Takagi TK-510u-i Vent Question

josephny

Can I use a sidewall concentric vent for a TK-510u-i?

I have read the docs, and so much more, and can't figure it out.

It's confusing, and the part numbers are obsolete, and there is no clear indication of whether concentric works for this non-condensing model.

The wall is 2x6 wood studs, fiberglass batting, sheetrock on inside, vinyl siding outside.

Thank you.

jesmed1

Are you wanting to use one of the direct vent concentric kits in this list?

https://www.takagi.com/products/tankless-water-heaters/tk-510u-i

josephny

Yes, I was hoping for 9008000005

But, it has a condensate trap and I was hoping to not have to have a condensate drain.

And, the product page does not include confirmation that it will work for the 510, and in wood frame wall.

https://www.takagi.com/products/venting/kits/9008001005-3x4-direct-vent-concentric-termination-5x10

jesmed1

I'm not a heating pro, just a homeowner/engineer who has installed my own direct vent flue for a Jotul gas stove. So I'm not going to give you advice, I'm only going to point out what I would pay attention to in the manual if I were doing this installation myself.

If this is the manual you're using, note that pg. 22 says a vertical condensation drain must be installed when there is more than 5 ft equivalent length of vent length, and a 90 degree elbow is 5 ft equivalent. So yes, by definition, if you have a 90-degree elbow, it does say you need a condensate drain. I don't think you can avoid it.

josephny

Makes perfect sense.

Do you think I need to be concerned about using a vent designed as non-combustible vs. combustible?

The kits that are not concentric (intake and exhaust) come in 2 varieties, but only in the manual. When I try to find the parts, the distinction is removed.

The concentric kit does not identify itself as non- or combustible.

jesmed1

If I were you, I would stick closely to the venting instructions in the manual, and use only the vent part numbers in the manual. I'm assuming you have the "indoor" model:

510U Indoor (AT-D3U-IN) (from pg 5 of the manual)

Manual pgs 13 and 14 list all the approved vent part no's for that unit. Based on the part no's in that list, it looks like the kit you linked to above (9008001005) appears to have the approved parts on the list in the manual.

So I think you're on the right track, but I would call their tech support on Monday and confirm that the kit # is approved for use with your model #.

I would also carefully follow the instructions requiring the backflow preventer and the condensate drain. Again, I'm not a heating pro. Just saying what I would do as a cautious homeowner.

And in general, the direct vent piping is designed for use in stud walls. You just have to read and follow the instructions for clearances, etc. Obviously you want to plan to go through the middle of a stud bay so you have max clearance to adjacent studs of possible.

josephny

The part numbers are discontinued. The replacement parts, as indicated only vendors (not AOSmith/Takagi), do not specify that these are compatible.

More importantly, the manual lists various ways to vent, but does not make clear what components are required for each.

For example, 9008147005 is the 5-10" concentric vent system. It does not specify what type of wall it should be used for, not the associated parts such as the flex hose for intake air. It also says that the 5-10" range is for wall thickness, but does not indicate is the exhaust will be a straight shot down to the 4" port on the heater.

Nor whether I need the 9007667005 - Direct Vent Conversion Kit.

jesmed1

If I were installing this for myself, I would do this:

Follow the graphic on lower left of pg 21 for the direct vent concentric termination. The part numbers given in the manual for that are:

4" exhaust / 3" intake DV concentric termination - 5"-10" adjustability 9008147005

4" 3-in-1 adaptor (F-F adaptor, condensatedrain, & back-flow preventer) 9008146005

Then the kit includes a generic piece of 3" flex aluminum for the intake. You can just buy that separately. The kit also lists a part number

9007667005	Direct Vent Conversion Kit

which appears to be simply an adapter piece that screws onto the air intake at the top of the heater and lets you connect the 3" flex intake line to the concentric termination for combustion air intake. Since that is not a safety-critical piece (ie no heat or combusion gas venting involved, I'd honestly make that part myself out of sheet metal if I couldn't find it. It looks like a simple duct port for the combustion air inlet. But if your heater already has a 3" round inlet port for combustion air, you may be able to hose clamp the 3" flex right into it.

So if I were doing this for myself, I would order the 9008147005 concentric termination and the 9008146005 adaptor, and then use generic 3" aluminum flex for the combustion intake as shown in the diagram and kit.

Direct vent flues are typically designed for use through stud walls, so I can't imagine it wouldn't be compatible with your wall. But it will come with installation instructions, and if it won't work with your wall type, it will say so.

josephny

Thank you so much!

That is a great analysis.

But, 9008146005 is discontinued without a replacement.

jesmed1

https://forum.heatinghelp.com/discussion/comment/1833998#Comment_1833998

Then I think your only option is the two-pipe direct-vent sidewall configuration shown on bottom right of pg 21, as that does not require the adaptor, as long as you keep the exhaust run short enough to not require the condensate drain.

Per pg 9 of the manual, look at the "optional" components that have check marks with your 510U indoor unit:

4" backflow preventer and F-F adapter for cold climate

4" Sidewall vent terminator and wall thimble

Plus you'll need a short vertical pipe section, a 90 degree elbow, and a short horizontal pipe section through the wall.

Those should all be compatible with your 510U.

josephny

Thank you.

I see lots of people using PVC for the exhaust. Is this okay?

jesmed1

Not for that heater. The exhaust temperature is too high and will melt PVC.

PVC, CPVC, ABS, or polypropylene exhaust can only be used on condensing heaters, because they recover more heat from the exhaust gases and reduce the exhaust gas temperature to a low level that's safe for plastic.

But then you have to deal with a condensate drain.

For example, here's a Takagi condensing heater that you can vent with PVC, CPVC, or polypropylene:

https://www.supplyhouse.com/Takagi-T-H3M-DV-N-T-H3M-DV-N-Indoor-Tankless-High-Efficiency-Condensing-Water-Heater-w-1-2-Gas-Supply-Lines-NG

josephny

Got it!

Thank you very much for the explanation.