Furnace Problems

[Tim Frank]

Re: Furnace Problems

When was the last time it was properly cleaned and inspected?

 

[jlinder]

Re: Furnace Problems

Your manual is here PDF file
http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/58ss-1si.pdf

Dolluper -
Thanks for the link. The manual is a big help.

In reading the sequence of operation it says that once the thermostat calls for heat the pilot valve opens, spark starts, and the inducer fan relay closes. Then the sail switch on the inducer motor closes a safety switch.

What is the inducer motor? Believe it is the motor at the top that draws combustion gases out, but it is not identified in the drawings.

I do not see or hear any motor start when the pilot lights. Suspect my problem is there. Either the relay or the motor has gone out. I will be checking when I get home today.

I will also check this web site for more information. Maybe they have another manual on the unit.

Thanks.

 

[dwco5051]

Re: Furnace Problems

Dolluper -
Thanks for the link. The manual is a big help.

In reading the sequence of operation it says that once the thermostat calls for heat the pilot valve opens, spark starts, and the inducer fan relay closes. Then the sail switch on the inducer motor closes a safety switch.

What is the inducer motor? Believe it is the motor at the top that draws combustion gases out, but it is not identified in the drawings.

I do not see or hear any motor start when the pilot lights. Suspect my problem is there. Either the relay or the motor has gone out. I will be checking when I get home today.

I will also check this web site for more information. Maybe they have another manual on the unit.

Thanks.

I believe your assumption is right that the inducer motor described is a short description for a "draft inducer."

 

[DaleT]

Re: Furnace Problems

Couple years back my parents furnace had a similar issue. The inducer (just learned what it was called here) was the culprit. During the summer months some condensation had built up and caused just enough resistance/rust on the motor to not allow it to start and spin freely. All it took was a spin by hand to free it up and the furnace worked perfect. Oddly enough, the scenario has not occurred since.

 

[tx1961whaler]

Re: Furnace Problems

What is the inducer motor? Believe it is the motor at the top that draws combustion gases out, but it is not identified in the drawings.

I do not see or hear any motor start when the pilot lights. Suspect my problem is there. Either the relay or the motor has gone out. I will be checking when I get home today.

Correct. It is the small motor attached to the vent pipe. It usually comes on for a few seconds before the starting sequence begins.

 

[dolluper]

Re: Furnace Problems

High efficiency operation.
24 vollts is always present to the thermostat R terminal.
1.Thermostat sends 24 volts through white wire to furnace.
2.Furnace checks pressure switch, and safety switch's for proper positions (open/closed).
3.Draft inducer blower motor, starts to run.
4.If vent and vacuum hoses are clear the pressure switch, closes. (only a few pressure switch's open to prove venting)
5.After inducer blower purges the heat exchanger, either a pilot lights, a hot surface ignitor (HSI), or a spark begins.
6.If the furnace is an intermittant pilot model, once the pilot lights, current is sent through the flame by a flame sensor, if current is present through the flame the main gas valve opens and the burners ignite.
7.If the furnace is direct ignition, The HSI or spark ignites the flame. A flame sensor passes current through the flame, if current is present the main gas valve stays open and heat exchanger begins to warm up.
8.Most high efficiency furnaces then use an electronic timer on the circuit board to start the blower after the burners are proved.
9.Thermostat opens when desired temperature is reached.
10.The gas valve closes, burners extinguish, and the timer starts again to turn off the fan.

 

[jlinder]

Re: Furnace Problems

Finally found the problem. After tracing and checking through all the electronics and relays (the diodes that power the inducer relay, tearing apart the relay, checking the motor, etc.) I found it.

There was no 120v supply to the motor even with the relay shorted. Tracked the wires backwards to a connector on a circuit board in the blower cabinet. I pulled the board out, flipped it over, and found this:

This summer after a thunder storm I had a blown circuit breaker to the furnace. Assume we had a lighting strike nearby. Reset the breaker and air conditioning was fine, so I assumed no problem.

OOPS !! If you look closely to the lower right of the black burn you will see a section of the trace is missing. I also see a couple of bites missing out of the trace at the bottom.

Now I either need to fix the traces with solder or see if I can find a replacement board and hope nothing else is bad.

BTW - the board has a model number HH84AA009 in case anyone has a lead on these

 

[dolluper]

Re: Furnace Problems

I bet the motor ground looks like that too if the wire isn't burnt
patrs link below,on ebay for 100 bones...cheaper here 60
http://part-s-mart.com/carrier-hh84aa009-icm275c-fan-blower-control.html

 

[jlinder]

Re: Furnace Problems

Actually the motor looks good. No burns on the wire, no marks anywhere else, motor has continuity and spins freely.

