Over sized steam boiler

Jack P.

Actually, the boiler had 3 pressuretrols. One is labeled “high fire” the second “low fire” and the third “operator”. The “operator” is set at one-half pound and when triggered the boiler switches into low fire. But being so oversized it still builds pressure to 4 lbs. at low fire. The boiler really should be a LGB-6 or even a 5. Especially with the tiny radiators. With these tiny radiators, I have guesstimated if the boiler was down for 10 or 12 hours and dropped to 50 degrees, it would take days to recover to a normal temperature setting of 68 degrees. The boiler is controlled with a manual stat of which I will change to a White-Rogers programmable with a remote sensor so I can control the temperature myself at the boiler. I have all White-Rogers and sensors on all 26 of my other heating plants. Which seven are steam boilers. On high fire the gas valve runs at 3.5 Water Column and at low fire 1.2 WC. I, by throttling down the gas cock, am certainly running below low fire WC of 1.2. Probably at somewhere around .7 to 1.0 I am guessing. I believe throttling down the gas cock is putting fewer loads on the gas valve than removing burners because with fewer burners than what the gas valve was meant handle, it would put a lot of backpressure on the gas valve. I certainly am open to being corrected with my lines of thinking.

Jack P.

Over sized steam boiler

I just bought a 24-unit apartment building with a Weil-McLain LGB-8 steam boiler installed in 1999. There are 5-inch mains. This building has very tiny, (not small, tiny) radiators in each room in the apartments. They do heat each apartment nicely. On a normal burn cycle it runs at one-half pound pressure until the large mains are filled and then builds up to 4 lbs. pressure after these tiny radiators are totally hot. This boiler has a two-stage gas valve. That is, high fire and low fire. Pressuretrol was set at one-half pound but it didn’t kick down to low fire. (must need cleaning) So, I manually triggered into low fire on the next cycle with little screwdriver at one-half pound of pressure and it still built up the pressure to 4 lbs. even on low fire. So even the low fire gas valve is not helping. Obviously, this boiler is way to large to for the small radiant in the building. I was not making useable heat, I was just making pressure and wasting lots and lots of money. So, rather than downsizing the boiler by take out 30 or 40 percent of the burners, I decided to throttle down the gas cock to just allow the pressure to get to a one-half pound pressure reading max. I was concerned the lower gas pressure would not light the ionizing pilot but low and behold it lit just fine. I checked the stream arrival time at the tiny radiators and most all of them heated simultaneously on all three floors. Perfect comfort in the building and I am now saving tons on cubic feet of gas. My only concern now is am I hurting the gas valve by throttling down the gas pressure. Any thoughts or comments.

Dave_12

I would recommend getting a contractor in to check combustion. Make sure they use a combustion analyzer and provide a report.

Jack P.

What could I expect on the negitive side having the combusion analyzed? Slow hood draft or ???

Bill Jirik,

weil McClain LGB

LGb's typically come from the factory with a two stage gas valve but only a one stage pressurtrol, I typically install a manual switch to give the owner the choice of high and low fire, there is a deffinat change in the burner when it switches between low and high, but my other question is what are you using to control the boiler i.e. time clock, thermostat or condensate aquastat, it may be time to upgrade that control

Rodney Summers

Ask the Experts and

CONFIRM with the Manufacturer (Weil McLain) about throttling the gas valve. I may be WRONG but I recall reading here on the wall that throttling gas valve is not a preffered procedure. Alfred

Bill Jirik,

lgb

someone must have ordered that boiler with the optional staging on the controls, so you are indeed utilizing high-low fire, remote sense programable is definately the way to go,I like the honeywell vision pro but if your comftorable with the white rodgers use that, I have got some lgbs that ran for a long time at around 1" wc due to a gas supplier delivary problem and seem to run ok, just took a little longer to build steam you might try installing an air conditioner time delay relay in series with the wire going to the high fire side of the gas valve, so it doesn't go to high fire right away.