Checking and Adjusting the Outlet Gas Pressure going to the Burner Tubes on a Gas Furnace!
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- Опубликовано: 7 сен 2024
- This HVAC Video is about how to check and adjust the outlet gas pressure in the water column for a natural gas furnace. I show you where you can find the target pressure on the rating plate, where the service port can be located, what tool to use to open the port with the gas off, and the connection to the digital water column manometer. I show how to increase or decrease the pressure to get it close to what the rating plate is calling for. as well as other tips! Supervision is needed by a licensed HVAC Tech before doing this as Experience and Apprenticeship garners Wisdom and Safety.
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What if your supply (inlet) pressure is 12.5" w.c. but your outlet (manifold) pressure is only 0.4" or 0.9" w.c. with screw adjusted all the way down (clockwise) and only one of 3 burners is lighting?
AC service tech is always on point with his videos. Probably the best out there. I didn't think you were going to do furnace videos. I was hoping you would. Thank you so much for these videos. A couple videos I think new guys would like to see would be: Static pressure test, heat exchanger examination, removing gas valve and installing. If you have a way for us to donate I would like to. You helped me this first summer of my refergeration apprenticeship. thank you so much.
I am really glad to hear that these videos are helping you! I love to hear those aha moments and that the videos and time making them are appreciated. The channel has a fan funding section on the channel home page which goes towards our parts and supplies if you would like to donate but I do appreciate your comments and your time to write out your thoughts, thank you very much!
I attended a two year HVAC program years ago before computers. This guy is a great instructor. Thanks for the info.
Excellent instruction...I have watched this more than once, compared to others, and this by far is the best.
Thanks Vern!
Excellent example of how to confirm and adjust Manifold Pressure. A word of caution for Service Techs. If using any electronic meter to do so, you must have it's calibration certified yearly and put that certification certificate in a safe. Should an incident occur, you have done your due diligence to ensure you are using a tested and accurate instrument.If you don't want to go through all that hassle, use an actual water manometer from Yellow Jacket. You calibrate it every time by filling the water up to the Zero mark.Stay safe,
I would rather go with a lower tech instrument but with everything variable speed or multi speed as well as the pressure switches, we need to read as low as .2" for gas and .001 for pressure switches. Thanks
Who verifies the digital meters at UEI. ? Send it back for service ?
Thanks,now it's clear for me how to adjust the manifold pressure with my manometer
Glad it helped
Thank you for a clear and easy
Video to follow while learning!
Aka, Single “stage” gas valve. (For homeowners)
Love your videos man. Always reference them for AC
your videos are quickly becoming my favorite.
Great to hear Fred D!
Best video I've seen on this, clearly explained. Thanks
Glad it was helpful!
Very cool and informative video , thanks . No matter how good you are at fixing broken stuff and fault finding , sometimes you just have to ask 👍 And extra credits for the link and tools list !!
very good video, quality and straight to the point
Thank you very much!
Great video. I have never set gas pressure before so thanks for sharing. Hopefully this winter I will become an expert. Lol👍😎
Thanks alot, there you go. Glad you enjoyed it!
I ordered a replacement 74W26 gas valve for my Lennox furnace and there is no adjustment screw. It does indicate that it is factory set to 3.5 WC. I installed it and it ran like a charm.
Excellent I like this video. It show everything on how to use a manometer. Clearly
Thanks Noelbi!
Loved the video.. Very informative, straight forward and direct, excellent and thoroughly explained. I endorsed this video..
I lowered the gas pressure on both my units by almost closing the shut off valve. Saves a fortune in gas.
Good job, nice and clear, thank you. I'm pretty sure I can do a single by myself now.
Great info. I am new and almost done with my technical cert. program at Ivytech. Nice to have detailed videos to help.
Glad to help Trey! Check out the playlists of videos by topic at ruclips.net/user/acservicetechchannel
I got one i did to work , since it was retrofitted in an older house , i had to turn down the valve a bit but it has a near 50 degree temp difference and works like a champ
Good explanation.
Need to do this process to all these stupid ultra lox NoX furnaces in California sB area.
