Changing a Rinnai gas heater from propane to natural gas

you don't because gas is not in the DIY domain
the conversion is done by a gas fitter
the correct size jets for the different gas are fitted and the air shrouds adjusted to get the correct burn color

Contact Rinna
Some water heaters allows changeover by installing new chipboard or changing dip switches... some do not.
Propane burns much hotter with higher pressure than natural gas
Gene

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Contact Rinnai, or look at product manual.
Products rated for natural gas do not work with propane.
Propane burns hotter and has more pressure... wrong gas can cause explosion
Gene

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Contact manufacturer.
Generally the answer is probably no, especially if you have a family, children, dog and neighbors.

Propane burns Hotter and has more pressure than natural gas.
Burner must be more robust cast iron.
Orifices must be changed to accommodate different gas.
Different gas control valve needed.
In some cases there are dip switch changes for type of gas and altitude above sea level ... the higher the elevation, the hotter gas burns.

Here is expected result from changing NG to LP.
But your good luck might lead to less volatile result
http://waterheatertimer.org/images/Exploded-house3.jpg

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Contact Rinnai.
Gas control valve is different, burner is different, burner and gas valve must match, threads are regular instead of reverse, dip switches probably have to be changed since combustion of NG is not as hot. Maybe different sensors. Pressures are lower with NG.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

It should be. You should be able to replace the oriface and the regulator. Propane is at a higher pressure than natural gas.

I think the part numbers listed in the solution are LPG injectors.The orifices (injectors) needed to change over from Propane (LPG) to Gas (NAT.) would be 2 High Injectors 100F-2031-B-1.80 and one Low Injector 1004F-2036-B-1.95.

yes you can, but is complicated, involves changing injector, burner, and reprogramming the PCB for the new gas type. Get a pro to do it for you

Rinnai New zealand conversion kit number, R1852.

VERY complicated - get a qualified gasfitter to do it.

i want to convert one to natural gas from LPG would u like to swap the pilot assy and jets i cant find a conversian kit anywhere...