Connecting gas kiln to house natural gas supply

[Mudfish1]

I am connecting an old gas kiln to my house natural gas supply. Does anyone know what natural gas pressure I need at the kiln? Does anyone know the natural gas pressure in a house? 

Is it as simple as connecting the kiln to the natural gas line under my house, or do I need to do something else to get enough pressure?

Richard

[Mark C.]

Most natural gas presures  for the home are 1/4 pound or 7 inchs on a manometer  .

That  works  fine for gas kilns as well. Just hook it up and start firing

If  you ever needed more pressure you would turn up the pressure at the main meter (which you will NOT need to do). The devices in your home stove ,water heater ,furnace etc all have presure devices built in, they regulate the presure to 1/4 lb.

You do not need any other device. Now propand is a whole different anamal.

[neilestrick]

I respectfully disagree. It depends on the kiln and how the burners are set up. What brand and model kiln are you hooking up?

[Mark C.]

1 hour ago, neilestrick said:

I respectfully disagree. It depends on the kiln and how the burners are set up. What brand and model kiln are you hooking up?

No problem Neil just every kiln I have  or have installed works on 1/4 lb pressure-a Geil-west coast,homemade ,olympic and a few others

as I noted you can crank up the main house regulator if you have a manometer (I have the water type manometer)

[neilestrick]

10 minutes ago, Mark C. said:

No problem Neil just every kiln I have  or have installed works on 1/4 lb pressure-a Geil-west coast,homemade ,olympic and a few others

as I noted you can crank up the main house regulator if you have a manometer (I have the water type manometer)

Yes, but Alpine worked on 14". And there's also the issue of pipe size being able to deliver enough volume. If this is not a big kiln it will probably work fine, but I think we need to know more before giving the okay. I'm also wary of recommending folks start messing with their gas lines and regulators, especially if they're living within city limits with local building codes.

[Bill Kielb]

6 hours ago, Mudfish1 said:

I am connecting an old gas kiln to my house natural gas supply. Does anyone know what natural gas pressure I need at the kiln? Does anyone know the natural gas pressure in a house? 

 

Post a picture of the kiln equipment tag and a picture of the gas valve train especially any regulators that are piped in this circuit - even if just a pilot regulator.

[Mark C.]

Pipe sizing is very important at low gas presures. Missed talking about that. Since all my supply is 2 inch from the meter. If you have a long run the size is very important. My Geil needs 1 inch for example .

How long is the pipe run? Most homes are 3/4 inch ,as Bill said we need more info on the spec plate of kiln or siome info on kiln burners and size of kiln?

[Mudfish1]

Folks! I love this Forum, and I am glad I found so many helpful people!

I don't have specs on the kiln because it is a "mystery kiln" that some of the people on this thread have been trying to help me identify. It's basically a 15CF kiln with 5 gas burners coming up from the bottom. The orifice size is 1/8", which (I believe) makes them natural gas burners. Is that correct?

From the replies, it sounds like a commercial natural gas kiln is designed to be connected to a typical home natural gas line at 7" of pressure, which is about 1/4 PSI?

My plumber is running a 1" pipe from my house natural gas supply out to my pottery shed, about 60 feet total distance. The gas line after passing through the gas meter and regulator is also a 1" line, so I figure using a 1" line out to my kiln won't restrict whatever flow I am getting from the meter.

So basically I am hoping the kiln is designed for home natural gas pressure (1/8" orifice size), and also that a 60 foot run of pipe won't reduce the gas flow enough to matter.

What does everyone think? Will I be OK? Or am I wasting my money running that natural gas line 6o feet out to this kiln?

 

[Bill Kielb]

3 hours ago, Mudfish1 said:

What does everyone think? Will I be OK? Or am I wasting my money running that natural gas line 6o feet out to this kiln?

 

I think it likely works, but I really want pictures to unveil if it has a regulator downstream, what is the regulator model #? 1/8” is ok - sort of, but I would rather have the number stamped on the orifice. If not, burner model, measure the orifice with a number drill instead of guessing.
Piping is easy to figure out, but knowing the actual required capacity is most useful. The piping chart below is for low pressure with 0.3” drop and probably at 3.5”. Operating pressure. Just looking at 1” 60 feet without fittings at the above referenced pressures, maybe 200000 btuh max ……….. Is that enough - no way to know - updraft, or down draft, again who knows? Pictures, a few measurements you can very easily get there but it will take some effort.

Will 1” pipe at house pressure work? It will do something that’s for sure. Will it fire well - maybe, maybe not, impossible to tell. I really need pictures to develop questions or estimate supply line sizing for real. Absent that - maybe it will work great.

