Furnace will not ignite
When I turn the heat on, the initial draft blower turns on, however, I never hear the ignition happen. The furnace is a Heil NTC5075BFE1. My question is if it may be an ignitor/sensor issue and resolve. I noticed last year the at times the furnace seemed to constantly have to reignite during times when the blower was on and sending heat throughout the house. Any suggestions? Did you check to see if you are getting power to the igntitor modular? or are the pressure switches closing? Are you talking about if the sensor/ignitor component is sending voltage to the gas valve? Can you give me steps to diagnose what you are asking? If you can give detail. I am assuming I would set the temp on lets say 80, which will turn the initial draft blower on, then open furnace and do ... ( need the steps...) I just don't want to do something that I should not be doing. This is the basic.. It may varies by company. Tstat calls for heat.. Power goes to the control board. Power turns on the small inducer fan.. Pressure switch(s) closes. Power from pressure switch goes though temp limit(s) switches. Then goes to the ignitor modular Modular then turns on the ignitor. Makes sense. So should I open the door to where the ignitor sensor is, turn on the furnace which will get the induction fan going and check voltage to the ignitor. The reason why I ask is I don't see the modular in the diagram. The diagram shows that the gas valve has a connection to the ignitor/sensor and there is a 24 volt pressure switch connection to the auxilary limit switch. I don't know Heil that well, the ones I been around the ignitor was near the burner area.. Is the inducer fan on the lower part near the burners ... kinda laying on it's side?? The modular is near that.. Some newer unit, the modular is part of the board. This model the inducer fan is on the top, below that is the gas valve, below that are the gas flutes, and underneath that is the ignitor/sensor. The main blower wheel is on the bottom of the unit. There is a furnace control board that looks as though it connects the thermostat to the components. Can I turn on the unit with the flutes exposed and check to see if the flame rod and the ignitor are working? Originally Posted by jscheufe I noticed last year the at times the furnace seemed to constantly have to reignite during times when the blower was on and sending heat throughout the house. Any suggestions? js, The fact that it was going into ignition again before the thermostat was satisfied sounds like it's short cycling on limit..... I know this might sound dumb but is the filter clean? If it is short cycling either a limit switch is bad or the switch is doing its job by de-energizing the gas valve. Then when things cool down, since the T-stat isn't satisfied, you have ignition and then burners....and the whole cycle may repeat until the T-stat is finally satisfied. Might not be your problem but worth looking into! Phil So if the furnace is no longer igniting would it be that one of the limit switches went bad, or is it that the ignitor/sensor possibly went bad. It does not look to complicated to replace either of the component. I can check the voltage, but how do I check if one of the switches is bad? I have checked the pressure switch and it is working because the ignitor is glowing and there is voltage to the pressure switch (24v). If the ignitor is glowing, what could be the problem? Should I check the limit switches, or is it something wrong with the ignitor? Now when you read 24 volts at the pressure switch, where are you reading? -wire connection on switch to ground? or - wire connection on switch to otherside of switch? If you are reading one side to other side on the switch, then that's your problem.. the switch is open.. It should read 0 volt on a switch from one to other side. The switch is not a load. The pressure switch has 2 connectors and I am reading 24v from each of the connectors to ground (using the frame as ground). I also have been checking the connection at the gas valve. It has 4 connectors to the furnace control, 24v common, 24v hot, pressure switch, and EFT (what is EFT?). When the ignitor is glowing, and I check the voltage, the 24v hot and 24v pressure switch connections show 24v (connection to ground of frame). The 24v common and EFT do not show any voltage (connection to ground of frame). EFT?? Is this on the gas valve?? I am guessing you have a Smartvalve?? If so, I hear there been alot of problems with them.. I never seen them here.. but heard alot about them.. What's the model # on the gas valve? Yes it is a smart valve. It is a honeywell SV9500..., not sure of the rest. I found out that EFT stands for Electronic Fan Timer. Honeywell now has an updated version of the model I have that is suppose to fail less often. Not sure if it still is the valve, what are your thoughts? Do I understand correctly that the ignitor will glow but not light the pilot? If this is indeed true, I suggest removing cleaning the pilot burner. Be careful, the ignitors on the Smartvalves are VERY fragile. Grady, you are correct. The problem is that I do not hear the valve open. So the pilot is not getting gas flowing to it. When I look at the honeywell manual, it looks as though if the gas is not flowing, the smartvalve would need to be replaced. If it is flowing, there must be at least 19.5v between the 24v common and 24v hot. They did have a