NG to lp conversion

dante421 · February 3

Hello all,
I have an 30+ year old Hydro therm natural gas boiler. I am trying to convert it to liquid propane. I changed out the orifices and the gas valve and adjusted it so it’s a pretty blue flame. But does not seem to be running very efficient. Should the burner tubes be changed be changed also or should the natural gas ones be fine? I am just looking for a quick conversion to get me through this winter until I am ready to install a whole new system. Thank you for your help in advance

Tim McElwain · February 3

How do you know if it is running efficienctly or not? Are you a trained gas tech? Why did you change the gas valve?

dante421 · February 4

I am assuming because the flame doesn’t look great and I burn through tanks what seems to be way too fast. I changed the gas valve because the old one didn’t have a way to convert to LP

pecmsg · February 4

Why are you converting a 30-year-old boiler from NG too LP?

Mad Dog_2 · February 4

Not for DIYers or the inexperienced...very serious business. Mad Dog 🐕

dante421 · February 5

I am converting because I do not have access to natural gas at this location. It is just to get me through the next month or so until I am ready to rip apart the entire system and start fresh. I was just curious if anybody knows if the burner tubes themselves need to be converted

pecmsg · February 5

OK

You moved a 30 year old boiler?

HVACNUT · February 5

dante421 said:

I am converting because I do not have access to natural gas at this location. It is just to get me through the next month or so until I am ready to rip apart the entire system and start fresh. I was just curious if anybody knows if the burner tubes themselves need to be converted

What do the combustion numbers tell you? What does the draft gauge tell you? What's the lockup and manifold pressures? Help us help you.

dante421 · February 5

I did not move the boiler. The boiler used to have natural gas running to it but that is no longer the case. It’s a long story but I am just trying to get through this winter with some heat. I was working with a boiler technician in the past but was hoping not to have to bother him anymore. Really all I need to know is if the burner tubes were changed to a propane style, would that make a difference? Are the flame holes smaller? Do propane tubes have some sort of venturi air flow set up to help? Please excuse me if that’s not the right term. I am just asking a fairly simple question so anyone that is familiar with burner tubes, your help is greatly appreciated

Jamie Hall · February 5

You don't need to change the burner tubes. Almost everything else does need to be changed or adjusted. And that requires a combustion monitor and someone who knows how to use it. It is emphatically NOT a do it yourself swap.

dante421 · February 5

Jaime,
Thank you for your response. Everything else was changed, lines, gas valve, orifices. I did it with the help of a local boiler tech. But something just doesn’t seem right as it’s going through a lot of gas quickly so really the last thing I can think of is the burner tubes

pecmsg · February 5

You need a combustion analyzer to properly set this up. If your buddy doesn't have one he's not the guy you want doing the work.

What about the LP Supplier?

gyrfalcon · February 5

Gas pressur set and combustion analysis must be done to not just have the boiler run optimally but safely as well.

As far as fuel usage, lp has over twice the amount of BTU compared to natural gas.

Cost between the two fuels will vary regionally and seasonally.

Are you comparing actual fuel usage or cost?

dante421 · February 8

I’m sure he has an analyzer but I didn’t want to bother him anymore. However if that is something I need to do then I will call him back over.

Gyrfalcon, when you say lp burns twice as hot, does that in a sense mean I shouldn’t go through as much fuel as NG? I am going by fuel usage, I am burning through a lot of propane quickly

Jamie Hall · February 8

The only way to compare fuel or energy usage from one type of source, whether its's LP, natural gas, oil, electricity, coal, wood, whatever, is by comparing the BTUs used You must convert each energy source into equivalent BTUs. Gallons to gallons or cubic feet cords or tons or whatever is useless -- never mind dollars.

gyrfalcon · February 8

Define a lot.

Natural gas is piped directly from the supplier, most people don’t watch or measure how much is being used . Just look at their bill and pay it. However, the bill may state how many cu ft or therms were consumed.

As far as flame temp- t lp is just a little hotter than ng. Not a considerable difference.

The volume to btu is different, however.

This is all measurable using some conversions.

How many gallons of lp has the boiler used?

Do you know how many cu ft of natural gas did the boiler use previously?

There shouldn’t be a different burner tube for the two gasses.

What happens when you redo your system and the new boiler is also using too much gas?

Maybe it’s not the boiler???

my boiler is way oversized for my house . When we had 0 deg weather last month, my tank dropped from 50% to 30% in about 2 weeks. This past week the needle barely moved at all.

I use about 750 gallons of lp a year for 1 big boiler, 1 water heater, 1 cook stove.

NG to lp conversion

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