 

Edited January 12 by Bill Kielb

[Rae Reich]

I think it’s better to overbuild than squeak by barely. When we built my original large catenary - 8 Venturis- we told the gas company our plans to possibly add a raku and we wanted no gaps in flow. They installed a massive meter (at no charge here in residential Orange, CA, ymmv.) and we ran 55’ of a separate 2” line to the kiln area. The Gas company still sent a man out during the first firing to see what the large increase in gas consumption was about, then  they added a note to my meter reading information  

Theoretically, I could fire the big cat, the raku and the small Geil simultaneously with no loss of pressure. The Gas Company was very helpful. (Note: here, kilns require no extraordinary permitting and are classed by the Fire Department with barbecues.) We did the digging, wrapping and installation of the pipe which was inspected and approved by the Gas Co. and the City.

Additionally, I invited the local Fire Station crew to see a firing and inform them and Dispatch that there might some reports of flames and possibly smoke. Also invited neighbors to see and be reassured. 

[Mark C.]

60 feet is a long run .It may work just fine. 1 inch is not overbuilt. The burners will tell the story. My soft brick small 12 cubic foot kiln with 6 burners hardley uses any gas. You may be fine -I'm assuming the kiln is all soft brick as well. Updraft? details would help again-photos of kiln burners etc

less bends in piping if you can will aid is flow.

I went back and found your kiln photos-it a what I call trash can kiln -My guess is its smaller than 15CF. (no burner photos). I think the 1 inch will work for that small kiln

 

Edited January 12 by Mark C.

[neilestrick]

Oh are we talking about that round kiln you posted about a week or two ago? That's probably 10 cubic feet at best. And I bet a 1" line would fire a kiln that size just fine. You'll just have to make sure the orifice size is correct.

[Mudfish1]

Folks! Thanks again for all the helpful information. Neil, the little kiln I posted a few weeks ago is indeed the one - it's about 10 cubic feet, but I was estimating 15 CF just in case I want to upgrade or build a larger kiln one day. (My pottery mentor told me I can't be a real potter until I build my own kiln, so I am planning for the future!).

Bill, those darn burners and orifices are just like the rest of my "mystery kiln" - not a mark on them, no type, no manufacturer markings, no size. I dropped drill bits down into the orifice and they are 1/8" - I confirmed the actual diameter with my micrometer.

In any case, I started from everyone's useful comments and I have been doing some online homework and additional calculations. I want to fly this by everyone, let me know what you think! From reading their online material, Ward Burner Systems recommends about 10,000 - 16000 BTU/hr for each cubic foot of kiln if you are firing to Cone 10. That would mean I need 100,000 - 160,000 BTU/hr for my 10 CF kiln, or 150,000 - 240,000 BTU/hr is I want to plan for a 15 CF kiln in the future.

I then tried to confirm these numbers by checking out new Olympic gas kilns from their website. Looks like their 10 CF gas kiln (Model 2827G) lists 280,000 BTU/hr on their Spec Sheet, so the Ward Burner System numbers might be for a better insulated kiln. Based on these larger numbers, I decided my goal should be to provide between 280,000 - 420,000 BTU/hr.  That should make me totally safe even if I build a 15 CF kiln one day.

Natural gas has about 1000 BTU/CF, so I then did the conversion to find that my pipe needs to deliver between 280 - 420 cubic feet/hr.

Bill, thank you for that handy table! It made me realize that plumbers and builders don't guess about these things, they have handy tables that help them size and design piping systems for homes with boilers, hot water heaters, etc. Not sure where Bill found that table, but it's solid - I did some more online searching and found several more that have about the same numbers as Bill's table. 

If I take the upper limit of what I could possibly need (420 cubic feet of natural gas/hr) and then consult Bill's table, it looks like for a 60' run of pipe the 1" will be too small - I will need 1 1/4" pipe to be safe.

What does everyone think? Is my analysis solid?

Now Rae asked the next key question - does my gas meter have the capacity to provide another 420 CF/hr of gas if it's cold outside and my home gas boiler is firing away at the same time? My home boiler is 210,000 BTU/hr (unlike my mystery kiln, it has an actual metal plate with all the specs!), so my worst case scenario would have me needing 3 times as much gas if I was running my home boiler and gas kiln at the same time.

Or maybe I tell the kids to just huddle around the gas kiln at night if the house gets too cold?

Anyway, thanks to Rae! I will ask my plumber what is the maximum CF/hr that my gas meter can provide, and see if I need some kind of upgrade to my meter.

Look forward to any comments or suggestions!

Richard

 

 

[Mark C.]

