Orphan Boiler


Old 04-20-19, 10:20 PM
Thread Starter
Join Date: Apr 2019
Posts: 3
Orphan Boiler

I currently have a small amount of carbon monoxide backdraft from my boiler/hot water heater. It is not enough to set the detectors off except occasionally. The water heater has melted caps on the top from the backdraft. I plan to hire a plumber to direct vent a power vent water heater. This should eliminate the water heater problem but will it create a new problem since the boiler will now be venting on it's own though the chimney flue? My understanding is that you cannot direct vent a boiler and leave the water heater orphaned to vent though the flue alone because it will not hear enough to create sufficient draft but if I orphan the boiler by direct venting the water heater will that also not create siffsuffic draft?
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Old 04-21-19, 02:38 AM
Join Date: Jan 2017
Location: USA
Posts: 487
There are many things that can be the cause of poor chimney draft, a back draft, or flue gas spillage into the room instead of up the chimney. Among the causes are; A very tight house, a poorly designed chimney, a chimney needing repair , exhaust vents such as kitchen and bath fans, a short chimney, a chimney being too large or too small for the device utilizing that chimney, a very efficient device or furnace creating a low temperature flue gas, not enough make-up air for the device or furnace and even placement of your house in relation to the surrounding terrain. Any of these or combination thereof can cause your problem. To correct your problem you need someone who knows chimneys. I would first try a good chimney cleaning company or a good furnace company with a few well experienced and older service techs. Good luck on your hunt for the right person.
Old 04-21-19, 04:33 PM
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Join Date: Apr 2019
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Thank you for your reply. I had a chimney company clean and inspect all 3 flues. There is no blockage/damage. The problem is there is no flue liner and not a great pitch in the piping. I have read that if you direct vent the boiler and orphan the water heater that the water heater won't draft properly so I'm wondering if the reverse is true or if the boiler is ok to vent by itself typically.
Old 04-21-19, 07:33 PM
Join Date: Oct 2013
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Only a draft test will tell you that for sure. A chimney flue has to get warm enough to draw a draft. It depends on the exhaust temp of your boiler and the size of the flue along with the other things SB mentioned. If you are having draft trouble with 2 units venting it's not going to improve with one less unit.

You may want to have your chimney lined with the proper size pipe.

This is my own personal opinion. You may want to get a heating company or tech that uses instruments and in this case not a plumber unless he actually sets up his own installations and has the equipment. I know people associate plumbers with boilers but personally I don't know of any that carry instruments to set up for efficiency which includes draft testing.

Just my opinion, don't mean to offend anybody. Hope this helps a little.
Old 04-22-19, 01:39 PM
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Join Date: Apr 2019
Posts: 3
Thank you for the quick reply. All of this information has been helpful and has given me direction in my next steps.
Old 04-22-19, 04:34 PM
Join Date: Oct 2008
Location: New England
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CAZ testing or Combustion Appliance Zone testing is a part of the services offered my certified energy auditors. Although many will debate the need for such testing those energy auditors do have the instruments and training to do so and your situation is a good example as to when it is needed.


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