Is my steam boiler way oversized?

livinthesteamdream

Unfortunately...

at a consumption rate of 600 gallons a month, 180 didn't last very long with my boiler.   A year...forgetaboutit! lol

Dave in QCA

You could just save the old burner

I operated a pair of large dual fuel boilers 25 years ago. At that time, the dual fuel option was not set up properly and I set out to make corrections and set it up so that the firing fuel could be changed with the flick of a switch, the way it was supposed to be. At that same time, we changed from firm service gas to interrupt-able, which saved 25,000 a year. These boilers were 238 HP Kewanee Scotch marine type, firing at around 9 Million BTU on high fire.



Set up and adjustment was a pretty complicated process as the the burners were fully modulating, not a simple hi-low operation. The first step required getting the oil firing correctly adjusted at hi fire, then at the low end of the modulating range. Second step was to adjust the air shutter linkage to provide the correct mixture of air through the full range of oil firing. The third step was to switch to gas and then adjust the gas firing rate to match the air shutter so that proper mixture was obtained all through the firing range.



While it does not sound too complicated, the process required a considerable amount of time. But, once it was done, fuel switching merely required a few steps to the boiler, turning the boiler off, turning the selector switch to the desired fuel, and turning the operating switch back to "on".



In your case, a dual fuel burner might be unnecessarily complicated and expensive. You could just save the old burner and of fuel oil prices ever get lower than natural gas, (not likely), you could simply install the old burner and you probably could change the nozzle and make it fire at the lower rate you need.



As for the option of 1 stage or 2 stage, I would opt for 2-stage, but there will definitely be a price difference. 2-stage firing would provide a benefit if your load varies from time to time because of some of the radiators being turned off and at other times, all of them being turned on. Also, if you frequently fire the system long enough to fully heat the radiators, this will cause the boiler to cycle off and on. This can be minimized in single stage firing by having a low pickup factor. But, if you do this, you will need to make sure that your main venting is good and fast and your radiator venting is slow, for example, no faster than a Hoffman #40. This arrangement will make your system slow to heat up, but it should be even and in most cases, on off cycling when fully heated will be minimized and may not occur at all.



Gas pipe size: You probably need 1 1/4" if running house pressure from the meter. 1" is too small.

When we bought our building, the boiler was a 1,050,000 BTU firing rate. We are on low pressure and there is a 2" main coming in from the street. The meter is a 2" meter, but the piping reduces to 1 1/2 to the boiler which is about 40 ft away. This piping was actually a little under sized. In addition to the 2" meter, there are 9 more meters connected to the incoming main, most are for kitchen stoves by 2 of them have forced air furnaces on them. It all works just fine and the pressures are adequate to deliver the required amount of gas.

livinthesteamdream

V908A steam rating

I just realized (if I'm reading this correctly) that although the V908 produces 2,888 sq ft of steam per the V908 series literature and what was mentioned earlier, my boiler being a V908A model actually produces 3,471 sq ft of steam under the Net I=B=R area effectively making my boiler 2.4 times too big!!

With this even larger discrepancy in the size it should be and the size it currently is, is a smaller NG burner still gonna work? Additionally, should I buy a burner that is sized to the V908A or one that is sized more to a V904A which puts out 1508 sq ft of steam? I'm still way up in the air as far as the burner is concerned so I'm trying to get an idea on what the burner itself is going to cost as well as what I could possibly get for the CF1400 oil burner if I decided to sell. I'm not asking for prices since that isn't allowed on here. I just need to decide which model would be best suited for my situation.

Any thoughts gas pros?

The Steam Whisperer (Formerly Boilerpro)

typical mod burners

installed on boiler have been at least 3 to 1 downturn, so usually going down to 1/3 input  should be safe.  Check out Burnham's recommended burners and their downturn rate.

livinthesteamdream

Whew...

I'm glad I'm still within reason despite the size discrepancy. Burnham has numerous recommended gas burners such as the following:

Beckett CG10.4S, CG10.4S, CG10.5S, CG10.6S, CG15.3S, CG15.4S

PowerFlame JR30A-10, JR30A-12, or JR30A-15, JR50A-15 

Plus, there were also gas/oil combination burners they suggested.

**Stupid question--How do I find the downturn rate?