Carrier Furnace - BLOWER ONLY, No Induction, No Flame

[whose2know]

I've got a Carrier 58SSB furnace with a problem that has been diagnosed as a pilot burner assembly issue. I have a separate thread that discusses the issue. However, since the part store was not open today, and it seems the problem was getting worse with the gas shutting on and off, it now appears the furnace hit a safety limit and now only the blower works (main blower, not induction). What do I need to do to reset the furnace so I can get it running again when I replace the pilot burner assembly? I've attached some links to pictures below of the wiring.

Carrier 58SSB Wiring on Flickr - Photo Sharing!

Carrier 58SSB Board on Flickr - Photo Sharing!

Carrier 58SSB Induction Fan & Pressure Switch on Flickr - Photo Sharing!

I've got the electric heaters and fireplace going tonight...luckily it has warmed up the past few days. Yes, I know this thing is a dinosaur, and I'm planning on replacing it in the spring when the prices aren't sky high due to cold weather.

Please be as specific as possible and refer to the pictures if possible when providing advice.

All help is appreciated.

[SeattlePioneer]

Carrier 58SSB Induction Fan & Pressure Switch on Flickr - Photo Sharing!

Two likely causes----

from the above picture, check the draft limit switch which may have opened with the erratic operation of the burner.

Follow the orange wires to the switch in the upper right corner of the cabinet. Push the red button to reset the switch if it's open. If it's the problem the fan will shut off and the inducer motor will switch on if the thermostat is calling for heat.


The other likely cause would be lack of necessary 24 VAC power for the furnace ---- when you turn the 120 VAC power to the furnace on, do you hear the "clunk" of a relay closing? If so, you have that voltage. No "clunk"? Check the transformer secondary for 24 VAC across the Sec! and Sec2 terminals on the circuit board --- the transformer looks like it might be toasted

[whose2know]

Thanks Seattle Pioneer. It turns out the system blew a fusible link on the way to the high limit switch. Hopefully I'll get a new fusible link tomorrow along with a flame sensor and give an update tomorrow.

I checked the volts before and after the fusible link and determined it unfused...I jumped it and the induction motor started running. Don't worry...I'm not leaving it on that way...electric heat tonight for me...but I jumped it to determine the system would kick on.

[SeattlePioneer]

And this is a perfectly respectable older furnace ---- on the order of 75-78% efficient.

There is a reasonable argument these days for replacing it with a 90%+ efficient furnace, but what you have isn't bad.

Among 90%+ efficient furnaces, there are commonly three styles---

single stage
two stage and
variable input furnaces.

Single statge furnaces have one fixed BTU input and depend upon the thermostat to maintain a constant temperature by turning the furnace on and off.

Two stage furnaces have a low BTU input used during moderate and mildly cold temperatures which permits the furnace to run longer at lower input and a slower fan speed, arguably increasing comfort somewhat, reducing noise and slightlyincreasing efficiency.

There's a high BTU input and fan speed for especially cold temperatures

At the high end are continuously variable input furnaces, which can adjust the input through a wide range, not just two stages.

The single stage furnace is the lest expensive, the two stage furnace in the middle and the continuously variable furnace the most expensive and complex.

Any of the three would be a reasonable choice. If cost is critical, a single stage furnace is a reasonable choice. You gain lower cost to purchase it and it's somewhat simpler to maintain at the price of being a little noiser and draftier.

Buy a continuously variable furnace if spending the extra money is not a concern of yours.

[whose2know]

I replaced the pilot assembly yesterday and tried to get a new fusible link (the parts supply shops don't have it in stock). So I jumped the fusible link to get the unit running and it is working well.

I called a HVAC service company yesterday, gave him the fusible link part # and told him to come out, do an inspection/cleaning and install a new fusible link...he said they had one in stock...so he came this morning. He didn't have the fusible link with him (said he had fuses on the truck) and said they normally just cut out the fusible link. He said he could get one and return in a few days. I told him not to bother with the inspection/cleaning. I ordered a fusible link and will replace when it gets delivered.

The sad thing is I specifically asked that they have the part with them when they come out and gave them the part number...the HVAC company would have been the first I would have called to bid on a replacement furnace this spring...now they won't even make the list.

Seattle Pioneer, what units do you recommend/why and which ones should I steer clear of/why? I currently have a Carrier, but I have read that Carriers now have a secondary heat exchanger that tends to break down, rather than using a stainless steel EX. I replaced a unit in my former house with a Trane. I'm looking for the right value/quality mix. Thoughts?