Miller CMF 80 (again)

[Paula39]

Hey everyone. I have posted before concerning our furnace problems, mainly the ignition process (intermittent) which was thought to involve the centrifugal switch on the booster motor. We also had low heat quality and cycling problems, etc. To update since my last post they tried an additive in case of condensation in the fuel, and we had run out of fuel completely only to discover a leak in the tank. It was repaired. Then, after a complete loss of ignition the glow bar was replaced (last one was a few months old also when we replace air cone as mentioned in last post). Things were good for awhile. The tech installed a new type Glow stick it was called, and said it was universall but did not guarantee would be perfect for our furnace. He also diagnosed the main switch not working properly and thermostat which most definitely helped the low heat quality and ability to cycle to achieve set temp. We were nice and toasty- for a week. Yet again booster motor would continually run with no ignition, however "resetting" (opening door, shut thermostat off & back on) did not cure the problem this time. With a tap with a rubber handle on the bottom of the motor, it seemed to trigger correct ignition. Although it would sometimes take 2-3 tries and it would ignite and heat. The motor felt a bit warm and we thought finally that had to be failing as we thought and it was time to replace. As he suggested we installed the new booster motor (& centrifugal) today. Ran fine for a couple of hours and brought the room back to temp. But once again motor runs but no ignition. It does signal the ignitor bar but it does not glow of course you hear it try to ignite but with no glow the gas shuts off and motor continues to run. Also fan switch was replaced months ago and we did try about three years ago (when we first had problems) a new HSI box. That never helped, though it is rather new. Since we have had successful ignition the glow bar must be fine. But still unsure of this "new type" he used.We are at a loss. It has been a rough winter and this is getting expensive paying the labor for after hours (isn't that always when you lose heat) There has been improvement but this one problem is so stressful. We will call the tech tomorrow but as of now no heat again and just wondered if anyone has any more suggestions. We think we find success but then we get surprised!!! And it is NOT a pleasant one!Thanks for any help.

[Paula39]

Just to update and maybe to help others, the tech just left. He has come to learn that Miller furnaces seem to prefer their own proprietary parts other that the HSI unit. He removed the "universal" Glow Stix ignitor to put back in the the usual. Works like a charm- again. The other seems to work well with furnaces that have a separate flame sensor. It burnt out in a week in our furnace. He said if any other problems continue he will refer directly with Miller experts for their advice, but that parts we did replace made a world of difference in the cycling and heat quality. Hope Dan-o made out ok with his too.

[Robert]

Those answers are here when asked. There are 2 ignition modules, one for remote sensor and one for a hot surface ignitor that also acts as a flame sensor once ignition is complete.


Alot of hvac equipment needs design components and do not work with universal, not just Miller.


You should never place a universal component on any unit without first hand knowledge of its workabilitity and if it's compatible to the unit in question.


We have all needed parts and knowledge/experience, what we do not have is the benefit of being there to see and test.


Hopefully, all is taken care of and remains that way.



Thanks for inquiring and update,
Robert