Combustion blower motor on CMF 100-PO runs continuously

[djohnson]

I'm stumped and so are the Pro's. Three different tech's from the propane company have worked on this furnace with no luck. They replaced the following 1) combustion (inducer) blower motor, 2) hot surface ignitor, 3) Honeywell primary controller. IS THERE ANYTHING LEFT???? The company's service manager said the tech's he's sent to work on this unit have a combined experience of over 30 years and their solution is a new furnace. They will not work on it any more. JUST GREAT. Here's the story. The furnace is a Miller CMF 100-PO with a serial #CMF8906-00385. The burner model is a Nordyne PGB-1-SP, PGB-1-DI. The whole burner gun unit did not come with this furnace. The original burner was gone when we bought the home. There was just a hole in the box. I purchased this used burner, bolted it in, plugged it in, and connected the thermostat. The propane company connected the gas and it worked fine for the first few days. Then I noticed the inducer\combustion motor running continuously and the heat cycle not going any further. I shut the furnace down for a minute, then started it again and it ran fine. This happens once or twice a day and requires you to reset the furnace by shutting it off and then restarting it by the thermostat. Otherwise the combustion motor will run for hours without the centrifugal switch at the end of this motor clicking in and continuing the heating cycle. Whatever activates this switch must be the problem. Is there a relay or a sensor that would cause this click that seems to open the gas valve and ignite the furnace? As I said before almost everything has been replaced and is new. All except the gas valve and the stuff in the little tan box that the Honeywell primary controller is mounted on. Any help or direction would be appreciated.

[Robert]

Hi,

I would start with the used burner. That is an Oil Gun furnace with a Gas Gun burner installed.


With that, then 3 Techs and numerous parts replacements, kinda hard to advise further from here.


Thanks,
Robert

[djohnson]

I had thought that these Miller furnaces were generically made to accommodate either a gas or oil gun. The nameplate under "Performance Data" lists gun models for both gas and oil. It says "Gas Fired Furnace: Listed Burner Model" - Nordyne PGB-1-SP, PGB-1-DI. "Oil Fired Furnace: Listed Burner Model" - Wayne M-SRH1, M-EG1 or Beckett AF-15. I had also thought that these could be changed "in the field". Is there a difference in the firebox?
I noticed something called a "time delay relay" for Miller furnaces in your parts section. Could this be a possibility? As I said almost everthing has been replaced with new and the symptoms are the same. The combustion motor is supposed to evacuate the box of residual fumes to prevent an explosion. This period lasts approx. 3 minutes then the "click" and the burner starts. Is this the relay that does that? It is part #105144000.

[hvac1000]

This is taken direct from Nordyne/Miller

Note: Type 12S Series are time delay relays used as sequencers on electric heating products. (((12S includes the part number you were asking about 105144000 time delay relay for electric furnaces only. )))

The time delay you are talking about is for a electric furnace.

At this time I can no longer be of assistance. The work that needs to be performed on your unit should be done by a professional.

Since the company you contacted did not help you after all the trips I suggest you contact a local company that ONLY services Mobile Homes and there style furnaces. This message is being sent to you for your own safety.

[Robert]

Hi,

I concur with HVAC1000 on this. As stated earlier, at this juncture, getting a experienced Tech in there is best and safest.


There is way more to this than you are thinking and the reply I gave is in your best interest.

Just for your knowledge, myself and HVAC have a combined 68 years between us in the HVAC Service/Repair/Install trade.


You are guessing at problem and it is dangerous enough with Nat. Gas, but way more so with Propane.


This is for your safety and your families.


If they could not resolve it in 3 trips, either they are not qualified, or the furnace is in need of replacement.


You will need someone on site with experience with that unit.


Take care and best wishes,
Robert