# Noritz tankless heaters



## ILPlumber (Jun 17, 2008)

I am looking at swapping out a large amount of tank type WH's for 
Noritz N-0931M-DV

Looks like I can get around 6 gpm out of one. High fire is 250,000 btu.

They want the 4 exhaust run out of the residences through 6" type B vent that is existing. I can't find anything in NFPA that says this can't be done. It just doesn't seem right to me. 

What say you?

Also, say it is legal to do this. What would a creative way be to flash this 4" vent exiting through a 6" high wind cap OR open ended 6" type B.

Is there a more reasonably priced heater I could spec as a deduct to possibly catch the job. 

I am just getting into this. I haven't recieved my prints yet. Just wanted to get some input.

Thanks.

Matt

Edit: Obviously, there are no other appliances venting through the 6" type B.


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## Master Mark (Aug 14, 2009)

*you are gonna burn the house down*

you are doing 4 of them??

you aren not supposed to use an old vent
with these things,,, you must run that expensive 
SS pipe out the side or you will get into troubles


running 4 exausts through a 6 inch b vent 
I could see that vent glow red if all 4 come
 on at the same time.....

the place could burn right down to the ground
sometime in thenext few months...

I was going to install a takagi in 
my house but was told not to even put them in a moarter chimmney


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## Plumber Jim (Jun 19, 2008)

Does the manufacture show that as a proper way to vent them? If not then no way. I don't know that brand well but you either do SS or get a condensing tankless and do pvc.


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## Plumbworker (Oct 23, 2008)

on some of those heaters they are so efficent the condensation will rott out galvy b vent and as far i know you have to individually vent them. but i did put in a aquastar unit that used 5" bvent the one with the hydro valve no standing pilot no electrical pretty sweet! i think it was a 425 hn?


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## Master Mark (Aug 14, 2009)

*its very hot*

when one of those tankless heaters comes on
it send out a blast like a f 15 tomcat

I would love to see how many already have been put 
in wrong over the past few years.

they want the SS and its pretty expensive ..


 

The navien tankless uses pvc pipe on theirs
maybe you ought to consider that brand


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## 422 plumber (Jul 31, 2008)

Are you talking about using the B-vent as a pipechase? I am going to do it at my house. I am putting in two Noritz 841's at my boss' house. It can be vented with pvc.


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## 422 plumber (Jul 31, 2008)

They get a tax credit on certain models. That might help you sell them.


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## 22rifle (Jun 14, 2008)

Hey y'all... I think he is talking about using the existing 6" as a chase for his 4" vents for each unit.


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## smellslike$tome (Jun 16, 2008)

NO B-VENT! Are these vertical or horizontal? I'm in a southern climate and the least expensive is an OD unit. Forget it if your in the north. 2nd best is locate on an exterior wall and use the horizontal vent kit. If units are located on 2nd story or higher residences you'll need a lift or some means of getting up there (wouldn't do it that way for only 1 but sounds like you are doing a bunch of them). 

Are these residences? Apartments? Condos?

Why only 6 gpm out of a 931? This is based on incoming water temp?

931 does not qualify for the tax credit.

751 does qualify but if you are up north this may prove inadequate, check the tables.


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## Plumber Jim (Jun 19, 2008)

Ok, I see what you are saying.. you are planning on using the old 6" bvent as a chase. could you cut the b vent flush with the roof then get a flashing that will cover it or cut it below the roof in the attic and have a roofer patch the roof and flash for the 4" through the new hole.


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## ILPlumber (Jun 17, 2008)

smellslike$tome said:


> Are these residences? Apartments? Condos?
> 
> Why only 6 gpm out of a 931? This is based on incoming water temp?
> 
> ...


 
The B vent will be used as a pipe chase.

57 degree incoming water. 60 degree rise is around 6 gpm. 

No tax credit. 

These are apartments.

The exhaust will go through the type B "chase". Intake will be sidewall.


