high gas pressure at burners

bob_50

in my experience a CI atmospheric boiler manifold press is usually 3.5 maybe 4 inches. Does the gas service on this house have a reg and then the meter? You say the press in the house was 13.5" and 9 something ahead of the boiler. It seems to me that is quite a press drop, probably under sized pipe. It should work ok though. If you changed the press in the meter that will change accuracy for sure. The higher the press in the meter the more BTU's per cubic foot.

computerwhizyeah

high gas pressure at burners

Last fall I looked at(and heard the roar) of a large 1,100,000 btuh ci sectional atmospheric boiler about 25 years old in the basement of a three and one half story house 90 years old, loosely constructed, with over double the amount of needed ci radiation. Owner was considering new boiler. After checking gas pressures:13.5 in wc in house, 9.3 in wc at boiler (checked several times) manifold with boiler running, usage 1,500,000 btuh, temperature ahead of diverter 435F, I said to put off new boiler until spring and installed proper regulator fully expecting a lowering of usage and bills over the winter. After new regulator, readings were 3.5 in at manifold, temperature 350F before diverter and usage 795,000 btuh. House heating habits were the same as previous winters. The local weather service indicated that degree days for heating were lower this past season than previous winter. Well, cu ft gas usage was higher than before. Burners and venting system (gravity) are clean. Other than what I did there were no changes to house. Can anyone explain what might be going on. Could this be a meter reading problem by gas company? Usage was 4237 cu ft for 06-07 versus 3589 cu ft for 05-06. Thanks in advance.

computerwhizyeah

high gas pressure at burners

Last fall I looked at(and heard the roar) of a large 1,100,000 btuh ci sectional atmospheric boiler about 25 years old in the basement of a three and one half story house 90 years old, loosely constructed, with over double the amount of needed ci radiation. Owner was considering new boiler. After checking gas pressures:13.5 in wc in house, 9.3 in wc at boiler (checked several times) manifold with boiler running, usage 1,500,000 btuh, temperature ahead of diverter 435F, I said to put off new boiler until spring and installed proper regulator fully expecting a lowering of usage and bills over the winter. After new regulator, readings were 3.5 in at manifold, temperature 350F before diverter and usage 795,000 btuh. House heating habits were the same as previous winters. The local weather service indicated that degree days for heating were lower this past season than previous winter. Well, cu ft gas usage was higher than before. Burners and venting system (gravity) are clean. Other than what I did there were no changes to house. Can anyone explain what might be going on. Could this be a meter reading problem by gas company? Usage was 4237 cu ft for 06-07 versus 3589 cu ft for 05-06. Thanks in advance.

Josh_10

Playing with Fire


Perhaps the burner was meant to run that high of pressure. In my experience working on larger boilers it isn't un-common for a manufacturer to specify higher manifold pressures.

A common myth is that you can't have too much air. Too much air can be just as bad as too much fuel. Did you check the combustion with an analyzer before changing the pressure?

In summary I think you may have caused the boiler to have poor combustion efficiency. Which on a higher BTU boiler can be significant.

tim smith

Regarding useage

Are you sure that was not therm useage rather than cubic feet. how big is the house? If it were therms and a fairly large house, I do not think the useage would be out of line any way. As far as the increase, hard to say if maybe the clients useage patterns changed from prior year even though degree days did not go up this year. Also, if you did not put analyzer on it, maybe you did change efficiency for the worse when you adjusted input and did not know it. Need little more info no matter what.

Bernie Riddle_2

Regarding the fact that some boilers can run at high pressures, there was a old iron reg on floor that had been taken out when a new diaphram gas valve (full on or off) was installed. The gas service to this house is low pressure without any regulation with a 2 in line to boiler of about 20 ft. The house is roughly 9400 sq ft with high ceilings. The flame was not rising off the burner and had a good blue center. Customer has a printout from Gas Co that indicates cu ft and not therms. There are TRV valves on a third of the radiators. I guess not having the unregulated burner operation analysis was a major mistake.

tim smith

Regarding cubic feet to Therms

4200 cubic feet would only be 42 therms, are you talking about 1 month or what? That would only be appx $70.00 useage, I would not see a problem with this for a month. Tim

Barbarossa

The billing may have been in CCF or 100 cf which equals about 100,000 BTU’s.With a lower firing rate, you may have lowered the overall efficiency and only gas analyses can clear up the uncertainty.