Two weeks ago we had a couple of hot days and the A/C wouldn't cool. The thermostat would kick the blower on but it never cooled. 2 weeks later it's in the 40's so the gas heat kicks on fine for a few days. One morning the heat kicks on blows hot to the preset temp and then heat stops but blower will not shut off, blower ran until the temp was well BELOW the preset temp so I killed power to the whole system by popping the thermostat off the base. As soon as I removed the thermostat the blower stopped. I reinstalled the controller and it worked fine for a few days.
Again in the AM heat kicks on and up to temp, heat stops but blower stays on until I play with the on off switch. When it not working correctly the heat will reach its preset and the blower will keep running without the heat kicking back on even though the temp will be well below the preset for heat.
I replaced the thermostat with same unit and everything is works right for about 6 hours then the same thing. Heat on then up to temp and blower stays on until I mess with the power or switches.

I replaced the programmable thermostat that I installed a few years ago and reinstalled the old analog thermostat I took out just in case some thing was frying the computers in the new style thermostats. Same thing, heat comes on then flames stop when temp reached but the blower keeps moving air but heat will not come back.

I opened the outside unit and did the snoop and wiggle on the sensors and wiring harness while the blower was on and flames had been out for a long time. Nothing found. I went back inside with the blower still on l I move the temp selector down on the thermostat then it cut right off. I move the temp back to normal and it is working fine at this time.

edited to removed PIC

The wife said the outside by the unit the smell is different. So I looked at the flames they seem OK.
There is some rust on the tubes the flames go into
Most of the connections for the sensors are shitty due to rust. So bad that I couldn't removed the connections to sensor 01 or 02. When I tried to pull/reinstall the connection for 02 the connector almost broke in half. The sensors need to be replaced if for nothing more than I cant trust the connections. Ploblem with them is the hardware holding them in is rusted beyond help. So I will have to clip the screw heads and make new clips and drill holes.

Edited to remove pic


I would like to fix myself  before I make that service call.
Can anybody help a brother out..... please ?

OK;

You have a gaspack or gas heat and ac unit packaged together.

#2 is a flame sensor, reads that flame has propogated from right to left of the burners.
#3 is a flame rollout safety switch, if the venting is plugged or the inducer fan is bad the flame will
not go into the rusty burners but flail about around that safety switch and shut down the system.
EDIT: #3 could be the hot surface ignitor. it would glow red hot when energized to light furnace.
#1 is unclear....

So now some background, IF the fan is belt driven it could be loose and slipping and not allowing enough airflow over the heat exchanger to which the unit will overheat. It has an automatic overtemp safety that will open the control circuit and shut down the burners and leaving that fan running as part of it's design.


Is the air filter clean? Airflow again which leads to overtemp and limit switch like I described above.

The inducer fan...if it has one, the photo is incomplete but the black cylindrical item could be the motor for the inducer fan. The inducer fan forces airflow from the rusty burners and through the heat exchanger and then out to the vent or exhaust tube or port. If the inducer overheats and stops turning the control circuit will be interupted and do the same thing as the limit problem described above....fan running.

Does the ac run ok?

Not enough information yet?
hvac-talk.com/vbb/

Railgun...HVAC TECH

Ok guy,I had to logon just to help you.Anyhow you have a sticking fan relay. bad news is the relay might be imbedded in your printed circuit board. Some older furnaces have a combination limit and fan control. Honeywell or white rodgers box with 4 wires and a dial behind a cover. I don't think your furnace is that old though. If you are lucky it has a seperate fan relay which is located inside (as is everything else i have talked about). Fan relays run about $8 at the part store. Printed circuit boards go for about $70-100 and you gotta be a hvac contractor to buy it. The a/c problem is something else and may be unrelated.

