transformer

bomag

Domestic oil burner seems to have a transformer issue.

It will work fine for 5 cycles or so, then not fire upon start-up for ten seconds or so, thus getting some nasty "explosion" issues.

The issue started with a pump replacement; maybe the pump is "leaking out", and when it re-fills and starts a flow, the fireworks begin.

Transformer works on a bench test. I'm wondering if they fail completely or intermittently.

It's been through several new nozzles; new electrodes; fussed with the settings.

EdTheHeaterMan

Old style transformers can have an issue of getting weaker as they warm up. Electronic ignition not so much but can have other intermittent issues, though more rare.

If your control is set up for intermittent ignition (Formerly call constant ignition until the 1970s) then as long as the burner is operating the transformer is energized with 115V allowing for the transformer to warm up. The warmer windings on the 5th try might not put out the full voltage causing a cooler spark or no spark at all.

Clean ignition parts, electrodes, insulators, turbulator/bracket, or flame retention head are very important. Carbon buildup can actually conduct electricity to a place away from where the spark is needed I would think about replacing the Ignition transformer with electronic ignition. Usually bolts up to the same place with little or no adjustment.

bomag

This would be the constant ignition. How does the electronic ignition differ?

The retention head has some carbon build-up; might be an issue.

SuperTech

If replacing an ignition transformer with an electronic igniter I would also consider installing a new interrupted ignition primary control. The electrodes and electronic igniter will last much longer with interrupted ignition.

STEVEusaPA

You should get some professional help. You're almost out of parts to replace, and you still need to do a proper set up of your draft, smoke and combustion.

I personally have gone back to the old school transformers and interrupted ignition. Old school can be tested and ohmed out, and is usually foolproof (to me).

Electronic ones can fool you. I've told the story before about a nuisance lock out burner a few years ago.
Checked the electronic ignitor (Beckett) every time (as well as all the other things we check) as per manufacturer's instructions. Thought I was going crazy because I couldn't find out why. Even brought my father out of retirement to go with me. When I went out to the truck, he wanted to show the H/O how he checks the spark and it was dead, right then, right in front of him. I replaced it with an old school one and it never happened again. However, I took that igniter and put it on my shop furnace. It's still running, at least 5 years now and never failed.
Also up to 3 years ago, I couldn't get more than a year out of some Carlin 41000 igniters. Spark good, coil resistance good, but would fail milliamps test, dipping below 300.
Maybe the new Carlin igniters are better, might give them a shot eventually.
Heat and poor ground seems to affect the electronic igniters, not so much on the transformers.

MaxMercy

I loved calling dad to help solve a head scratcher. Reminded me of the old days when we worked together and it made dad feel good if he cracked the problem, and he often did. Wish he was still around to call..

STEVEusaPA said:

Old school can be tested and ohmed out, and is usually foolproof (to me).

One word of caution with using an ohmmeter, the ohms don't always tell the whole story. A transformer winding can read (for instance) 500 ohms, but have a single shorted turn. If there's a few thousand turns, the resistance won't change for a shorted turn but a single shorted turn will kill the Q of the coil turning it from an inductor into a resistor.

If a transformer fails an ohm test, it's bad. But if it passes an ohmmeter test, it can still be bad.

STEVEusaPA

Interesting.
But I've never had that situation with iron core transformers for oil burners. If it fell out of range it was replaced and the problem was solved, if it was in range, it stayed and the problem was solved with it being something else.

Big Ed_4

What is the pump pressure set to , What is the CO2 reading ? If you can not answer call in a pro . My guess it would have been cheaper from the start ...

EdTheHeaterMan

Carlin now has a 5-year warranty. So maybe they fixed the issue and need a marketing ploy to get the @STEVEusaPA's and myself who had bad experience (I also switched from Carlin for the same reason) to try them again.

I had one on each truck in case I needed to replace one. Was easier than redesigning the old one with a different brand.

I still like the electronic over the transformer.

TRANSFORMER LOOKS LIKE THIS

This is essentially a squared-off bowl filled with a Tar-like insulator that the actual transformer is submerged into. The insulating mixture cools and hardens then the base plate is added so the part can be affixed to the oil burner


ELECTRONIC IGNITION LOOKS LIKE THIS




This is a picture of a fouled ignition system

If the carbon builds up and bridges the gap between the electrodes, there will be no ignition spark. This can happen with either ignitor, electronic, or transformer.

