Lochinvar KHN085 Boiler Venting Questions

Pidge

I'm installing a KHN085 boiler and the installation & operation manual seems to require CPVC for the venting material, unless I'm misinterpreting the manual. So, I'd appreciated feedback on where I may be incorrect.

The link for the I&O manual (Rev F 7/11/2017) is here:
http://www.lochinvar.com/products/documentation.aspx?mode=filetype&filetypeid=2
On page 7, it says:
"This appliance requires a special venting
system. If using PVC the vent connection
to the appliance must be made with the
starter CPVC pipe section provided with
the appliance. The field provided vent
fittings must be cemented to the CPVC
pipe section. Use only the vent materials,
primer and cement specified in this
manual to make the vent connections.
Failure to follow this warning could result
in fire, personal injury, or death."

I interpret page 7 to say it is okay to use PVC downstream of the "CPVC pipe section provided with the appliance." The CPCV section includes two CPVC pipes each 3-1/4" long plus a 2" Tee with a 1/2" NPT port for a combustion analyzer sensor. The total length of CPVC is 9 inches.

The problem starts on page 19: the approved pipe cement/primer for PVC is a different than the approved cement/primer for CPVC. The pipe cement/primer requirement for CPVC is ANSI/ASTM F493, but for PVC the requirement is for ANSI/ASTM D2564.

I interpret page 19 to say there is not a pipe cementthat is compatible with both PVC and CPVC. But a different way to read it is - use the PVC cement on the PVC connector socket and the CPVC cement on CPVC pipe - but that looks to be ruled out on page 15,

In the third paragraph on page 15 it says:
"DO NOT mix components from different
systems. The vent system could fail,
causing leakage of flue products into the
living space. Mixing of venting materials
will void the warranty and certification of
the appliance."

I went to the Oatey website FAQ page https://www.oatey.com/PlasticPipeCement and it said you can't use PVC cement on CPVC and you can't use CPVC cement on PVC. And their "All Purpose Cement" can not be used to join PVC to CPVC. So there is no OATEY cement available to transition from CPVC to PVC. That's probably why Lochinvar says you can't mix venting materials.

But page 15, in the second paragraph says:
"This appliance requires a special venting
system. Use only approved stainless steel,
PVC, CPVC or polypropylene pipe and
fittings listed in Tables 3D, 3E, and 3G for
vent pipe, and fittings. Failure to comply
could result in severe personal injury,
death, or substantial property damage."

So Lochinvar says PVC can be used, but requires that the supplied CPVC starter pieces must be used. Given that NONE of the approved cements in Lochinvar's manual can be used to join PVC to CPVC. Fernco fittings sound like the only alternative, but page 15 says "Mixing of venting materials will void the warranty and certification of the appliance."

Finding 2" CPVC pipe in southeast Michigan has been fruitless this weekend. Am I missing something or have you found a way to use PVC on the KHN?

Thanks,
Pidge

Zman

This discussion probably needs to start with. PVC pipe was never intended to vent boilers. Charlotte pipe has taken a fairly firm stand on this and the boiler manufactures are gradually getting on board.

There are several issues with using PVC, the biggest is that it is not designed for the high temps you see close to the boiler. For his reason Lochinvar is requiring CPVC for the first section. As far as cements go, I believe that some CPVC cements are rated for use with PVC if you go that route you would need to make a few calls and track down the right product. Also note that cellular core PVC is not rated for any venting, it must be solid core.

Poly pipe or stainless is a better option.

JUGHNE

I use Oatey #30821 all purpose cement for that transition and have not had any issues with the connection.
The cement states it is for ABS, CPVC or PVC. I have only read what is on the can.
May not state good for joining the 2 together....but does not prohibit it either.
Maybe I have been wrong all along.

You are someone who is actually reading the book!!

kcopp

Just pipe in Poly Pro and you will be far better off. No glue and you can pull it apart later for inspection.
Centrotherm and Duravent are 2 mfg.
You cab still do the intake in pvc.

Pidge

Wow, another case where context is everything! The actual quote from the Oatey website is:

"Can I use All Purpose Cement to join PVC to CPVC?"

"No. It is not recommended because it takes longer for CPVC to finish the curing process necessary to complete a strong bond after the cement is applied. CPVC is also rated for hot water use which will affect cure times. PVC is not rated for hot water temperatures."

I stopped reading at "No". The PVC won't be seeing hot water unless something goes wrong with the boiler. Thanks JUGHNE and Zman. You opened my eyes.

I did a search for 30821 on the Oatey website and it says: "Meets performance requirements of ASTM D2564, ASTM D2235 and ASTM F493."