Quoted: Ok guy,I had to logon just to help you.Anyhow you have a sticking fan relay. bad news is the relay might be imbedded in your printed circuit board. Some older furnaces have a combination limit and fan control. Honeywell or white rodgers box with 4 wires and a dial behind a cover. I don't think your furnace is that old though. If you are lucky it has a seperate fan relay which is located inside (as is everything else i have talked about). Fan relays run about $8 at the part store. Printed circuit boards go for about $70-100 and you gotta be a hvac contractor to buy it. The a/c problem is something else and may be unrelated.

Those types of fan switches are not generally used in gas packs. That would be a helical temp driven fan switch and limit switch. Not with an inducer fan.

Railgun....

Quoted: OK; You have a gaspack or gas heat and ac unit packaged together. #2 is a flame sensor, reads that flame has propogated from right to left of the burners. #3 is a flame rollout safety switch, if the venting is plugged or the inducer fan is bad the flame will not go into the rusty burners but flail about around that safety switch and shut down the system. EDIT: #3 could be the hot surface ignitor. it would glow red hot when energized to light furnace. #1 is unclear....

01 Is a two wire connection unit that start above the sheet metal shelf and protrudes through to almost in the flame. The body of the swtich looks ceramic with a opening or hole in the middle of it

So now some background, IF the fan is belt driven it could be loose and slipping and not allowing enough airflow over the heat exchanger to which the unit will overheat. It has an automatic overtemp safety that will open the control circuit and shut down the burners and leaving that fan running as part of it's design. Is the air filter clean? Airflow again which leads to overtemp and limit switch like I described above.

I have a washable filter in and it was cleaned about 30 days ago. The  A/C wouldnt  cool like it should so that was the first thing I checked and I cleaned it

The inducer fan...if it has one, the photo is incomplete but the black cylindrical item could be the motor for the inducer fan. The inducer fan forces airflow from the rusty burners and through the heat exchanger and then out to the vent or exhaust tube or port. If the inducer overheats and stops turning the control circuit will be interupted and do the same thing as the limit problem described above....fan running.

The inducer fan seems to be working flow wise. It kicks in a second before the flames light and stays on untill I turn the system off. The fan will stay on even though the flames go out.

Does the ac run ok?

NO and that is why I replaced the thermostat because I thought since I was having problems with both a/c and heat it would be a good starting point. About 30 day ago we had a few days in the 80's so I turned it on, the air moved like normal but it did not cool the air. I check and cleaned the filter and made a note to have it check before the spring

Not enough information yet? hvac-talk.com/vbb/

I am going to check out the link EDITED TO ADD : I checked the link out and its a damn good site. THANKS

Railgun...HVAC TECH

Ok so this AM I turned the heat on and put the temp up to 80 and the system turned on and the flames turned off at about 73 not at the 80 I had set. The flames stopped but the inducer fan and system blower kept moving air untill I moved the system switch on the thermostat to off.  I may have been mistaken when I said the heat would stop when it reached its preset temp it may be cutting off before the preset as it did today.

clean the flame sensor with some sandpaper.

and try again.

If the inducer is still running then the t-stat is still calling for heat meaning it isn't the t-stat.

Find the control panel and look  for the control box. Is this a YORK gas pack?

Railgun....

#1 is indeed a hot surface ignitor.....very delicate so watch out ya dont break it OR touch the elemet with fingers....oil from skin will kill it as a hot spot develops and it burns out.

Do you have a volt meter preferably digital and know how to use it?

Railgun....

Well hell,

You ain't here so...

From  what is said,

I see the t-stat is still calling for heat and the gas valve is dropping out leaving the inducer fan running.
IF there is a box with wires connecting to the gasvalve and flame sensor then that could be bad and need replacing...get the same one.

If it's a circuit board then it could be that.

If you had a volt meter and could waatch it run while monitoring the voltage at the gas valve you could prove if the voltage drops out feeding the gas valve. If the voltage is good but valve drops out i's
the valve that would be the culprit.

AC is another issue, if it is low on refrigerant then that would be the problem and you will need to call a tech to add refrigerant. One other thing...if  the evaporator coil is dirty then that is an airflow problem like a plugged filter in the house airstream, so is the evaporator coil.

Railgun....

