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The Value of a 'Priming' Door on a Batch Box Masonry Heater

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When I built my 5" Batch Box combined Masonry/Water heater last December I incorporated a cast iron access door near the base of the brick bell.
The purpose of the door was to allow access to the original brick chimney that I use for the BB exhaust, for inspection and sweeping. I also made provision to light a 'priming' fire at the base of the stack to start the draw in the system (if needed) after not using the BB for some time.
Well, today is cold and wet in North Wales (UK) and I duly fired up the BB for the first time for several weeks to humour my Daughter who is revising for exams and is feeling the cold...

Disaster!! I forgot to light a priming fire and the BB smoked the room out! I tried to light a priming fire (with the BB firebox still well alight) but the downward gasses and smoke put the newspaper out...
Once doors and windows were open to clear the smoke and the fire in the BB was down to coals, I was able to light a priming fire and the BB is now working perfectly

The moral of this story is -

1/ If using an old masonry chimney for your BB exhaust in cold, damp climates, it would be well worth building an inspection door into the bell near the base of the stack, so that you can light a priming fire to establish a draw if needed.

2/ If in doubt, light a priming fire...! Don't risk smoking the house out.
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Location: Massachusetts, 6b, urban, nearish coast, apartment building, landscaping, help!
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Thanks for the tip!  This is so valuable, experiential info from an actual situation, where you had actually built that door in place and could test out the need for it.  Now if I ever have this problem I'll know what to do, and will consider that in a design.

Thanks for sharing it, and glad no one got hurt!
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