So the 30821 cement is approved by D2564 for PVC and F493 for CPVC.

Lochnivar says: "Mixing of venting materials will void the warranty and certification of the appliance." But there is a context issue there also. The paragraph begins with:

"DO NOT mix components from different
systems. The vent system could fail,
causing leakage of flue products into the
living space.

I won't be mixing components from different systems. My vent will be a one-system vent, and the CPVC and PVC are both PVC based and Lochinvar says "Use only approved stainless steel,
PVC, CPVC or polypropylene pipe...

So, most of Lochinvar's warnings were stacking up to seem like PVC could not be used. Now with the Oatey 30821 being approved for both, I'm satisfied that PVC can be used with the CPVC as the first section.

I wish I posted yesterday! - lost a lot of time on this non-issue. Thanks so much!
Pidge

Harvey Ramer

Why not just use Poly Prop? That's what it's made for.

JUGHNE

Eventually poly prop will be the law of the land.....I imagine.

Ultra Vent was also an approved method for a while.
I used that twice and couldn't imagine the RTV/couplings could be good.

Pidge

@kcopp & @Harvey - I didn't know anything about polyprop until kcopp's comment. Went looking and found the @keynote discussion back in 2016 titled "CENTROTHERM for KHN 085 Boiler." I'll look into it - thanks.

kcopp

Poly pro is all but the law of the land here in New Hampshire.
The only time you can use pvc is if there is a stack limit switch tripping the boiler off if the temp exceeds 140F. That would be on all boilers and many tankless water heaters. Some FHA furnaces would still be ok.

Henry

Most boiler manufacturers now supply a CPVC transition fitting. You can then use PVC, CPVC, Poly P or AL29-4C. The manufacturers of all these products specify in their instruction manuals how the transition from CPVC transition fittings or the boiler to their product. Both PVC and CPVC manufacturers specify that only their glue is to be used or an approved connector. OATEY is NOT approved by them. We use a mechanical connection on PVC pipe. As to which is better, the AHJ has the final say in your area. In Canada that has much colder weather, S636 PVC is approved. But it is only a different colour SCH 40 PVC pipe and fittings that costs more. LOL

Boon

@Pidge >>>. Finding 2" CPVC pipe in southeast Michigan has been fruitless this weekend.

The brand name is Corzan and Ferguson stocks it but not all of their locations carry it. When you call them you'll need to ask for someone in the hydronic division. They offered to transfer what I needed to a location close to me.

I would've liked to use polypro. It's slick. As a homeowner I couldn't find anyone who'd sell it to me! That isn't entirely true. I was able to buy some pieces but other parts were special order, really expensive (for a not-in-the-trade customer), and lead time was too long so I was stuck with CPVC.

Also, I called Lochinvar tech support to ask about transitioning from CPVC to PVC and they said I could use threaded male & female adapters so that is how I made the transition.

EBEBRATT-Ed

Ipex is the only manufacturer that their PVC is listed for venting, says it on the pipe.

That being said CPVC is better than PVC and polypro is better than both of them.

Around here (western MA) there is still a lot of PVC being used

hot_rod

interesting that the Centrotherm shows different temperature ratings for gas and oil fired??

I suspect some mod cons, especially dirty ones can run close to that max temperature rating.

Those poly vent systems were originally developed for Euro systems where they run boilers around 70°C max. We will see how it holds up on high temperature US systems, especially the EPDM gaskets?

Some of the early stainless had gasket issues also, until they went to the red silicone gaskets.

rick in Alaska

I wish I could get the cpvc here. I have seen too many gasketed vent systems where the gasket has failed, and most importantly, I don't like the looks of all those clamps on the polypro. But... I do use it. Also, with the cpvc, it is easier to cut exact fits than have to use the clamp setups with the polypro.
Rick

Henry

Royal is listed as S636 PVC and is available. You cannot mix IPEX or Royal pipe, fittings or glue! The expansion of CPVC is greater than PVC. Using a male to female adaptors will most probably ended up leaking. That is why we use clips that are listed.

Pidge

Pidge said:

@Boon >>>. The brand name is Corzan and Ferguson stocks it but not all of their locations carry it.

Thanks Boon! The local Ferguson's says they'll have have a 10ft stick with CPVC elbows and a coupling on Wednesday morning.

So the first 10 ft will be CPVC with some PVC downstream. The intake air will be PVC. The CPVC will allow precise custom lengths - fitting polypro seems more difficult.
Pidge

Boon

So the first 10 ft will be CPVC with some PVC downstream.

btw, the only reason I transitioned to PVC downstream of the CPVC is because I was using the concentric kit, which is PVC. If you're not using the concentric kit I don't think there is a need to transition.

