Venting of mid efficiency via chimney

Stenty

Hello,

The current water heater is a 20yo gas fired tank atmospheric vented into a masonry chimney with single wall 26ga 3" pipe. Its making those wonderful gurgling sounds whenever a faucet is opened.
I'm looking to replace it with something with a higher efficiency but not necessarily a condensing unit.
Maybe a mid efficiency tank or tankless.
I looked at the Rheem EcoSense direct vent but the venting accessories are all double wall steel and I'm assuming that its a coaxial setup where supply air is brought in via that piping. I wouldn't be able to support the piping every 4' as required in the instruction so that's a no go.
Any suggestions?
Mid or high efficiency, masonry chimney vented, tank or tankless.

SWEI

Any utility rebates available? How hard is the water, and what kind of chloride levels?

Stenty

Municipal water. There is very little scale issues and it tastes pretty good, no sense of chlorine in the taste of it.

Stenty

The Noritz NR981-SV-NG has single wall venting.

SWEI

I would suggest a condensing TWH with PP flexible venting. Installs in the existing chimney in about an hour, costs far less than stainless vent material.

Stenty

Would the upfront costs of a condensing unit outweigh the cost of SS vents?
Would a condensing unit also require piping for outside air?

SWEI

Stenty said:

Would the upfront costs of a condensing unit outweigh the cost of SS vents?

By far, IME.

Would a condensing unit also require piping for outside air?

Generally yes, but depending on the TWH manufacturer and the leakiness of the basement -- maybe not.

Steamhead

What other units are venting into that chimney?

Stenty

No other appliances.

Steamhead

That would let you do pretty much whatever you want, within the limits of safety. It's possible, as others have stated, to use the chimney as a chase for a concentric venting system. You want to avoid venting an appliance directly into the chimney that is so small it doesn't create proper draft, allows the exhaust gases to condense in the chimney, or both.

Whatever you do, avoid the use of PVC pipe for venting combustion appliances. Polypropylene (PP) or stainless steel are the way to go- they are UL listed for venting combustion appliances whereas PVC/CPVC is not. Yes, we see a lot of PVC combustion venting, but that doesn't mean it's the right way to go.

Stenty

The Noritz NR981-SV is listed as Category III.
The Polypro Duravent pipe is listed a Category II and IV. Does that qualify it for Category III ? I don't know enough about the categories.
I once bought aluminum flue liner from my supply house for a gas boiler

SWEI

Stenty said:

The Noritz NR981-SV is listed as Category III.
The Polypro Duravent pipe is listed a Category II and IV. Does that qualify it for Category III ?

No.

Takagi/AO Smith and Rinnai both use Category IV on their condensing TWH models. I'm sure there are others.

Stenty

The Noritz NR981-SV is non-condensing.

Category II
An appliance that operates with negative static pressure in the vent and a temperature that is low enough to cause excessive condensation in the vent.

Category III
An appliance that operates with positive static pressure in the vent and a temperature that is high enough to avoid condensation in vent.

Category IV
An appliance that operates with positive static pressure in the vent and a temperature that is low enough to
cause excessive condensation in the vent.

SWEI

Right, so it needs stainless venting.

ChrisJ

What about lining the chimney with the appropriate size liner and installing one of these guys?

http://www.supplyhouse.com/Bradford-White-RG2D50S6N-50-Gallon-40000-BTU-Defender-Safety-System-Damper-Atmos-Vent-High-EF-Energy-Saver-Residential-Water-Heater-Nat-Gas


I'm suggesting this due to simplicity and silence. A standard atmospheric would be the cheapest, but I hate the pilot and all of that heat always going up the flue.

4Johnpipe

http://www.htproducts.com/poly-pro.html