At 5:33 you say " you gotta make sure you're zeroed out with the inducer motor running". Is that right? Don't you mean without the inducer motor running? I'm just wanting to make sure I'm not missing something here. I appreciate your videos a lot, by the way! You speak clearly and not to slowly. And you get to the point without added peripheral stuff just to drag out to 10 minutes. Thank you!
As a comparison, I just checked my furnace's installation manual. It's fairly precise with it's instructions (Rheem) and it makes NO MENTION of zeroing out the manometer while the inducer motor is running. If this had an important/critical step, I'm pretty sure that it would have been in my furnace's installation manual.
@@ginobean737 Thank you!
great job,,,,,,,,,thanks,,,,,please don't stop,,,,,you teach us a lot,,,,
Thanks Rod!
Great job and video like always
I appreciate that
Thanks, excellent service for all. Thanks so much
Thanks Eduardo Hdez!
Very nice you have the best videos on utube
Excellent presentation.Thanks,
Glad you enjoyed it!
What is the size of the fitting of the gas valve.
What size Allen key to take off port to hook up my barb fitting?
great teacher you are man, thank you
Valuable info -- thanks for the excellent training.
Thank you for the Comment! Glad to Hear!
Thank you for another excellent video.
Thanks!
Another informative and detailed Video!
Thanks PanzerFaust 6th!
Is it OK to run the natural gas furnace below its spec pressure? The issue is that my furnace yellow flex CSST line whistle like a mad orchestra when at full blast. It's a big single stage 80% 110000 BTU Lennox. So I cut the pressure at the CSST flex line by 30%-40% and the whistle has gone. The flame looks the same and it is perfectly blue, but I don't know what the actual pressure at the valve is. It's probably better to replace that crappy yellow CSST to whistle free version of CSST, but should I really worry now?
Great job.. great video 👍👍👍
Our furnace is oversized. 100,000 BTU carrier comfort plus 80 for a 1600 sq ft house. It says 3.0-3.8” WC. If ours is set to 3.4, can i safely drop it to 3.0”? About to buy a manometer
Mine is oversized too and was wondering the same.
Hello I have a 2 stage Honeywell valve. I believe the valve is bad and here's why. When the blower comes on the igniter lights up the flame starts with no issues initially. After the flame starts say maybe 3 or 4 seconds it begins pulsating. I seen another video someone had to tap on the valve and it worked np. I had watched mine and it began pulsating I tapped the valve and it had a perfect flame. The other LP appliances have no issues it seems to be just the furnace. I had purchased another identical valve and it's for natural gas. I don't want to buy a conversion kit since the unit is already converted just wanted to change out the springs. I looked at the manufacturer specs and it's between 10 and 11° water column. I see a manometer online for $37 but to be honest I had never used one before so I'm not familiar with the settings. From my description does it sound like it's the valve. I had cleaned the heart sensor as well just in case it was that. It's just odd it will pulsate and just a tape the flame seems to be perfect until the next time. I already have the other valve and just not 100% in tightening the springs. I read it is 11 turns to the adjustment. If I tried without the meter and it was under the specs on over would it just not fire correctly? I want to be sure just wanted to pick your mind. Hate to pay $200 for a tech to install 2 springs but I guess worst case scenario I will. Just want to be safe ..Thanks
good information for the DIYer, thank you ...
Thanks!
Good Afternoon, very informative video. I have a valve that is different than the one on the video, it is the honeywell vr8215s1248 where would I hook up the manometer to adjust it? Thank you for your help
Really appreciated !!
I have that same digital manometer but mine has a negative and positive connection on top which side would be connected to gas valve output?
I checked pressures today on a Trane gas furnace but I had to turn the screw counter clockwise to make the pressure go up and clockwise to make the pressure go down. Has any of you guys had that happen to you before?
hi my manometer doesnt have a water column.what should i use?
Hi, my low stage reads 3.8"wc. I've tried turning the adjustment screw to bring it down to around 1.7"wc. But turning the adjustment screw has no effects. Is it a bad gas gave then? Thanks
So after years my furnace stopped working and they told me the pressure was too high and somehow it triggered a safety shut down. Solution was to lower the gas pressure? Does that make sense?
on a furance i was working, it was a high efficient 2 stage. and it had tubing going from the valve to the pressure switches. the tubing had a red line on the black tube. can i test gas pressure from this tube?
