Gas line sizing .. can someone confirm?

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Beachfront71

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Hello and thanks to all.
I bought a Noritz tankless to install in the near future and had a quick question about the gas line w/ regards to feeding the house.

I have a 1" main coming into the house and it goes to the following:

1. 3/4 up to the kitchen for the range
2. 3/4 up to the attic for a 60k btu furnace ..a 75gallon water heater also uses this line for its 3/4 feed

The Noritz is a model 751 which needs 199k btu's per specs..

My question is since the 60k furnace and the 199k Noritz will use the same 3/4 line, is it large enough to handle the requirements?

From the 1" main, the Noritz is only 8 or so feet away, then the line continues up through the first and second floor to the attic for the furnace ... maybe 25 feet from the 1" main to the furnace..

If the single 3/4 does not work, would I just have a plumber splice another 3/4 in the main so the furnace and noritz each have a dedicated line .. or can they share as it is now..

Thanks again.
 

Jimbo

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3/4" pipe will only support 260K btu for 10' max, so if the TOTAL run is more than that, you will have problems. It will only support just the 199K for less than 20'
 

Beachfront71

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Thanks Jim, I figured that would not be enough but wanted to hear from a pro.

Sawyer, why waste the time to even post an answer? I know my plumber can answer the question, I also know that if my plumber worked on sundays he would have been here while I am planning things out.
Next time if you have absolutley nothing to say, just skip the question and save a minute of your life, if you do it sixty times you will end up with an extra hour to do nothing.
 

hj

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To calculate gas pipe capacities we have to know the TOTAL length of the piping from the meter to the last appliance, and then, since this is an existing system, we have to know the pipe sizes and lengths as installed.
 

Tom Sawyer

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Thanks Jim, I figured that would not be enough but wanted to hear from a pro.

Sawyer, why waste the time to even post an answer? I know my plumber can answer the question, I also know that if my plumber worked on sundays he would have been here while I am planning things out.
Next time if you have absolutley nothing to say, just skip the question and save a minute of your life, if you do it sixty times you will end up with an extra hour to do nothing.

What planning do YOU have to do? Your plumber will properly locate and install the unit and PROPERLY size the gas line as well. So why would you even bother to ask the question here unless you either plan on doing the job yourself or you plan on second guessing your plumber?

If you don't like that answer try this one. Go spend a hundred bucks and get a copy of the national fuel gas code, sit down and have a good read. That should take you at least an hour of YOUR time yes? Then put in 2000 OJT hours and another 600 or so in the classroom, get your CEU's and you too can give sage advice just like me...LOL
 
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Jimbo

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Well, Tom.....this is a DIY forum. Not everyone agrees that homeowners should do any plumbing, and everyone is entitled to an opinion.
Many of us here feel that consumers are going to just DO IT anyway, even gas work, and if we can give them advice about how to do it right, well, the public is prbobably better off for that effort.
 

Beachfront71

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thanks to all, I am going to measure and post if valuable.. There is not that much gaswork under the home so it should not be too big of a deal.. I have read about it online but it gets confusing when you are trying to understand volumes of 2 different sized lines..

For the record, I asked this for a couple of reasons, none of which involves me doing any type of gaswork whatsoever... I do handle a lot of the grunt work but anything to do w gas or H20 I want a reciept from a contractor.

1. I have/had drywall guys here all day Sat/Sun/Monday patching and retexturing walls, around new windows, new walls, etc. I did not want to have to mud, tape, texture, prime, paint, only to have that whole wall reopened as it is a shear wall and lined w plywood .. On the other hand if someone would have said all is good, I would have been happy to finishs the drywall as moldings are showing up Wednesday anyways..
2. Plumber is out and will not be back until Thursday

Tom had a point that my plumber would know what to do but he is also making a very general assumption that all contractors are up to par in terms of knowledge and dedication, even the ones we may know personally or have used in the past.

The problem is I could go out and get some install quotes from the market who would not question the pipe sizing or location, it happened when I was getting quotes on the unit itself from the local "tankless water heater" company.

This is not just in the plumbing field nor is it pointed towards the field .. A real life example would be my quotes recieved for installing a furnace/ductowork on the second floor of the house after we ripped all the old out...
The bottom line was I got 5 quotes and all 5 had different sizes of furnaces.. some 50% larger than the others...

Only 1 took the time to calculate the BTU needs and the other 4 quoted based on walking through the house ...

I went with the guy who calculated the numbers and he proposed the smallest unit of all the quotes but it is perfect and I am positive anthing larger would be major overkill ...

All 5 companies seemed like good guys but 4 of them are technically installing HVAC that is not the right size for their customers homes.

Prob making too big of a deal on a small subject but you only need to get burned once to understand the value of research and knowledge on a subject..

Again, not just plumbing but life in general.
 
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BenWara

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that's pretty good to research what you need so you have some knowledge. If everyone did that america would be way different.


anyway, I don't know what size gas line you need but i would suggest checking out the install manual that came with it. I read the one for my furnance (wanted to see if i could put closet doors in front of it) and it has LOADS of info about what it needs.

Hope it all goes well for you
 

hj

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quote; but i would suggest checking out the install manual that came with it.

The information he needs to determine his systems capacity CANNOT be found in the heater's installation manual.
 

Beachfront71

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THanks, so here is my question .. how do I read this chart?

If I have a 1 inch gasline that goes 20 feet, then a 3/4 inch branch that goes an additional 20 feet ... do you read that as 3/4" at 40 feet and a max of 171 ?

What I mean by that is you need to first know the total distance from the main (in the example above it would be 40') then you find out the smallest pipe used in covering the distance (example 3/4") .. then find that on the chart.. correct?
 
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Jimbo

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In the current example, lets say one pipe runs from the meter towards the furnace. THAT section of pipe must carry the total BTU load of the furnace, and the fixtures further down the line, in this case the tankless. The pipe from where tees off near the furnace, that section only carries the tankless load.

if there are more appliances in the picture, or the piping is not straightforward, it can get more complicated. But each section of pipe has to be looked at and sized for the length of the section can carry the entire load that may flow through it.
 
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