I've been having problems with my 60k furnace flame fluttering or chattering when the gas valve first opens, and I'm wondering if it has to do with the input gas pressure either being too high or too low. I'm wondering if they call this "hammering" because it reminds me of water hammer in reverse. I've ruled everything else out (burners, flue pipes, flame rod, etc).
So what is the proper gas pressure you should have coming from your meter for natural gas service? I've done a little research and found the value of 7 inAq or ¼ psia. What flow rate is the value for? How high should the pressure go with no gas flow (lockup pressure)?
It looks like there is a tamper tag over the gas regulator pressure adjustment screw, so I assume that means I'm not allowed to adjust the pressure? If the pressure is wrong, do I have to pay the gas company to come out and change it or will they do that for free (Alliant energy)?
Update:The fluttering happens in the first 2 sec the flame is lit, then it's just fine. The blower motor doesn't run for another 64 seconds. The furnace is only three years old.
Answers & Comments
Verified answer
Residential gas pressure is 4-7 inches Water Column. It depends on your supplier, but usually they set the regulator at 5.5". Do not even think about changing the pressure unless you have had proper training and the proper equipment. You can cause an explosion
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The regulator will maintain it's set pressure at any flow rate up to it's maximum capacity. The regulator lock-up pressure depends on the model of regulator being used. Flow rate and lock-up pressure are immaterial to your problem.
A fluttering for 2 seconds is a normal thing while the flame stabilizes. If you think you have a problem, ask the gas company to check the pressure and see if the Tech. will listen to your furnace while he is there. They do not charge to check the pressure.
Gas Pressure Meter
As this is a UK site I take it to be a question of UK pressure in which case Gary M is quite correct in stating the pressure after the govenor on the meter would normally be 21 mb but also this may drop in some areas due to heavy demand. The important question is does your pressure remain at 21 mb when your appliances are all in operation. If the new pipe they have run into your house is of insufficient bore, the pressure on the outlet of your meter may drop to an unacceptable level when the boiler and cooker are in operation. Therefore the pressure check must be made with the appliances in operation. My own service has just been renewed the same as yours and a new service is about to be laid in the road. I suspect at the moment my pressure is low when the boiler is running which I will check when all work has been completed..
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The service pressure can vary from city to city,a lot depends on the demand. A regulator is fitted on the service pipe before the meter to govern the amount of gas passing through the meter when the appliances are running. The working pressure should be 21mb at the meter and 20mb on the inlet test point to each appliance. Modern boilers are fitted with multi function control valves which will prevent the appliance burning to much gas,these valves can go faulty and need to be tested at least once a year during routine servicing. Employ the services of a CORGI registered engineer to service the boiler and to check the pressure for you.
There should not be a "flutter" when it comes on, and it depends on what you are calling a flutter? Could be a lot of things but if it is 3 years old you should have it serviced any way. So Call a HVAC company and have them service it, explain your problem, when you call them make sure they know that know you want the pressure checked, (they should carry a manometer, or gas pressure test meter on board, but sometimes they don't") While it will drop it should not drop below 3.5" which is the manifold pressure needed for natural gas. If it passes this test then something wrong with furnace, and the tech should be able to fix it, He will also need to check the manifold pressure while standard it will say on the plate what it wants for manifold pressure, standard is 3.5 this can be adjusted at gas valve. It could be a lot of things but the tech should explain.
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RE:
Correct gas meter pressure?
I've been having problems with my 60k furnace flame fluttering or chattering when the gas valve first opens, and I'm wondering if it has to do with the input gas pressure either being too high or too low. I'm wondering if they call this "hammering" because it reminds me of...
You should have 12 inches of gas pressure, but it can only be tested using a manometer on the gas Meter. If it is below this, it can be adjusted at the Gas Governer.
call an hvac tech,,,,u r messin with big trouble
MORE THAN LIKELY YOUR HEAT EXCHANGERS CRACKED & THE FAN MOTOR IS BLOWING THE FLAME AROUND. A CRACKED EXCHANGER LETS CARBON MONOXIDE INTO YOUR HOME - AT HIGH LEVELS YOU GO TO SLEEP & NEVER WAKE-UP.