when you use two 45 degree to replace a 90 degree, to have less flue "resistance" (not sure what is the proper term) do you have to put a small section between the 45 or you can simply connect them together?
Connect away. You may choose to add a short straight piece in between the two 45's but only if you have the room and this will increase the sweep (radius) of the turn. Is this going to be used for venting? Or air ducting? Is this single wall pipe? If so, you can always buy an adjustable 90 and spin it down to a 45....in your case, buy two, no?
Just so you know, I used two 45's in order to offset the vertical rise of my single wall stove pipe into a ceiling class A pipe. The new stove needed to be moved for clearance requirements; thus the two 45s. I did get the adj 90s since this was single wall pipe. If I had vented into a wall thimble, I would have used one 90. Just preference as it would be much easier to take apart one 90 (in a wall thimble application) for cleaning as opposed to two 45s.
I'm looking into replacing my double wall here I'm not 100% comfortable with the top clearance and the airflow "opening" in the double wall at the top/bottom and far left there is only about 6-7 inch between the pipe and the ceiling and I don't know who made these pipe so I don't want to mix pipe (and it is not recommended anyway) so I'm looking into completely replacing these pipe and while at it switching from 90 to 2x 45
OK, now I understand. (pics=) Too bad you can't find out the specs on the existing pipe clearance requirements. Looks like it was alright but peace of mind goes a long way!
But, going back to the original question, it looks like you may need a short piece in between the 45s if you choose not to move the stove closer to the corner. This is assuming that you will be installing a 45 right at the wall thimble to keep away from the ceiling, no?
I am doing the reverse of the op 2 45's to to connect stove to celing flange - had to move ceiling box out further in to room due to interference with roof support construction in actic- not possible to sister anything. as it was right in line with the valley between 2 wings can't load pic too big no time to mess with resizing
it's going to be: 12 inch, 45, 45, down to stove, the long section from the kit that I have doesnt allow 45, something, 45, down to stove Yeah i'm/will fixing that too ;-)