Quoted: #1 is indeed a hot surface ignitor.....very delicate so watch out ya dont break it OR touch the elemet with fingers....oil from skin will kill it as a hot spot develops and it burns out. Do you have a volt meter preferably digital and know how to use it? Railgun....

I am not sure of the brand and I am at work right know so I cant check.

I have a fluke meters and am versed in its use.

Quoted: Well hell, You ain't here so... From  what is said, I see the t-stat is still calling for heat and the gas valve is dropping out leaving the inducer fan running. IF there is a box with wires connecting to the gasvalve and flame sensor then that could be bad and need replacing...get the same one. If it's a circuit board then it could be that. If you had a volt meter and could waatch it run while monitoring the voltage at the gas valve you could prove if the voltage drops out feeding the gas valve. If the voltage is good but valve drops out i's the valve that would be the culprit. AC is another issue, if it is low on refrigerant then that would be the problem and you will need to call a tech to add refrigerant. One other thing...if  the evaporator coil is dirty then that is an airflow problem like a plugged filter in the house airstream, so is the evaporator coil. Railgun....

I will locate the brand and then try to find the color code or schematic and do the check for voltage loss at the valve.


Coils on A/C are clean

I removed the panel for the printed circuit control board. It seems to have a trouble code system that uses a red LED. I was getting a code 5 (five steady blinks) I don't have the code sheet so I moved on.

I since I don't have a schematic I did the hunt and peck cold and then once with it running.
24 volts to the gas valve

01= hot surface ignitor
02=Flame sensor
03= flash over switch. It read 26V in 26V out cold but as the fuel burned the voltage stay pretty close to the supplied voltage. After running for 10 mins the voltage dropped a few volts then down to 0v.  As soon as the sensor cut the voltage it seems the control unit dropped power to the gas valve. The two yellow hot wires on the valve lost voltage and the valve closed.

It set a code 5 right away.  I put a jumper on the flash over switch and rebooted the system.  
00:00Flush blower on
00:01Burners kick in. Flame blue with 90 % going in to tubes some flash over. I don't know how much flash over is OK, some? None?
00:02 air handler fan comes on. The flame on the far right tube starts to flutter a little 15% of the flame starts to swirl about the tube opening but the other flames seem steadier.
00:10 System seems to be working fine. The flame shuts off 10deg too soon.
00:10 through voltage was dropped at the flash over switch.
00:11 Code 5 on board.
00:12 I jump the sensor and reboot the system
00:13 System restarts
Flame starts doing the same thing as soon as the air handler kicks in? I run the system temp up a little higher than last time. No cut off. It seems it will keep running. I then turn the temp done and it works.
I reconnect the flash over sensor and turn the temp up to kick the gas on. Will not come on so I check the voltage out of the sensor 0 nothing 26v in and nothing out and a code 5 blinking.

Check me if I don't have a clue?
I see the heat exchanger is cracked and causing the flash over sensor to trip a code five thus turning the gas off but leaving the blowers running because that what the control unit is programmed to do.

The flash back to me isn't that bad so it could be an out of spec switch but then that doesn't explain why the burner that closest to the sensor starts to swirl when the air handler starts up?

I don't think I like the sound of a cracked heat exchanger. Could that be what it is? Am I off base? I have never worked on a heater before so I am clueless to what the norm is.
Any idea on the repair cost ?????????????????????????????

sounds like a cracked heat exchanger to me .what is the age of your system? it could be under warranty part only labor will run about 600.00.

Cracked heat exchanger is deffinately the culprit, when the fan starts it pressurizes the area around the outside of the heat exchanger or your house recirculated air. It blows the flame back and causes flame rollout. The other MORE nefarious problem with that is CARBON MONOXIDE in the airstream into the house, kids and pets or old people...hell even you will get poisoned from CO gas.

Shut the damn thing off forever and buy some new gear. Or replace the heat exchangers.

Railgun...

    It may just be a "Superheat" adjustment...     6 to 8 Degrees for Medium Temp.....    