Thank you good explanation
love these vids. I need refreshers as im still novice in this field. Thanks.
Question. The brass barb fitting, do they come in smaller sizes (referring to the threaded tap)? If so would it still give me an accurate reading?
Replacing gas valve with different model, is it ok to do so, even not on manufacturer's part list? I think it is ok, as long as functions are same, I mean both same pressure, both have no pilot. BTU rating shouldn't be a issue. This is my opinion. My tech friend disagree it. He said wrong valve will change flow, even pressure are adjusted to same.
I have a manometer that has + and - which port do i stick the hose in to check natural gas pressure like you did in your video?
+
thank you for all your help. on the shutoff gas ball valve why does it say 1/2 psig on it? i thought it would have a higher rating than this, like 200psig or something. thanks.
low pressure natural gas runs at 5-8wc (water column) and propane runs at 11-13wc. 1psig=27.6wc. All gas valves in appliances have a max pressure of 1/2psig which=13.8wc . They are not to be included in pressure tests at 6psig on 30lb pressure gauges. Thanks Mark!
Hey Mark, the wog psi value is the highest they are tested to but the 1/2 psi is put on there to say it is rated for indoors per csa and ansi standards. They have to state 1/2psi even though they test it to higher standards. Seems silly to me but they need to, thanks
Great video once again. I have a gas valve that is White-Rogers Model 36J22Y-204. I says to back outlet pressure test screw out one turn counter clockwise then attach 5/16” hose over boss. Is there a reason to do this compared to removing screw and inserting barb fitting?
so for a 2 stage gas valve how would you go about setting the second stage gas pressure? do you just jumpered R and W2 to get it into 2nd stage and use same procedure as single stage? also for a 2 stage gas valve there's still only one output for manometer hook up correct? thank you for all your help.
Yes you can look up what dip switch to set or jump in the manual, you could jump the control board 2nd stage heat and if you are specifically just checking gas pressure only, most gas valves power 1 and 2nd speed with 24v at the same time so I just jump across the two hot terminals while firing, not the common obviously. This would not work on modulating furnaces though, thanks!
I just finished a natural gas to L.P. conversion. I got the first stage manifold pressure set to spec, but 2nd stage maxed out at about 2"w.c. below spec. What causes this?
Without measuring Delta t that number is pretty useless. I can almost guarantee you that furnace is overheating.
Also, depending on the specific gravity of the gas, you should be able to have a vast greater adjustment capability. In addition to that, only a combustion analyzer would be able to tell you if you were truly performing as close to complete combustion as possible.
Thanks for the informative video. I am troubleshooting a no ignition issue with my furnace. The igniter glows and the gas valve opens; however, the igniter stops glowing just (0.1second) before the natural gas reach it for ignition. I have check and confirmed that inducer motor, pressure switch, limit switches, flame sensors and even control board are working properly and in sequence. The gas will ignite if I manually bring the ignitor closer. Do you have any idea as to what may be the problem? Im thinking that the pressure may be too low.
How do you adjust for elevation in correlation to the 0 to 2000. If the water column range is 3 to 3.8 does the higher elevation make you set toward the upper limit of 3.8 or the lower limit of 3?
My ranges are the same and my elevation is 800.
Thanks matey🙏🏻👍🏼
fryers i have get noisy when thermostat goes on.. somewhat loud air noise will decreasing the gas pressure fix this??
Great video! When you are replacing a gas valve couldn't you count the number of turns as you are taking it off to get the same orientation!
Its a great question, but in my opinion it is best to check it properly so you know you're getting the correct reading with the new part replacement.
I have a new White Rogers 36J model, and the inlet and outlet taps are not threaded like the ones I'm used to check. How do I hook up my manometer tube to those taps or my barbed nut?
If someone took the boss screw completely out of the gas valve outlet test port instead of just turning it out one full turn and using the manometer, would you get a different reading?
What would cause the outlet/manifold gas pressure change over time?
It’s not often that it does, if it is a little over or under normally it hasn’t been set properly by factory standards.
Good video. So I have an old Warm Morning gas heater, LP. The gas valve does not have pressure taps to check manifold pressure. Could I use the plug/cap as access to connect the manometer that sits at the "T" after the gas valve? one side of the T is the cap, the other is the orifice leading to the burner, of course the third leg comes from the gas valve. I have an intermittent problem with pre ignition and I believe it is being caused by low inlet pressure. Also the stove does not indicate W.C. pressure on the rating plate.