EdTheHeaterMan

If you replace all the parts and still have an issue, Will you have saved anything money with this course of action? If the nozzle and electrodes are fouling like the picture I just posted, there may be a problem with the adjustments. This may be a result of poor ignition over time, causing wet fuel to blowback onto the nozzle and electrodes. As the burner operates the heat from the flame cooks the oil and a thin carbon coating is baked on to the parts. Layer after layer builds up over the season .

This is only one possibility, there are many others including poor draft, wrong pump pressure, wrong nozzle... the list goes on.
Fix THAT problem and you may find no parts were needed in the first place.

MaxMercy

STEVEusaPA said:

Interesting.
But I've never had that situation with iron core transformers for oil burners. If it fell out of range it was replaced and the problem was solved, if it was in range, it stayed and the problem was solved with it being something else.

It's not all that common, but when your career is electronics, you see this happen. I remember coming in on a job where another technician spent half a day trying to troubleshoot an issue with a machining center. When I told the tech the solenoid coil was bad, he said it was impossible because the plunger moved freely and it read 210 ohms, the same as a brand new one. It was a two hour job so he didn't want to change it. The coil had at least one shorted turn so it read OK on the ohmmeter but had virtually no pull and was drawing ridiculous current.

In the case of these particular transformers, it's not really an issue. If you put 120V on the primary, you get 12-15KV or so on the secondary and draw a nice arc, so they're easy to check and only two minutes to swap out. But any transformer can pass an ohmmeter test and be just a chunk of iron and copper.

bomag

Thanks for the responses.

This is a ranch house in eastern MT, far from anywhere. A technician with the knowledge of this board is probably a thousand miles away. The infrastructure here is for propane heat; anyone I talk to just wants to replace the whole furnace.

The unit dates from the 1950s; I started maintaining it in 1972: just tips, filters, cleaning and oiling; everything else is original to me, until an overdue change of the pump last year (it just wouldn't prime after any glitch from the supply tank, unless I pressurized the system, and eventually that didn't work anymore) and the electrodes this year.

Unit runs really quiet and smooth; seems exceptionally well built and trouble free compared to what my neighbors have.

The transformer is now failing my bench tests, so I think I'll get one of these: here, unless someone has another suggestion.

mattmia2

BTW the potting in tar is mainly to make it quieter, to make parts less able to resonate in the magnetic field.

With the xfmr having a high voltage secondary, it can develop a break in the insulation that can short to ground when it is energized but won't show up with an ohmmeter.

How did you adjust the new pump?

STEVEusaPA

Why wouldn’t it show with an ohmmeter, the leads are disconnected and the transformer isn’t grounded.

mattmia2

The 10kv or so can jump through the air in a crack in the insulation. The ~4v from the ommeter can not. Usually if the insulation is organic it carbonizes and sometimes you can measure that with an ohmmeter.

ChrisJ

Ergo, the reason Meggers exist.

Testing things with only a few volts often doesn't cut the mustard.

STEVEusaPA

I appreciate all the expert transformer/ohming info. But for these transformers, I'm talk about a simple, manufacturer-recommended test I've been using for at least 20 years:
-When the test says the transformer is out of their recommend range, replacing the transformer solved the problem.
-When the test says the transformer is in their recommended range, the problems was something else that was solved.
Simple example:
-Allanson iron core transformer, disconnect leads.
-Read primary leads, should be 2.4 ohms.
-Read each secondary post to ground, should be 9200 ohms, and should be same reading each post to ground.

And other manufacturers have different ohm ranges for France, Webster, & Dongan. They've never failed me with a simple meter.

MaxMercy

ChrisJ said:

Ergo, the reason Meggers exist..

And ringers. A shorted turn in any coil will collapse most of the magnetic field rendering the coil useless. One or two shorted turns do not show up on an ohmeter since most coils have at minimum dozens of adjacent windings and many of them having thousands of windings. A winding shorted to the one next to it may reduce the total resistance of the coil by .01 ohms or less depending on how many windings on the coil. When a normal coil reads (for instance) 520 to 530 ohms, what does a tenth or less of an ohm change tell us?

What I always told my students was that if a coil failed an ohmmeter test, it was bad. If it passed an ohmmeter test, look for high resistance leakage between any winding and the case, or any winding to each other and of course look for shorted turns. Not common, but it happens enough to test for.