HVAC experts

[Platypus]

Background: Sometime in the last two weeks my furnace (electric) has started to act strange. It usually kicks on when needed to keep the temp in the room constant, however in this time frame it has started to run completely randomly. It will kick on for 10 minutes, turn off for 10 minutes, etc. Or, it will just stay on for 30-40 minutes and then stop for 5 minutes and kick back on. It seems to get better if I turn it off and turn it back, but only for a little while. The filter is new, I changed it right when this started happening because I was worried it might be the cause of it.

I had my landlord take a look at and she brought a maint guy out who claims he couldn't find anything wrong with it. I didn't have time to deal with it last week but she said if it still acts up to call her again but that the HVAC guy she called didn't find anything wrong.

To me it sounds like the temp sensor is fucked up somehow or that there's a blown fuse or something going on. To add further annoyance to the problem, since the HVAC lad visited there is now a low annoying buzzing sound coming out of the exhaust area (not the vents).

Any ideas would be helpful so when I call back I can suggest he look at something specific. I've seen some coherent HVAC replies here before so I'm hoping you can come through for me on this one.

 

[meltdown75]

Mine was acting similar a few weeks back and I was able to find the solution by Googling the furnace make & model. If you are as lucky as me you can find a forum where someone has posted a similar issue with the same make of furnace.

Mine's an Armstrong Ultra V... the flame sensor was dirty / gunked up. All I had to do was unscrew one screw, pull it out and sand it down a bit with some fine sandpaper... voila, good as new. Works awesome now...

 

[Vette73]

Could be the thermostat, its over heating and turning off, and/or the sensor to detect over heat is kicking on early.

 

[Platypus]

Originally posted by: Marlin1975
Could be the thermostat, its over heating and turning off, and/or the sensor to detect over heat is kicking on early.

That sounds like the opposite of my problem; it runs forever...

 

[amdskip]

Originally posted by: Platypus

Originally posted by: Marlin1975
Could be the thermostat, its over heating and turning off, and/or the sensor to detect over heat is kicking on early.

That sounds like the opposite of my problem; it runs forever...

The thermostat is the brains of the operation though. I'd vote thermostat too.

 

[DarrelSPowers]

Originally posted by: amdskip

Originally posted by: Platypus

Originally posted by: Marlin1975
Could be the thermostat, its over heating and turning off, and/or the sensor to detect over heat is kicking on early.

That sounds like the opposite of my problem; it runs forever...

The thermostat is the brains of the operation though. I'd vote thermostat too.

Yeah, controls guys always screw everything up.

 

[Platypus]

What specifically would be wrong with the thermostat to just have it run forever without turning off / and or / run randomly?

 

[Vette73]

Originally posted by: Platypus
What specifically would be wrong with the thermostat to just have it run forever without turning off / and or / run randomly?

Could be the switch inside is bad, reading temp is off, if its old and use mercury then dust can effect it, etc....


But since you rent have them come out again.

 

[meltdown75]

cheap digital thermostat FTW

they're easy to install

 

[Platypus]

Originally posted by: meltdown75
cheap digital thermostat FTW

they're easy to install

Mine is digital and about 2 years old max. The entire HVAC system is that old.

 

[CPA]

I can tell you it's not a blown fuse. There is generally only one or two in a system and if it's blown nothing would work.

 

[Platypus]

Originally posted by: CPA
I can tell you it's not a blown fuse. There is generally only one or two in a system and if it's blown nothing would work.

Ok, thanks

 

[nakedfrog]

Have you been changing the filter? I'd hope the HVAC guy checked that, but you never know.

 

[Platypus]

Originally posted by: nakedfrog
Have you been changing the filter? I'd hope the HVAC guy checked that, but you never know.

Yeah I changed the filter. Is it possible there is shit gumming up the works in there from a previous 'full' filter?

 

[effowe]

Originally posted by: meltdown75
Mine was acting similar a few weeks back and I was able to find the solution by Googling the furnace make & model. If you are as lucky as me you can find a forum where someone has posted a similar issue with the same make of furnace.

Mine's an Armstrong Ultra V... the flame sensor was dirty / gunked up. All I had to do was unscrew one screw, pull it out and sand it down a bit with some fine sandpaper... voila, good as new. Works awesome now...

I am about to do the same thing with my furnace. Me and my roomate were out of town for Thanksgiving and the heat was broke when we got back. I am meeting my landlord in a couple of hours so we can go clean the heat sensor, pain in the ass I tells ya.