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## ILPlumber (Jun 17, 2008)

Plumber Jim said:


> Ok, I see what you are saying.. you are planning on using the old 6" bvent as a chase. could you cut the b vent flush with the roof then get a flashing that will cover it or cut it below the roof in the attic and have a roofer patch the roof and flash for the 4" through the new hole.


I was trying to keep from having to pay a roofer to re-flash. There may be no alternative.


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## 422 plumber (Jul 31, 2008)

Call Noritz, bro. I would bet you can use the B-vent, I would leave the end of the pvc about 6" shy of the vent cap.


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## Tankless (Jun 12, 2008)

Ok, here's the deal: it is not 6gpm @ a 60degree rise it is 7 gpm.
I have done a lot of applications like this and here's some experience for you.










It is frowned upon to sleeve CAT III venting. The correct way to do it, is to remove (or new penetrations) the existing venting and reflash it. Sometimes you can leave the roof jacks and just reflash it with Henrys.
The cheepie way would be to sleeve it and flash the transition from the B vent to 4" with a galvi ring. It's hookie but it will work. There is nothing in the manual that says to not sleeve it (especially now) but I was told not to do it but....it's not illegal. 

As for venting, if your vent pieces are longer than 3 feet than you need to use a condensate tee, it's important and you will void the warranty if you don't use it.

Now for the unit, you may use that unit, but ya gotta know that you will lose the residential warranty. The warranty will automatically be reduced to the commercial warranty. 4 yrs on parts, 5 on the heat exchanger.
It needs to be mentioned that if there is a recirculation system that is NOT an OnDemand style you will also have the warranty revert to commercial lengths.


You also need to consider water hardness. Effective....about 6 months ago Noritz is now stating the hardness has to be at least at a certain PPM. This is important because, the units won't fail in a year if water is too hard, they will fail in 3 or 5 years. They are expensive to buy and a bit of work to replace (not too bad on that unit). if there is a softener or a softener service you STILL need to make sure the water is soft enough. I have had a few apartment buildings that I have done the repairs for free, because I didn't know better when I installed them...no one knew back then. Please believe this is an important one, and I have actually unsold tankless in a few commercial applications for this reason. Commercial water treatment is expensive, and I didn't want the headach in a few years. 


Now, the unit:
As Smells mentioned the 931 does not come with the Obama tax credit. It doesn't because this particular unit is not as efficient as the others.

You can do 4 9.31 units and max out at 28 gpm, or you can do 5 7.51 and max out at the same 28 GPM. You will also need a multi unit controller once you pass 2 units. It's just a box, you install in one of the units and plug a handful of clips into....it's easy, but you better do your homework or you will spend hours having tech support walking you through it.
Now, even if you dod the Obama rebate, I don't know if it is applicable to commercial investment property owners (they need to call their CPA). AND the credit is for 30% of the entire job, up to 1500. As you know 1500 is not much on a job like this. 

My point: The correct way to do this installation is to use the ASTM models. The only difference is the heat exchanger is made with a thicker copper (K) and it is designed for longer run times and more cycles. But pricing is affected by a lot.

If this was my job, I would push for th 831 commercial unit. It's condensing, PVC venting (3" for very short runs or 4" for the rest). They are damn fine units, quiet and spec out a little higher than the printed numbers. Now, if the 931's have been bought and you were told to simply install them here's some tips:

Combustable CLEAN air makeup is VITAL. You will destroy the exchangers and the air inlets / fan will get filthy, start making noises, the flame will degrade causing more gas for the same flow as well as a pile of other problems, believe that, cuz I deal with it all the time. 

Next, gas: 4 of the 9.31, is 1 million CFH. Better gas it correctly. Make sure your gas supplier has the meters. Took me about a month for SoCal Gas to get one for me at that size but it should be available.

Install the isolation valves. It's the professional way to do the installation and if you sell a service contract with it you will be making your future job a hell of a lot easier. And please for the love of God, do not use flex connectors to the gas inlet. it's a 3/4" inlet but please hard pipe it. You will (and this is a gaurentee) lose anywhere between .5" to 1" of water collum (i can't spell that word).

