Anyone Know about Furnaces

[arbita1]

I'm having a problem with my furnace/AC system for the past year or so. It is a relatively new system, probably only about 4 or 5 years old.

The fan is clicking on and off frequently for no reason. It is usually just a short burst...like someone turns it on and then right off. I can hear the relay on the furnace clicking on and off when it does this. Sometimes it will click multiple times. It happens intermittently and nothing seems to trigger it. If it happens too much, I will usually just shut the power off to the unit and turn it on the next morning.

The previous owner of the house had the system installed. I had the company (Bell Heating and Cooling) who installed the unit come and take look...twice. They charged me $ 100 and did nothing. So I've been living with this for now, but it is getting annoying. I feel like it may be the control board, or the relay that is going bad, but I don't want to just start replacing parts for no reason.

Anyone have any ideas? I can provide more information if needed.

[unclebilly]

Most furnaces are pretty darn simple.

Usually, a furnace start sequence goes something like this:

Run the fan for 30 seconds to a minute.

There is a pressure switch or 2 that must see either mild suction or pressure from the fan to go to the next step which is where the burner is fired.

Pull the cover off of your furnace and turn it on. Watch the LEDs for an error code - usually there is a sticker inside the panel that explains the error codes which will be 3 short flashes and 2 long flashes or whatever.

My guess - your problem is a pressure switch. Depending on the model these can be fairly expensive but for around $15 you can get a universal replacement that is adjustable for your application at any heating supply store.

[nynor]

the positive and negative wiring is reversed. this is easy to test.

[Brian 162]

Sometimes if you have one of those cheap set-back thermostats they will allow a small amount of stray voltage to activate the ventor or fan motor relay.Once the relay is energized the circuit breaks because the trace voltage can't keep the relay pulled in.

[arbita1]

Originally Posted by nynor

the positive and negative wiring is reversed. this is easy to test.

I think you may be on to something. I checked the LED light for an error code as Unclebilly suggested. I came up with "Line Voltage Polarity Reversed".

So what do I do now? Reverse the connections?

[GH85Carrera]

Originally Posted by arbita1

I think you may be on to something. I checked the LED light for an error code as Unclebilly suggested. I came up with "Line Voltage Polarity Reversed".

So what do I do now? Reverse the connections?

No, un-reverse it

[stomachmonkey]

Originally Posted by arbita1

I think you may be on to something. I checked the LED light for an error code as Unclebilly suggested. I came up with "Line Voltage Polarity Reversed".

So what do I do now? Reverse the connections?

Yes, then call heating co and get your $100 back.

[GH85Carrera]

Originally Posted by stomachmonkey

Yes, then call heating co and get your $100 back.

+1 And scratch that company off of your list of service providers.

[arbita1]

Originally Posted by stomachmonkey

Yes, then call heating co and get your $100 back.

Originally Posted by GH85Carrera

+1 And scratch that company off of your list of service providers.

LOL...both times they came, I wasn't home so they dealt with my wife/me over the phone. The first time they said the cover was loose. The guy tightened the thumbscrews on the cover and charged $ 100. I knew that wasn't the problem. I called them back and told them WTF...it's not fixed. The second time they came they changed the batteries in the thermostat. Now you see why I've been living with this.

There is an emergency shut of switch on the wall that goes to a switch mounted on the unit (like a light switch). Both of them do the same thing, I'm not sure why they put an extra switch on the unit. I guess from there it must go into some sort of juction box inside the unit? Would this be where I switch the connections?

[billybek]

There should be a junction box inside the furnace where the power comes in. Have a look at the colour of the wires. The white neutral (designated conductor) must be connected to the white wire in the furnace. Even it they are correct, that doesn't mean that it hasn't been switched at another connection box somewhere along the way.
Do you have an electrical meter?

[arbita1]

Originally Posted by billybek

There should be a junction box inside the furnace where the power comes in. Have a look at the colour of the wires. The white neutral (designated conductor) must be connected to the white wire in the furnace. Even it they are correct, that doesn't mean that it hasn't been switched at another connection box somewhere along the way.
Do you have an electrical meter?

Yes.

[nynor]

check at the breaker box to make sure they aren't reversed there. if they are correct, reverse them at the furnace.

Originally Posted by arbita1

I think you may be on to something. I checked the LED light for an error code as Unclebilly suggested. I came up with "Line Voltage Polarity Reversed".

So what do I do now? Reverse the connections?

[billybek]

The black (red, blue whatever) lead should read 120 VAC aprox. to ground. The neutral white lead shouldn't read a voltage to ground (maybe a small residual voltage).
You could just reverse them but I would suggest finding out where the problem lies and correcting it there. It is actually dangerous to run an appliance or chassis grounded tool with the polarity reversed as you might end up with a potential voltage to ground (think sink/tap) and if you are touching both you might end up getting lit up a little (or a lot, more people are killed with 120 than any other voltage)
Cheers!

[arbita1]

Ok. I'll check it out tonight and report back.

When you say "to ground", am I checking, say the black wire to the bare copper ground wire and getting 120VAC?

I'm good with DC, but have not mastered all the aspects of AC yet.

[Zeke]

Yes, if you jump the black to the white or ground through your meter, you should read 120v. Then, check the white to copper, should read nothing. If you have reverse polarity, the white to copper will be hot. At that point, bare copper to black would read nothing. If both white and black to bare copper are hot, that's 220v. I don't think you want that.

So, if the white to bare is hot and the black to bare is not reading, you have classic reversed polarity. Something up the line is not right.

At that point, given that you know little about AC electricity, I'd hire an electrician.

[arbita1]

I checked the polarity today. Everything seems fine. The black wire has 120V to ground and to the white wire. The white wire has nothing to ground. I then checked the connections from the line voltage junction box to the control board. The black one goes to a contact on a relay labeled L1 and the white one goes to a group of contacts labeled Neutrals. So that all seems correct.

I turned it back on. It hasn't done the on/off thing yet, but the diagnostic code is still blinking 10 times which refers to Line Voltage Polarity Reversed (if twinned see Installation Manual). I don't know what twinned means...I'm guess two furnaces connected together?

Any ideas what I should do next?

[azasadny]

I would post the problem, along with the model info on Fixitnow.com Samurai Appliance Repair Man: Do-It-Yourself Appliance Repair Help for all Brands and Models!. I'm not affiliated with the website, just a very satisfied customer. It's really focused on appliance repair, but they have a HVAC forum, too.

[billybek]

Now make sure the transformer for the board is wired correctly. It may be as simple as reversing hot and neutral on the transformer.
On new equipment, you might see two black wires, but one should have a small white stripe on it. It is worth a look.

[arbita1]

I tried that website. I didn't find much...but I'm not sure what the best words are to search for. I've tried a few combinations. And you have to pay to post new topics.

I checked the transformer. It looks like everything is correct. The white wire goes to the same group labeled neutrals. The black wire goes to a contact on the control board labeled XFRMR. So I think that is all right.

What next?

[billybek]

Could be a board issue. Is it still under warranty?