Running a natural gas line to an outdoor kitchen

[Richard Spackmann]

I have a 1" black pipe main trunk inside my house coming directly off the meter as shown on the attached diagram.

I am in the process of adding an outdoor kitchen - the specifications of the bbq is also attached - total of 85,000 BTUs.

I already have 1" pipe to run from the trunk to the outdoor kitchen, I obviously know that bigger pipe won't hurt, but I'm concerned about the 3/4" tee that it will be connecting to.

In looking at tables regarding BTUs, pipe size and length (also attached) - it looks like a 3/4 pipe would be more than enough to provide somewhere around 110 BTUs (at 60') - but the problem is that if you take into account for a potential of adding a gas fueled fireplace at some point (TBD) - that 3/4" probably won't supply enough for both.

Questions:

1. will the 3/4" tee negatively affect the available capacity - and by how much? (i.e. will it negate the upsize to 1" all together and negate the advantages?)

2. do I need to remove that tee (a fair amount of work) and just replace the 3/4" tee with a 1" tee so that everything going out to the bbq is 1"?

3. is there any concern about the possible outdoor fireplace? (obviously I don't have a spec or anything so I realize in advance that is hard to answer, looking for more of a gut feel - i.e. "because you ran 1" unless you have a nuclear sized firepit you should be fine")

Many thanks in advance...

 

[buckyswider]

I can't answer the line questions, but did you confirm that your meter is large enough to supply all of your current appliances + the new grill and fireplace? https://jmcinspections.com/is-your-gas-meter-too-small/

 

[Sponsor]

 

[Sylvan]

If your in NYC you had better contact an architect as it cannot be filed under an LAA and then you must hire a LMP to do the installation and call for a physical inspection.

This protects you from a serious fine and you gas service shut down

 

[Richard Spackmann]

thanks all so far - I am NOT in NYC and @buckyswider my gasmeter says 250 CFM @ 1/2" DIFF - its a standard residential national grid (gas supplier) meter - also posted a pick of the meter plate. In looking this up online, it looks like this meter can provide a maximum of 250,000 BTU/h. I'm assuming that even with my hot water heater, furnace, stove and dryer - this will not be an issue - especially since I won't be running all of them at the same time.

 

[Richard Spackmann]

thanks all so far - I am NOT in NYC and @buckyswider my gasmeter says 250 CFM @ 1/2" DIFF - its a standard residential national grid (gas supplier) meter - also posted a pick of the meter plate. In looking this up online, it looks like this meter can provide a maximum of 250,000 BTU/h. I'm assuming that even with my hot water heater, furnace, stove and dryer - this will not be an issue - especially since I won't be running all of them at the same time.

Update - @buckyswider - I did some calculations of existing applicances and this is what I came up with:

(in BTUs)

dryer = 20,000
hot water heater = 40000
boiler = 87000
stove/oven = 51000
bbq = 85000
------------------------------
total = 283000
gas supply = 250000

deficit of 33000 BTUS

 

[wwhitney]

I already have 1" pipe to run from the trunk to the outdoor kitchen,

What kind of 1" pipe, black iron? Because each type of pipe has its own chart for distance/pressure drop.

1. will the 3/4" tee negatively affect the available capacity - and by how much? (i.e. will it negate the upsize to 1" all together and negate the advantages?)

Yes, but probably only a little. I'm not clear on whether there are equivalent length tables for reducing fittings. For a 3/4" tee, the tables I found show that the equivalent length for the side path on the tee is a bit over 4'. If you put a close nipple and a bell reducer on it, call that 5' of 3/4" pipe.

So for capacity purposes, you end up with a mixed run of 3/4" pipe (5' equivalent) and some equivalent length of 1" pipe (call it L). You can use the tables to check the allowable length of 3/4" pipe (call that L1) and the allowable length of 1" pipe (call that L2, bigger). Then you want to be sure that 5/L1 + L/L2 < 1. Basically 5/L1 is the fraction of your pressure drop budget the 5' of 3/4" uses, and L/L2 is the fraction of your pressure drop budget the 1" portion uses.

Cheers, Wayne

 

[Richard Spackmann]

What kind of 1" pipe, black iron? Because each type of pipe has its own chart for distance/pressure drop.


Yes, but probably only a little. I'm not clear on if there are equivalent length tables for reducing fittings. For a 3/4" tee, the tables I found are that the equivalent length for the side path on the tee is a bit over 4'. If you put a close nipple and a bell reducer on it, call that 5' of 3/4" pipe.

So for capacity purposes, you end up with a mixed run of 3/4" pipe (5' equivalent) and some equivalent length of 1" pipe (call it L). You can use the tables to check the allowable length of 3/4" pipe (call that L1) and the allowable length of 1" pipe (call that L2, bigger). Then you want to be sure that 5/L1 + L/L2 < 1. Basically 5/L1 is the fraction of your pressure drop budget the 5' of 3/4" uses, and L/L2 is the fraction of your pressure drop budget the main 1" run uses.

Cheers, Wayne

@wwhitney - many thanks - in terms of materials, it'll be a mixture of poly line and black pipe - technically i'll be running black pipe inside the house, then transitioning to the poly to run outside to the bbq (it's direct bury)

Regarding your comments about allowable lengths - not following the "allowable length" concept? is there some table somewhere you can share (I'm not finding it online anywhere??)?

 

[wwhitney]

I guess tables are more often in terms of "allowable flow for a given length" rather than "allowable length for a given flow," even though the latter is more flexible. I recall finding some of the latter type of table in the installation manual of Wardflex CSST 10 years ago, but I don't have a current reference.

Since you're in New York, I think the table you want to use for black iron pipe is this one (I believe 0.5" w.c. is the allowable pressure drop for a typical 1/4 psi = 7" w.c. system):

https://up.codes/viewer/new_york/ny...pter/4/gas-piping-installations#table_402.4-2

For this type of table you can interpolate. E.g., take the 1" column and suppose you have a segment that is carrying 200 kBTU/hr (when all appliances are simultaneously drawing their rating). The table says for 90', the allowable kBTU/hr is 207; for 100' the allowable kBTU/hr is 195. Interpolating gives you an allowable length of 96' for 200 kBTU/hr. Then if your segment is 32' long, that segment uses 32/96 = 1/3 of your allowable pressure drop (the pressure drop will be 1/3 *1/2 = 1/6" w.c.).

Cheers, Wayne

 

[buckyswider]

Update - @buckyswider - I did some calculations of existing applicances and this is what I came up with:

(in BTUs)

dryer = 20,000
hot water heater = 40000
boiler = 87000
stove/oven = 51000
bbq = 85000
------------------------------
total = 283000
gas supply = 250000

deficit of 33000 BTUS

IMHO- which has no basis in code- you'll be OK. If you read that link all the way, they say that meter CFM ratings are extremely conservative, and even the utility itself adds 10% to their calcs. So you'd be close to break-even right there.

And the appliances are rated at their MAX draw. So DWH and boiler should always pull their max, but the dryer should only pull its max when on "HI" heat; the stove/oven only when the oven and all cooking elements are on and cranked to 10 (or 11, if you have the spinal tap stove); same with the BBQ- something with that high a draw definitely has multiple burners which are set independently. So unless it's a really cold day and you're hosting 200 people and the chefs are using all resources both inside and out, as well as drying all the napkins at high heat, you should be OK.

I liken it to an electrical panel- I can have several multiples of my 200A main breaker in individual breakers. But I thought this calc was worth mentioning because I have heard in the past of homes exceeding their gas service capacity. Maybe meters were much less capable in the olden days when I heard these stories!