Author Topic: Combustion Testing - Induced Draft  (Read 7825 times)

SLS Construction

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Re: Combustion Testing - Induced Draft
« Reply #10 on: February 18, 2011, 08:45:12 AM »
Hatherly - I agree on the semi-contradiction, but that is not mine, but rather taken directly from BPI

The problem with their standard is how does one understand it, which is influenced by your trainer / reading of it --- For the field tests, as I mentioned in other threads, you basically just parrot back what they taught you & your good - in real life, well therin is the issue

Back to the "you must do a draft test," well guess what needs to be accomplished from the roof based on their standards? Does that help, or make it worse?


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Re: Combustion Testing - Induced Draft
« Reply #11 on: February 19, 2011, 06:33:28 AM »
Thanks, yes I agree, there are contradictions in the BPI standards and also places where things could be spelled out more clearly. One example I always come across if testing the gas line. If your instructor teaches you to move along the line fairly quickly (1 foot per second in a very well know curriculum)  you hardly ever pick up any gas leaks. If your instructor taught you to go slowly (1 inch per second) you are much more likely to find them. I have asked BPI what they recommend and they don't have a specific answer.

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Re: Combustion Testing - Induced Draft
« Reply #12 on: March 26, 2011, 08:18:39 AM »
Rstarr how are you. Induced draft " power combustion" furnace or boiler or tank hot water....... Normally on induced draft boiler or furnace would be an 80% unit with either single wall or double wall flue. When BPI talks about not drilling power vented induced draft unit you should never drill thru PVC pipe and you shouldn't drill thru double wall b-vent metal pipe. But if the unit you are testing is single wall you can drill a hole to get SSE and CO.


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Re: Combustion Testing - Induced Draft
« Reply #13 on: March 01, 2012, 10:43:05 PM »
I have been on many sites where it is unsafe to test from the termination of a sealed combustion unit. Recently a 9/12 pitch, metal roof, with 12" of snow, and warming temperatures forced me to seek out a solution. an expert in home performance training recommended drilling into a positive pressure flue at the typical 12 inches and inserting a brass threaded plug afterwards. This has worked very well in the past and allows the tester much more accurate results, ie no more SSE's of 99.8%. However, I have noticed on some furnaces there have been fenco rubber couplings with testing ports, I am now on the search for how to order some in quantity although I feel the brass plug creates a better seal if the hole size is appropriate. For B vent induced draft testing I drill through both walls and insert a stainless fine thread bolt with high temp furnace cement as an outer gasket. I've toyed with adding a sealant to PVC after drilling but have detected no spillage after the brass plug alone is inserted. Honestly I'd imagine a rubber cork would work well too but could be easily removed by the wrong people.


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Re: Combustion Testing - Induced Draft
« Reply #14 on: March 02, 2012, 02:17:24 PM »
Induced draft does not mean power vented. Before you drill (regardless of what BPI says) check with the code officials. Some jurisdictions require that flues only be drilled by licensed HVAC contractors.

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