I could help better by seeing a burner photo in reguard to burner type

[Bill Kielb]

@Mudfish Fantastic post! Go at this logically, not rocket surgery for sure. You should be able to read your meter size , something like : AC250, 5 PSI, 1/2 PSI differential @ 250 cfh flow. So read it or post it if in question. A 250 Cfh meter can supply more, just the pressure drop across it will be 1/2” at that flow. The regulator on the meter will be key. It drops meter pressure to home system pressure of 7”, so its rated capacity will be very important. Again it should be on the tag for the regulator. For a house your street pressure is likely 2 psi or 55.44” wc. We won’t know this, so an assumption likely can be made your regulator has 2 psi input minus meter losses of 1/2 psi at 250 (or rated) cfh flow …….. etc. In other words the gas company really has to determine the total service capacity. It’s just stuff we will never know.

To operate on your existing service 
Your house pressure - very likely 7-8” wc and most of your appliances have 3-1/2” regulators on them. So important to use the right sizing chart for your line sizing and pick a reasonable starting pressure and ending pressure under full flow to get the btuh needed.. We would like to leave your system pressure as is, all your other appliances depend on it. Stove, water heater, boiler, furnace …. All of them regulate your current pressure form prox. 7” down to 3-1/2” (typ)

Start with what does the current kiln require or what will you expand into in the future

How much = orifices @ desired pressure X no of burners - let’s pick a pressure less than max (7”) leaving some room for pressure drop in the pipe run, fittings and valves… let’s use 5” wc

Sizing existing
Pick from your favorite orifice table: https://www.gordonpiatt.com/wp-content/uploads/2021/07/Natural-Gas-Orifice-Chart-7.E.80.5-Rev-3-05.01.pdf. 1/8” Dia. Orifice @ 5” wc = 48,200 btuh per burner X 5 = 242,000 btuh total. Is that enough? Not sure but let’s finish.

pick piping from chart knowing you likely can drop from 7” to 5” if need be. Most charts limit to 0.3” wc drop so 2” buffer is somewhat conservative here.

Table pg 4-3 http://ecodes.biz/ecodes_support/free_resources/Virginia/fuelgas/pdfs/Chapter 4_Gas Piping Installations.pdf

This manual will let you add equivalent lengths for fittings etc… but by now you get the idea of leaving yourself room by way of pressure drop, orifice sizing etc…. To make the situation best work for what you have available. As long as you can move the desired btuh at a realistic dependable pressure your design should be good. There are lots of ways to get there. Solid knowledge of the basics, likely gives you many options for best solution.

Only other last thought, work in inches of water column. All low pressure stuff is measured that way. 1 psi = 27.72”. Low pressure stuff = Water Column. Medium pressure stuff, 2 PSI. While folks will refer to ounces or 1/4 - 1/2 psi it tends to lead to mistakes. Stick with water column unless venturing toward medium pressure stuff.

Other than that, it looks like you are on the right path to figure out just how many btuh you need or will need in the future to run this for and now should have a way to reasonably size it.

 

Edited January 14 by Bill Kielb

[Rae Reich]

12 hours ago, Mudfish1 said:

Anyway, thanks to Rae! I will ask my plumber what is the maximum CF/hr that my gas meter can provide, and see if I need some kind of upgrade to my meter.

Chuckling at the idea of your family huddled around the kiln - they do put out a lot of heat, even well insulated.

After we calculated what we’d need, my plumber called the Gas Co and told them we needed a million btuh and they decided what size of meter was needed. They will take into account what your home has been using.

We also have the kiln line running from the meter separate from the house supply so they can run individually without affecting each other. Kiln line can be shut off by itself if necessary for line service, etc. Just to be prepared, though we’ve never needed it yet (earthquake country), we hung a wrench on the meter for emergency shut-off.

Best wishes!

Edited January 14 by Rae Reich

[Mudfish1]

Folks!

I finally got the natural gas line installed and did my first test fire of my mystery kiln. Loaded with shelves and cones, but no ware.

To remind everyone, it's about 10 CF, with five venturi burners coming up from the bottom.

No matter what I tried, I could not get above 2218 F. It wasn't a lack of gas pressure, I never even opened the valve all the way.

With no damper, kiln stalled at 2218 and never went higher. I tried less gas, and the temperature dropped. More gas led to a standing flame above the vent, and the temperature dropped. I fine-tuned the gas flow for 2 hours (no visible flame, light visible flame, heavy visible flame, etc) and I just could not get above 2218. The picture on the right shows the best setting I could find, a small 6-8" flame gave me the maximum temperature.

I am assuming that the venturi burners just weren't pulling in enough air to burn enough gas to keep heating up the kiln?

Are there other possible causes for the I described? Do I need to try and adjust the burners? I want to get to Cone 10!