The only indication I have of any problem is the picture shown (and of course that it does not work)

 

[dolluper]

Re: Furnace Problems

Check the post above link for parts

 

[Gary H NC]

Re: Furnace Problems

Is this the same board? It has a PDF link with it for install....46 bucks...

http://www.patriot-supply.com/products/showitem.cfm/21756

 

[jlinder]

Re: Furnace Problems

It sure does look like it. Thanks.

Really appreciate everyone helping to save me money.

 

[dolluper]

Re: Furnace Problems

Thats an upgrade board Gary found for you ....cheap and neat the way they use an auto fuse

 

[jlinder]

Re: Furnace Problems

Glad to hear it. I just ordered it. Should have it around Tuesday. I will let you know how it works.

Thanks everyone

 

[jlinder]

Re: Furnace Problems

One odd thing to note. When I went to remove this board I of course turned off the power at the switch on the side of the furnace. This is in a small single gang box that has a screw in fuse on it.

Just for safety I thought I would remove the fuse. To test this (not sure why I felt the need to test it) I turned the switch back on to see if there was power. Yep, there was power even with the fuse removed. Pretty obvious the fuse is bypassed and just for show. (I turned the power off at the breaker box once I realized the fuse was not in the circuit)

Question: how important are these fuses on the side of the furnace? The circuit is protected from the main circuit breaker box so it should be safe. If so, why did they put a fuse right on the side of the furnace to begin with? I have seen a number of furnaces with this same configuration.

Should I rewire to put the fuse in the circuit?

 

[bruceb58]

Re: Furnace Problems

I don't think the fuse is bypassed. It may seem like it but it isn't. How did you measure this?

 

[dwco5051]

Re: Furnace Problems

One odd thing to note. When I went to remove this board I of course turned off the power at the switch on the side of the furnace. This is in a small single gang box that has a screw in fuse on it.

Just for safety I thought I would remove the fuse. To test this (not sure why I felt the need to test it) I turned the switch back on to see if there was power. Yep, there was power even with the fuse removed. Pretty obvious the fuse is bypassed and just for show. (I turned the power off at the breaker box once I realized the fuse was not in the circuit)

Question: how important are these fuses on the side of the furnace? The circuit is protected from the main circuit breaker box so it should be safe. If so, why did they put a fuse right on the side of the furnace to begin with? I have seen a number of furnaces with this same configuration.

Should I rewire to put the fuse in the circuit?

The branch that the furnace is on could have a greater capacity than the furnace is rated for. Today SOP is to run a dedicated circuit to the furnace. If the furnace is on its own circuit of the right ampacity I would replace the fuse/switch combination with a service disconnect or a switch only. The next person to work on this unit may not be as smart as you and could stick their fingers in where they don't belong after removing the fuse only.

 

[dwco5051]

Re: Furnace Problems

I don't think the fuse is bypassed. It may seem like it but it isn't. How did you measure this?

It is possible the present fuse/switch combo was wired wrong and they broke the neutral rather than the hot side if it is a 120v feed. Ran into this once where a circulator was switched this way and I wasn't smart enough to check for power after turning off the switch. Had the pump in my lap after unbolting it, squatted down on a wet boiler room floor, and started to disconnect the wires. Almost did a somersault trying to let loose of that pump. Never made that mistake again

 

[jlinder]

Re: Furnace Problems

The way I "measure" to see if the fuse was in the circuit was to remove the fuse entirely and found the furnace still powered up.

Is the circuit breaker bigger than what the furnace should be fused at and is the fuse to protect that? Maybe that was the reason the fuse was added. I will check the size of the fuse when I check the switch. Of course that does not answer why the furnace still has power with the fuse removed.

Could the fuse be in the neutral instead of the hot wire? Possibly. Perhaps the circuit completes using the ground with the fuse out (if the fuse is breaking the neutral). I will find out tomorrow when I open the switch box. (I opened the breaker so the power is removed for now.)

Reminds me of my first house. Alone in the house and woke up in the middle of the night covered in sweat. Winter but 85 degrees in the house. Furnace cranking out the heat.

Lowered thermostat but furnace still running. Turned switch off at furnace but still the furnace would not turn off!! By now starting to think I was in the twilight zone. Finally killed the breaker and the furnace went off.

In the morning I found that both the thermostat and the switch were bad. Replaced both and all was good again. Maybe the switch was bad for a long time. If the thermostat had not gone bad I could have shut the power off at the switch and found out it was bad the hard way.

Old trick I was taught a long time ago was if you had to touch a wire that could be hot (like rewiring a switch or ceiling lamp) do a quick slap of the wire with the tips of your fingers from the back of your hand. That way if there was power on it for some reason your muscles could not latch onto the wire and the slap would make the contact very short.

 

[rbh]

Re: Furnace Problems

We deal with lightning issues every so often, and it is incredible how it will jump to the ground side, all it takes is a carbon trail or for that matter dust build up.