whats this mean?

[ssupercoolss]

Clearances and Dimensions

Rear 24 inches
Side 18 inches
Front 36 inches
Clearance To Flue Pipe 18 inches

i am now in phase 2 of my multi phase boiler install. phase 2 is the permiting. can someone explain to me what "clearance to flue pipe" means? is that the clearance to combustibles for where the flue will go through the wall?

thanks

 

[heaterman]

It means that the clearance required around the single wall "breeching" pipe, going from the boiler to the chimney needs to have a clear area of 18" around it. If you are going through a wall you need to change from a single wall pipe to an insulated double wall using the correct fittings. The double wall pipe will have a special collar which needs to be installed in the wall and they are made by each manufacturer specifically for their brand of pipe.

Back to the 18" thing. You can reduce that clearance by using metal flashing, spaced an inch or two off the combustible surface. This allows air to circulate behind the metal and keep the combustibles safely cool. Your inspector will have details on what he or the code requires for this. He/she has the final say because every code book I have read always includes the statement "subject to local jurisdiction". Get him in the loop at an early stage of the game and your job will go smoother. Most are very helpful but there are some that are just on a power trip and are arrogant donkeys ......or whatever word you want to substitute.

 

[ssupercoolss]

makes sense now. but since we are on the subject, my pipe will exit the house through a stone foundation wall. i would have to assume that my double wall pipe going through the wall would have to be at least 18" from any joist, since this single wall flue pipe will be going into it. unless of course i do something with the metal flashing. there is a question on the permit about distance from flue to joist.

 

[heaterman]

Exactly. You probably don't want to penetrate the foundation at two feet below grade and you may also run into issues of the flue collar height on the boiler being higher than what the 18" from the joist will allow. Hence the reduced clearance situation. Basically, about the only situation you can't get away with is running the breeching up in between the joists.
Note that the clearances listed are to combustible material. Your stone foundation wall is not combustible. You would use a heavy metal sleeve through the wall which would connect your breeching pipe to the chimney or else make the penetration large enough to get the breeching pipe all the way through to the chimney itself. I like to open the wall into the chimney and use a heavy gauge metal pipe, flush with the chimney liner and the basement side of the wall and cement it permanently in place. Your breeching pipe would connect to that.

 

[ssupercoolss]

it never crossed my mind about the height of the flue on the boiler, i am going to have to lay this out on the wall and double check my math. quick math says i should be ok with 18" below the joist, but i wont have quite the difference in height that i thought i was going to. my chimney will be all class A insulated, which means my pipe going through the foundatin will be a piece of class A, correct?

 

[heaterman]

it never crossed my mind about the height of the flue on the boiler, i am going to have to lay this out on the wall and double check my math. quick math says i should be ok with 18" below the joist, but i wont have quite the difference in height that i thought i was going to. my chimney will be all class A insulated, which means my pipe going through the foundatin will be a piece of class A, correct?

You certainly want to check that dimension and yes, Class A through the foundation will work well and satisfy the code requirements. Make sure that you get it sealed securely into the chimney.