Thx

 

 

 

[Bill Kielb]

Well, I can tell you that you don’t have enough power to offset the shell losses.  As to why, for me I would figure out just how many btuh the burners are producing? From there I would decide on the best way to get more. It looks like you have 1/2” or 3/4” csst gas  piping so pressure drop will probably be significant. If you had a gauge and operating valve at the kiln then it would be easy to tell.  One thing I would ask is did you ever fine tune using a damper? This is a fairly small updraft kiln and that hole in the top is gonna let a lot of heat out if it’s not just the right size.

The more we know for certain the better, but I would test again and make very very very small adjustments to the damper to see what I could get this to (peak temperature) and figure out a way to know approximately how many btuh you were at. From there some logical decisions could be made and tested.

Edited February 19 by Bill Kielb

[Russ]

4 hours ago, Mudfish1 said:

am assuming that the venturi burners just weren't pulling in enough air to burn enough gas to keep heating up the kiln?

This.  One thing Ive found with fuel burning kilns not reaching temp is not enough oxygen. It seems like youve found the correct amount of gas by adjusting pressure up and down. .. but at 5000ft plus above sea level we have way less oxygen per cubic ft than at sea level.

[Bill Kielb]

2 hours ago, Russ said:

but at 5000ft plus above sea level we have way less oxygen per cubic ft than at sea level.

Just under 3% less inspired ! But to your excellent point, when estimating burner output elevation needs to be corrected for as well as the heat content of your natural gas supplied. Both can combine to be very significant in mid and high altitude burner deigns. While as a percentage O2 is still just under 21%  more space exists between air molecules so quite a different mixture and burner settings sort of  like quite a bit different O2 absorbed with every breath! Your body can adjust or acclimate much more so than your burners. Good catch! This is definitely an important part of understanding what you have and designing for what you will need.

[Mark C.]

You need a damper-I suggets thin broken kiln shelve say 1/2 inch thick so that the weight is minimal -or just a soft brick which is light still

Also I would run as the larger pipe (I thought you said it was 3/4) all the way to kiln. It looks like you necked it down somewhere in last 10 feet with smaller flex? Its usually not a pressure issue with natural gas its a volume issue, so keep the pipe as big as you can to the kiln.

I have those same type of burners on an updraft .  You cannot change your altitude  so you need to have all the other functions perfect 

 

Edited February 19 by Mark C.

[Babs]

Wondering if a  pipe chimney would draw more  air through, and damper needed for sure.

 

Edited February 19 by Babs

[Mark C.]

2 hours ago, Babs said:

Wondering if a  pipe chimney would draw more  air through, and damper needed for sure.

 

Yes small metal pipe may help with the draft draw-great idea Babs

 

[Bill Kielb]

5 hours ago, Mark C. said:

7 hours ago, Babs said:

Wondering if a  pipe chimney would draw more  air through, and damper needed for sure.

 

Yes small metal pipe may help with the draft draw-great idea Babs

 

Might want to just fire with a damper initially to see what this needs. Lots of updrafts just fire into a hood without a direct connect flue for simplicity.

[Mudfish1]

Folks;

Thank you for the excellent suggestions!

Bill, it's a 3/4" line. I was worried about not having enough gas. I nursed it up to about 2200 F and never opened my valve more than 2/3 of the way (no pressure gauge, just a ball valve on the gas line). When I stalled at 2200 I decided to see how much I could still increase the gas flow rate - with the valve wide open I had about a 4 foot standing flame coming out of the kiln and started dropping the temp fast. I think that means I have plenty of gas flowing into the kiln, but as Russ was saying I don't have enough oxygen coming in from the venturi burners to get complete combustion, so all that extra gas doesn't burn and just cools things down.

I haven't looked carefully at the burner orifices to see if there is a way to adjust airflow into the burner - should there be a twistable part or something that lets more air mix in? I'll have to crawl down there and take some pics and see if there is something I can adjust.

Mark, I do have a shelf I use as a damper, but I wanted my first test firing to have the most air/gas flow possible through the kiln. When I used the damper to block about 1/4 of the opening, I got a higher exit flame and started losing temperature. I think I was reducing the oxygen flow into the kiln by restricting the exit vent, and getting more un-combusted gas out the top. 

As Bill said, I probably have significant heat loss through that large vent hole. If I can reduce the opening with a damper and then reduce the gas flow rate to avoid too much unburned gas, maybe I can nurse it up to 2300? I should have played with the damper/gas valve at the same time and seen if I could keep the temp climbing. 

In case I want to try Bab's idea, would adding a short chimney really help draw in more oxygen? How big an effect is that, and how tall should the chimney be if I want to try it?

I'll give it another shot this weekend and see if I can get to 2300.

As always, thanks for the good advice and suggestions! I did get to 2218 F, and as you can see from the picture (Cone 7, 8, 9, and 10 from left to right) I did get Cone 9 to go horizontal. However, I want to see Cone 10 flat as a pancake!