Co-linear Venting

[pgf001]

Hi,

I just purchased a used natural gas fireplace insert. This insert was made by Superior around 2000 but still works fine. It has a 2" intake and a 3" exhaust co-linear vents. I have done a lot of research and cannot find a kit that comes with a chimney cap and the 2" & 3" liners. I have called a few companies that could fabricate me one for around $550.

My question is can I save money by buying a single 3" exhaust liner kit with chimney cap ($60) and then buy a separate 2" liner that would pull fresh outdoor air from the side of the chimney ($25)? The exhaust will run to the top of the chimney about 30 feet and the intake will run up the chimney about 6 feet where I would tap a hole for the 2" to run outside.

Option 2: I could run the intake down into the basement (through my fireplace ash clean out) and pull fresh air down there.

Option 3: I have read that some people don't even run the intake liner all the way up the chimney. That they run the exhaust all the way up then leave the intake half way and let it draw air at that point... any disadvantage to this?

Correct me if I am missing something but I do not see the advantage of running both intake and exhaust liners up the chimney for $550. Especially since the insert is 18 years old and is no longer under warranty. All opinions and advice is appreciated!

 

[DAKSY]

I would get the liner kit with (2) 3" flexible liners & run BOTH all the way to the cap.
I have seen them available for about $325 (https://www.efireplacestore.com/cui-46dvacl33.html)
Find, fabricate or have fabricated a 2" - 3" increaser to use on the 2" intake side,
or simply crimp the end of the 3" liner down to a 2" configuration & secure it to the intake port.
My reasoning:
(1) If, in the future, you change out the insert to a newer one with 3" intake & exhaust ports,
you can simply remove the increaser, or cut off the crimped section & you're ready to go...
(2) Running BOTH to the cap allows you to insulate just under the adapter plate at the top
of your chimney & also insulating the damper area where the liners enter the firebox.
This will effectively create a dead air space between the insulation areas & that is nearly
as good as insulating the entire flue.
Hope this helps...

 

[pgf001]

I think that is a great idea. However, when I talked to the fireplace companies (That I received the custom cap quotes from) they said that too much air intake could give me issues. This could just be the salesman in them trying to sell me a $500 kit versus a $300. But what you said gives me another idea... Im thinking ill do what you say and then add a 2" inside of the 3". Then ill mount the 2" to the fireplace and leave the 3" hanging . This way the 3" is there for the future and the 2" can just be pulled out. Or the 2" can be abandoned in the 3" at a later time... I wouldn't think it would choke the new fireplace being in there

 

[DAKSY]

What the salesman is probably getting at is too much incoming air can agitate the pilot &
if the flame moves off the thermocouple (TC), the gas flow will stop as a safety measure.
I would try the 3" & if you have a pilot issue, fabricate a small restrictor or pilot surround to
mitigate the effect of moving air on the TC...