I had an LUF80B84 installed about 5-6 years ago. I’ve had to replace the transformer 2 times already and it produces alot of soot, a tremendous amount. I heard a boom and the furnace stopped working about a month ago and the service company came out and said it needed a cleaning. It looked like it had not been cleaned in 5 years the guy said, but it was only a year and a half. He said it was probably a delayed ignition which is usually a bad transformer, but he did a cleaning and changed the nozzle, filter. The guy also said my stack was very soft and should be replaced soon. Since the furnace sounded good he thought the very dirty furnace might have caused the problem and to see what happens.
Well the very next night I heard an even bigger boom and the stack literally blew into 5 pieces. I had them come out again (different guy) and he said the same thing, it is usually a weak or bad transformer. So he changed it and replaced the stack. He changed the nozzle again to be sure. Everything seemed good for about 3 weeks, but now since friday my furnace reset button trips about 3 times a day since Friday, 3 days now.
I have been reading alot on the web and see a note about the A coil for the AC can get clogged with dust, etc and cause too little air flow. This causes the exchanger to get too hot and this can trip the reset. This could be the cause since my air filter was dirty about 6 months ago and I took it out and meant to buy a new one. Well I never did and we have alot of dust and spiders where I live.
The furnace seems to run for a few minutes then turns off for a couple of minutes then comes back on. It just seems to happen so often and yet the temperature in the house doesnt get up to the set temperature. I have read that if there is too much back pressure that the air flow rate goes down and may cause the temperature on the armstrong furnace to go outside the stated range. Go to pages 19 and 20 for LUF80B84/95D12R http://www.eccohtg.com/links/Product%20Listing/Heating%20Equipment/Armstrong%20Oil%20Furnaces.pdf
If I leave the thermastat on AUTO, the furnace blower runs in low mode, i think, so the temperature may go outside the range on page 20 above. The reset button trips more often when I do that, so I have been leaving the FAN in ON mode for the higher flow pressure. The reset still trips, but not as often.
I’m gonna clean the A Coil tomorrow, but I was wondering if there is anything else I should consider. Thank you very much for any information.