Improperly installed flue vent cap cause of boiler fire?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by tenderkat, Aug 21, 2009.

  1. tenderkat

    tenderkat New Member

    Aug 21, 2009

    This is my first time posting, so thank you for any answers to my questions.

    We had our roof replaced recently, the 2nd week in July. The roofing company also replaced our boiler flue vent cap, as it had been damaged in a hail storm. It seemed as though around the same time our roof and vent cap were replaced, our hot water starting coming out extremely hot. Sometime around the 28th of July, our hot water stopped working. We called our plumber, and upon inspection, it was determined that the heat exchanger had become plugged, resulting in the flame to roll out and burn up the gas valve. Thankfully, the wires burnt up which caused the gas valve to shut off, so we are very lucky that nothing tragic happened. Apparently, the boiler was covered in lint from our dryer vent, which we have since rerouted.

    Well, our plumber came out the day before yesterday, and was down in our crawlspace all day cleaning the unit, and replaced the burned up gas valve, a pressure relief valve, and the domestic hot water zone valve. He also replaced and fixed a few other components that had been damaged. When he went to fire up the unit, he realized another problem. He tried to explain it to me, something about a restriction in the combustion gasses, which he said was extemely dangerous. He went up on the roof to check the vent pipe, and discovered that when the roofers installed the new vent cap, they pushed it on way too far, about 2 1/2 inches too far. So basically, none of the gases were able to escape. He mentioned that this probably exacerbated the already poor conditions within the boiler, and most likely contributed to the boiler malfunction and fire.

    So, everything is now fixed and working safely. I'm wondering if I should contact the roofing company and inform them of the situation. What are the potential dangers involved if the vent cap is not installed correctly? Had my unit not malfunctioned now, with just the hot water, what would have happened this fall when I turned on the heat? Any advice and guidance will be greatly appreciated. I don't wish to necessarily hold the roofing company liable, but are they endangering people and homes by putting on the vent caps this way? If so, I think somebody should be notified, so that nobody gets hurt.

  2. hj

    hj Master Plumber

    Aug 31, 2004
    Cave Creek, Arizona
    roof cap

    A proper roof cap CANNOT be inserted too far because its design forces it to stop when it is inserted, so I am not sure whether they did not use a flue roof cap, or the plumber is mistaken as to his evaluation, but then he should have installed the proper cap.
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