Questions on chimney liners

Back in '91 when the efficiencies of gas equipment were mandated to a minimum of 78% the whole chimney lining industry took off, aside from that which had been done for solid fuel burning appliances. It was a lot of fun doing the trainings and having the conversations on what was happening in masonry chimneys. No one wanted to hear it, but the evidence was irrefutable and over time each subsequent edition of NFPA 54 became more and more stringent on the requirements for re-lining masonry flues. I was representing Z-Flex, Metalbestos and Tjernlund in those days so I had a really good view of what was going on.

I applied and was accepted to be a member of the NFPA 31 Committee in, I think it was '93. Closely following that was when the Brookhaven report on Oil Fired Vent System Operation came out. Richard Krawjewski and John Strasser were the project engineers and they did an exhaustive study on the operation of chimneys on oil fired equipment. Their findings, which strongly supported re-lining, were reported to the 31 group and ended up being put into Appendix E, so as to not become a part of the code. No one, almost no one, in the industry wanted to add costs to oil fired installations due to competitive fears, so E is still an appendix item regardless of what the Brookhaven report said. The sizings in "E" are right on the money from those I have spoken with who have used them over the years. I solved more than a few problems actually relining a couple well known oil systems using 4" pellet vent, and the systems purred.

Oil systems do condense. As HG has noted the purpose of a liner is to reduce the "wet time" in a flue. Every system on a cold start will condense. Yes, you do want to have a flue designed to heat up quickly and SS will certainly do that while the mass of masonry MAY not. Every system has a personality. How is yours doings? A properly designed flue , in my experience, does improve light-off and does , or at least can, improve efficiency. Establishing good draft faster, by having a warm flue gets the draw going through the appliance faster, sooner and better. As with all combustion equipment you don't have pristine operation at start-up. If you are going to get any dirty combustion it is then. Over a long season if that condition lasts longer due to slow draft the small amount of soot finds its way onto the interior of your appliance and it sticks. It only takes a few mils of scale to reduce heat transfer. Of course you will never notice it because that will reduce heat transfer and your stack temp will go up and the chimney will operate better. Problem solved;) A high mass, oversized masonry flue will not operate as well as a properly sized low mass SS flue! High mass oversized masonry is 11th Century technology venting 21st Century appliances.

Net/net, you have a professional sweep on site examining YOUR chimney. Every system has its own personality. You just hope yours is more Jeckyl than Hyde. Evaluate the operation of your system.

It was pointed out, and thank you Kurt, that my model numbers on the double wall were incorrect. Duravents is a DVL. I went to Selkirk's site and was so confused I gave up looking, but was informed it is a DSP. My apologies for the error.

Happy Heating!

That's high,with all the baffles in and at max firing rate, 280* is average