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Gas supply problem?

MikeJL Member Posts: 9
Have a question on gas supply.  Seems my small Utica cast iron boiler 50,000 btu input and my Bradford White tank water heater 40,000 BTU input will no longer run at the same time.  Both are fed with 1/2 black pipe dropped from overhead 3/4 black pipe less than 15 feet or so from the outside meter.

Both units were installed at same time about 10 years ago and have been working fine all these years.  This morning we turned on the dishwasher and as it uses up hot water the water heater fires normally (standing pilot).  However when the boiler tries to fire (ignition system) it will start and run for a few seconds and stop, refire and stop, etc etc.  Hearing this constant start/stop I went down to the boiler to see what was going on.  Hot water heater was firing normally and boiler was doing the on/off thing fairly rapidly.  Boiler seems to me to be starving for gas?

So I turned the hot water tank thermostat down to "Vacation" setting which killed the burner and the boiler started right up and ran fine.  I let the boiler run for a few minutes and then tried turning up the temp on the hot water heater again and I get this scary "whummmppp" and little flash out of the bottom of the hot water heater as it lights off and again the boiler goes screwy.

As it is only 20 degrees out right now I shut the gas off to the hot water heater to let the boiler run.

One more note:  A few weeks ago we moved the location of our gas stove so  I shut the gas off at the exterior meter while the pipes were relocated. The stove is downstream from the boiler hot water heater drops. Both boiler and water heater have drip/sediment extensions near the gas valves.  Could I have loosened some dirt in the line which is goofing up the gas valves somehow on the hot water heater/boiler.  Any ideas on where to start? Who do I call to check/fix this?  Boiler guy or plumber?


  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    edited February 2012
    Your piping is sized

    correctly - as using Schedule 40 black pipe 3/4" at an allowable pressure drop of .3 " W.C. 20 feet of pipe can handle 188,000 BTU's and 10 feet can handle 273,000 BTU's

    I would call the gas company first, it is possible that when the meter was shut off it was not turned back on correctly. If you have an outside meter with a pounds to inches regulator it could have been damaged when it was turned back on. The gas should always be turned on slowly and listen for the internal seat in the regulator to do a soft "whump" sound, other wise you can damage the regulator. The gas company will direct you from that point on. Have the gas company do a gas pressure measurement at the different appliances in addition to checking the regulator.

    Another question, what size is the gas line to the gas stove, and is it an extension of the existing 3/4" line and if so how long is the total run from the meter to the gas stove? Gas ranges can be upwards of 65,000 BTU's and sometimes higher with a double oven. Four top burners at 10,000 BTU's each gives 40,000 plus the oven at 25,000 is 65,000 and a double oven can be another 20,000 for a total of 85,000. If it is a commercial model it is even more.

    Be sure and get back to us and let us know how you make out.
  • MikeJL
    MikeJL Member Posts: 9
    will call gas company first

    Thanks for your response.  I have call into gas company to have them come out.  Stove supply line is 1/2 inch black pipe also but probably about 30 feet further downstream of the boiler/water heater.  Dual fuel with electric oven, biggest burner is 13K, if all 5 are going might be 40 or 50K total.  Again, everything was working ok up til now.  Will let you know what gas company discovers.
  • MikeJL
    MikeJL Member Posts: 9
    Gas company was finally here today

    to check the meter/regulator. 

    Because it was going to be two days before my appointment with them I got impatient and tried closing and opening the main gas valve slowly as you described above.  I waited until the temperature had warmed up into the 40's that first day and I could hear the little "whump" sound you described as I slowly opened the valve.  Re-lit the pilot on the water heater and turned the boiler back on and everything started working OK again.

    So the gas company comes today and says everything is fine outside at the meter but they were not interested in checking gas pressures at the boiler/water heater because they are working OK right now.  The guy did give me his direct number so I can call him if it acts up again on the next real cold day.   Hope that was all it was as they did not change/replace anything on the meter/regulator.

    Thanks for your help! 
  • MikeJL
    MikeJL Member Posts: 9
    Final Solution?

    Since last post on Feb 22, have had the problem couple more times on real cold days, say less than 20 degrees overnight.  Had the gas company out again and they got there in time to see the problem for themselves.  Boiler and water heater would not run at same time as described above.

    Gas guy took apart the regulator at the meter and cleaned/replaced some parts, said there was visible dirt in the regulator.  Gas back on and boiler and water heater fired right up, everything works fine.  Temps are now up in the 50's only 40's overnight so will have to see if we are really fixed when we get another cold snap.
  • Zman
    Zman Member Posts: 7,466

    I think you need to find out what is going on with the pressure. I sounds like everything is working fine until the water heater fires. Is it possible the water heater is malfunctioning?Perhaps a regulator issue? If you temporarily choke the water heater gas shut off valve, does the problem go away?  I think a good gas/heating guy could get to the bottom of this fairly quickly.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Frozen vent / Diaphragm

    I see this all the time. Everything is fine till it gets cold. Usually below freezing. Sometimes only at night.

    The regulator outside at the meter was either unable to breath through the vent, limiting the flow of fuel (blocked with ice or snow), or the diaphragm (made of rubber) was just too stiff in the cold. This happens to older regulators.

    I suspect the gas co solved the problem by replacing the diaphragm or regulator at the meter.
  • MikeJL
    MikeJL Member Posts: 9
    Proud owner (renter?) of brand new meter/regulator

    from my local gas company.  Couple more cold nights and same problem with boiler and water heater as described above.  Gas company guy comes out again and checks gas pressure at boiler (first guy to put a manometer on the line).  Confirmed low pressure and proceeded to change out meter and regulator.  Pressure back to normal and everything has been working fine. (waited a few days before posting to make sure)

    Pretty sure this is the final solution......just disappointed it took 3 tries to solve.  Thanks again for pointing me in the right direction.
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    My mistake

    I thought I had read in a previous post that they did replace the regulator.

    Well, they did now and problem solved.

    Best of luck.
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