You need to pay particular attention to the recirculation system, it can and will kill your heaters if it runs 24/7. You will still have the warranty, but you won't be getting paid to do the repairs. In a job like this the correct way to do it is with the use of a standby tank and two pumps. I am hoping to get a small hotel to try it out on.

These are just a few of the main components on a job like this that need to be addresses. Again, it's just from my experiences.

Take pictures, but don't post them on here, because there will always be somebody that can do it better:no:

Let me know if I can help you out with the job.


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## Tankless (Jun 12, 2008)

hmmm, not that I think about it, I think I was told that sleeveing the CAT IIi with B vent can create condensate on the outside of the CAT III pipe and cause it to rot out....I have to think about that a little longer, but it's along those lines....I can find out if you really want to know


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## Master Mark (Aug 14, 2009)

*good post*



Tankless said:


> You also need to consider water hardness. Effective....about 6 months ago Noritz is now stating the hardness has to be at least at a certain PPM. This is important because, the units won't fail in a year if water is too hard, they will fail in 3 or 5 years. They are expensive to buy and a bit of work to replace (not too bad on that unit). if there is a softener or a softener service you STILL need to make sure the water is soft enough. I have had a few apartment buildings that I have done the repairs for free, because I didn't know better when I installed them...no one knew back then. Please believe this is an important one, and I have actually unsold tankless in a few commercial applications for this reason. Commercial water treatment is expensive, and I didn't want the headach in a few years.
> 
> 
> good post , it souinds like you have had some bitter experiences with the units getting limed up ..
> ...


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## SewerRatz (Apr 25, 2009)

Mr. Tankless sir, great post, very informative, but I hate to correct you on a couple things in your post. Nothing big though.

First of the 751 units you can only quick link two units together. They are not compatible with the multi system controller.

Second there is no 831 unit its the 841 (simple typo mistake). 

As for water temperature yes IL said 57º with a 60º rise. I am not sure how far south IL is but around here in the winter our temperatures can get as low as 50º, so that will be a 70º rise which will only yield 6.0 gpm. I will let IL clarify this himself, but I have a feeling he was taking winter water temperatures in account.


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## Cal (Jun 17, 2008)

I just signed up for these Mark . Am looking forward to getting a lot of info !! Still have NO IDEA on a cost for these units but the info looks real good !!

http://www.eternalwaterheater.com/


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## ILPlumber (Jun 17, 2008)

Tankless said:


> hmmm, not that I think about it, I think I was told that sleeveing the CAT IIi with B vent can create condensate on the outside of the CAT III pipe and cause it to rot out....I have to think about that a little longer, but it's along those lines....I can find out if you really want to know


I can call. Thanks though.


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## Master Mark (Aug 14, 2009)

Cal said:


> I just signed up for these Mark . Am looking forward to getting a lot of info !! Still have NO IDEA on a cost for these units but the info looks real good !!
> 
> http://www.eternalwaterheater.com/


 
I have been quoted 22oo for the smaller one and 25oo for the larger one.

and the they still ahve a 1500 tax credit on them..

personally I think they are sweet....

with a SS tank that cant lime up,

no need for a recirulatino line

it cant be any worse than all the rest 
of the tankless junk out there...


they claim that they are useing them in parallell 
for commercial laundry mats and college dorms...


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## TheMaster (Jun 12, 2009)

I didn't read everything in this thread but I have a question. Noritz gives their GPM and temp rise based on Propane last I checked. The GPM at temp rise goes down with natural.....did you take that into account? Propane has more energy per unit than natural gas.
ILPLUMBER,I have a test for you to give Noritz tech support. Call them three times with the same question on three different days. See how many different answers you get. It has to be a question thats not addressed in the manuals.....they will nail those. Your vent question would be a good one. Many manufactures will default to their instruction book and not deviate as you know for legal reasons. Noritz may have straightened out their tech support by now and changed how they spec the GPM. I must say the Noritz i installed is still working perfectly......but afterall it was installed by THEMASTER.:laughing: I'm not all gloom and doom,hopefully they are better now than they once were. Goodluck on your project.


