Getting ready to convert electric stove to gas. How do I determine the size of gas pipe needed for new stove?

Asked By: luisfr on Wednesday, March 31, 2010
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Answer I have an existing gas line to my pool heater that is connected directly from the gas meter with 1 1/2" pipe which is connected to a 1" pipe into the pool heater. This is the source that I will tap into for the new gas stove line. It is about 30' from the new gas stove area. What size of pipe will I need to tap into the 1 1/2" line to run to my new stove. I am guessing 3/4" or 1/2" but don't know. Another question does the gas pipe line have to be underground from source to new stove area?
Answer

luisfr, thanks for your question. In considering your question there are a few things you need to take into account. The first is the number of connections will you have running on gas after you install and hook up the stove. For example, a furnace, water tank, dryer, pool heater and stove.

You will also need to determine the amount of Btu's these items will be using. For the stove, it will depend on the length of pipe you will be running from the 1 1/2" pipe at the place of connection, to the new stove. In your case, it is 30' and you also need to take into account and any fittings, like elbows or tees etc, that will need to be factored into the calculation. Each of these adds about 5' per fitting.

Here is a natural gas pipe chart from Aaladin a major manufacturer of industrial equipment, parts and supplies. You can click on it to enlarge.

natural gas pipe chart

Natural Gas flow is given in thousands of BTU/hr.
One cubic foot of Natural Gas = 1000 BTU
Pipe length must include "additional length" for all fittings.  Add approximately 5 feet per fitting.
Nominal pressure at the burner for Natural Gas is 3.5" of water.  (Typical machine supply 5"-7")
Aaladin uses the same orifice for all propane burners: #52

Natural Gas Example:
Looking at the chart, an appliance needs 129,000 Btu's would need a 3/4"pipe to run a length of 30'. Notice under the 3/4" pipe size listed horizontally that 129, representing 129,000 Btu's, is the second number listed. Going over to the left under the Length of Pipe in Feet table, it corresponds to 30'. As you can see the pipe size may change for appliances needing pipe to run 30', as you do, if they require more Btu's.


Using a gas range as an example, most gas ranges have four burners, measured in British thermal units per hour (Btu/hr.): one or two medium-output burners (about 9,000 Btu/hr.), a small burner (about 5,000 Btu/hr.), and one or two large burners (about 12,500 Btu/hr.). If it has a high-output burner it will provide a higher level of heat—usually up to 15,000 Btu/hr. They you would need to take into consideration the oven portion of the stove which uses about 39.000 Btu/hr. 

So based on these figures if you had two small burners at 5,000 Btu/hr and two medium burners at 9,000 Btu/hr and the oven at 39,000 Btu/hr, your total Btu/hr for all of these would be 58,000 Btu/hr, and according to the chart above 61,000 Btu/hr would work at 30' using a 1/2" pipe.

So you are right that your choice would be either a 1/2" or 3/4"pipe based on all the factors talked about here. Again, all stoves will be different so you will need to be sure of the Btu/hr to determine the right size pipe for the length.

Again, based on the manufactures Btu's listings, you can determine the total amount of Btu's that could be used if everything was operating at the same time, and then using the chart above, you can then figure out the size of the pipe needed based on how much pipe you have to run to make the connect to the 1 1/2" pipe you mentioned.

On some of the jobs we have done, we had to have our plumbers increase the size of the main line to accommodate the number of appliance we upgraded to, while on others, the main line was just fine. To be sure, it would not be a bad idea to have a professional plumber or even the gas company come out to look at your project and determine what would be best for the job. Most of the time you can get them to do this for free and then if you are going to do the job yourself, you can feel more confident that you will be using the most safe and proper way to make the connection.

Plus, you should always keep in mind that depending on where you live, your building department may require that you use a licensed plumber to make the change and or require a permit. So it is best to check this out before you start the job.

I hope this helps, Rick

Rick Maselli is Founder and Editor of Showroom411.com and Ask Rick.

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