lot of trouble with them. In fact some equipment manufacturers have stopped using then entirely. ICP, who makes Heil, Tempstar, others is one of those manufacturers. If you decide to replace the valve, make sure you get the whole part number take it with you when you go to get the new valve. The whole part number would be something like SV9500M1234. The letter last four digits are important. The SV9500 is no longer made is replaced by either the SV9501 or SV9502. That letter the last four digits make the difference in which is the correct replacement for yours. thanks, I used the part number from the heil model and came up with SV9501M2528. I have not replaced a valve before, so are there any precautions aside from turning the gas off that I need to take prior to removing the old valve? Once the new valve is in place, I know to perform a gas leak test with soapy water. Just make sure you got pipe dope on the threads, and also do not over tighten it.. otherwise. may strip the threads.. can ways tighen it more if needed. Hi to this list, searching for help I found this thread which almost perfectly matches our problem. so if this isn't incorrect, I would like to add to this thread and ask here. the model of furnace we have is just about the same as described here - same model number but the make is Tempstar. the unit is about 11 years old and we just recently got to own it. in our case the problem is a little different. here the heating element for the pilot starts to glow and gas actually get's to the pilot and lights up (as mentioned in an answer, yes the heating element is VERY fragile - I broke it and had to replace the unit! so the pilot is clean and new - should have read this list first). it seems to get to glow, so should signal the flame to the logic. I did check on all the electric elements (thermo couples and pressure switch) I can reach and they seem ok. there are however two more far inside the 'lower' box with the main blower I can not get to. from reading the manul I guess they are further thermo couples of the resetting kind. this unit is mounted horizontal with the exhaust to the left. so the main blower 'box' is to the right. again, from your previous answers I do suspect the Honewell valve but would like to exclude any other possibility befor trying to spend money on it. one final detail. the unit worked first for 2 brief test but stopped working after a first longer use this year AND the filter was not changed but very clogged/dirty at that time. thanks for any input/help. Anton Normally if any limit switches are open, the fan will run constantly the pilot would not light. After the pilot lights, does the ignitor continue to glow as if trying to light the pilot? I have a Snyder General gas furnace and while the ignitor works fine and all the burner tubes ignite, they quickly shut off and I have no heat. Along the 4 tubes is an ignitor tube that streches across all four burner tubes, and I believe, when the first tube is ignited by the ceramic starter, this tube stretches to the other 3 burner tubes and ignites them. Right in the middle of the igniter tube, it is pinched and divided. I think it is leaking and when the flame moves back along the tubes, the sensor shuts it off. I have tried to find a picture of what the ignitor tube looks like, to see if it is suppose to be pinched and cracked in the middle, but it is not in the manual. Any suggestions? Thanks If all the burners are lighting, the ignitor tube is not your problem. On the end opposite the one with the ceramic ignitor there should be a metal rod with a ceramic base which sticks into the flame. That is your flame sensor. Remove clean it with a Scotch Brite pad. sorry, it is a little confusing to discern which answers are new - probably should have started a new thread. yes, the heating element stays on. sorry I forgot to mention that. that too I think is a pointer to the valve being the problem, right? Anton cool by the way how alife/responsive this forum is!! The ignitor staying on is a very strong indication the system has not recognized the pilot is lit. Here's a link to the instructions for the Smartvalve. http://customer.honeywell.com/techli...it/69-1270.pdf Make sure all of your grounds are good the flame sensing electrode is clean. whow! really, really nice to find such a responsive place for help. will try and feed back some information so others might learn from my troubles here. I do suspect that the entire system has suffered quite some neglect over the years and for us this is new stuff. how and why is the ground so important? Anton Hi again, just went under the house one more time to check. the heat sensor does stick in the pilot light flame - after a few minutes of running it it afterglows yellow/red until it cools down. so this part od sensing the flame should be fine. however I tried to measure a voltage drop between the temperature switches and/or the pressure switch to ground and there seems to be none. isn't there supposed to be 24Volts on those? Anton Most flame rectification only uses millivolts or microamps so there isn't a lot of current there to fight its way thru a bad (loose or dirty) ground. If you are measuring across the switch, there should be none. From each side to common should give you 24v. On your pilot assembly, how many wires do you have? there are 3 wires, two blue connecting to the heating element and a black one connected