Nice video. Can you make a video or explain how to test gas outlet pressure for a dual stage furnace by using jumpers to jump the control board and bypass the stat for low fire and high fire
Thank you for letting me know what you would like to see!
I just checked my furnace installation manual and it had instructions re: high fire vs low fire.
Hi Craig. Do you have a video on how to hook up the manometer on a 90+% gas furnace to adjust gas pressure? ie where you need to reference the sealed burner for proper gas pressure?
I lost the brass screw for adjustments . Do I need it?
Good vid !
Thanks Noel!
Thanks Great video.
I appreciate it!
Great vid thanks
Thanks therover616!
Is this the same procedure for a propane gas furnace valve?
I just bought uei and I can’t fine water column. Which one should I select if I want to use it for natural gas ?
It may say wg instead of wc, thanks
Do new gas control valves come preset from the factory? It looks like it was pretty much spot on for you in the video. I need to replace a valve that is buzzing loudly and I don’t have a manometer and it doesn’t have a brass screw only a silver one
Most likely no, and its better to check the pressure accuracy than trusting the random employees that put this thing together.
This is a video on how to check the pressure, not an installation video. He could have changed the reading to make it slightly off just for the educational video.
As for the brass/silver screw, he mentioned it in the video...hit the play button again. 😉
Hi. I just bought a LP 15,000 btu Empire Direct Vent for use at my cabin located at 7200' elevation. I have just run the heater for 30 hours after installing the High Altitude recommended orifice #57. The one it came with was #56. I am currently just above sea level and it seems to be operating great on a 20# LP tank with low pressure regulator. When I get to 7200' is it advisable to check the pressure with a manometer? It should be 11 WC. I have not checked it at sea level, but would altitude make it change? Finally, you turned the heater on to check, should I do the same? I have in and out valves marked and following your video it seems I only need connect to the out side (that goes to the burners,) turn it on and then I will get a reading. I can adjust at the screw under the brass cover if adjustment is needed. Am sounding like I am doing this safely and correctly? Your thoughts are appreciated. Thank you.
Great videos, how do you purge the gas valve before first start up?
I either purge at the union or tee but it is preferable to just let the system run if it is a direct ignition and the amount of gas needed to be purged is not that much. This is to avoid the smell of gas in the house, thanks
Thanks for the reply, again great videos.
What about a gas valve that has smaller ports so that you can’t screw in your barbed hose fitting? How are you supposed to check the inlet and outlet gas pressure for these types of gas valves? I’m working on a Goodman to speed gas valve and it’s inlet and outlet port test fittings are smaller than the standard threaded/barbed manometer fittings.
Those you have to put a rubber hose adapter onto the hose or use the hose itself. No threaded connection is needed.
Somone tested my outlet gas pressure of my Natural Gas Furnace, he said it was reading over 9 and he adjusted to 3.5, a few days later I borrowed a Manometer and tested, it was only 1.1 water column, I think he had his Manometer set to Millibar Scale instead of water column Scale, his was a new meter that he used for the first time. I have acquired a UEI M-150 Model and adjusted to 3.5 Mg and have re-checked several times. what is your opinion on that one???? I also have checked my inlet with my Manometer and it is reading 5.90 which I think is about right for normal incoming gas pressure to the gas valve. Please Reply anyone ....???????.......Thanks....
If it is natural gas and single speed then yeah 5-8"wc input and 3.0-3.8 output typically and then we adjust for efficiency within the range when using a combustion analyzer, thanks
@@acservicetechchannel do you have a video adjusting for efficiency using a combustion analyzer?
Is that 3.4 inch wc set for minimum gas pressure?
Will the gas pressure reading on the regulator output be lower in the middle of winter on the coldest days? My furnace starts fine but has a problem starting on the coldest days. I thought perhaps my replacement regulator needs to be adjusted to account for the lower supply pressure on the these coldest days? It works fine on the average winter day.
I am assuming that you are talking about propane. The issue would then be the tank size with the available vapor area in the tank. Are you talking natural gas or propane?
