Service of the 80% gas furnace. Check the firing rate by clocking the meter part 10

[@Fireship1]

Excellent videos. I wish I had you as an instructor back when I learned the heating/cooling trade!

[@earthishome1866]

Wow, I can't thank you enough for all your help!!!! Information takes away the fear in humans and that's what you do when we watch your videos. Never stop educating us. I also believe in educating others as well. Wish you great health!!!!!!!!

[@grayfurnaceman]

Thanks for the support. GFM

[@AlexBianco100]

Great video! 1000 btus per cubic foot is a good rule of thumb. Here in California PG&E publishes heat content data for natural gas. In some areas it's all the way up to 1100 in others as low as 900.

[@JoeLinux2000]

Your videos are extremely helpful although some of the questions I have posed need to be answered.

[@edilsonserafim4784]

Excellent video

[@MJ-iy4fb]

Excellent breakdown, you really helped understand this . Thanks a million.

[@averyalexander2303]

I never thought to do this. Great idea!

[@rodgraff1782]

The heat content of the gas varies across the country 1000-1100. It is best to call the utility company to find the heat content of the gas in your area. we used the average of 1050. Clocking the meter is a good way to fine tune the gas pressure. I was told I was wrong to use this method and it was outdated. The guy wanted to use static pressure to set the gas pressure. What do you think Gray?

[@grayfurnaceman]

If you mean manifold pressure, You are closer to accurate. In the end, it makes little difference as the manufacturers have at least 10% wiggle room. GFM

[@rodgraff1782]

@@grayfurnaceman Yes on the manifold pressure. Carrier used to specify 3.2 to 3.8 inches of WC, as a range that you could work with. If that didn’t work you had to derate the furnace. Of course you have to derate the furnaces anyway, if used at high altitude . It used to be anything over 2000 feet above sea level.

[@grayfurnaceman]

@@rodgraff1782 The 2000 ft level is still correct. GFM

[@rodgraff1782]

@@grayfurnaceman Something tells me you must have been an instructor of apprentices.

[@grayfurnaceman]

@@rodgraff1782 Yup, for 9 years. GFM

[@sasansaadi5229]

simple explanation. well done!

[@JoeLinux2000]

Using this video and other information you provided, I have adjusted my two stage gas valve by clocking the meter and using the 4% per 1000 feet derate for altitude which in Denver works out to 20%. I used this chart for the BTU value of the gas supplied to residents of Colorado: www.eia.gov/dnav/ng/ng_cons_heat_a_EPG0_VGTH_btucf_a.htm It's important to base the derate on the gas input rating of the manufacture not the actual BTU output of the furnace depending upon its efficiency rating. The information provided by GFM has been a huge help. Tweaking the gas valve is as temperamental as tuning a piano. After tweakig the adjusting screw, I give the valve a gentle "boink" with the handle of a rubber handled screw driver just to insure the diaphragm responds to the screw adjustment.

[@grayfurnaceman]

Did you remember to replace the regulator cap before checking the rate? GFM

[@arnsberg1975]

Great series of videos! Thank you.

[@grayfurnaceman]

+Andrew Arnsberg Merry Christmas GFM

[@grayfurnaceman]

Most manufacturers recommend 4 percent per 1000 feet of altitude. Hope this helps. GFM

[@JoeLinux2000]

Is that 4 % for every 1,000 feet above sea level or is it 4% for every 1.000 feet above 2,000 feet? Stated another way would a furnace in Denver be derated 20 % or 12%? Also I've heard that high efficiency 96% furnaces are only derated 2% per 1,000 feet. In either case is it total feet above sea level or total feet above 2,000 feet?

[@granttheplumber]

@@JoeLinux2000 "When an appliance is installed at elevations above 4500ft, the certified high-altitude input rating shall be reduced at the rate of 4% for each additional 1000 ft" - CSA B149

[@tellmesomething2go]

Thank you for your excellent work.