to the flame sensor. that sensor rod glows yellow/red after turning off the unit so it is getting hot. the entire pilot thingy is new, from this week. I measured one more time (all against ground) but there is neither 24 volts for all the red cables (attaching to the a set of 4 thermo couples in series) nor for the pins connected to the pressure switch which has 2 blue wires attached. can one include photos here? these wires are all connected to the Honeywell fan control which is mounted right next to the main blower just upstream of the heat exchanger in the airflow. thanks again for all the help. I will try and see if I can find out why I do not see any voltage. I learned that there are some 'manual reset' switches in use for these units and there are two components I can not get to. they are mounted deep in the back above and blow where the main blower sits. could they be of the manual rest type? Anton They could be manual reset but usually if a limit is open, the fan will run constantly the pilot won't even try to ignite. The easiest way to do pictures is to post them on photobucket.com or similar photo hosting site post a link here. well, so much for my knowledge on electricity - since this is low voltage circuitry I simply assumed it would be DC. so that is why I did not find anything. indeed there is a sound 24V AC on both the 'red' and the 'blue' wires mentioned before. sorry for that. as one can tell this is not what I usually do. how does that flame sensor work? does it actually measure a current across to ground when it gets hot, sorta like for the old tubes/valves that preceeded semiconducting transitors? is that why the ground is so important? the ground is carried to the pilot by the small gas tube from the Honeywell gas valve and that part looks ok. how does the Honeywell get it's ground? also by re-reading all these manuals, there is one thing I have not checked and probably will have a hard time to do so. that is the actual pressure on the gas supply. it used to work so I assumed that part should be ok. BUT the manual asks for some extra gas piping such that dirt and fluids drop past the valve and this has not been implemented by whoever installed the unit - tried to get in touch with them but the business has disappeared. could that stop the valve to open for the main burners and still let the pilot do its thing? so, I feel more and more as if all this is telling me that I will have to find a replacement for the Honeywell valve. seems to be about $240 and I did see one place on the web only asking about $175 - does that sound about right? Anton As I understand it, there is actually a very small current either generated by or conducted thru the flame. The furnace should be grounded via the ground wire where household current connects to the furnace. This ground must go all the way back to the main panel's ground. I've seen bad grounds cause all sorts of strange actions on gas furnaces. Hi Grady, compliments again, your forum is awsome - if I had a chance and lived close by I sure would want to take you out for, well, a german beer for example? I am still fighting this. you are correct about the flame sensing rod though. I found an article on the internet: http://www.achrnews.com/CDA/Archives...00f932a8c0____ which gives a good explanation on the physics behind it. so I will try and make sure this is not the problem here. if there is trouble with the gas pressure though would the symptom also be a pilot that comes on and the valve refusing to light the main burners? Anton The likelihood of the gas pressure being that low are really remote. Do you have natural or LP gas? If you don't have or want to buy a manometer, here is something you might be interested in: RV U Tube Manometer I just thought of something: Remove clean the burners paying particular attention to the crosslighters (small slot in tube between burners). Also remove the orifices use a small wire to clean them. Sometimes a spider will get in there, make a nest stop the gas flow. Something else to try: Initiate a call for heat quickly put a screwdriver blade end against the gas valve the handle firmly against your ear. Allow the furnace to go thru a complete ignition cycle. Did you hear the main valve click open? Hi Grady, let me answer the last one first. I hear 1 clear click from that valve and that is when it lets the gas flow start to the pilot. that click is pretty audible and then there is never a second click. so I do think the valve does not undestand the flame is present as you pointed out earlier. I did monkey with the ground a bunch and even if not perfect there should have been some change - nothing. not one time for the days I am trying this did the result show any change - the main burner never gets gas. you mentioned ground problems before. just so I understand. it is important to have a good connection from the valve's ground to the base of the pilot flame. if or if not this also means a good connection to the ground of the powerline should not be important, correct? and the ground of the gas valve probably is made by the mechanical mounts and/or maybe through the connecting wires from the fan control module, correct? at this point I will go ahead and try to order a replacement gas valve and try to change out the old unit. the steps in both the manual for the furnace and the gas valve seem straight forward - the factory settings seem also what the