Converting from propane to natural gas

giardina850

I am converting a propane heater from propane to natural gas. The unit is 100,000 btu. The propane was 11 inch water column. The natural gas is max 7 inches water column . Changed gas valve no problem. I need to drill out the nozzle. Polished off one of the nozzle and found a number 55 on it. How do I know how big of a hole to drill nozzle out. Can some direct me to a chart that would show some options. I had a hard copy of one years ago, but its long gong. It’s not to often that I convert from propane gas to natural.

Zman

Here you go

STEVEusaPA

@Zman can’t seem to open the pdf.

Zman

Try it this way

ratio

It's not downloading properly. What I got for the pdf link was a pdf, but the name was a file called 'Gas, no extension & note the single quote at the beginning. After I renamed it, it opened fine. The spreadsheet wouldn't download at all.

Might be a Valillabox issue, @Erin Holohan Haskell?

ChrisJ

Maybe it'll work this way

ChrisJ

Nope.
All well, I tried.

giardina850

Thanks Zman.
I successfully downloaded chart. Found the 55 for the nozzle. Then I go across to the proper pressure and I see number. How to I convert that number to a drill bit size?

Zman

That orifice will supply 18,888 btu/hour with 11" propane,do you have 5 of them to add up to ~100,000?
You then need to find the correct size orifice for the pressure you are running in natural gas. If your manifold pressure is 7" (definately check your actual pressure), a NO. 49 would be pretty close at 19,135.

STEVEusaPA

For some reason it's not recognizing it as a pdf, probably because it has put single quotes around it.
But you can download it to your desktop, then right click and choose 'Open with' and choose Acrobat.
The Excel file didn't open either. I sent a message off to Erin.
Maybe it's a browser issue, not necessarily a website issue.

Zman

Zman said:

Try it this way

Did this work with the xcel file.?

Erin Holohan Haskell

Thanks for the heads up, guys. We're looking into it.

mattmia2

Note that 7" is almost certainly the input. The manifold pressure will be much less and you will likely need to convert the manifold regulator as well.

Tim McElwain

With 100,000 BTU's how many burners do you have? The outlet pressure from the gas valve on natural gas should be 3.5" W.C. Give me the number of burners and I will give you an orifice size.

Erin Holohan Haskell

STEVEusaPA said:

For some reason it's not recognizing it as a pdf, probably because it has put single quotes around it.
But you can download it to your desktop, then right click and choose 'Open with' and choose Acrobat.
The Excel file didn't open either. I sent a message off to Erin.
Maybe it's a browser issue, not necessarily a website issue.

After some tests, it looks like this is what's happening. I'm not sure what's going on with the file, but you have to choose what to open it with.

KC_Jones

When downloading the file it adds an apostrophe before and after the file name, if those are deleted from the file name it opens normally.

Not sure where the apostrophe's came from, but that appears to be the issue.

JUGHNE

I believe you said you changed the gas valve?
It may be set for 3.5" WC output.

If there is a pilot burner, that orifice may have to be changed also. IMO

giardina850

ok, thanks guys. I think I got this now. Good heads up on checking gas pressure on the new gas valve. I will check out.

Tim McElwain

For the pilot you want an .018 size orifice. Again if you will give me the number of burners you have I will give you the orifice size for natural gas on the burners.

BrianBee2501

I have a slant finn boiler 200000 btu plumbed for natural gas, and the book says LP kit is part number 81 7304 000 . Is the kit manufacturer specific or can I convert to another manufacturer such as a GE, with the same specs such as WB28X29962 3/8"

mattmia2

Manufacturer specific unless the the ge is the same boiler rebranded. You also need someone with a combustion analyzer that knows how to use it to do it.

hot_rod

Lance

all conversions require gas pipe sizing check. This is master gastfitter work. typically, natural gas requires a larger pipe size than propane to deliver the same BTUH. Pressure drop due to incorrect sizes will create problems. design size engineering required. If you did this, then it's all in the appliance controls and setup. combustion test required also. The life you save may be your own.

Bob Harper

Fuel conversions are not DIY projects. Let a pro do it. You do not drill out orifices- you buy the correct ones specified by the mfr. Also, some gas appliances require a different burner from LP-NG or air shutter adjustments.

The inlet gas pressure is not at best case but worst case with everything firing on high fire at once.

As Lance noted, you may have to convert to a 2-psi system in order to use the same piping. Again, contractor work. If you are a contractor, you should state so. The sizing charts are available both in the gas codes and from Anderson Forrester, who makes gauging drills.

Once you feel you're done you need to run combustion analysis to see if you need to tune it.

Some jurisdictions require a licensed pro to pull a permit and do this work.