RicM from HVACTV.com needs help with heating question

Nron_13

check the polarity of the power coming in to the system and make sure the ground is working properly ,ghost voltage from bad wirring can cause problems too

Ric Murray

problem with induction fan

Guys:

I hope you might be able to help me with this problem. I have had 5 service calls and spent over $500 and it's still not resolved. Recently my hot air furnace started making noises, even though the thermostat in in the "off" position. I went down to look and the induction fan was coming on, running for about 5-8 seconds then turning off. Repeating this every few minutes. The unit is 3 years old, nameplate on it is "Concord". Made by Armstrong/Lennox. 100,000BTU single stage 80%. The only way to stop it is to kill all power to the unit. First tech said fan control circuit board. Replaced that, still did it. Next tech said Honeywell smart valve. Replaced that. Still doing it.
Smart valve flashes 6-5 error code which is "soft lockout, flame has gone away". But of course the flame was never there, as thermostst is in off position. Tried disconnecting the thermostat and circuit at the unit, still did it.
Were should I go next? The original installer is out of business, and I have little confidence in the techs that have been showing up.
Sure hope you guys have ideas, it's getting cold this weekend!

Thanks,
Ric

Jeff Lawrence_24

Ric

I'm not that familiar with Concord or Lennox, but did the problem just start? Was there a storm or another tradesman (or you) doing electrical work in the house?

Just kinda thinking out loud, but are you sure it's wired on the high voltage side correctly? If the hot and common are reversed, that may be causing your problem.

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Dale

Fan board

If the fan control board was replaced and the inducer starts with the stat wires removed at the board terminal screws I think you may have a limit switch that's intermittent. I would pull a wire off a limit and see what happens, some furnaces start the main blower for instance. Some go through a purge. Does your furnace have a purge timer separate from the board, if so that may be the problem. The other thing is to make sure the back of the fan board isn't touching anything and transferring power to the inducer relay from the back. As the other post suggested a lightning hit makes alot of weird problems.

Glen

all good suggestions -

and to add one wrinkle. Measure the ac voltage between L2 and ground. Any spurious voltage there will set off the fan control board into overload and recycle mode with the subsequent error you are reporting. Could be caused by any number of electrical problems - have you hung any pictures recently????

Dave Yates (PAH)

polarity, ground & a pinch

Ric,

Where can I find customers who pay for non-functioning work??? We'd be expected to return at no charge or put back the original parts with credit for the new ones if we failed to corectly diagnose the problem.

That said, polarity is critical for high eff equipment. We had a furnace behaving much the same way. Power wiring was color-correct (black to line, white to neutral & green to ground), but the "electrician" who installed the new breaker panel had run the black wire (on this breaker only!) to the ground bar and placed the white wire on the breaker - D'OH! Damn near got our mechanic electrocuted.

We've seen very erratic behavior when proper grounding was lost too.

And, there's been far too many instances where we've encountered wires pinched behind controls or in wire-clamps that have caused a compromise in the shielding that lets voltage stray at times. A close examination of wiring anywhere it can be pinched and come in contact with a neighboring wire or metal is something we'd pursue. We once had a Sanyo unit acting up at odd times in an old folks home and after several very frustrating non-productive trips - at our expense - my lead tech and I were standing on the attic walkway above the deep blown-in insulation. We'd checked everything and beyond - to no avail. An 8-conductor communication cable ran between the indoor and outdoor unit. While standing there scratching our heads, I tugged at the communication cable. It had planty of slack, so I kept pulling it up out of the blown-in insulation. Imagine our surprise to find an octopus-shaped tangle of bare wire where some lunk-head had joined two cables together! Each splice was neatly tied in a knot and some care had been exercised to spread them apart. Unfortunately for us, the insulation had settled and two of the wires were just barely gapped - but close enough for stray voltage.

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Unknown

Ric's problem

Do you have a power stealing programmable thermostat or one with a triac backplate. This will cause the inducer to come on then shut off itermittently for no reason at all due to "white noise" (electronic interference) All you need to do is put an isolating relay between the thermostat and the electronic board. It is not polarity because the SmartValve you have has a 10 flash code for polarity problems.You did say you disconnected the thermostat so if it kept going after that it has to be either the board of a limit opening.

I am not at home or I would give you a call, I am in Georgia on my way to Florida.

Is the system fan also coming on? If so it could be one of the limits is opening prematurely causing what is called the "self healing" feature of the board to function.

Feel free to give me a call on my cell phone tomorrow 401-580-2149.

rick in Alaska

connections

I don't know about this unit either, but if it has molex style connectors on it, try pushing in on all of the wires.I had a couple of Coleman oil furnaces go in to a constant fan mode because of loose plug wires. Might be worth a shot. Best of luck. Rick in Alaska

RoosterBoy

could it be a temp sensor safety devise?

something that would force a fan to roll would likely be a safety.