Downsizing steam boiler w/oil to gas conversion

ahelm

Hello All,

I have a Utica Starfire 3 steam boiler that has been converted from oil to a Carlin EZ gas burner. The boiler is over sized. Is it okay to downsize the BTU input from 140K BTU to about 90K? Any concerns with downsizing that much? Feedback much appreciated!

Steamhead

What model Starfire- maybe SFE-3100?

How much radiation is on the system?

ahelm

SFH3100S EDR 260

Steamhead

We've converted several of these units. That basic boiler was marketed in several firing rates- the smallest being 0.65 GPH which translates to 91,000 BTUH. So yes, it could be done.

But you would need to verify what diffuser was installed at the end of the burner's air tube, also what size the orifice nipple was drilled out to. You may end up having to have both these items replaced. Also, the resulting configuration must be tested with a digital combustion analyzer to make sure the flue gases are hot enough for the chimney to work, and that you're not making carbon monoxide.

For these reasons, you need to hire a pro. Where are you located?

EzzyT

@Steamhead I already spoke to Bruce Graham and carlin tech support and they both verified that the burner shouldn't not be downfield no more then 10% of the boilers input rating plus the dual action biometric damper is in the wrong place and yes the orfice size needs to be upsized

ahelm

Thanks Steamhead. Izzy is already checking it out as he notes above. It is already at ~90K input (13/64 orifice, diffuser . I was just looking to understand if is okay or not to down fire this boiler to ~90K BTU input or if there are issues in doing so. Thanks guys.

ahelm

That is diffuser b.

ahelm

I just spoke with Utica tech support. He said they "recommend" down firing by 10% max. When I first looked into this conversion Utica said they did not recommend converting to a gas burner for this boiler. If I had not found the experts on this site I probably would not have converted to the gas gun. So again I question Utica's direction re: 10% max and why I am checking here again about the % to down fire. With the oil burner prior the boiler was short cycling.

Steamhead

EzzyT said:

@Steamhead I already spoke to Bruce Graham and carlin tech support and they both verified that the burner shouldn't not be downfield no more then 10% of the boilers input rating plus the dual action biometric damper is in the wrong place and yes the orfice size needs to be upsized

I think you need to turn off auto-correct

Double-check to see if they have an EZ-Gas spec for the SFH- or SFE-365. That boiler has the exact same cast-iron block as the 3100. ISTR they do but can't lay my hands on it at the moment. It would use either the B or the 9-slot diffuser.

The current incarnation of that boiler is the SFE-3090, whose input is 126 MBH, with a net of 333 square feet EDR.

ahelm

EzzyT just did a great job completing some changes to my Utica Starfire steam boiler/Carlin EZ burner to address combustion issues. He replaced B diffuser with 9 slot, increased orifice slightly to 7/32 and moved the damper.

I highly recommend Ezzy in the NJ area!

Steamhead

Glad it worked out.