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## Protech (Sep 22, 2008)

Looks like a nice piece of hardware.



Master Mark said:


> Tankless said:
> 
> 
> > You also need to consider water hardness. Effective....about 6 months ago Noritz is now stating the hardness has to be at least at a certain PPM. This is important because, the units won't fail in a year if water is too hard, they will fail in 3 or 5 years. They are expensive to buy and a bit of work to replace (not too bad on that unit). if there is a softener or a softener service you STILL need to make sure the water is soft enough. I have had a few apartment buildings that I have done the repairs for free, because I didn't know better when I installed them...no one knew back then. Please believe this is an important one, and I have actually unsold tankless in a few commercial applications for this reason. Commercial water treatment is expensive, and I didn't want the headach in a few years.
> ...


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## Tankless (Jun 12, 2008)

SewerRatz said:


> Mr. Tankless sir, great post, very informative, but I hate to correct you on a couple things in your post. Nothing big though.
> 
> First of the 751 units you can only quick link two units together. They are not compatible with the multi system controller. I totally forgot about that. You are correct. While it is possible to split the lines up and have 2-pairs of 751's, it sorta defeats the benefits of a linked system.
> 
> ...


That's a simple calcutaion he can do for his job. May I suggest you not size the system to have to run at max to provide nominal hot water. 70% to peak is the most efficient.


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## Tankless (Jun 12, 2008)

Read the specs carefully. You are paying TOP dollar for a glorified Navien Tankless Heater. The heat exchanger is a little different, that's all. It actually performs rather poorly, but their graphics look cool! Not very detailed but I like the pretty colors




Master Mark said:


> Tankless said:
> 
> 
> > good post , it souinds like you have had some bitter experiences with the units getting limed up ..
> ...


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## Tankless (Jun 12, 2008)

Loor for yourselves at how poor they actually perform. If I ran this company, I would NEVER post this data on the web. But I am sure his investors want a return, and this thing is no where near ready for the compeditive market.

http://www.eternalwaterheater.com/files/pdf/products/2008_eternal_flyer_040208%20back.pdf


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## ILPlumber (Jun 17, 2008)

Tankless said:


> That's a simple calcutaion he can do for his job. May I suggest you not size the system to have to run at max to provide nominal hot water. 70% to peak is the most efficient.


Our water is anywhere from 46 - 72 degrees.

What do you shoot for? 85%


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## TheMaster (Jun 12, 2009)

The way I read it is that for the tankless water heater it gets less efficient as its pushed to its limits. So you you should look at the gpm temp rise charts then deduct about 30% of that if you want maximum efficiency. Thats almost 1/3 lower than the chart shows.


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## Tankless (Jun 12, 2008)

ILPlumber said:


> Our water is anywhere from 46 - 72 degrees.
> 
> What do you shoot for? 85%


 
It's dynamic. In your situation here that is a fair number. The goal is NOT to simply supply hot water, the goal is to supply hot water with as minimal maintinance as possible. That was the reason for my posts to you. Clients are not happy when there are issues with a system that you designed. So planning for issues at this stage is what seperates the men from the boys with respect to this sort of thing. Anyone can plumb them up, but not just anyone can install a system that will keep these units performing as advertised. Clean air makeup - treated water (if needed) - recirculation design, are very important for life after a few years. 841MC would be my choice of heaters, but you would need 5. @ 200K btu's that's still one million btu's but they are a better performing unit that uses less energy for the same output. But they cost a little more per unit (not much) but you need that 5th unit, plus the controller board. If done correctly and you do your homework you will have installed a system that will perform well above average for years to come. That is my goal in my designs.....and let me tell you, experience is your best friend with stuff like this. Attention to details is key. This is what I have spent hundreds of hours working on and learning from a whole range of installations. It is not uncommon for me to spend an entire day on a system after installation is complete....testing and restesting. Messing with settings to see the results...poking and prodding for a reaction, checking manufacturers settings and not just ASSuming they are correct......