My furnace is natural gas line from the utility. I had the gas valve replaced but the tech never checked the output pressure after installation. It is odd it only has problems igniting on the coldest days.
Yes the output gas pressure definitely needs to be checked. If it is a 90% efficient or higher, it may have to do with the colder combustion air mixed with the improperly set output pressure.
I'll definitely have it checked. It's an older 80% furnace with a 24V 60hz valve (2 solenoids) LH33CM601. Thx!
does this increase burners? What does one get out of this?
good day AC Service tech. Just wondering how would you go about adjusting a modulating gas valve? Are these valves supposed to be adjusted?. I see on some Lennox there's a red tape on top of the brass screw that says DO NOT ADJUST. But on other manufacturers there's nothing that says that. Thank you.
Honesty how I learn with each manufacturer is to just read through that section of the installation manual because each furnace is different. Other units, you enter the settings through an action on the board and adjust the modulating valve by turning the electrical screw adjustment not a spring pressure, so not sure on that particular unit, thanks
Why does it have to be zero'd out with the inducer motor running?
This will give a true difference in pressure when the inducer is running. Depending on your seal level height or inaccuracies, always zero the manometer first, thanks
Thanks, if someone took the boss screw completely out of the gas valve instead of just turning it out one full turn and using the manometer, would you get a different reading?
Does the uei 151 manometer measure M-bar? Thanks 😜
Very informative! Is it a common practice to take this reading after installing a new valve?
Of course. It is always good to check the gas valve is correct according to the gas furnace plate.
@@abdelouahhabmellouk4351 I'm asking if it's done as part of the job of the tech.
If you get a better co2 reading with water column set at 2.8 inch instead of 3.4water column, is that ok?
Great Question! That could be ok but you want to make sure that you do not have a rough fire start because that could become an intermittent problem but if that is ok after testing 5 times then it should be ok. The other thing is knowing that you may not be receiving the total btu for furnace input which will mean less output heat. It depends on how close you are on heating the house on the coldest days via your load calc. You can do what is called clocking the meter to verify gas cfh input while the system is running. Thanks!
hi, for sealed combustion( with a hose connecting gas valve to burner box) do you have to remove the cover to adjust the manifold pressure? thank you.
That is what the tube is for so that you don't have to take the cover off unless the manufacturer says to do so. Then you follow that up with a combustion analysis, thanks
what happens if the gas pressure is not properly regulated what damage the machine would have
You don't want the furnace to overheat or to have the combustion incorrectly occurring, thanks
Hi. I have the Goodman GDS8703AX gas furnace, and after replacing the gas valve, it seems I need to wiggle or remove and reconnect the 24VAC line that goes from the valve to the big connector to the back of the furnace panel somewhere to make it work for a few days then now, nothing. I measure the voltage and it does not switch to 24VAC from about 14VAC when it is supposed to happen.
My question is where is the 24VAC that drive the gas valve coming from. I thought it is from the controller board but here it is not. Thanks.
Usually it is directly from the control board. Is there a wiring diagram?
Thanks. Like some people encountered and posted on the web, I wiggled, unplugged and replugged the connectors and it is eventually working now but not sure for how long. I will have to look into the diagram.
hi, so the 5-7"wc at the input is provided by the gas supplier? you can't change this? i believe your smart gas valve video mentioning there's an adjustment screw where you can adjust the gas input going into the gas valve. does all gas valve have this feature? thank you for all your videos.
You can only adjust the output to the orifices. For nat gas, incoming is usually 5-7 but could be 5-8" wc and that is only adjusted by the gas company. Propane can be adjusted at the regulator outside by the 3rd part propane supplier if it's too low, thanks
@@acservicetechchannel so when tech support asks what the inlet gas pressure is we really don't have a way to check. Usually they want to know inlet and outlet gas pressure.
hi, i have this sealed combustion lennox furnace. When i open the brass screw my pressure reads 3.5"w.c. But strange when i put the brass screw back my pressure drops to 3.1"w.c. Is this normal? I've tried with another same lennox furnace and the same result. thanks.
With those type, you may need to set them with the combustion door open, then put the screw on and shut the door, and then read the pressure to see if it is measuring what you want it too, thanks
so the final correct gas pressure reading (around 3.5"w.c.) should be with the combustion door closed and the brass screw tightened. Is this correct? thank you.