Quoted:     It may just be a "Superheat" adjustment...     6 to 8 Degrees for Medium Temp.....     Gaspack, Natural Gas or Liquid Petroleum {propane} heat source and Air Conditioning packaged in the same unit outside and ducted into the house. Mostly a commercial application but what the hell maybe no room in the house for a furnace. Railgun....

   No Shit RG......    I wuz just messin' around.....



       Heating problem..... / ........Superheat settings ?????




     C' mon....



     



     

Quoted:    No Shit RG......    I wuz just messin' around.....        Heating problem..... / ........Superheat settings ?????      C' mon....

Well yes I get the joke but Superheat is a measurement on the A/C side of the system, how much superheated vapor prior to entry into the compressor to ensure no liquid slams or "slugs" the compressor.

Railgun....

sounds like a new furnace to me.  get a nice 95% efficient one and put the old one out to pasture.

Just replacing the Gas pack will cost roughly 3000 to 5000, but to update the ductwork to reposition the unit inside for a 90%+ furnace would cost much more.


Railgun....

Quoted: Just replacing the Gas pack will cost roughly 3000 to 5000, but to update the ductwork to reposition the unit inside for a 90%+ furnace would cost much more. Railgun....

Holy crap thats gonna hurt.

The unit was there when I bought the house 5 years ago. So I dont know how old it it. It seems like it was moved outside when the house went to a central system.

I have a service guy coming tomorrow any hints on what to ask and what to look out for ?

  As soon as I saw all that rust in the pic. I was thinking cracked heatexchanger.


 A 80 percent gaspac is standard. If you go to 95 percent, expect to pay some bigger bucks.



  The two main things you need, are A/C Tonage and Heating in BTU's.

 example:  4 ton A/C with 120,000 BTU's.

   Get at least 12 or 14 S.E.E.R  rating for the A/C.

  Get at least three bids. That are apple to apple.

whenever you get it fixed, remember to clean out your A/C coils

just wash em out w/ a garden hose+some a/c solution (optional) (straight on so you wont bend the coils) itll clean out all of the dirt and bugs and crap stuck in em

gets the place a lot cooler

  To wash out the condencing coil correctly.

  First turn off voltage to whole unit.

 Seconed pull fan motor out from top of unit.

 Third wash coil from inside to outside. Opposite of air flow.



  Also another thing.   THROW AWAY that Washable Air Filter. They suck/ Restrict Airflow. Which can cause overheating of the heat exchanger.

Quoted:   Also another thing.   THROW AWAY that Washable Air Filter. They suck/ Restrict Airflow. Which can cause overheating of the heat exchanger.

Well that could have been the problem. I looked at the filter a few time and it really didnt look bad so I left it alone close to a year. When The A/C wouldnt cool so I took it out and cleaned it damn thing was full of dirt so it was plenty resticted.

Thanks for all the help guys and Railgun thanks for the e-mails.

I will post what the tech says. He should be here before noon.

Ok tech just left.
Guy looked like he was 12 years old, I thought he was the paperboy at first.

I told him the problem and showed him the unit.  I asked him if he needed any help to let me know I would be inside.  I hate people watching me work.
20 mins later he called me out.
He ran the system and first thing he said was the flames seems larger than normal. He let it run until the flame roll out switch cut the power to the valve.

He had hooked up a pressure gauge to the burner feed line and said the pressure was 9.5 and should be around 3.  The higher pressure meant bigger flame and could be why the system was going into fail safe.
He tried to remove the brass plug on the gas valve that covered the adjustment screw and it was seized in valve.  It HAD a flat head on it but it stripped.  He tried to grab the sides with a pair of channel locks that were too big and they just ate of away.  He said he would need to replace the valve and that was around 500.00 BUT putting that kind of money in to a system of unknown age I might just want to look at replacing the unit as a whole. BIG MONEY

I asked him if he could get to the adjustment valve would he had been able to adjust it down enough or was it so far out of spec its not worth trying?  He said it since we can get the blind plug out it doesn’t matter.  But if you could ? He said maybe.
I asked him if he could look at the rest of it and let me know the general condition and I would be right back.

