Boiler efficiency

Mark A Bruns

Dear Hot Heads,
I am a home owner with a 2 year old Burnham Independence PV boiler with steam outfitting. The system appears well piped and vented, and properly sized. It runs smoothly, but I am not sure it runs as efficiently as possible. Heat gets quickly (15-20 minutes from a cold start) to my radiators, but if the house is cold, the thermostat will continue to call for heat even after the radiators are hot. After the boiler has run for over an hour the pressure begins to approach cut-off (2psi) and much of the water is out in the system as steam. If the house has not fully warmed, the gas burners continue to fire at full force until either the pressuretrol or low water cut-off is tripped. As soon as the pressure drops or some water returns to the boiler, the burners kick back in at full force. What would seem more efficient would be to have the burners run at a lower level once a working level of steam and pressure had been built in the boiler and the thermostat still called for heat.
I callled Burnham and discussed the posssibility of some sort of burner set back control once the boiler had generated adequate steam. The Burnham techs have been very helpful, but indicated that the less than efficient (my opinion) pessuretrol/burners-fully-on-or-off system was all that is available. I am hoping that in this sophisticated age some one has devised a more efficient burner control arrangement. Does anyone have a suggestion on controls that could provide for burner set back (or other efficiency ideas) once the boiler has reached an operating level of steam and pressure? Thanks.
Mark A Bruns

Jim Davis

Steam system

You are running your steam pressure too high. 8 oz or 1/2 lb. is plenty for most homes. Need to change pressuretrol to a 16 oz control. Running burners at lower firing rates can increase fuel consumption 25-30%/

Unknown

Techs are correct

The gas valves that we use on our boilers are step opening gas valves. On natural gas they step open at 0.7" w.c. to 3.5" w.c. to ensure a smooth and proper burner lightoff. I would assume that this is what you are referring to as low stage. These boilers are only made for on-off operation and not modulation of any sort. Lowering the pressure with a vaporstat as mentioned will conserve fuel, but the controlling factor is the thermostat. If the rooms are not satisfied, the boiler will continue to cycle on and off until it becomes satisfied. Is the thermostat in a conditioned room with radiators? Be aware that operating a boiler with ounces of pressure may account for very short cycles on some systems that may not be as tight as desired. This can account for shorter ineffecient cycles and a lot more of them too causing much more long term wear and tear on your induced draft fan and ignition system components. If it were my option, I'd stick with the somewhat higher pressure and longer on cycles. Just my two cents for what it is worth. Hope this helps.

Glenn Stanton

Burnham Hydronics

[Deleted User]

How low

are you setting that thermostat when you leave home? Sounds like it must be a lot. Steam is not scorched air.

If the system operates well at the desired temperature, why not leave it there? Or, try setting the stat back just a bit at a time, until the boiler says "NO." Then back up that last bit.

True. It is possible to save 3% for each degree below 72. But setting back too far can kill much of that.

Happy steaming.