't insult me. Been in this business for more than half a Century and used TEK digital scopes (also used their analog memory scopes, remember?), HIOKI and Siemens recorders, BMI and Dranetz and many other equipment to record that elusive "spike" without getting anything better than around 200% overvoltage in the us range or 50 - 70% of sine peak in the ms range. I have met hundreds of field problems that were supposed to be caused by "spikes". Yes, some were, but then it was elaborate overvoltage protection in paper machine drives or gas turbine plants that over-reacted. Not your standard automation system that was in any way killed by the spikes.

Once again, Bill: You are soo right. PLS for you.

Gunnar Englund

http://www.gke.org

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

 

[waross]

Hello Gunnar;
Such kind words from someone of your education and experience are more valuable to me than a multitude of PLSs.
How many times have we both been the second or third or fourth person called and found that in addition to fixing the problem, we have to undo several other problems that were someone else's attempt to fix the wrong problem.
How do we make the point that the very first step in effective problem solving is to determine what the problem actually is.
An anecdote, true story, to illustrate waste and futility of fixing the wrong problem.
I was working on a panel and nearby some mechanical guys were replacing a 3 HP motor with a belt drive to a fan.
They started the fan up but something didn't look right. They stopped the motor and found that it had "Gone out of alignment".
They readjusted the motor base and tried again. Again it had "Gone out of alignment".
A third man showed up to help.
Try again.
Again, "Gone out of alignment".
This was repeated all day and all the second day.
At one point the motor was found to be tilted. The amount of tilt was carefully measured and they were gone for awhile.
They returned with a wedge to put under the motor so as to be able to properly align the drive.
Start, stop. "Gone out of alignment!"
Midway through the third day, someone discovered that the pulley was cocked on the motor shaft.
When the pulley was installed on the replacement motor the bolts on the taper lock hub had not been tightened evenly.
The fix?
Remove three bolts and insert them in the jack screw holes.
Remove the pulley.
Reinstall the pulley properly.
Check the pulley for square with the shaft. Always the first step in an alignment job.
Time? 15 to 30 minutes for one man.
Time actually wasted, about 7 man days.
Again.
The very first step in effective problem solving is to determine what the problem actually is.

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

 

[ruggb]

Skogsgurra, thx. This spike isn't killing anything, just causing the ckt to trip out and requiring a finger to reset it. Which is not a big issue if someone is there. But mostly, no one is.

Waross, DUH! you can't determine what the problem really is if you are a parts jockey. And most people won't pay the price for an engineer to figure it out. Have you called for technical support on your computer, ever? It is all about asking the right questions, logic, thinking, and testing skills which you can't get from someone you hire off the street corner. My brother-in-law thinks......he is smart, but it is self-deception. He called a "professional" to fix the burner when I told him I would handle it. Guess what, the pro had no clue, admitted he was an AC guy from SC and just moved to NC and really didn't know oil burners. So who fixed it, me of course.
So, proof that it takes more than thinking.
A final question....I don't know what I should use for the breakdown voltage of the TSV . I'm thinking 40V to cover line variations up to 130V, 36V (actually 36.7) would be closer if the input stays below 130. What is your experience with rural line voltage variations?

 

[LionelHutz]

I find it ironic that 3 people point out that it's not likely a "voltage spike" but you're forging ahead with that idea anyways.

I think you're looking at a UPS or a CVT to actually fix the issue. Or else changing/modifying the system with a design that works better when subjected to the power isssues your vacation home.

 

[waross]

Have you considered that the control board may be failing?

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

 

[ruggb]

LionelHutz It isn't a power failure - my TD relay handles that. It isn't a furnace issue - I have serviced it many times. It only happens when there is a weather or maintenance related issue like a blown up xfmr. A brown out won't do it based on my circuit analysis. 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.
I am not reading that 3 people are saying it is NOT a spike. But I may be totally missing something. If you can define the failure mechanism for something other than a spike then I would be oh so glad to investigate it. AND you can be VERY technical as I am a BSEE.

 

[ruggb]

waross - I have considered that there may be an issue with the control board. The fact that it only takes 15 sec for it to trip instead of 30 may mean the R/C ckt values have changed or were never right. It has been doing this since 1996 when my inlaws purchased this dbl wide.
Based on its history, and the fact that it only happens when there are power anomalies, my conclusion is the control is OK.

 

[Skogsgurra]

Well, I said it isn't a spike. And Bill said so too. Not to mention Smoked. And, by the way, your eyes are way to slow to observe a spike. All human's eyes are too slow for that. Add the time constant of an incandescent lamp and there you are. No chance to "see" what is happening. At least not if it is a spike.

Are you asking for advice? Or not?

Gunnar Englund

http://www.gke.org

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

 

[ruggb]

Thank you for your time answering. You've been most helpful and I appreciate the insight.