specs for chimney liner and insulation

JackFre

Your local code enforacement official...if there is one. Inside the chimney, if you go with a "clean out/drip leg" on the liner it has to be able to be accessed for cleaning. Yes, it can be formed/blocked above prior to the pour. This is all very dependent upon what you have there. Sounds like you are pretty squared away on this by the questions you are asking. The wye fitting I was talking of should be turned so the branch leg tips down. That way any moisture "should" run to the lateral and create a drip, thereby protecting the rest of the vent connector and boiler from harm.

D107

2nd thread on chimneys for another house

This is for my mother's house and upcoming boiler replacement.
outside 7x7 chimney (actual flue size) 22'ft high. Existing terra cotta lining. The proposal is for a Buderus G115-21 oil fired or GA-124 similar sized gas fired.

1-Install 5-6" double wall Round UL316 stainless steel (corrugated on outside, smooth wall inside) liner top to bottom with direct 6" T connector insulated throughout with Thermix. Top Plate for support, re-install cap at top. Hi temp refractory cement at Base. Lifetime Guaranteed. Looks like this is a continuous coil of liner; I had thought they'd lower it in sections, but I guess this is the way they do it now.

Interesting that another company only wanted to insulate the top portion. This company says no mesh is required since the thermix will adhere to the walls. They pump up and pour the cement into an inverted traffic cone down chimney instead of lugging up big buckets of the thermix.

As for exact size, buderus g-115 calls for a 5" flue,smaller than usual since with the new efficiency flue temps are down and condensation could be a problem with a larger flue. Chimney co says: "The liner size is based on GPH of the nozzle (firing rate) and the steady state efficiency of the oil-fired appliance,chimney height and the lateral length of the connecting pipes."

So my question is, how does their chart take into consideration the newer efficiency of the modern boiler? (or is that the 'steady state efficiency' part?) You could have two boilers, one old burnham atmospheric and one buderus G-115 with same gph, etc. and the chart would tell you different flue sizes. Or perhaps the chart will agree that the 5" flue falls in the workable range.

By the way I was told they can insulate with a sarafoil blanket, then put sock mesh over that instead of the thermix, but not with a 7" chase and 5" liner--too tight if chimney has any projections or bends.

Thanks,

David

PS I'm seeing how each of these major tasks breaks down into all the components and subcomponents. Interesting how it all works together (or might not if it's not done right.)

Bob Harper

oil liner

They are referring to charts in the back of NFPA 31, which goes up to 86% SSE. While not required for oil, insulation will improve that exterior chimney. You can wrap it with ceramic fiber blanket w/ mesh or pour Thermix. Note" if they are pumping Thermix, it is too wet. Should be the consistency of potting soil. At 22 ft. for a Bed, I'd go with a 5.5" liner. If it was 30 ft., I'd say the 5" is fine.
You must incorporate a clean out into the base of the liner. You can use that tee but it will require a separate access door. Lay out the chimney connector for a nice rise off the top then ell to the breech. The water pipes can fit around the smoke pipe.
HTH

D107

condensate trap required?

Thanks Bob. I assume 'Bed' is a typo, you meant Bud i.e. Buderus re: flue size/chimney height. fyi Buderus G115-21 firing rate is .60gph (84KBtu)

I guess the boiler people would be the ones installing a condensate trap, but would you recommend that to catch any potential condensate before it dripped into boiler? The traps I've seen are sleeved into the horizontal flue pipe between boiler and chimney.

Thanks,

David

Bob Harper

this bud's fior me

Yup, sorry for the typo-

All masonry chimneys require clean outs and so does NFPA 31, 54, 211, ASHRAE, IRC, GAMA, and just about any body that mfrs nat. draft combustion appliances. Even with liners, you still need the clean out to catch oil soot instead of chunks of failing terra cotta.
Some guys put the clean out/ trap just inside the basement wall. As long as the crud doesn't obstruct the flue, your Building Offical might approve this setup. I like it better as long as you can make a hockey stick and get a broad radius curve.

JackFre

Prior to doing this

get approval from the ahj. If You cannot run a clean-out leg to the inspection door in the chimney and access it once the chase is insulated, I've put as long a sweep as I could fit exiting the cent connector. Reverse a wye fitting to that sweep and then connect back to the boiler. Cap the branch. That branch becomes your clean-out access, but of course you loose the sump. This works pretty well...as long as you inspect for leaf debris, etc. Vermiculite is a pretty good insulation. Just make sure you don't have a blow out,

D107

Already is a cleanout below breech

Thanks for your alternative specs. If I understand you, we should try to make sure that the thermix doesn't block up that cleanout; I guess the chimney company can put some kind of gasket or fiberglass below the breech to block it when it's poured. (what is ahj?)

I was under the impression that aside from a cleanout below the breech, a condensate trap was also required to catch any flow down the inside of the front wall that might find its way into the horizontal flue pipe and then into the boiler. The cleanout would pick up debris and condensate from the other walls. I'll be happy if all I need is the standard cleanout, which I guess all of us homeowners should remember to inspect a few times a year for debris so that it doesn't accumulate above the breeching and possibly cause a blowout.

Thanks,

David