furnace manual is asking for. is there anything in particular to watch out for when replacing the entire unit? thanks again for all the help and info - it sure appreciate this. Anton It is important for the furnace to be grounded via the incoming power wiring. There should be a black (hot), a white (neutral), a bare (ground). It is important the ground be connected to the ground screw in the electrical connection box go all the way back to the electrical panel. Something else which will set electronic controls in a fit is reversal of the hot neutral. Use you meter to check both the black white to ground. The black should give you 120vac. The neutral should be virtually zero but often shows a volt or two. If by some chance the white turns out to be the hot, connect it to the furnace black the line black to the furnace white then try again. If you will give me the Honeywell number off the valve, I'll see if I can cross it to a current model. Hi Grady, thank you so much. I probably would have given up since as I mentioned this is new stuff to me - AND I DO NOT LIKE GAS related things. as said I ordered the replacement for the Honeywell gas valve which is used in our furnace. just for the record, this is a Tempstar appliance with the SV9500 M.... Smart Valve. I tried to be careful and checked that the replacement is the SV9501. to make it short, for about 1 hour now it is actually working. had it go through 2 cycles at this point. now I can hear that second click which opens the gas to the main burners. a few notes. the Honeywell manual states that for this valve the line ground is NOT important, only the connection between valve body and pilot base. found this in the manual which came with the valve. to mount the valve I removed the burners, in the case of the Tempstar it's mostly a pipe with 3 holes. there was quite some brown/black stuff inside that U shaped pipe and blowing through the 3 little holes and revers through the big openening I tried to clean it somewhat. did not go back to check if that would have made all work even with the old valve. the professional installation did not have the 3 trap for stuff as asked for - I did implemet that one now. are there any tips on make sure that all those gas pipe connection are done safe? I tried to smell but there is definitely not more of the natural gas smell than was before, if anything then less. also tried that soap bubble test but probably need to redo that one. however did not see anything obvious. do they tire with time? there are 2 more questions I have. how can one tell if the heat exchanger is still ok? it is after all a unit with about 11 years of operation. I noticed that the original design has the gas valve in proximity of the exhaust fan - and that one does get hot. the manual states that the valve should not see ttemperature above about 70C I think, maybe I should place some insulating stuff between them? now, you know I am NOT a HVAC expert nor professional. so things are working again but I was considering to have a professional come by now and have them do a season check up - considering that this will cost an extra bundle, do you think that would be a wise step? necessary? again, many thanks and I wish you many more years of such a great place/space for help - I will now have a deserved beer in your honor. http://i64.photobucket.com/albums/h1...eersmiley1.gif Anton Certainly glad to hear all is now well. Honestly I'm really surprised about the line ground but wonder if that means a ground directly from the valve or the line ground to the furnace. I can understand not needing a ground wire from the valve because of the mechanical connection but have a difficult time believing no ground at all is needed. As far as I'm concerned there is no excuse for not having a sediment trap. Congrats on installing one. The soap bubble test is as reliable as you can get short of an electronic 'sniffer'. Apply the solution inspect promptly. Give the joint a minute or so inspect again. This delay gives a very small leak a chance to create a bubble. Use a mirror to view all the way around each joint. To be certain the heat exchanger is still intact an inspection testing by someone with the training, tools, ethics to do the job the way it should be done would be prudent. I can't see where a piece of insulation between the fan valve would hurt a thing. Just be sure not to restrict air flow to the fan. If this is a horizontal furnace, I suggest leaving the front door off. By doing so, you get more air flow thru the burner compartment less tendency to trap heat. Thank you for the compliments on the site. We have dozens (hundreds?) of professionals knowledgeable hobbists who volunteer their time to help others with nearly any kind of problem or project around the house, car, RV, so on. Hope you enjoyed your cold one. I am honored will reciprocate by saluting your success by having one myself. Beer 4U2 after a recent cleaning of my heat exchange, I'm having an issue with the pilot light on my Heil. I hear all the clicking and igniting happen as it should. But it all seems to light up with one big whoosh. Shooting a flame back out a couple inches. My thought is the pilot isn't lighting before the burners as it should, and the igniter is lighting it all at once instead. Any thoughts on why this would be and how I can correct it would be appreciated.
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