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## Tankless (Jun 12, 2008)

TheMaster said:


> The way I read it is that for the tankless water heater it gets less efficient as its pushed to its limits. So you you should look at the gpm temp rise charts then deduct about 30% of that if you want maximum efficiency. Thats almost 1/3 lower than the chart shows.


 
You are more correct than you know. The carbon deposit buildup inside the air/gas chamber will tell how the system is performing. While they can be wiped clean and blown out, there are places that cannot be simply cleaned without major surgery. The (once again) clean air makeup will also dictate this progression of buildup. This buildup can cause havoc years down the road. Some of it is normal, some of it is advanced. In very advanced situations the discoloration of the copper exchanger will also tell what's going on. The computer can also tell you what temps different sections of the system are experiencing. All these things are designed to point you in the right direction. The engineers that designed these onboard systems are a hell of a lot smarter than the basic tech's you will encounter on the phone. The more experience one has with this, the faster you will become at fixing them. Very common for me to hear I am the third plumber on the job and the only one able to fix it. Last two repairs were referrals from plumbing companies that I have never met or heard of, nor do I know how they found out about me. I have designed my business to BE that guy that is the holy grail (sp?) or as a few clients have said, you are the tankless whisperer. People give me the strangest looks when I just stand there and listen to the unit talk to me.....but they all whip out their check books when the job is done. I undeerstand most guys don't want to BE that guy, as they are geared for other things, but I like the challenges and learning new things. It should be mentioned I do not know everything about everything. There are a lot of systems out in the market and I don't know them all, but I do know how to get the info I need and I understand the flow charts (not water) to where I can get it figured out. This was EARNED not from some silly tech support or a basic service manual but from hours of trial and error. I still screw up but not nearly as bad from when I first started...I believe they call that paying your dues....


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## Protech (Sep 22, 2008)

After reading further, it seems that they could increase the efficiency even further by adding a ss heat exchanger on the exhaust right before the fan that captures the last bit of heat into the incoming water.

Seems like a very high quality unit. Costly though.


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## ILPlumber (Jun 17, 2008)

I just wanted to give a public thanks to you Tankless. You dish out excellent tankless advice. Glad you are here.


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## TheMaster (Jun 12, 2009)

Tankless said:


> hmmm, not that I think about it, I think I was told that sleeveing the CAT IIi with B vent can create condensate on the outside of the CAT III pipe and cause it to rot out....I have to think about that a little longer, but it's along those lines....I can find out if you really want to know


Isn't cat 3 vent stainless and the purpose of the condensate tee is to protect the tankless heater itself from condensation drip back and not the pipe? Also I thought ILPLUMBER was using sch.40 pvc for the vent for his install...is that correct? Ok now another question. How could your vent ever be 3' or shorter when venting a conventional tankless unit vertically through the roof?
..............................................................................................................................................................................
Noritz venting guide says venting cat3 vent pipe through another vent/chimney is a no go. No reason given.


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## ILPlumber (Jun 17, 2008)

Just got off the phone with Noritz tech support. They are not sure about using a 6" b vent for a chase for 4" SS. He is going to talk with his manager and email me a response. I told him I needed it in writing..

I'll post an update when I recieve it.


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## ILPlumber (Jun 17, 2008)

TheMaster said:


> Isn't cat 3 vent stainless and the purpose of the condensate tee is to protect the tankless heater itself from condensation drip back and not the pipe?.


Yes



TheMaster said:


> Also I thought ILPLUMBER was using sch.40 pvc for the vent for his install...is that correct?


No, SS vent here. There is only one model capable of using sch 40 for venting.





TheMaster said:


> Noritz venting guide says venting cat3 vent pipe through another vent/chimney is a no go. No reason given.


They are leaning away from it due to the fact that the joints in the vent pipe are supposed to be accessible.


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## TheMaster (Jun 12, 2009)

ILPlumber said:


> Just got off the phone with Noritz tech support. They are not sure about using a 6" b vent for a chase for 4" SS. He is going to talk with his manager and email me a response. I told him I needed it in writing..
> 
> I'll post an update when I recieve it.