That is correct as that is what it will run at all the time if that is the wc the furnace is calling for, thanks
What about when there’s a vent?
What if the plastic cap is missing? I'm having issues adjusting gas pressure on a 2 stage American standard..have you ever changed a blower motor and then it started to trip high limit? This is my issue. EXCHANGER IS GOOD,VENTS OPEN,FILTER OK,COIL IS DIRTY..WHY WOULD IT START ACTING UP NOW? EXPLAIN. THX
It sounds like the blower motor speed is set too low. what is the temp of the air that is tripping the sensor? The temp rating of the sensor is on the sensor itself. If the temp you are reading is lower than the sensor then the sensor is bad. On high speed the temp rise of the gas furnace is usually about 50 degrees so if the return is 70 then the supply is 120.
HIGH LIMIT is suppose to trip at 170F. I'm a tech. I was just there to replace the blower. I replaced it and didn't change any speeds but it trips. Filter new,vents open,new cap.
Please be more specific...why would it trip after only changing blower. Why wouldn't coil have been issue before if it has been dirty?
Straightoutofchiraq, the reason is either low airflow or a high limit that just happened to go bad. What was the delta T across the furnace and was it increasing while the furnace was running? How long before the high limit tripped. What was the supply temp?
Great video! Quick question, what size is that barbed fitting??
Thanks
Mike
That is an 1/8" threaded barb fitting
Is it always usually 1/8?
Where can I get that brass fitting that goes in to valve , does that have a specific size,name? Good video. Thanks
Here is the link to the 3/16" x 3/16" x 3/16" brass barbed tee used for checking pressure switches- amzn.to/2INSRhQ
Here is the link for the 1/8" NPTF x 3/16" barb fitting for reading wc pressure in the gas valve tap- amzn.to/2G563Bq
I have a gas stove that has propane tank outside feeding it, HAD line checked for leaks, he said NO LEAKS but he is still getting half a psi reading when turned off ..........is this normal for a gas stove ? Maytag Gemini double oven
Propane is 1/2 a psi and if nothing is running then that 1/2 psi would still be in the line, thanks
Yes but does that mean he would still be getting a reading on his meter even though everything is turned off he said it goes down to less than half a PSI he says which is very very very mynute
He said he thinks it's an issue with the stove itself but I'm thinking maybe it's normal for the stove to be like that is that what you are saying it this is a normal thing?
propane runs at 11-13" wc which is roughly 1/2 a psi. 27.6wc= 1 psi so 1/2 a psi is not mynute. It is the gas pressure of a propane line with the valve off and nothing running, with the valve on and nothing running, and also when the valve is on and the stove is running. I would rely on a licensed company but if you don't trust your current tech then I would call a different company, thanks
This is great! thank you. Is there a standard size on the gas valve manometer test port ?
Yes , they are all the same and that comes with the tester. I would highly recommend the Fieldpiece SDMN6 Dual Pressure Testing Manometer with Pump- amzn.to/2jyK5Ka -- I started over the years with the standard gauge manometer, then went to the UEI and now I am loving the SDMN6 due to it's self pumping while measuring feature for isolating and testing pressure switches. This tool is also used for checking gas pressures, thanks
Спасибо!!!!
How do you turn on the pilot with this model?? I need to turn on my furnace but don't know how.
It would depend on if it was to relight the pilot, or if you have intermittent spark ignition or intermittent pilot ignition, or direct ignition, thanks
Hello, If a 95% eff. gas furnace runs at 3.5 in of water, can you downsize the furnace, by changing the gas outlet pressure to 3.25 in of water? I did this to my furnace, and the burners look the same as if they where set at 3.5 in of water. [ I believe my furnace is over sized for my size house ]
Most nat gas furnaces call for 3-3.8 or 3.2-3.8 so that is quite normal. The inducer speed is matched for the gas input for combustion so keep that in mind because you don't want to get the combustion mix air/gas off and burn inefficiently, that's the main thought. Also the blower speed is matched for the gas output to keep the temp rise across the furnace asa 50 degree rise from return to supply, thanks!
Thanks again
Glad to help Ronald!
what size the brass fitting is?