[@grayfurnaceman]

+Arthur Bradley Welcome GFM

[@smoothbcuz]

thank you sir. I always learn something new from your videos.

[@grayfurnaceman]

Welcome GFM

[@SaintWilliamIII]

Thank you, very nice video; you give very clear and indepth instructions. What about derating the furnace input Btu rating based on altitude?

[@RODALCO2007]

Great video and explanation.

[@boneGT]

thanks. your videos are helping out a lot

[@Shahzad5814]

Thanks for sharing your knowledge in easy to understand language. How do I read my natural gas meter in order to compare it with the bill that I receive from the utility company? Your comments will be greatly appreciated.

[@grayfurnaceman]

+Shahzad Akhund The top 4 dials are for billing. Left is the highest. Read each dial to the lower number. That is if it reads about 7.5 read that as 7, the the next dial will tell you the fraction. Hope this helps. GFM

[@Shahzad5814]

Thanks for your response. I thought that a number from each of the four dials, read from left to right, would make the four digit number that will relate to that mentioned on the utility bill. So I did not follow your comment about the next dial showing fraction.

[@grayfurnaceman]

+Shahzad Akhund I will do a video on it. Should be out in about a week. GFM

[@Shahzad5814]

+grayfurnaceman thanks, looking forward to that.

[@scottshingleton384]

Very helpful. That way I can predict how much gas I will use in a month by knowing the firing rate per minute and timing how long the furnace runs per hour. Multiply by 24 gives me my daily usage. One thing I did notice was that the firing rate per minute for my furnace was .46 cubic feet meaning 27.6 cubic feet per hour roughly if it ran for a solid hour, however the furnace is rated at 77000 btus per hour. It is a Coleman dgaho77 mobile home furnace. Is it possible that the firing rate is variable? Just curious to know why the btu input is lower than the factory specs.

[@steventhury8366]

This is good information. What I intend to do is sub meter a building I'm renting out. The building sits adjacent to my main building. The tennant plans to heat the building and I have a line close by. I purchased a meter on craigslist that looks very similar to yours in the video. I need to connect the incoming and outgoing lines. The male threads on the meter are 1 5/8" diameter for input and output. I'm looking for a coupler with a washer to hook up to the meter, then connect standard 3/4" black pipe. Where would I get these connectors to go directly off the meter? Any help would be appreciated.

[@grayfurnaceman]

The only source I know of is the local utility. GFM

[@steventhury8366]

@@grayfurnaceman I called them, Northwestern Energy, and they said they do not get involved with anything after the meter. This will be a sub meter, after my main meter, negotiated between my tenant and I. I'll have to call around on Monday.

[@grayfurnaceman]

@@steventhury8366 I would try going to the utility, and if you can find the meter shop, they may help you. GFM

[@johansalazar4701]

hey @grayfurnaceman if my meter instead of 2 ft is 1 ft my equation will be the same except that I wont have to divide the time by 2 correct? meaning I got 48.5 seconds for full rotation of the 1 ft meter then I would divide that 3600/49 = so on. and I will get the exact same result as you 7400 BTU and the spec on mine was 75000 as well.

[@grayfurnaceman]

You have it. GFM

[@JoeLinux2000]

Is it possible to adjust the gas valve by simply clocking the meter or do you always have to have 3" of water pressure and then clock the meter to verify consumption as compared to the specification plate? Another question. Should not a derated furnace consume the derated % for altitude adjustment? In other words would a furnace in Denver clock out at 20% or 12% less than the rated consumption on the specification plate if properly adjusted?

[@grayfurnaceman]

In the end result, I use the meter as the final arbiter of consumption unless the meter is obviously wrong. As for derating, I just use the chart to determine the derating number. GFM

[@brettradecki]

My furnace is rated at 66,000 BTU and my gas meter is saying it’s using 64,900 is this too far off for proper gas pressure?

[@TheLightningStalker]

How can I check the firing rate on propane? There is no meter.