 

[nakedfrog]

Originally posted by: Platypus

Originally posted by: nakedfrog
Have you been changing the filter? I'd hope the HVAC guy checked that, but you never know.

Yeah I changed the filter. Is it possible there is shit gumming up the works in there from a previous 'full' filter?

I wouldn't think so, but I don't know that much about this stuff.
Oh, you might also check to make sure any return vents are clean/not blocked.

 

[Platypus]

blah this sucks.. I want my heat to work normally

 

[Rubycon]

Remove the thermostat from the sub base (typically two screws). If the intermittent issue stops your thermostat is the culprit. In a rare case the subbase can cause this but that is very unusual.

Any experienced heating service tech could find the problem in short order.

 

[Platypus]

Originally posted by: Rubycon
Remove the thermostat from the sub base (typically two screws). If the intermittent issue stops your thermostat is the culprit. In a rare case the subbase can cause this but that is very unusual.

Any experienced heating service tech could find the problem in short order.

So remove the entire digital therm from the wall and disconnect it? Will the system still power on? Thanks for the reply

 

[Rubycon]

Yes it will. The power is provided by a transformer in the air handler (furnace). The 24VAC comes up on the RED wire. Bringing the RED wire in contact with the GREEN wire for example will run the blower. Bringing the RED wire in contact with the white or black wire will turn on your heat. (electric heat energizes the resistance wire heater contactor, oil/gas will energize the flame safeguard which will then start a burner on cycle).

The thermostat is nothing more than a multiple position switch with a temperature sensor and connects/disconnects circuits depending on changes in temperatures around it.

 

[Platypus]

Thanks for the great info, I'll try and mess with it tonight. I'm also having another service call put in to have this lad come check it out.. hopefully someone who is competent this time. I can't imagine what my power bill is going to be like this month

 

[meltdown75]

Originally posted by: Rubycon
Remove the thermostat from the sub base (typically two screws). If the intermittent issue stops your thermostat is the culprit. In a rare case the subbase can cause this but that is very unusual.

Any experienced heating service tech could find the problem in short order for $80/hr minimum

fixed

 

[Scarpozzi]

When I moved into my house it had the old lever-style thermostat. When the temp moved the needle, it would kick on when it was over or under the range. I replaced this with a digital thermostat ($35). It basically has 4-5 wires that go down to the control unit that turns on the AC/Heat whenever the thermostat is tripped.

As Rubycon stated, these wires are fed into the thermostat and it acts as a switch. The question is do you have a manual thermostat or a digital one. If it's digital, I would start there. Try looking for a reset button or replacing your battery....or both!

 

[daveymark]

the reason it "gets better" when you turn it off and back on is because it continuously will try to kick heat on for a limited number of times before it says "hey, there's something wrong with me, I'm going to shut down until you figure out what's wrong." so when you restart it, it resets the kill switch and starts the cycle over again.

what is the make and model? do you see a flashing light anywhere inside when it's on?

does it always blow hot air? without knowing more info it sounds like a flame sensor issue, try sanding the metal part with 100 grit sandpaper. be careful not to touch the ceramic/porcelain. then turn it off and back on again and see what happens. sometimes the flame sensor needs to be replaced too, and they are usually pretty cheap.

 

[Platypus]

Originally posted by: daveymark

the reason it "gets better" when you turn it off and back on is because it continuously will try to kick heat on for a limited number of times before it says "hey, there's something wrong with me, I'm going to shut down until you figure out what's wrong." so when you restart it, it resets the kill switch and starts the cycle over again.

what is the make and model? do you see a flashing light anywhere inside when it's on?

does it always blow hot air? without knowing more info it sounds like a flame sensor issue, try sanding the metal part with 100 grit sandpaper. be careful not to touch the ceramic/porcelain. then turn it off and back on again and see what happens. sometimes the flame sensor needs to be replaced too, and they are usually pretty cheap.

Interesting, thanks.

I tried just turning the system off last night for awhile and I think I'm convinced it's the thermostat now because the temperature never changed on the display after an hour or so and it got noticeably colder in the room. It doesn't always blow hot air, when the blower turns on, it's cool air initially for a few minutes and then it becomes warm.

Where is the flame sensor?

Make/Model is a York(?) F2RP024H06G

Thanks!