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drewhart 01-13-2009 08:43 PM

converting propane boiler to natural gas
what is involved in converting a boiler that runs on propane to natural gas? i want to buy this used one to put in my house and run it off of natural gas. the guy said it used to run on natural gas but was converted to propane, so i assume i could convert it back.

drewhart 01-13-2009 11:21 PM

is it just a matter of putting a different valve on?

hvaclover 01-13-2009 11:35 PM

How do you know the boiler is the right size for your home and if it's in working order?

Is it steam or hot water?

drewhart 01-14-2009 08:05 AM

it is hot water. i dont know if its the right size. the house is 1900 sq.ft and the boiler is a weil mclain 140,000 btu. will this suffice? i just need some heat! this one i can get a good deal on, i just dont want to spend 3,000 on a new one.

hvaclover 01-14-2009 09:23 AM

seems way over sized to me.

drewhart 01-14-2009 12:35 PM

is it ok to use one way oversized?
seems to me i could run it low which would preserve it's usefull life.
this seems better that running one high which is too small right?
so what is involved in switching to natural gas?

beenthere 01-14-2009 01:06 PM

Proper sized orfices, gas valve and or spring, new burners on some models.

Also need a Manometer.

Takes the same water temp weather the boiler is over or undersized.

If the the boiler holds more water then the current one, the you also increase its standby lost, increasing how much more gas you will use.
Also, if its larger then the old boiler(BTU wise) it will need more combustion air, meaning it draws more fresh air into the house. Which you have to pay to reheat.

Your chimney may not be able to handle the larger boiler.

Attempting to derate a boilers input, can cause condensate troubles in both the boiler and chimney.

Improper conversions have caused more then one fire.
And way too many CO posionings.

hvaclover 01-14-2009 04:21 PM

Been correct me if I am wrong: Derating in excess of 20% will definitely cause condensation. For a 1900 sqft home you don't even need 100k, no?

So wouldn't derating this boiler be a very chancy since the amount of reduction far exceeds 20%?:huh:

beenthere 01-14-2009 05:07 PM

Some units have problems if you try even 10%.

Might only need 80,000 for it.

Gary_602z 01-14-2009 07:09 PM

I am not an HVAC tech nor do I play one on TV!:laughing: But wouldn't the type of house,insulation ,windows and geographic area come into play?


drewhart 01-14-2009 07:20 PM

its a stucco house in cleveland ohio. the upstairs 4 bedrooms have been framed-in with insulation. downstairs is the original stucco/plaster walls with no insulation. all new windows up, all old windows down. i just read today on the boiler that it is 131,250 btu. it doesnt indicate whether thats input or output. there is a rating called "water sq. ft" of which it says 700. the one i want to put in here has a btu rating of 140,000.

JohnH1 01-14-2009 07:26 PM

Think about why you are getting this boiler for such a deal. Someone els removed it for some reason. That is a lot of work to install a used boiler and then have problems. If not a leak.

drewhart 01-14-2009 07:33 PM

of the two i am trying to decide betweem, one was replaced because they invested in a new high efficiency boiler, the other because they switched over to furnace heat. before i buy it, i want to attach a fitting so i can compress air into it to see if it leaks. is this a viable test?

beenthere 01-14-2009 07:40 PM


Originally Posted by Gary_602z (Post 212740)
I am not an HVAC tech nor do I play one on TV!:laughing: But wouldn't the type of house,insulation ,windows and geographic area come into play?


Which is why I said "might" only need 80,000.

yuri 01-14-2009 07:42 PM

NO! Boilers have to be heated up and full of water to see if they leak. It may lose air pressure but hold water when the sections expand. Boilers are tested with hydrostatic (water pressure).In my area there is no such thing as DIY major furnace repairs/conversions as you have to take out a permit/be licensed etc for safety and liability and insurance co. reasons. Beware if something goes wrong the fire inspector and insurance company will hang you by your neck/lawsuits etc etc.

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