 I dont see a problem with it unless it causes condensation to form inside the chase and drips back to the heater casing or somthig else in the room....the condensation formed in the chase should not be any more corrosive than typical water would be. I bet they are gonna shoot the idea down......I would be very very surprised if they put it in writing.


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## ILPlumber (Jun 17, 2008)

I learned a very long time ago. If it's not in writing, it never happened.

Still nothing back from them. His manager's office must be a long ways away.........


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## Protech (Sep 22, 2008)

Never was there a truer statement.



ILPlumber said:


> I learned a very long time ago. If it's not in writing, it never happened.
> 
> Still nothing back from them. His manager's office must be a long ways away.........


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## ILPlumber (Jun 17, 2008)

They responded with the vent clearances table....:blink:

I then re-asked the question. I just took a screen shot of that email.

I think they should read their installation manual. What about accessibilty to the joints of the SS pipe. I thought sure they would tell me I could not do this.


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## TheMaster (Jun 12, 2009)

ILPlumber said:


> They responded with the vent clearances table....:blink:
> 
> I then re-asked the question. I just took a screen shot of that email.
> 
> I think they should read their installation manual. What about accessibilty to the joints of the SS pipe. I thought sure they would tell me I could not do this.


 Call back and ask the question about the accessibility and you will prolly get a different answer about sleeving it. I said along time ago that noritz tech support sucks. I'm very very surprised you got that in writing:thumbsup: good job......but I bet you could very well get another e-mail shooting the same idea down tomm. if you call them back. They have always been wishy washy with me.


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## ILPlumber (Jun 17, 2008)

If I was to argue against running the SS pipe through the type B to the architect. I would not come to the conversation un-armed. That would be stupid.


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## TheMaster (Jun 12, 2009)

ILPlumber said:


> If I was to argue against running the SS pipe through the type B to the architect. I would not come to the conversation un-armed. That would be stupid.


 Thats for sure...we collectivly will have thought of every angle


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## 422 plumber (Jul 31, 2008)

Whats the difference between using a 6" B-vent for a pipe chase and running the s.s. vent in a pipechase that gets drywalled? Accessibility is the same either way.


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## TheMaster (Jun 12, 2009)

I looked it all over again. I cant find anything that says the joints must be accesible. In anything other than a one or two family structure the vent if enclosed must be in a chase that has a fire rating equal to or greater than the roof and the ceiling its enclosed between.
IL's 6" old "B" vent would meet that requirment for sure.
Condensation could drip back down in the chase between the b vent and the cat 3 vent.
The vent manual says you cant run the cat 3 vent for the Noritz through another vent. But in IL's case the B vent is no longer being used as a vent....its a pipe chase now...thats its sole purpose. 
At the roof termination I would expect them to want it terminated witha cap.
Putting a 4" inside a 6" would give you a 1" space if centered perfectly.
I never found a minimum chase size....only minimum clearences from combustibles and that was 4"
Could this cause the flue gas temp to rise and make the unit flash a trouble code? On a very short distance I dont think so but I'm not sure about that if you were to push the limits of the vents allowable over all lenght combined with an unusually high demand that it couldnl't become a factor.


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## ILPlumber (Jun 17, 2008)

jjbex said:


> Whats the difference between using a 6" B-vent for a pipe chase and running the s.s. vent in a pipechase that gets drywalled? Accessibility is the same either way.


I don't have a problem with it. I will do as the architect requests. I don't have enough ammo to argue.
Snipped from the Noritz instructions.


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## Tankless (Jun 12, 2008)

The reason galvi chase was/is frowned upon is that condensate can now develope on the exterior of the CAT III pipe, dripping onto the flu collar and corroding it out...not my scientific view point but that is what was said to me.

Buring CAT III piping in a wall is a pain in the arse due to the distance to combustables rules but I can see their poing on making the clip locks accessable for the inspector to check that they are secured correctly. If they are getting boxed in I guess one could leave the drywall off till inspection.....


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