Pidge

Henry said:

@Henry > Most boiler manufacturers now supply a CPVC transition fitting. You can then use PVC, CPVC, Poly P or AL29-4C. The manufacturers of all these products specify in their instruction manuals how the transition from CPVC transition fittings or the boiler to their product. Both PVC and CPVC manufacturers specify that only their glue is to be used or an approved connector. OATEY is NOT approved by them. We use a mechanical connection on PVC pipe. As to which is better, the AHJ has the final say in your area. In Canada that has much colder weather, S636 PVC is approved. But it is only a different colour SCH 40 PVC pipe and fittings that costs more. LOL

I'm not too worried by the CPVC and PVC manufacturers' assertions, because Lochinvar's manual says that the cement requirement for CPVC is ANSI/ASTM F493, and the requirement for PVC is ANSI/ASTM D2564. @JUNGHE said he uses Oatey #30821, and according to Oatey, it meets both F493 and D2564.

Again, context is important. If a pipe assembly with mixed PVC and CPVC is carrying 160F water under pressure, I'd keep my distance! The same pipe used as condensing furnace vent, used with low temp radiant panels, is a much more forgiving condition, and approved by Lochinvar.
Pidge

Pidge

Boon said:

I transitioned to PVC downstream of the CPVC is because I was using the concentric kit, which is PVC.

The reasons I'm adding PVC is because finding 2" CPCV is hard, and a 10ft CPCV stick costs 15 times more than solid core PVC in southeast MI.

JUGHNE

If the transition from PVC to CPVC is worrisome, how about "Fernco"'s or No-Hub couplings. EDPM that seems similar to most rubber coupling in many condensing furnaces and boilers.

I have PVC vents on cond FAF installed since when they first were on the market. If there was a serious issue I would have heard about it.....this is a small town....you own a system forever.
I realize that they don't approach the temp of a ModCon doing DHW on an indirect, but the 30 year factor of baking the PVC has not surfaced yet. FWIW

hot_rod

JUGHNE said:

If the transition from PVC to CPVC is worrisome, how about "Fernco"'s or No-Hub couplings. EDPM that seems similar to most rubber coupling in many condensing furnaces and boilers.

I have PVC vents on cond FAF installed since when they first were on the market. If there was a serious issue I would have heard about it.....this is a small town....you own a system forever.
I realize that they don't approach the temp of a ModCon doing DHW on an indirect, but the 30 year factor of baking the PVC has not surfaced yet. FWIW

Raises the same question as PVC, does Fernco or Mission approve their couplings for venting combustion byproducts

kcopp

All the more reason to ditch the pvc/ cpvc and do the polypropylene.
Its much easier to work with....

JUGHNE

When a condensing furnace/boiler manufacture includes the CPVC starter pipe and/or also connects the inducer blower with a "Fernco-type" connector, also include a 2" PVC tee for condensate drainage, we all make assumptions that included parts are approved for the intended purpose????

NY_Rob

^ yeah, especially when you see this in the install manual...
"NOTE: The included 6” length of 3” CPVC pipe MUST BE INSTALLED in the exhaust vent connection BEFORE venting the boiler.
Failure to properly install the included 6” length of 3” CPVC pipe BEFORE venting the boiler could result in product damage, severe personal injury, or death."

Back to PVC.... I can already see a slight color difference between the intake pipe and exhaust pipe on my MOD-CON just after one year of use. I can't imagine the outdoor section of the PVC exhaust could hold up to 30yrs of sun and weather exposure.

hot_rod

The PVC that goes yellow quickly are often seen on systems that run continuous high temptation operation. Yes some installers run 180F mod cons for fin tube. I doubt this is 30 years old, maybe not even 20?

NY_Rob

^ One "support tech" at HTP told me he runs his UFT as a regular 180F boiler.

The indoors section of my PVC (both intake and exhaust) have not discolored at all, only slight loss of shine and slight but noticeable discoloration to the outdoor straight pipe (no discoloration to the outdoor elbow and coupling) for the exhaust PVC pipe. The outdoor section of the intake PVC still looks like new after one year's use.

JUGHNE

Sunlight UV is supposed to cause PVC to waste away.
But look at the thousands of PVC stubs venting thru the roofs for DWV systems. Do they ever fail for this reason?

It was the reason I used 3" grey SCH 80 PVC electrical sunlight resistant pipe to poke thru the roof. Looks better than white IMO.