I went to the shop and got my 90 degree air-drill and a 3/8 inch bit, ran some airline to the corner of the house and waited untill he was done with his check.  I then offered to get the plug out while he was writing up his EST.  He said he rather I not because I could blow us both up.  OK how about I shut the gas off and purge the line and then get the plug out?  He said he would have to charge me for adjusting the pressure IF I got it out.  COOL 9 minutes later he was adjusting the pressure down to spec.

He fired the system back up and the flame was smaller.  It was contained in the tubes now and the flash back was gone.  System worked fine for 20 minute and the tech said he could not see any blowback from the exchanger, but from rust its time is coming.

The fee started 82.00 for the checkout, one hour or four hours.  Then the repair or adjustments was by the hour.

UNLESS I want to purchase a maintenance agreement and then the repair or adjustment would be taken care of under that and I would also get adjustment and system checks twice a year.  BFD I though.  I asked him if that was it?  He handed me the pamphlet for the agreement and it had another benefit.  25% off and repairs and all parts.  So I bought the package with the knowledge that I will need another whole unit in the future 25 % of a few thousand bucks would be nice. If not a whole unit maybe just the gas valve.

Total 82.00 for two hours of work and 203.00 to hedge my bet of any work later. I never buy maintence contracts but this time with the rust and the unit being old than ten years if I need to replace it I would save at least 750.00 with the discount.
Glad it wasnt more it was so that much.



Thanks for all the help guys ......................................................

I thought I read you did in fact see a crack in the heat exchanger.

Did the Kid-O-Tech do a carbon monoxide check of the supply air in the house????

Damnit Man, that is what kills people, CO poisoning.

Yes Natural Gas is set at 3.5" water column pressure to the burners but the system had to of been set up at 3.5" at install otherwise it
would have been running rich for all this time????

9"W.C. is the supply side gas pressure usually. Which side of the vavle was he measuring? Manifold side where the burners connect?


I sell maintenance contracts all the time and then service em regularly. They are a good idea.

Get him back to do a CO check...his detector should be much more effective than the cheap ass ones at Wallyworld.

Railgun....

Quoted: I thought I read you did in fact see a crack in the heat exchanger.

I never could see a crack. When blower came on I noticed a change in one of the burners.
It wasnt much of a change but it did change. I pointed it out to him when the blower kicked in the first time. HE didnt notice it . He adjusted the pressure and popped it on and off a few times and I couldnt see any difference with the flames at the correct level.

Did the Kid-O-Tech do a carbon monoxide check of the supply air in the house????

No I didnt see him do one but I did leave him alone for long periods of time.

Damnit Man, that is what kills people, CO poisoning.

I have a wally world on right at a vent and it works. I also have some really nice 4 channel gas meters here at work so I think I will bring one home and check it. I hate to miss work to meet him again.

Yes Natural Gas is set at 3.5" water column pressure to the burners but the system had to of been set up at 3.5" at install otherwise it would have been running rich for all this time???? 9"W.C. is the supply side gas pressure usually. Which side of the vavle was he measuring? Manifold side where the burners connect?

I didnt notice where he was getting his reading but I did watch the pressure drop as he adjusted the gas valve so it must have been on the maifold side ??????

I sell maintenance contracts all the time and then service em regularly. They are a good idea.

That make me feel a LOT better I NEVER buy them but the 25% discount seemed like a good idea if the gas valve sticks again or the exchanger is cracked.

Get him back to do a CO check...his detector should be much more effective than the cheap ass ones at Wallyworld Railgun....

I hate to take off for their 3 hour service service window.If it is cracked when would the level of CO be highest ? When the blower first kicks in or after the exchanger gets good and hot ? Could the exchanger heating up and expanding plug the crack untill it cools down again ?

I will use a meter from work. I just had one calibrated, we use for confine space work so it should be fine.
Thanks again.