[@capitolrefrigerationheatin7501]

What if your over by 10,000 btus and you are at proper inches of water column at manifold. What does that do to the furnace,would it cause it to burn to hot or screw up combustion? Also does it mean the unit is know good?

[@grayfurnaceman]

First, check orifice size to be sure it matches the model plate. It will burn hot and combustion will not be right. The unit does not need to be thrown out. The last thing to check is the accuracy of the meter. That last one is for the utility. Hope this helps. GFM

[@JoeLinux2000]

I'm not a furnace guy but it seems to me that it would be an indication of over sized orifices. It has to get those 10,000 BTU's from somewhere so it more or less has to mean that it is consuming more fuel than it should. On the other hand, perhaps the fuel is not fully burning which I think one might be able to tell from the color of the flame. I read that high altitude furnaces that are not properly derated can carbon up to the point they stop working. Could the grayfurnaceman describe a proper colored flame? I think it probably should be more blueish than orangish.

[@estrelladelnorte1308]

thanks! i guess if you are burning to much or less you change the orifices?

[@grayfurnaceman]

estrelladelnorte1308 The first thing to do is adjust the manifold pressure down. That usually fixes it. If you have to drop below lowest on the model plate to get there you would change orifices. At that point I would be looking at the entire install because if you have to go that low (or high) it does not look right. GFM

[@JoeLinux2000]

I saw a video where the technician placed a probe in the discharge exhaust vent (96%). I presume that is like the air pollution monitoring stations for gasoline vehicles. It must be an indication of how efficiently the fuel is being burned.

[@libertasvirtus6948]

Can you explain the correction factor? Both: difference in atmospheric pressure and difference in calorific value.

[@grayfurnaceman]

Diane Jarvis I don't know. I would try the gas supplier. GFM

[@JoeLinux2000]

1 BTU = 252.164436 calories www.calculateme.com/Energy/calories/ToBTUs.htm At this point I'm not sure about how BTU's relate to atmospheric pressure, but from what is being said the amount of fuel has to be reduced by 4% per 1,000 feet because of the reduction in oxygen at altitude. Again, I don't know if this means measured from sea level or above 2,000 feet. Here's an oxygen altitude chart, which I need to study in more detail. I should be able to figure the furnace derating values from this chart: www.higherpeak.com/altitudechart.html

[@libertasvirtus6948]

Sorry. I didn't explain that clearly. When is it necessary to do a correction factor when it comes to calorific value. Say, the calorific value of natural gas happens to be 1050 in one's region instead of 1000.

[@JoeLinux2000]

I would think the answer would be yes, I also read in an article that the quality of natural gas can vary and it is somewhat withing the control of the gas supplier. www.achrnews.com/articles/136057-furnaces-must-be-modified-for-high-altitude-applications

[@LouisWilen]

In some areas, the BTU content of natural gas is 1050 BTUs per cu. ft. or higher nowadays. This is due to "ethane rejection", a relatively recent practice of suppliers where they leave the ethane in natural gas instead of extracting it and selling it to the petrochemical industry. The high BTU content should be factored into the calculation when clocking the meter. Otherwise, you'll be paying for energy that you won't be using. See: www.eia.gov/dnav/ng/ng_cons_heat_a_EPG0_VGTH_btucf_a.htm. Also Google .

[@grayfurnaceman]

+Louis Wilen Good thoughts GFM

[@LouisWilen]

6 years later -- We're back to about 1030 BTUs in most areas. Ethane rejection is no longer a thing.

[@badass657]

Doesn’t clocking the meter show your output? Not your input? Just curious I’m just wanting to make sure I understand this right

[@grayfurnaceman]

Clocking the meter shows the amount gas supplied to the appliance. GFM

[@badass657]

Gotcha so the output rating means? The true btu output you’re getting with the heat loss due to the flue gas correct?

[@grayfurnaceman]

Yes. GFM

[@mikhail6518]

What if I run less BTUs than what my unit is rated for? What are the negative aspects of that?

[@grayfurnaceman]

First, if you are trying to save on gas usage, this is not the way to do it. Low gas pressure may not let all burners light off. The fuel air mixture will be incorrect with too much air. Condensate may form in the heat exchanger which will rust out the heat exchanger or vent pipe. GFM

[@mikhail6518]

@@grayfurnaceman thank you. Is execessive soot formation also an indication that the gas pressure is low?

[@jamieabee1283]

When the gas is on at the meter and it has a spring loaded regulator but it's not coming into the house, what can you do? I understand this type of regulator is supposed to reset it's self? It's a itron b-42 and its tagged.

[@grayfurnaceman]

Call the gas supplier. Its their meter and you are not authorized to mess with it. GFM

[@jamieabee1283]

grayfurnaceman ok, thanks for responding, I would have already if not for the holiday.

[@enzoamore9173]

So the furnace has to be running in order for the clock to move?

[@grayfurnaceman]

You got it. GFM

[@enzoamore9173]

grayfurnaceman if you don't mind I'm getting into natural gas field and wondering what tools I will need?

[@grayfurnaceman]

There are man. Not the least of which is a manometer to check gas pressure. GFM

[@AndrewIlies]

Thanks. I thought that's how you do it. Now I'm right

[@cooldog60]

So if the numbers are not what they should be does it mean the gas pressure is to high or to low?

[@grayfurnaceman]

+cooldog60 If the result is a higher than normal BTU input, pressure is probably too high. Opposite for too low. GFM

[@mishiimran3699]

Pakistan electricity generations LNG and furnance oil rates increase

[@JoeLinux2000]

All depending on the altitude of course which complicates things.

[@JoeLinux2000]

What about two stage gas valves?

[@grayfurnaceman]

You must check in both firing rates. GFM

[@superoks]

Thank you for the great post, GMF! I've recently replaced a gas valve and I'm about to estimate gas/heat flow by the furnace with the new valve. I have general question on the making sense out of furnace specs. Here is info printed on my furnace wall Model No: P3HUA12L06401A Input BTU: 80000 Output BTU: 64000 Manifold pressure: 3.5'' WC Orifice: #45 DMS So Output BTU/Input BTU = 80% which makes great sense, it's 80% efficiency furnace. Now let's derive Input BTU out of Manifold pressure and Orifice. As it's posted in "Gas Orifice Capacity Chart " (www.hvacredu.net/gas-codes/module2/Gas%20Orifice%20Capacity%20Chart.pdf) one orifice with #45 @ 3.5 WC pressure will deliver 17072 BTU. The furnace has 4 burners so all of them will deliver 17072*4 = 68288 BTU. This is only 68288/80000= 85.36% out of input capacity listed above. So why is there a big disconnect between 3 parameters of the furnace - Input BTU, Manifold pressure and Orifice size - posted in the furnace?

[@grayfurnaceman]

Are you sure its 45? Most of these are 42. GFM

[@superoks]

grayfurnaceman Im positive. Its clearly posted on the side/wall AND its stamped on the orifice itself. I think the question is "which specific table of orifice-diameter-to-gas-flow is the number 17072 coming from?" For example on your webpage www.grayfurnaceman.com/determine-gas-flow-to-the-burners.html different table is shown. In that table the orifice #45 is mapped to 19150.

[@JoeLinux2000]

Glad you posted the link to his website.

[@JoeLinux2000]

KoO, the disconnect is because a lot of equipment does not perform as rated. Tolerances during manufacturing are not always perfect. That's why things need to be adjusted. Adjusting the gas pressure regulator can help, but only to a certain point and then the orifices need to be sized up or down. At some point your measuring instruments and methodology of measurement has to become very precise. I think you are expecting too much precision in the manufacturer's claims. Most appliances and I assume that includes furnaces are in large part junk. It's kind of like a radar gun, the car's speedometer, and a GPS. They are all slightly different, which one are you going to trust?

[@geoos]

7446

[@vabeach1989]

thanks. Your videos are so helpful.